Description:TECHNICAL FIELD
[0001] The disclosure generally relates to a petroleum test kit and method for testing petroleum, and more specifically, to an on-site petroleum alcohol test kit and method for testing petroleum that allows for qualitative and quantitative determination of ethanol.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Globally, most of the countries are moving towards bio-fuel substitution due to growing environmental concerns and energy security. Alcohol is rapidly becoming a familiar component of gasolines known as gasohols, wherein the alcohol content is often found to be as much as 10%, and in some specialty fuels it can approach nearly 100%. In countries like Brazil more than 80% of ethanol is being blended in Motor Spirit (MS). Govt. of India has mandated ethanol blending in gasoline. Currently, in metro cities, 5% ethanol is being blended with MS, while some states/cities allow for blending even 10% ethanol with MS depending upon the availability. Ethanol blending with gasoline (MS) help reduces particulate emissions and improves the combustion. However, the propensity of alcohols to absorb water from environment has long been known as a fact and theoretically, it is possible to find as much as 10% disbursed water in alcohol which would translate into about 1% water disbursed in gasohols (EBMS) containing 10% alcohol. The adverse effects of excessive water in a fuel system can’t be overstated as ranging from corrosion to poor engine performance. Hence, as a matter of standard practice, ethanol is stored in separate moisture resistant tanks and blending with MS is done online at TLF gantry and then the product mix is filled in tank lorries. To check the ethanol content in tank lorries, conventional Annex. E of IS 2796:2014 method is currently being practiced at most of the installations/depots. However, qualitative and quantitative estimation of ethanol in EBMS using this method is impracticable at the supply point of installations and retail outlets.
[0004] A significant amount of research has already been done in this technology domain to devise methods and kits that can allow for quick on-site qualitative and quantitative estimation of ethanol in petroleum. US patent no. 5,229,295 discloses a colorimetric test for alcohols (any alcohol) using 0.1% gentian violet dye in mineral oil suspension which when shaken with fuel causes the fuel to become purple when there is at least 1% alcohol present. However, the purple color is proportional to the alcohol concentration only in the range of 1% to 5%. The non-linearity of color (purple) over a wide range of alcohol concentration in EBMS or any other petroleum products makes this method practically non-viable as in most cases concentration of ethanol in EBMS exceeds 5%. US patent no. 5,229,295 further discloses that where more than 5% alcohol is found in gasohols (EBMS), a volumetric measurement is imperative to determine its percentage.
[0005] There is therefore a need in the art for improved kits and methods that can enable quick on-site qualitative and quantitative estimation of ethanol over a wide, and more importantly, commercially available concentration ranges of EBMS.

OBJECTS OF THE INVENTION
[0006] An object of the present disclosure is to overcome disadvantages associated with conventional methods and kits that allows for detection of ethanol content in petroleum or Ethanol Blended Motor Sprit (EBMS).
[0007] Another object of the present disclosure is to provide a kit that allows for quantitative estimation of ethanol content in petroleum or Ethanol Blended Motor Sprit (EBMS) over a wide range of concentrations.
[0008] Another object of the present disclosure is to provide a kit that allows for qualitative determination of ethanol in petroleum.
[0009] Another object of the present disclosure relates to a simple and quick test method for testing ethanol content in Ethanol Blended Motor Spirit at TLF gantry during dispatch of EBMS tank lorries at supply locations.
[0010] Another object of the present disclosure relates to a simple and quick test method for checking the ethanol content at installation site itself without using any sophisticated instrument or calibrated glassware.
[0011] Another object of the present disclosure is to provide a kit that allows for better control of Ethanol doping system in MS in addition to current test methods.
[0012] Another object of the present disclosure is to provide a kit that can allow for quantitative estimation of ethanol content ranging from 6% to 10% in Ethanol Blended Motor Sprit (EBMS).
[0013] Another object of the present disclosure is to provide a color chart for quantitative estimation of ethanol content ranging in Ethanol Blended Motor Sprit (EBMS).

SUMMARY
[0014] The disclosure generally relates to a petroleum test kit and method for testing petroleum, and more specifically, to an on-site petroleum alcohol test kit and method for testing petroleum that allows for qualitative and quantitative determination of ethanol.
[0015] In an aspect, the present disclosure relates to a method for quantitative estimation of an amount of ethanol in a petroleum sample, said method including the steps of: (a) contacting an appropriate amount of the petroleum sample with an appropriate amount of a dye suspension, wherein the dye suspension comprises about 0.5% crystal violet dye dispersed in paraffin oil; (b) obtaining a color, based on a reaction between the petroleum sample and the dye suspension after a pre-defined time interval, wherein the obtained color is proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) estimating the amount of ethanol based on the obtained color.
[0016] In an embodiment, at least about 10 mL of petroleum sample is contacted with the dye suspension. In another embodiment, at least about 50 microliters of the dye suspension is contacted with the petroleum sample.
[0017] In an embodiment, the amount of ethanol is estimated based on one or a combination of visual chart, a computing means and a spectroscopy means. In an embodiment, the computing means is configured to take an image of the obtained color and analyze the color to estimate the amount of the ethanol.
[0018] In another aspect, the present disclosure relates to an ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit including (a) a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; (b) a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) a chart configured to enable comparison of the color of the petroleum sample with colors present in the chart to estimate the amount of the ethanol in the petroleum sample.
[0019] In still another aspect, the present disclosure relates to an ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit including (a) a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; (b) a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) a computing device configured to take an image of the color of the petroleum sample and analyze the color to estimate the amount of the ethanol in the petroleum sample.
[0020] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0022] FIG. 1 illustrates exemplary views of obtained colors on contacting the petroleum samples containing different concentrations of ethanol with the dye suspension in accordance with embodiments to the present disclosure.
[0023] FIG. 2 illustrates an exemplary plot depicting linearity of detection over a concentration range of 6% to 10% ethanol in EBMS in accordance with embodiments to the present disclosure.

DETAILED DESCRIPTION
[0024] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0025] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0026] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0027] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0028] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
[0029] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0030] The disclosure generally relates to a petroleum test kit and method for testing petroleum, and more specifically, to an on-site petroleum alcohol test kit and method for testing petroleum that allows for qualitative and quantitative determination of ethanol.
[0031] In an aspect, the present disclosure relates to a method for quantitative estimation of an amount of ethanol in a petroleum sample, said method including the steps of: (a) contacting an appropriate amount of the petroleum sample with an appropriate amount of a dye suspension, wherein the dye suspension comprises about 0.5% crystal violet dye dispersed in paraffin oil; (b) obtaining a color, based on a reaction between the petroleum sample and the dye suspension after a pre-defined time interval, wherein the obtained color is proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) estimating the amount of the ethanol based on the obtained color.
[0032] In an embodiment, at least about 10 mL of petroleum sample is contacted with the dye suspension. In another embodiment, at least about 50 microliters of the dye suspension is contacted with the petroleum sample.
[0033] In an embodiment, the amount of ethanol is estimated based on one or a combination of visual chart, a computing means and a spectroscopy. In an embodiment, the computing means is configured to take an image of the obtained color and analyze the color to estimate the amount of the ethanol.
[0034] In another aspect, the present disclosure relates to an ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit including (a) a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; (b) a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) a chart configured to enable comparison of the color of the petroleum sample with colors present in the chart to estimