TEST PIECE FOR HEAVY METAL ION, PROCESS FOR DETECTING
HEAVY METAL ION, KIT AND SENSOR
TECHNICAL FIELD
[0001] This invention relates to a test piece for detecting heavy metal ions in an
aqueous liquid, a process of detecting heavy metal ions using the test piece, a portable kit for
detecting heavy metal ions by the detection process, and the detect sensor for identifying
heavy metal ions.
BACKGROUND
[00021 The heavy metal (ion) pollution refers to the environmental pollution caused
by heavy metals or their compounds. The increase of the heavy metal content in the
environment, especially in the case of heavy metal pollution in an aqueous system, is mainly
due to human factors, such as mining, waste gas emission, sewage irrigation and the use of
heavy metal-contaning products, which results in the deterioration of environmental quality.
10003] A commonly used method for the detection of heavy metal ions in an aqueous
system is to add a heavy metal ion detecting agent to a sample to be detected, wherein the
metal ion detecting agent binds the heavy metal ion to form a colored complex, that is, the
existence of the heavy metal ion can be determined from the color change of the system.
Recause ofthespecificity of the--colorof the heavymetal ion-detecting _,gent-heavymetal ion_
complex, the species and concentration of the heavy metal ion can be determined. For
example, by selecting dithizone as the heavy metal ion detecting agent, chelates can be
formed by dithizone and heavy metal ions such as I-Ig(ll), Pb(II), Cd(II) and Zn(II) existing in
the assay sample. Since different metals form metal-dithizone complexes exhibiting
different colors, low level of Hg(II), Pb(II), Cd(II), Zn(II) and the like in the aqueous solution
can be detected by UV-Vis spectrometer (such as the Chinese National Standard Methods for
Hg(II) (GB7469-87), Pb(II) (GB7470-87), Cd(II) (GB7471-87) and Zn(II) (GB7472-87)).
However, because this method generally requires lab-scale instruments such as UV-Vis
spectrometer and the identification of the detection results of the spectrometer requires expert
experiences, it is not suitable for in situ rapid monitoring.
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[0004] Moreover, the heavy metal ion detecting agents may be fixed in a substrate
(also known as carrier) such as a test paper or a membrane for the detection of the heavy
metal ions. When such a detection method is conducted by directly coating the detecting
agent on the carrier such as a test paper or a membrane, the heavy metal ion detecting agent
tends to leak (escape) due to the weak bonding between the heavy metal ion detecting agent
and the carrier, thereby affecting the detection of the heavy metal ion. In addition, the heavy
metal detecting agent on the test paper develops color during detection by reacting with the
heavy metal ions in the aqueous solution to form a colored complex, so that the type of the
heavy metal ion contained in the aqueous system can be determined by comparison with the
Color Chart and meanwhile the concentration of the heavy metal ion can be qualitatively or
quantitatively determined from the shade of the color. However, the heavy metal detecting
agent such as dithizone, which is fixed on the substrate, is oil soluble and water insoluble,
and thus when the test paper is immersed into the aqueous solution to be detected, the
chelation between the heavy metal ions and these agents is inhibited due to their difference in
solubility, which directly results in a typically higher detection limit of the test paper than
that of the Chinese National Standard method.
[0005) Therefore, currently there is still a need for a heavy metal ion test piece which
can be used to detect the small amount, even trace amount of heavy metal ions in an aqueous
system in a simple, low cost, highly sensitive, highly reliable and stable manner. Meanwhile,
it is-required that the-test_piece -is-available or in_situdetection, and is capable -of detecting
heavy metal ions with high sensitivity. Moreover, it is desired that the heavy metal ions can
be not only qualitatively detected, but also quantitatively or semi -quantitatively detected.
SUMMARY
[0006] The present invention provides a test piece for detecting heavy metal ions in
an aqueous system, comprising a substrate, a polymer coating layer and a layer of heavy
metal ion detecting agent, wherein the polymer coating layer is a coating layer of a
hydrophobic or water-repellent polymer.
[0007] According to a particular embodiment, the invention provides a test piece for
detecting heavy metal ions in an aqueous system, comprising a substrate, a polymer coating
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layer and a layer of heavy metal detecting agent, wherein the polymer in the polymer coating
layer comprises, but not limited to, polyethylene; polyvinyl chloride; polystyrene;
polypropylene; polybutene; polyisobutylene; polyformaldehyde; polyamides; polycarbonates;
polylactic acid; polytetrafluoroethylene; poly(ethylene terephthalate); epoxy resins; phenolic
resins; polyurethanes; polyacrylonitrile-butadiene-styrene; and poly(methyl methacrylate).
[00081 According to another particular embodiment, the invention provides a test
piece for detecting heavy metal ions in an aqueous system, comprising a substrate, a polymer
coating layer and a layer of a heavy metal ion-detecting agent, wherein the polymer is
selected from polystyrene and poly(methyl methacrylate).
[00091 The present invention further provides a process for detecting heavy metal
ions in an aqueous system: bringing the test piece for heavy metal ions into contact with the
aqueous system to be detected; shaking the aqueous system to be detected so as to contact
with the test piece sufficiently; and observing whether the color of the test piece is changed.
Herein, an organic solvent capable of dissolving the heavy metal ion-detecting agent is
contained in the aqueous system.
[00101 According to a particular embodiment, a process for detecting the heavy metal
ions in an aqueous system is provided, wherein the process comprises adding an organic
solvent capable of dissolving heavy metal ion-detecting agent into the aqueous system to be
detected; bringing a test trip coated with a polymer coating and a heavy metal-detecting agent
into_contact-with the_a.qucous system-tobe detected;-shaking the aqueous ;system to be
detected to contact with the test piece sufficiently; and observing whether the color of the test
piece is changed.
[00111 The invention further provides a kit (test suite) for the detection of heavy
metal ions in an aqueous system, comprising a test trip for the detection of the heavy metal
ions in an aqueous system (solution), an organic solvent and a color chart.
[0012] According to a particular embodiment of the invention, a kit for the detection
of heavy metal ions is provided, which comprises a test trip for the detection of the heavy
metal ions in an aqueous solution, an organic solvent capable of dissolving the heavy metal
ion-detecting agent, a sampling container, a color chart, wherein the color chart is the color
chart corresponding to various heavy metal ion-detecting agents.
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[0013] According to the invention, a test sensor for the detection for heavy metal ions
is provided, which comprises a test trip for the detection of the heavy metal ions in an
aqueous solution, a sample cell containing an organic solvent capable of dissolving the heavy
metal ion-detecting agent, a color chart, and a test piece color identification sensor.
[0014] According to one embodiment of the invention, the provided test sensor for
the detection of heavy metal ions comprises a test trip for the detection of the heavy metal
ions in an aqueous solution, a sample cell containing an organic solvent capable of dissolving
the heavy metal ion-detecting agent, a color chart and a test piece color identification sensor,
wherein the test piece is coated with an heavy metal ion-detecting agent and a polymer
coating.
[0015] Further scope of applicability of the present invention will become apparent
from the detailed description given hereinafter. However, it should be understood that the
detailed description and specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various changes and modifications
within the spirit and scope of the invention will become apparent to those skilled in the art
from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
-[00-16} The resent invention will-become mor-eful-lL-umderstood from the detailed
description given hereinafter and the accompanying drawings which are given by way of
illustration only, and thus are not limitative of the present invention and wherein:
[0017] Fig. 1 is a schematic graph for the detection principle of the heavy metal ions
in an aqueous solution by using a dithizone test piece (test paper) coated with a lipophilic
polymer coating.
[0018] Fig. 2 shows SEM micrographs of (a, b) a normal filter paper and (c, d) a filter
paper having a polystyrene coating.
[0019] Fig. 3 shows selective adsorption ability of the filter paper having the
polystyrene coating. In the Figure, the aqueous solution on the left side is the aqueous
solution of the water soluble ink (water phase, red); the organic solution on the right side is
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the dithizone solution in carbon tetrachloride (oil phase, green). Figs. 3a and 3b show
photos of water droplets (left side, red) and oil droplets (right side, green) on (a) the normal
paper and the filter paper having the polystyrene coating (the filter paper with a lipophilic
coating) and (b) the filter paper having the polystyrene coating after removing the water
droplet. Figs. 3c, d are photos of the normal paper and the filter paper having the
polystyrene coating after immersed into a layered oil-water mixing system (shown in Fig. 3c,
the upper layer is an aqueous solution, the lower layer is an organic solution) and an
emulsified oil-water mixing system (shown in Fig. 3d)and being taken out.
[0020] Fig. 4 shows capability of preserving dithizone for the filter paper substrates
having different polymer coatings. Fig. 4 shows capability of preserving the heavy metal
ion-detecting agent for the dithizone pieces made with polyvinylidene difluoride (PVDF),
blank filter paper (Owt%, PS), 2wt% polystyrene solution and 8wt% polystyrene solution
after standing for 1 minute to 24 hours at room temperature under natural light in the air
environment.
[0021] Fig. 5 shows the detection principle of Pb(II) in aqueous solution by using the
dithizone test piece made by the filter paper substrate having the polymer coating. Fig. 5a
shows the photo of the water droplets containing Pb(II) (water droplets on the left side of Fig.
5a) and the water/C2C14 mixing droplets containing Pb(Il) (droplets on the right side of Fig.
5a) after standing on the surface of the dithizone piece for 2 min. Fig. 5b shows the photo
of the_dithizone-piece_fer placing into-an aqueous solution containing 2b(II) and shat uug-for
2 min. Fig. 5c shows the photo of the dithizone piece after placing into a water/C2C14
mixing solution containing Pb(II) (C2Cl4/water volume ratio = 1/20) and shaking for 2 min.
In Fig. 5c, dark (red) C2CI4 droplets of Pb-dithizone complex adsorbed onto the surface of the
test piece can be observed.
[0022] Fig. 6 shows the color changes of detecting different concentrations of Pb(II)
ions in an aqueous solution by using the dithizone detecting agent piece without a polymer
coating (Test piece 1), the dithizone test piece without a polymer coating (Test piece 2, the
same to the Test piece 1) and the test piece having the polymer coating and the dithizone
heavy metal ion detecting agent (Test piece 3). Fig. 6 (upper) shows photos of the color
changes of test papers obtained after placing the Test piece 1 into aqueous Pb(II) solutions at
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different concentrations and reacting. Fig. 6 (middle) shows photos of the color changes of
test papers obtained after placing the Test piece 2 into Pb(II) water/C2C14 mixing solutions at
different concentrations and reacting. Fig. 6 (lower) shows photos of the color changes of
test papers obtained after placing the Test piece 3 into Pb(II) water/C2C14 mixing solutions at
different concentrations and reacting.
[0023] Fig. 7 shows detection of Cu(II) in water by using the dithizone test piece
having the poymer coating.
[0024] Fig. 8 shows detection of Zn(II) in water by using the dithizone test piece
made by the filter paper having the poynier coating.
[0025] Fig. 9 shows detection of Cu(II) in water by using the dithizone test piece
made by the filter paper having the poymer coating.
[0026] Fig. 10 shows detection of Hg(II) in water by using the dithizone lest piece
made by the filter paper having the poymner coating.
[0027] Fig. 11 shows detection of the color change of high concentration of Pb(II) in
the aqueous system by using the dithizone piece made by the filter paper having the polymer
coating.
[0028] Fig. 12 shows selective adsorption ability for oil phase and ability of detecting
the heavy metal ions of the test piece having the PMMA polymer coating. In Fig. 12, the
left is the droplet of the (red) aqueous solution (water phase), and the right (green) is the
droplet-of the organicsolution_(oil phase). Fig.12a_shows the-hydraphobicily (on-the-left _
side, droplet is present) and the hydrophilicity (on the right side, the droplet is absorbed) of
the hydrophobic polymer coating; Fig. 12.b shows photos after removing the water droplets
on the test piece having the PMMA coating (paper having the polymer coating); Fig. 12c
shows photos for the dithizone test piece having the PMMA solution coating after dripping
the deionized water/ C2C14 or Zn(I1)-containing aqueous solution/C2C14 mixture (with the
volume ratio being 20/1) onto it, wherein water does not change its color on the dithizone test
piece having PMMA coating while the solution containing Zn ion caused the color change of
the test piece.
[0029] Fig. 13 shows a multi-sample detection in aqueous solutions of different
heavy metal ions on the same dithizone test piece having the polymer coating. For Fig.13a,
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the same test piece exhibits different colors for different types of heavy metal ions, and for
Fig. 13b, the same test piece exhibits different colors for aqueous Pb(tl) solutions at different
concentrations.
[0030] Fig. 14 shows the dithizone pieces (test papers) made by normal A4 printing
paper. Figs. 14a and 14b show photos of water droplets and oil droplets on (a) the normal
A4 paper (normal paper) and the A4 paper having a polymer coating, and (b) test paper after
removing the water droplet. Fig. We shows multi-detection of water samples with different
types of metal ions by using the dithizone test piece (test paper) having the polymer coating
made by A4 paper, wherein different colors were shown, pink for Zn(II); amber for Cu(11);
off-orange red for Pb(II); and light yellow for Cd(II).
[0031] Fig. 15 shows detection of Ag (I) using the rose red silver test piece having the
polymer coating (test paper of polymer coating - rose red silver test reagent). (a) the Ag(I)
test paper was made from a rose red silver solution and an A4 paper coated with the polymer
coating (upper) or a normal A4 paper (lower). (b) Detection of Ag(I) was conducted by
using the rose red silver test paper made by the filter paper having the polymer coating (test
paper of polymer coating - rose red silver test reagent, upper) and using the rose red silver
test paper made by the normal A4 paper (lower).
[0032] Fig. 16 shows stability test of the dithizone test piece prepared from the filter
paper substrate having the polymer coating.
[0033] Fig. l - shows a schematic graph or- the grin- ciple of the heavy-metal
ion-detecting sensor.
[0034] Fig. 18 shows the change trend of R value (Pb(R)) and G value (Pb(G)) of the
color of the dithizone test piece (test paper) read by the test piece color identification sensor
after the detection of different concentrations of Pb(II), wherein Pb(R-G) is the difference of
R value and G value.
DETAILED DESCRIPTION
[0035] A test piece for the detection of heavy metal ions in an aqueous liquid.
[0036] A test piece for the detection of heavy metal ions in an aqueous liquid,
comprising a substrate, a polymer coating layer and a layer of heavy metal ion-detecting
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agent, wherein the polymer coating layer is provided such that the surface of the test piece is
hydrophobic.
[0037] The polymers which can endow the surface of the test piece with
hydrophobicity comprise, but not limited to, at least one of polyethylene; polyvinyl chloride;
polystyrene; polypropylene; polybutene; polyisobutylene; polyformaldehyde; polyamides;
polycarbonates; polylactic acid; polytetrafluoroethylene; poly(ethylene terephthalate); epoxy
resins; phenolic resins; polyurethanes; polyacrylonitrile-butadiene-styrene; and poly(methyl
methacrylate). In the test piece according to the invention, the use of polystryrene and / or
poly(methyl methaerylate) is preferable.
[0038] The substrate for forming the test piece can be any substrate material that can
carry the heavy metal ion detecting agent, including glass sheet, film, adsorbing material such
as cellulosic materials and the like, as long as it can carry the heavy metal ion detecting agent.
Preferably, the substrate material can be any porous material with adsorbency, for example, a
cellulosic material such as paper, including filter paper and normal printing paper (for
example, A4 paper). There is no particular limitation to the shape of the substrate material,
but a sheet, which has a high specific surface area, is preferred. Moreover, a sheet shaped
substrate is preferred in view of portability and convenience of use. In practical use, the
substrate can be designed to have suitable size and shape as required. Since the test piece
having a polymer coating layer according to the invention has high sensitivity of detection,
_unly_very small -volume-is needed to effectively_detect the_hea_vy metal-ions in an aqueous
system (for example, as shown in Fig. 14). Usually, the substrate is preferably a strip or a
tape due to the stability of preservation and sensitivity of detection of the test piece having a
polymer coating layer according to the invention, and considering portability and
convenience of use. The test piece according to the invention is small and thus portable and
convenient in use.
[0039] The method for coating or applying the polymer coating on the substrate can
be any means to apply a polymer on the substrate, such as the means of dip coating, spin
coating, and the like. Preferably, the polymer to be coated is dissolved in its (good) solvent,
especially an organic solvent, to form a polymer solution, such as a Iwt% to 20wt% polymer
solution. The polymer solution is thereby applied to the substrate and dried to obtain the
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test piece having the polymer coating. There is no particular restraint on the thickness of the
polymer coating, as long as the substrate is completely coated so that the coated test piece
becomes hydrophobic.
[0040] The heavy metal detecting agent used for the test piece can be various heavy
metal ion detecting agents commonly used. Preferably, the heavy metal ion detecting agent
used for the invention is an organic heavy metal reagent (or called as an oil soluble organic
heavy metal ion detecting agent), preferably an oil soluble organic heavy metal ion detecting
agent, for example, dithizone, which forms a colored substance with a particular color based
on the chelation between dithizone and heavy metal ions. These heavy metal ion detecting
agents comprise, but not limited to, dithizone, 5-(4-Dimethylaminobenzyliden(,)rhodanine,
diphenylcarbohydrazide, developers based on triphenylmethane (such as Victoria blue B,
crystal violet, malachite green and the like).
[0041] These heavy metal ion detecting agents form complexes with heavy metal ions
that specifically develop color. This can be used to identify the heavy metal ions in an
aqueous system, including the heavy metal ions such as Hg(II), Pb(II), Cd(II), Zn(II), Cu(II)
and the like that exist in the environment, especially in aqueous systems. Based on the color
that is developed, the existence, type as well as the general level/concentration of the heavy
metal ions in the system can be qualitatively and/or (semi-)quantitatively determined.
[0042] The heavy metal ion detecting agents are specific to the color of a complex
(chelate)of heavy metal ion-detecting agent heavy metal_i-an formed by a particular heavy
metal ion. Based on the color appeared and the darkness of the color, the level of heavy
metal ion pollution of the environment, that is, the concentration of the heavy metal ion in the
system, can be determined. A person of ordinary skill in the art is capable of identifying the
heavy metal ion according to the specific color. For example, dithizone reacts with different
heavy metal ions such as Hg(II), Pb(II), Cd(Il), Zn(II), Cu(II) and the like to form complexes
with different color, for example, the dithizone detecting agent develops yellow for Cd(II)
and develops red for Pb(II). The heavy metal ion detecting agent (layer) on the test piece is
preferably located on (within) the polymer coating on the test piece. The heavy metal ion
detecting agent can be applied to the heavy metal ion detecting agent layer in any manner.
The test piece having the polymer coating and the heavy metal ion detecting agent, which has
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a hydrophobic surface, can be obtained by coating the heavy metal ion detecting agent on
(within) the polymer coating by applying the heavy metal ion detecting agent layer in situ on
the test piece already coated with the polymer layer by applying the solution of the heavy
metal ion detecting agent before the detection, and using after dried.
[0043] In the aqueous system to be detected, if there exist more than one heavy metal
ion, pH value can be adjusted or a masking agent can be added to exclude other ions
(interfering ions) other than the heavy metal ion to be detected as required in order to avoid
interference . The masking agent can be a commonly used masking agent in the art, such as
hydroxylamine hydrochloride, ethylenediamine tetraaeetic acid (EDTA), potassium sodium
tartrate, ammonium citrate, and the like, which can be chosen according to the prior art.
When the target to be detected is a solid, for example, when it is desired to detect whether
soil contains heavy metal ions, the target to be detected is pre-treated to be dissolved in water
or a solvent system of water and an organic solvent that can dissolve the heavy metal ion
detecting agent, so that the heavy metal ion in the target to be detected is dissolved in this
aqueous system, and the test piece of the invention is used for detection.
[0044] Because the test piece of the application has the polymer coating and the
organic heavy metal ion detecting agent, it has a hydrophobic surface. Preferably, the
aqueous system to be detected contains an organic solvent, especially an organic solvent that
can dissolve the heavy metal ion detecting agent and/or the heavy metal ion detecting
-agent-heavy -metal ion chelate Preferably, --said- rganicsolvent is_i mnisciblewith water--
The amount of the organic solvent in the aqueous system is not particularly constrained as
long as it is trace amount. Preferably the ratio of the organic solvent : aqueous solvent (the
aqueous system) is 1:5 to 1:50 (volume ratio), preferably 1:10 to 1: 50 (volume ratio).
When the system does not contain any organic solvent, it is preferred that the organic solvent
is added. Depending on the heavy metal ion detecting agent, alkane, for example CI-C6
alkane, benzene, toluene, chlorine-containing CI-C6 alkane; chlorine-containing C2-C6
alkene such as CC14, CHC13, and C2C14, can be used. C2C14 is preferred as required.
[0045] Because the test piece of the invention contains a hydrophobic polymer
coating (that is, the surface of the test piece is hydrophobic), the binding strength between the
organic heavy metal ion detecting agent and the test piece is elevated. Meanwhile, the
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polymer layer shields the air and the ultraviolet light in sunlight to some extent, enabling the
heavy metal ion detecting agent in the test piece to be maintained for a longer period.
[0046] Due to the structure of the test piece described herein and the appeared
hydrophobicity of its surface, without bound by any theory, a double extraction process
occurs during the detection of the heavy metal ions with this test piece. Firstly, the polymer
coating in the test piece favors selective adsorption of liquid with low surface free energy (oil
phase) in liquid with high surface free energy (aqueous phase). Therefore, the test piece is
modified by the polymer coating (to become lipophilic / hydrophobic). Said test piece leads
to the first extraction in the aqueous system, wherein the organic heavy metal ion detecting
agent in the surface of the test piece is dissolved in the organic solvent in the aqueous system
(organic solvent/water = 1/20 by volume ratio), which extracts the heavy metal ions in the
aqueous solution to form heavy metal ion detecting agent-heavy metal ion complexes
(chelates) which is soluble in the organic solvent, and said complexes have specific color
(appearing to develop colors). Subsequently, the test piece leads to the second extraction
through the oil soluble polymer coating, which causes the extraction (the second extraction)
of the oil soluble heavy metal ion detecting agent-heavy metal ion complex to the test piece,
thereby said test piece appearing to develop specific color. - Furthermore, the test piece is
taken out, and the color developed in said test piece is compared to the color piece on the
Color Chart, thereby qualitatively and/or quantitatively identifying the heavy metal ion to be
-detected. Therefore, by_combining _the-hydrophobic polymer _coating _and the heavy metal
ion detecting agent on the substrate of said test piece, it is possible to increase the limit of
detection of the heavy metal ions by double extraction (for example, heavy metal ions as low
as 0.02 mg/L in the aqueous system can be detected). The reasons lie in that (1) compared
to a simple aqueous solution system, the non-water soluble and oil soluble heavy metal ion
detecting agent more readily reacts with heavy metal ions to form the heavy metal ion
detecting agent-heavy metal chelate after being dissolved in an organic reagent and
thoroughly mixed with the aqueous solution by means of agitation and the like; (2) compared
to a simple aqueous solution system, since the volume of the organic solvent is far smaller
than the volume of water in the aqueous system to be detected (such as a volume ratio of
1/20), the heavy metal ion in the aqueous solution can be enriched to some extent by the
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reaction between the heavy metal developer and the heavy metal ion (concentrated and
enriched 20-fold under the conditions of complete reaction), thereby the organic solvent
which accounts for only 1/20 volume can cause more significant color change of the test
piece after being adsorbed by the test piece.
[0047] Fig. 1 illustrates the principle of the double extraction of the Pb(II) ion by the
aforementioned test piece with the example that uses test paper as the substrate and dithizone
as the heavy metal ion detecting agent. Firstly, the test piece is placed in a water/C2CI4
mixture. Then the mixture is shaken to form a water sample/C2CI4 emulsion. During the
shaking, the emulsified C2C14 is adsorbed by the test piece due to the selective adsorption
ability of the test piece, which causes a portion of the dithizone which initially adheres to the
test piece to be dissolved in the droplet of the organic solvent (step a in Fig. 1), followed by
the reaction between the green dithizone-C2CI4 droplet and Pb(II) in water (step b in Fig. 1).
Subsequently, the reacted red Pb-dithizone-C2C14 can be again adsorbed by the test piece
(step c in Fig. 1). The whole process (step a to step c) will not stop until the completion of
the Ph-dithizone reaction and the adsorption of the, organic droplets by the test piece reaches a
balance. Therefore, during the whole process, the Pb(II) in the water sample is first
extracted to C2C14 and reacted with dithizone (the first extraction), followed by the further
extraction of Pb-dithizone by the test piece (the second extraction). In such way, the limit of
detection of the test piece can be greatly lowered by double extraction of Pb(II) from water,
camparedto that_vhen_a usual test-paper is used,_dithizone can-only react with l'b(II)in the
aqueous phase.
100481 _ The double extraction process during color development in Fig. 1 occurs by
the aforementioned structure of the test piece. The peculiarity of the structure of the test
piece lies in that after the coating of the hydrophobic polymer on the substrate material, this
coating of hydrophobic polymer covers the initial substrate and masks its property, which
causes the whole test piece to be hydrophobic (lipophilic), thereby significantly changing the
surface structure of the substrate material. Fig. 2 shows results of a scanning electronic
microscopy (SEM). Based on the SEM results, compared to untreated normal paper (Fig. 2a,
2b), the microstructure of the normal paper (Fig. 2a,b) and filter paper coated with polymer
(filter paper with a polymer coating) (Fig. 2c,d) can be clearly observed which shows that the
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treated filter paper (Fig. 2c, 2d) has a polymer coating on its surface fibers.
[0049] Fig. 3 shows the difference between the capability of the normal paper and the
filter paper coated with a polymer to adsorb liquid with different surface energy, in particular
the selective adsorption of the low surface free energy liquid (oils) in the high surface free
energy liquid (water). In Fig. 3 (a, b), the left panel shows an aqueous solution, and the
right panel shows a dithizone-organic solvent solution. According to Fig. 3a, the uncoated
filter paper material has the ability of adsorbing the aqueous solution and the organic solvent
solution; the filter paper coated with a polymer has lowered surface free energy and is only
able to adsorb dithizone-organic solvent droplets; in contrast, the normal paper can adsorb
both water and oil (Fig.3a, b). These two types of filter paper are immersed in a
water/organic solvent mixture, which further reveals that the treated filter paper has the
ability of selective adsorption. No matter whether the mixture is layered or,emulsified, the
filter paper covered by the polymer coating (the filter paper with a polymer coating) only
adsorb oil from water, but the normal paper is virtually covered by water (Fig. 3c,d). The
Figs 3(a, b) are photos of the left side (red) water droplet and the right side (green) oil droplet
on (a) the normal paper and the filter paper having a polystyrene coating (the test paper with
a polymer coating), and (b) the filter paper having a polystyrene coating (the test paper with a
polymer coating) which has the water droplet on it removed. Figs. 3(c) and (d) are photos
of the normal paper and the filter paper having a polystyrene coating after immersed into (c) a
layeredoil-watermixing system-and (b) an emulsified oil-watermixing system and taken out_
[0050] Among the test pieces with a polymer coating, it is preferred that the polymer
layer is a polystyrene or poly(methyl methacrylate) layer. Test pieces coated with
polystyrene or poly(methyl methacrylate) have higher capability to retain the heavy metal ion
detecting agents. Take the heavy metal ion detecting agent dithizone as an example. Fig. 4
shows the capability of various dithizone test papers made from different filter paper or films
to retain dithizone. Polyvinylidene difluoride (PVDF) film is a microporous filter having a
hydrophobic surface for filtering organic solutions or suspensions, which can only adsorb
organic solutions. Therefore, both PVDF film and normal paper (filter paper treated with
Owt% styrene) are used as control. Filter paper is immersed into a dithizone-organic solvent
solution (1 mg/mL) for 10 seconds, followed by drying in air and being placed in a place with
18/07/2012 13
LiuShen Docket No.PUH71438
good ventilation under natural light at room temperature for 24 hours to observe the color
change. It can be seen that after 24 hours, the filter treated with 8wt% polystyrene (PS) still
remains green, indicating that the dithizone test paper formed from filter paper with PS
retains dithizone better than a normal paper filter membrane.
[0051] The polymer coating in the test piece can be on all regions of the test piece,
including both or either side of the test piece; or it can be on all or partial regions on one side
of the test piece. The thickness of the polymer coating in the test piece is immaterial, as
long as the polymer coating exists in the region to be detected.
[0052] Preferably, the level of the polymer in the polymer coating is usually
immaterial. For example, when the polymer coating is obtained by dipping the test piece in
the polymer solution, it only requires that the test piece is moistured thoroughly by the
polymer solution.
[0053] The test piece coated with polymer has complete water resistance, and is able
to selectively adsorb liquid with low surface free energy (oil). Fig. 5 is a photo of the
procedure of detecting Pb(II) in water with dithizone test paper with a polystyrene coating.
Pb(N03)2 is dissolved in deionized water to form a Pb(II) water sample (I x 10-4 M). Due to
the protective effect of the polystyrene layer, only the Pb(II) containing water dropped on the
polystyrene coating of the dithizone test paper does not react with the dithizone on the test
paper. However, after the double extraction of Pb(II) by the test paper, the droplet of Pb(II)
water(water -sample-or aqueous systen C2C14 mi-xture4vohime_ratio_of waterto_C22C14
20/1) turns the dithizone test paper with a green polystyrene coating to red (Fig. 5a). The
difference is further demonstrated by placing the dithizone test paper having polystyrene
coating in different aqueous solutions and shaking. It can be seen that due to the protective
effect of the polystyrene layer, the dithizone test paper with the polystyrene coating placed in
Pb(Il) water does not experience Pb(II)-dithizone reaction. However, the dithizone test
paper with the polystyrene coating placed in the Pb(II)-water sample/C2C14 mixture (the
volume ratio of water to C2C14 = 20/1) experiences the reaction so that the green test paper
completely turns to red. Moreover, it can be clearly seen that the droplets of reacted
Pb-dithizone C2C14 is adsorbed by the test paper (Fig. 5c). This proves the principle of the
detection by dithizone test paper with a polystyrene coating as illustrated in Fig. 1. Fig. 5
18/07/2012 , 14
LzuShent Docket No.PUH71438
shows the extraction of Pb(11) by the dithizone test paper with a polystyrene coating. (a)
Pb(II) water and Pb(Il)-water C2Cl4 mixture droplets on the surface of the dithizone test paper
with the polystyrene coating. Both droplets are dropped onto the test paper almost
simultaneously and let stand for 2 minutes. (b) The dithizone test paper with the
polystyrene coating on the surface of the Pb(II) water sample. The test paper is placed in a
sample bottle which is shaken for 2 minutes. (c) The dithizone test paper with the
polystyrene coating in the Pb(II) water sample/C2C14 mixture. The test paper is placed in a
sample bottle which is shaken for 2 minutes. It can be clearly seen that the droplet of the
Pb-dithizone C2C]4 is adsorbed in the test paper.
[0054] According to one preferable embodiment of the invention, nanomaterials, for
example, materials such as nano silica or nano titania, can be introduce into the heavy metal
ion-detecting agent. Herein, the roughness and the specific surface area of the substrate can
be increased so as to obtain oil/water separating materials with better hydrophobicity and
lipophilicity, i.e., better ability of oil phase-selective adsorption, such as oil/water (or organic
solvent/water) separating filter paper, after treatment.
[0055] Other materials, for example, adjuvants for improving the adhesion among the
layers, can be added in the test piece as required. A color-developing adjuvant of the heavy
metal ion detecting agent such as a color-developing adjuvant for the dithizone detecting
agent can also be added. The adjuvants can be added in an amount as required.
10056]--- During the preparationof-the test-piece, a-po-l-yiner coating can b(, first-applied
to the substrate, for example, by coating the polymer coating, or by immersing the substrate
in the polymer solution. The test piece with the formation of said polymer layer can be
again coated with a layer of heavy metal ion detecting agent, such as a dithizone coating.
Fore example, a normal paper is immersed in a polystyrene (PS) - toluene solution (8wt%)
for 30 seconds, and dried with an electronic dryer to form a filter paper covered with the
polymer coating (the filter paper with a polymer filter).
[0057] According to one embodiment, the process for preparing the test piece
comprises:
applying a layer of heavy metal ion detecting agent on the substrate; and coating a
polymer protective layer on the heavy metal ion detecting agent layer. When an adsorbent
18/07/2012 15
LiuShen Dochal No.PUH71438
material is added into the polymer coating, it can be introduced into the polymer coating
before, concurrently with or after the application of the polymer coating.
[0058] Process for the detection of the heavy metal ions in an aqueous system
[00591 Process for the detection of the heavy metal ions in an aqueous system
according to the invention comprise bringing the test piece coated with the polymer coating
and the heavy metal ion-detecting agent into contact with the aqueous system; shaking the
aqueous system so as to contact with the test piece sufficiently; and observing whether the
color of the test piece is changed. Preferably, the aqueous system to be detected contains an
organic solvent. As required, organic solvent is additionally added into the aqueous system
to be detected. Preferably, the organic solvent is selected from chlorine-containing C 1-C6
alkane and chlorine-containing C1-C6 alkene, for example, CCIL, CHC13 and C2Ch4.
10060 1 In a particular embodiment, a process for detecting heavy metal ions in an
aqueous system is provided, said process comprising:
(a) bringing the test piece for detecting the heavy metal ions in the aqueous system in
contac with the aqueous system to be detected;
(b) shaking the aqueous system so as to contact sufficiently with the test piece; and
(c) observing whether the color of the test piece is changed.
[0061] When the color of the test piece changes, it is compared with the Color Chart
to-determine-whether-the heavy metal- ion exists-and/or the type-of the heavy inetal-iAan.
When other interfering ions exist in the system, a masking agent can be added. The type of
the masking agent can be determined by the interfering ion to be masked, such as Fe3+, Cat+,
or Mgt+. -
[00621 According to a particular embodiment, a method for detecting a heavy metal
ion is provided, including:
(a) adding an organic solvent into a solution to be detected;
(b) contacting the test piece with the solution to be detected;
(c) shaking the sample solution so as to fully contact with the test piece; and
(d) the color of the test piece changing.
[0063] Firstly, in step (a), the organic solvent added to the solution to be detected is
18/0712012 16
LiuShen Docket /l/o.pUH71438
an organic solvent that does not react with the heavy metal ion to he detected, preferably CCI4,
CHC13 or C204. Other organic solvents can also be used.
[0064] Subsequently, in step (b), the test piece coated with the polymer is placed into
a water sample/organic solvent mixture, followed by shaking the mixture to form a water
sample/organic solvent emulsion. During the shaking, a portion of the detecting agent that
originally attaches to the test piece is dissolved into the droplet of the organic solvent to form
an emulsified detecting agent. Due to the selectively adsorbing ability of the test piece, only
the emulsified detecting agent is adsorbed by the test piece coated with the polymer, and not
water droplet is adsorbed onto the test piece. Subsequently, the detecting agent for color
development - organic solvent droplets react with the heavy metal ion to be detected, such as
Pb(Il) in water. In step (b), the reacted heavy metal ion detecting agent-heavy metal
ion-organic solvent can again be adsorbed by the test piece. The whole process will not stop
until the Pb-detecting agent reaction ends and the adsorption of the organic droplets by the
test piece reaches a balance.
[0065] Therefore, during the whole process, the heavy metal ions in the water sample,
such as Pb(II) is first extracted to the organic solvent to react with the detecting agent (the
first extraction), and then the Pb-detecting agent is further extracted by the test piece coated
with the polymer (the second extraction). In such a way,'the limit of detection of the test
piece coated with the polymer can be greatly lowered by double extraction of Pb(II) from
-water compared to_that whennom atpaper isused, the_detecting agent only reacts with Pb(II)_
in the aqueous phase.
[00661 }, In step (c), the detecting agent binding to the heavy metal ions is again
extracted to the test piece and develops the specific color.
10067] The color developed by the binding of the heavy metal ion detecting agent to
the heavy metal ion is specific. A person of ordinary skill in the art can understand the
difference caused by the type of the heavy metal ion detecting agent.
[0068] Because a polymer coating is combined in the test piece, the selective
adsorbency, binding ability, and resistance to aqueous solvent during the detection of the
heavy metal ion detecting agent is significantly elevated. Therefore, the duration of
detection of the test piece of the invention is significantly shortened. Moreover, because of
18107/20/2 17
LiuShen Docket No.PUH71438
the protective effect of the polymer coating on the heavy metal detecting agent, the color of
the heavy metal color developing agent in the test paper does not change within 24 hours of
standing at room temperature in an open environment, indicating that no leakage or oxidation
of the heavy metal color developing agent occurs.
[0069] The detection sensitivity of detecting the heavy metal ion is significantly
increased due to the incorporation of the polymer coating layer in the polymer coating layer.
[0070] Kit for detecting heavy metal ions in an aqueous system
[0071] A kit for detecting heavy metal ions in an aqueous system is provided,
comprising a test piece coated with a polymer coating and a heavy metal ion detecting agent,
an organic solvent able to dissolve the heavy metal ion detecting agent, and a Color Chart.
[0072] The organic solvent included in the kit is a solvent able to dissolve the heavy
metal ion detecting agent and the heavy metal ion detecting agent-heavy metal ion complex,
preferably selected from chlorine-containing CI-C6 alkane and chlorine-containing C2-C6
alkene, including CC14, CHC13 and C2C14. C2CI4 is preferred in view of the environmental
friendliness.
[0073] The Color Chart in the kit is not limited to one kind. Depending on the
different type of the ions to be detected, the Color Chart may differ accordingly, which can be
chosen by a person of ordinary skill in the art.
[0074]--Moreo-ver, theicit may further-comprise-an interfering ionskingagent,-a
color development adjuvant, or other adjuvants; and a means to extract the aqueous system
sample to be-detected.
[0075] Because the test piece of the invention has a hydrophobic polymer coating and
has high sensitivity of detection to heavy metal ions, the kit may be made small, compact and
portable, and can identify the heavy metal ions in the aqueous system to be detected lower
than the usual limit of detection.
[00761 The color sensor for the detection of heavy metal ions in an aqueous system
[0077] On the basis of the test piece coated with a polymer coating and a heavy metal
ion detecting agent, a detection sensor that can be used to detect the heavy metal ions in an
18/07/20/2 - 18
LiuShen Dockel No.PUH71438
aqueous system is provided, which comprises a sample cell containing an organic solvent, a
Color Chart, and a test piece color identification sensor.
[0078] The sensor for the detection of the heavy metal ions also comprises a sample
preparation system, a set position for the test piece, a detection (color developing) segment
for the test piece, an input/output system for the color developing data, a color sensor system
to detect the developed color, a data processing/storage system and/or a data storage system.
[0079] In a particular embodiment, the ratio of the organic solvent to the aqueous
system is such that the aqueous system is excessive in volume relative to the organic solvent.
[0080] In the detection by the sensor for detecting the heavy metal ions, the reader
reads R value (red), G value (green), and B value (blue). The type and/or concentration of
the heavy metal ion are determined according to the reading of the test piece color
identification sensor.
[0081] Specifically, according to the principle of color sensor, the test piece color
identification sensor will use a color sensor chip, such as TCS 230 chip produced by TAOS
(Texas Advanced Optoelectronic Solutions) to identify the heavy metal ion based on the color
sensing principle according to the RGB data of specific colors. This color sensor has a
simple structure, which projects white light LED toward the object; the color sensor chip
receives the reflected light, and converts the light signal into digital RGB data signal using
red/green/blue filter and the CMOS circuit embedded in the chip. Moreover, the type and
concentration _oLtheheavy metal ions can be. determined-b3 combination of a digitalcamera---
and a smart phone that has photo-taking function with a graphic RGB analyzing software
based on PC or smart phone operating system. The graphic system takes pictures of objects,
and the RGB analyzing software analyzes the photo to obtain the RGB data of the objects.
Because the color sensor is highly integrated and modulated, which can read almost every
kind of color, a. portable test paper detector produced based on the color sensor system is
more convenient and simpler than a traditional test paper reflectometer.
[0082] The color sensor of the invention is a portable test paper detector by
combining the color sensor system with the colorimetric test paper for the rapid in situ
detection of the heavy metal ions or residual pesticides in water source, soil, or vegetables
and fruits.
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Lii,Shen Doclcel No.PUH71438
[0083] Fig. 17 is the structure of a portable test paper detector based on the color
sensor system, and a diagram of the detection procedure using said detector. Said portable
test paper detector comprises five parts: multiple test paper/test paper carrier slip, a data
input/output system component, a color sensor system component, a data processing/storage
system component, and an operating software. Accordingly, the detection process
comprises five steps: 1. preparing the sample; 2. detecting the sample with the test paper, and
putting the reacted test paper on the test paper carrier slip; 3. selecting the specific detection
program in the operating system according to the type of the test paper (for example, the
dithizone test paper for the detection of heavy metal ions or AChE enzyme test paper for the
detection of residual pesticides); 4. reading the color of the test paper by the color sensor; and
5. comparing the test paper RGB data and the stored reference RGB data by the data
processing/storage system, and storing and finally outputting the detection results.
[0084] Fig. 18 is a trend graph for the change of R value and G value of the color of
the dithizone test piece after the detection of different concentration of Pb(II) by the test piece
color identification sensor. From the figure, it can be clearly seen that the R values and G
values of the color of the test piece corresponds one by one to the different concentrations of
Pb(II). The corresponding R values and G values of the test paper in these fixed
concentrations can be saved as reference values.
[0085] On the other hand, the instrument of the present application can be assembled
- o a detection-assembly comprising the_nstr-ument af-thepresent-application and a-container
filled with the coloring agent solution. After the detection region of the detection material
of said instrument is contacted with the aqueous solution to be detected, it can be inserted
into the coloring agent solution for in situ determination so as to facilitate the detection
process. The coloring agent can be a water soluble coloring agent, including a water soluble
dye such as red ink, blue ink, and the like.
[0086] In another specific embodiment, this detection assembly can further include a
container filled with a water-soluble solubilizer, and/or an electrolysis equipment. As
mentioned above, duration of detection can be shortened and the sensitivity of detection can
be elevated by using a water soluble solubilizer and/or electrified procedure. Said water
soluble solubilizer includes water soluble alcohols, such as CI-C4 aliphatic alcohols,
18/07/2012 20
Liz Shen Docket LVo.PUH71438
preferably ethanol. By using this electrolysis equipment, the electrified procedure can be
conducted during detection. This electrolysis equipment can comprise an electrolyte tank, a
reference electrode, a counter electrode, and a power supply.
[0087] The detection assembly can be used for the following detection: taking a
sample of the aqueous solution to be detected and poured it into the electrolyte tank of the
electrolysis equipment, optionally adding a certain amount of water soluble solubilizer;
immersing the detection region of the detection material into said aqueous solution to be
detected; then connecting the electrolysis equipment to apply a negative voltage to the
detection material for the electrified procedure; subsequently, taking out the detection
material, and immersing the detection region of the detection material after contacting with
the aqueous solution to be detected into a coloring agent solution; and determining whether
the heavy metal ion exists in the aqueous solution to be detected by whether said detection
region adsorbs said coloring agent solution (that is, whether color change appears).
[0088] As mentioned above, the instrument and the detection assembly of the present
application can in situ detect the heavy metal ions in water with low cost. The heavy metal
ions primarily include ions of cadmium (Cd), lead (Pb), mercury (Hg), copper (Cu), and zinc
(Zn); especially the common ions of cadmium (Cd), lead (Pb), mercury (Hg) and the like that
are highly hazardous to human body. Moreover, the instrument and the detection assembly
of the present application can be conveniently used without constraints posed by
environ-rmentalconditior
[0089] ,. These specific illustrations are merely intended to provide a person skilled in
the art with aid or teaching that may be needed for carrying out the invention, and is not
intended to limit the invention by any means. Hereinafter, the invention is described in
more details by, way of examples. It should however be understood that these examples are
for illustration only and are in no way limiting. Unless described otherwise, all raw
materials used are commercially available.
EXAMPLES
EXAMPLE 1
18/07/2012 21
LiuSleen Docket No.PUH71438
[0090] Detection of Ph(11) in water using the normal dithizone test papers made by
the normal filter paper substrate and using the dithizone test pieces (test papers) made by the
filter paper substrate coated with a polymer coating.
[0091] The filter paper coated with polystyrene (PS) coating (filter paper having a
polymer coating) was prepared by dipping the filter paper into 8wt% polystyrene (PS)
solution in toluene for 30s and then drying by a hair dryer. The normal dithizone test paper
or the dithizone test paper having the polymer coating was prepared, respectively, by dipping
the 'normal filter paper or the filter paper having the polymer coating into 1 mg/mL
dithizone-C2'C14 solution for 1 Os and then drying at room temperature.
[0092] The detection of Pb(II) ions was performed by placing the normal dithizone
test paper or the dithizone test paper having the polymer coating into disposable sample
bottles which contain 10 mL of aqueous Pb(II) solution, with various concentrations (prepared
from Pb(NO3)2 and deionized water) or 10 mL of aqueous Pb(II) solution/C2CI4 mixture
(volume ratio of water to C2C14 = 20/1). After the sample bottles were shaken for 2 min, the
test papers were taken out to observe the color change.
[0093] Fig.6 depicts the color change of the normal dithizone test paper or the
dithizone test paper having the polymer coating after being treated with an aqueous Pb(II)
solution or an aqueous Pb(II) solution/C2Cl4 mixture. Fig. '6 shows the detection of Pb(Il) in
an aqueous solution using the normal dithizone test pieces (test papers) made by the normal
filter paper _and-using the-dithizone-test papers made by-the -filter paper substrate having the
polymer coating. (Upper) The photos show the color change of the test papers obtained
after the reaction by placing the normal dithizone test papers into the aqueous Pb(II) solution
with various concentrations. (Middle) The photos show the color change of the test papers
obtained after the reaction by placing the normal dithizone test papers into the aqueous Pb(II)
solution/C2C14 mixture with various concentrations. (Lower) The photos show the color
change of the test papers obtained after the reaction by placing the dithizone test papers made
by the filter paper having the polymer coating into the aqueous Pb(II) solution/C2C14 mixture
with various concentrations.
[0094] It is apparent that the dithizone test pieces placed into the aqueous Pb(II)
solution/C2C14 mixture have the most distinguished color change. It was found that the
18/07/2012 22
I,iuShen Docket No.PUH71438
addition of C2C14 into water can improve slightly the detection effect of Pb(II) for the normal
dithizone test piece, but still much worse than that for the dithizone pieces having the
polymer coating. When the dithizone test paper having the polymer coating prepared by
8wt% PS and I mg/nil, dithizone-C2CI4 aqueous solution is used to detect Pb(II), the lower
detection limit thereof is 0.02 mg/L, and the detection range for Pb(II) is 0.025 mg/L.
EXAMPLE 2
[0095] Detection of Cd(II) in water using the dithizone test paper having the polymer
coating.
[00961 The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dithizone test piece having the polymer coating was prepared by dipping the filter paper
having the polymer coating into 1 mg/mL dithizone-CCI4 solution for 10s and then drying at
room temperature.
[00971 The detection of Cd(II) ions was performed by placing the dithizone test paper
having the polymer coating into disposable bottles which contain 10 mL aqueous Cd(II)
solution (prepared from CdCl2 and deionized water) /C2C14 mixture (volume ratio of water to
C2Cl4 = 20/1). After the bottles were shaken for 2 min, the test papers were taken out to
observe the color change.
[0098] F-ig.Tlepictsthe-calmchange-af the dithizone niece having the polymer
coating after being treated with an aqueous Cd(II) solution/C2C14 mixture. When the
dithizone piece having the polymer coating prepared by 8wt% PS and 1 mg/ml,
dithizone-CC14 solution is used to detect Cd(II), the lower detection limit thereof is 0.01 mg/L,
and the detection range for Cd(II) is 0.01-11.2 mg/L.
EXAMPLE3
[0099] Detection of Zn(II) in water using the dithizone test paper having the polymer
coating.
[00100] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
18/07/2012 23
LiuShen Docket No.PUH71438
The dithizonc test paper having the polymer coating was prepared by dipping the filter paper
having the polymer coating into 1 mg/mL dithizone-CC14 solution for 10s, and then drying at
room temperature.
[00101] The detection of Zn(II) ions was performed by placing the dithizone test paper
having the polymer coating into disposable bottles which contain 10 not, aqueous Zn(II)
solution (prepared from ZnSO4 and deionized water) /CC14 mixture (volume ratio of water to
CC14= 20 / 1). After the bottles were shaken for 2 min, the test papers were taken out to
observe the color change.
[00102] Fig.8 depicts the color change of the dithizone test paper having the polymer
coating after being treated with an aqueous Zn(II) solution/CC14 mixture. When the
dithizone piece having the polymer coating prepared by 8wt% PS and 1 mg/mL
dithizone-CC14 solution is used to detect Zn(II), the lower detection limit thereof is 6.5μg/L,
and the Zn(II) detection range is 6.53250 μg/L.
EXAMPLE 4
[00103] Detection of Cu(II) in water using the dithizone test paper having the polymer
coating.
[00104] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dilhizone_tesLpaperhaving the polymer coating wasprepared by dipping the filter paper
having the polymer coating into 1 mg/mL dithizone-C2C14 solution for l Os and then drying at
room temperature.
[001051 The detection of Cu(II) ions was performed by placing the dithizone test paper
having the polymer coating into disposable bottles which contain 10 mL aqueous Cu(I1)
solution (prepared from Cu(N03)2 and deionized water) /C2C14 mixture (volume ratio of
water to C2C14 = 20/1). After the bottles were shaken for 2 min, the test papers were taken
out to observe the color change.
[00106] Fig.9 depicts the color change of the dithizone test paper having the polymer
coating after being treated with aqueous Cu(II) solution/C2C14 mixture. When the dithizone
test paper having the polymer coating prepared by 8wt% PS and 1 mg/mL dithizone-C2C14
18/07/20/2 24
LiuShen Docket No.PUI171438
solution is used to detect Cu(II). The lower detection limit thereof is 6.4μg/L, and the
detection range for Cu(II) is 6.43200 pg/L.
EXAMPLE 5
[00107] Detection of Hg(II) in water using the dithizone test paper having the polymer
coating.
[00108] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dithizone test paper having the polymer coating was prepared by dipping the filter paper
having the polymer coating into 1 mg/mL dithizone-C2CI4 solution for 10s and then drying at
room temperature.
[00109] The detection of Hg(II) ions was performed by placing the dithizone test paper
having the polymer coating into disposable bottles which contain 10 mL Hg(II) aqueous
solution (prepared from HgSO4 and deionized water with pH value adjusted to 1 -2 by HCI)
/C2CI4 mixture (volume ratio of water to C2CI4 = 20/1). After the bottles were shaken for 2
min, the test papers were taken out and to observe the color change.
[00110] Fig.10 depicts the color change of the dithizone test paper having the polymer
coating after being treated with aqueous Hg(II) solution/C2,C14 mixture. When the dithizone
test paper having the polymer coating prepared by 8wt% PS and 1 mg/mL dithizone-C2C14
--solution- is used to-detect Hg(II), the-lower -deteetianlimit4hereaf-is 0-02ing/L,_and the
detection range for Hg(H) is 0.021 Omg/L.
EXAMPLE 6
[00111] Detection of Pb(II) with higher concentrations in water using the dithizone test
paper having the polymer coating.
[00112] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dithizone test paper having the polymer coating was prepared by dipping the filter paper
having the polymer coating into 2 mg/mL dithizone-C2CI4 solution for I Os and then drying at
room temperature.
/8/07/20/2 25
LiuShen Docket No.PUH71438
[001131 The detection of Pb(IT) ions was performed by placing the dithizone test paper
having the polymer coating into disposable bottles which contain 10 mL aqueous Pb(II)
solution (prepared from Pb(N03)2 and deionized water)/C2C14 mixture (volume ratio of water
to C2C14 = 20/1). After the bottles were shaken for 1 min, the test papers were taken out and
to observe the color change.
[00114] Fig. 11 depicts the color change of the dithizone test paper having the polymer
coating after being treated with aqueous Pb(II) solution/C2C14 mixture. The detection range
changed significantly due to the increase of the loaded dithizone in the dithizone test paper
having the polymer coating. The detection range for Pb(II) by using the dithizone test paper
prepared by 8wt% PS and 2 mg/mL dithizone-C2C14 solution is 1200 mg/L.
EXAMPLE 7
[001151 Alternative polymer materials for preparation of the dithizone test paper
having the polymer coating.
[00116] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% poly(methylmethacrylate) (PMMA)-tetrahydrofuran solution for 30s and
then drying by a hair dryer. The dithizone test paper having the polymer coating was
prepared by dipping the filter paper having the polymer coating into 1 mg/mL
dithizone-C2C14 solution for I Os and then drying at room temperature.
[00-1-17] -The redaqueous-solution isprepared by-diluting a-red ink n_leionized eater.
The green organic solution is 1 mg/mL of dithizone-C2C14 solution. The aqueous Zn(II)
solution is prepared from ZnS04 and deionized water.
[00118] The selective absorption test was conducted by dropping the red water and the
green oil onto the normal filter paper and the PMMA coated filter paper having the polymer
coating (paper having the polymer coating), standing for 2 min, and then removing the water
drops from the paper having the polymer coating.
[00119] The heavy metal detection capability test was conducted by dropping
deionized water/C2C14 mixhue (20/1) and Zn(II) water/C2Cl4 mixture (20/1) on the PMMA
coated dithizone test paper having the polymer coating, and then standing for 2 min.
[00120] Fig.12 depicts the selective absorption ability of the PMMA coated separation
18/07/2012 26
LhiShen Docker No.PUH71438
filter paper and the capability of detecting heavy metal ions for the PMMA coated separation
filter paper having the polymer coating. Fig. 12 a and 12b show that the filter paper having
the polymer coating prepared by the PMMA solution also possesses the selective absorption
ability towards water and C2C14. Fig.12c depicts that the PMMA coated dithizone test paper
having the polymer coating has the capability of the detection of heavy metal ions as well.
EXAMPLE 8
[00121] Multi-sample detection using the dithizone paper having the polymer coating.
[00122] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dithizone paper having the polymer coating was prepared by dipping the filter paper
having the polymer coating into 1 mg/mL dithizone-C2C14 solution.for 10s and then drying at
room temperature.
[00123] The aqueous Cu(II) solution is prepared by dissolving the CdC12 in deionized
water. The aqueous Pb(II) solution is prepared by dissolving the Pb(N03)2 in deionized
water. The aqueous Zn(II) solution is prepared by dissolving the ZnSO4 in deionized water.
The aqueous Cu(II) solution is prepared by dissolving the Cu(N03)2 in deionized water.
[00124] The multi-sample detection was conducted by dropping 50 μL heavy metal ion
solution in water/C2CI4 mixture (20/1) on the same dithizone test paper having the polymer
oatingandstanding -far 5 nun._
[00125] Fig.13 depicts the photos of the detection of different types of heavy metal
ions at the, same molar concentration and aqueous Pb(II) solutions with different
concentrations using the dithizone paper having the polymer coating. In Fig. 13, the
multi-sample detection was carried out in the different aqueous solutions on the same the
dithizone test paper having the polymer coating: (a) different types of heavy metal ions and
(b) aqueous Pb(II) solutions with different concentrations. Different colors correspond to
different types of heavy metal ions (Fig.13a), and different shade degrees of red color
correspond to aqueous Pb(II) solutions with different concentrations (Fig.13b).
EXAMPLE 9
/8/07/2012 27
LiuShen Docket No.PUH71438
[00126] Alternative paper substrates for the preparation of the dithizone test paper.
[00127] The paper having the polymer coating was prepared by dipping the normal A4
printing paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair
dryer. The dithizone test paper having the polymer coating was prepared by dipping the
normal A4 paper having the polymer coating into 1 mg/ml, dithizone-C2C14 solution for 10s
and then drying at room temperature.
[00128] The red aqueous solution (water) was prepared by diluting a red ink in
deionized water. The green organic solution was 1 mg/mL dithizone-CCI4 solution.
[00129] The aqueous Cd(II) solution was prepared by dissolving CdCl2 in deionized
water. The aqueous Pb(TI) solution was prepared by dissolving the Pb(N03)2 in deionized
water. The aqueous Zn(II) solution was prepared by dissolving the ZnSO4 in deionized
water. The aqueous Cu(II) solution was prepared by dissolving Cu(N03)2 in deionized
water.
[00130] The selective absorption test was conducted by dropping the red water and the
green oil onto the normal A4 paper (normal paper) and the A4 paper having the polymer
coating (the paper having the polymer coating), and standing for 2 min, then removing the
water drops from the paper having the polymer coating.
[00131] The multi-sample detection was conducted by dropping heavy metal ion
solution in water/C2C14 mixture (20/1) on the dithizone test paper having the polymer coating
prepared by A4-printing paper, andthen standing for 5 rnia--
[00132] Figs. 14 a and 14 b depict the selective absorption ability towards water and
CCI4 forthe A4 paper having the polymer coating. Fig. 14e shows that the dithizone test
paper having the polymer coating obtained by treating the normal A4 printing paper with
8wt% PS solution and 1 mg/mL dithizone-C2CI4 solution has the ability of multi-sample
detection.
EXAMPLE 10
[00133] Detection of Ag(I) using the rose red silver test paper having the polymer
coating.
[00134] The paper having the polymer coating was prepared by dipping the normal A4
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LiuShen Docket No.PUH71438
printing paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair
dryer. The normal p-dimethylaminobenzal rhodanine test paper and the
p-dimethylaminobenzal rhodanine test paper having the polymer coating was prepared
respectively by dipping the normal A4 paper or the A4 paper having the polymer coating into
0.5 mg/mL p-dimethylaminobenzal rhodanine solution in acetone/C2C14 (the volume ratio is
1/1) for 10s, and then drying at room temperature. The aqueous Ag(I) ion solution was
prepared by dissolving AgN03 indeionized water.
[00135] The detection of Ag(I) was conducted by dropping the deionized water/C2C14
mixture (20/1) and the aqueous Ag(I) solution/C2C14 mixture (20/1) on the
p-dimethylaminobenzal rhodanine test paper having the polymer coating or the normal
p-dimethylaminobenzal rhodanine test paper, and then standing for 5 min.
[00136] Fig. 15a depicts the p-dimethylaminobenzal rhodanine preserving capability of
the normal A4 paper' (normal paper) and the A4 paper having the polymer coating (the paper
having the polymer coating). In Fig. 15, the p-dimethylaminobenzal rhodanine test paper
having the polymer coating was employed in the detection of Ag(I). (a) The test paper for
the detection of Ag(I) was prepared from the p-dimethylaminobenzal rhodanine solution in
acetone/C2C14 and the PS-coated A4 paper or the normal A4 paper. (b) the
p-dimethylaminobenzal rhodanine test paper having the polymer coating was employed in the
detection ofAg(I).
---[001.37I It is obvious from-the-colors-of the prepared test papeers and the
p-dimethylaminobenzal rhodanine solution that the paper having the polymer paper has a
better heavy, metal reagent preserving capability than the normal paper. Fig.15b depicts the
detection of Ag(I) using these _two types of test papers. It is clear that the
p-dimethylaminobenzal rhodanine test paper having the polymer coating has a better color
contrast than the normal test paper.
EXAMPLE 11
[00138] The stability of the dithizone test paper having the polymer coating.
[00139] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
18/07/2012 29
LiuSiten Docket No.PUH71438
The normal dithizone test paper and the dithizone test paper having the polymer coating were
prepared, respectively, by dipping the normal filter paper or the filter paper having the
polymer coating into 1 mg/mL dithizone-C2Cl4 solution for 10s and then drying at room
temperature.
[00140] The stability test was conducted by comparing the colors of four dithizone test
papers having the polymer coating after different treatments. One test paper was prepared
by dipping the filter paper having the polymer coating into the newly prepared
dithizone-C2CI4 solution (newly prepared one). Another test paper was prepared by dipping
the filter paper having the polymer coating into the newly prepared dithizone-C2C14 solution
and placing in the open air at room temperature for a month (the test piece after placing in the
open air for 1 month). The third one was prepared by dipping the filter paper having the
polymer coating into the newly prepared dithizone-C2C14 solution and placing in a sealed
brown bottle shielded from the light at room temperature for a month (the test piece shielded
from the light after I month). And the last one was prepared by dipping the filter paper
having the polymer coating into the dithizone-C2C14 solution which had been kept in a sealed
brown bottle shielded from the light at room temperature for a month (the dithizone solution
after shielding from the light for 1 month).
[00141] Fig. 16 depicts the stability of the dithizone test paper having the polymer
coating. From the color, it is apparent that, under the protection of the polymer layer and
shielding Siam the_light,_dithizone_ can-be-preserved in-thefilter paper having the-polymer
coating very well. And even in the open air, the dithizone can be also preserved better than
the dithizone, solution which is shielded from the light.
EXAMPLE 12
[00142] Change trend of R value (Red Value) and G value (Green Value) of the color
of the dithizone test paper having the polymer coating read by the test piece color
identification sensor after the detection of Pb(II) at different concentrations.
[00143] The filter paper having the polymer coating was prepared by dipping the filter
paper into 8wt% polystyrene (PS)-toluene solution for 30s and then drying by a hair dryer.
The dithizone test paper having the polymer coating was prepared by dipping the filter paper
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LhS11en Dockel 1Uo.PUK71438
having the polymer coating into 2 mg/mL dithizone-C2C14 solution for l0s, and then drying at
room temperature. The aqueous Pb(II) solution was prepared by dissolving Pb(N03)2 in
deionized water.
[00144) The detection of Pb(II) ions was performed by placing the dithizone test paper
having the polymer coating into disposable sample bottles which contain 10 mL of aqueous
Pb(II) solution/C2C14 mixture (volume ratio of water to C2C14 = 20/1). After the sample
bottles were shaken for 1 min, the test papers were taken out for reading the color values by
use of the color identification sensor.
[00145] Fig. 18 depicts the trend of the color change of test paper after the detection of
Pb(II), taking the detection of Pb(II) by use of the dithizone test paper having the polymer
coating as an example. The color of the dithizone test paper having the polymer coating
changes from the green color of dithizone into the red color of Pb-dithizone, and the shade of
the red color arc continuously deepened with the increase of the Pb(II) concentration, as
shown by the trend graph of the color: R value has a trend of increasing with the increase of
the Pb(II) concentration; G value has a trend of decreasing with the increase of the Pb(II)
concentration, and the difference between the R value and B value tends to increase.
Therefore, the R value and G value corresponding to a certain Pb(II) concentration can be set
as the reference value for the determination of the Pb(II) 'concentration (range) in the real
water sample by comparing with the color values of the test paper after the detection of Pb(II)
in a-practicaldetection-
[00146] The embodiment of the invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be regarded as a departure
from the spirit and scope of the invention, and all such modifications as would be obvious to
those skilled in the art are intended to be included within the scope of the following claims.
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WHAT IS CLAIMED IS:
1. A test piece for detecting heavy metal ions, comprising a substrate, a polymer coating
layer and a layer of heavy metal ion-detecting agent, wherein the polymer coating layer is
provided such that the surface of the test piece is hydrophobic.
2. The test piece according to Claim 1, wherein the polymer in the polymer coating layer
is selected from the group consisting of polyethylene; polyvinyl chloride; polystyrene;
polypropylene; polybutene; polyisobutylene; polyformaldehyde; polyamides; polycarbonates;
polylactic acid; polytetrafluoroethylene; poly(ethylene terephthalate); epoxy resins; phenolic
resins; polyurethanes; polyacrylonitrile-butadiene-styrene; and poly(methyl methacrylate).
3. The test piece according to Claim 1, wherein the polymer coating layer is disposed on
the substrate, and the detecting agent in the layer of the heavy metal ion-detecting agent is
distributed within the polymer coating layer.
4. The test piece according to Claim 1, wherein the heavy metal ion-detecting agent in
the layer of the heavy metal ion-detecting agent is an oil-soluble detecting agent for heavy
metal ions.
5. The test piece according to Claim 1, wherein the heavy metal ion-detecting agent is
selected from the group consisting of dithizone, p-dimethyfaminobenzal rhodanine (rose red
silver reagent), diphenylearbohydrazide, or a developer based on triphenylmethane.
The test piece-according-to Claim 1, wherein the-test pieceis used for the detection of
the heavy metal ions in an aqueous system, and the aqueous system contains an organic
solvent capable of dissolving the oil soluble heavy metal ion-detecting agent, or an organic
solvent capable of dissolving the oil soluble heavy metal ion-detecting agent is added to the
aqueous system.
7. The test piece according to Claim 6, wherein the organic solvent is selected from the
group consisting of chlorine-containing alkane or chlorine-containing alkene, preferably at -
least one of CC14, CHC13 and C2CI4.
8. A process for detecting heavy metal ions in an aqueous system, comprising:
a. bringing the test piece according to any one of Claims I to 7 into contact with the
aqueous system to be detected;
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LiuShen Docket /vo.PUH71438
b. shaking the aqueous system so as to contact with the test piece sufficiently; and
c. observing whether the color of the test piece is changed.
9. The process according to Claim 8, comprising:
comparing the colored test piece with a color chart to determine whether a heavy metal
ion is present and / or determine the species of heavy metal ion.
10. The process according to Claim 9, wherein the aqueous system to be detected
contains an organic solvent capable of dissolving the oil soluble heavy metal ion-detecting
agent, or an organic solvent capable of dissolving the oil soluble heavy metal ion-detecting
agent is added to the aqueous system to be detected.
11. The process according to any one of Claims 9 to 10, wherein the organic solvent is
selected from the group consisting of chlorine-containing alkane or chlorine-containing
alkene, preferably from at least one of CC14, CHC13 and C2C14.
12. A kit for detecting heavy metal ions in an aqueous system, comprising the test piece
according to any one of Claims I to 7 and a color chart.
13. The kit according to Claim 12, comprising an organic solvent capable of dissolving
the oil soluble heavy metal ion-detecting agent.
14. The kit according to Claim 13, wherein the organic solvent is selected from
chlorine-containing alkane or chlorine-containing alkene, preferably from at least one of CC14,
CHC13 and C204-
--15. The kitaccording to Claim 13_ur--1-4, wherein a volume_ratioMf the_oxganicsohient to
the aqueous system is between 1:10 and 1:50.
16. A detecting sensor for detecting heavy metal ions in an aqueous system, comprising
the test piece according to any one of Claims I to 7.
17. The detecting sensor according to Claim 16, comprising a test piece color
identification sensor, a color chart, and optionally a sample cell containing an organic solvent.
18. The heavy metal ion-detecting sensor according to Claim 17, wherein the ratio of the
organic solvent to the aqueous system is such that the aqueous system is excessive in volume
relative to the organic solvent, and preferably a ratio in volume of the organic solvent to the
aqueous system is between 1:10 and 1:50.
19. The heavy metal ion-detecting sensor according to Claim 17, wherein the test piece
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color identiiicailon sensor is capable of identifying the cOneelllraiton of the respective heavy
metal ions by comparing the color values read by itself, such as R value (red), G value (green)
and B value (blue), with the reference color values.
20. The heavy metal ion-detecting sensor according to Claim 17, wherein the species of
the heavy metal ions and/or the concentration of the heavy metal ions are determined
according to the reading on the color recognition sensor of the test piece.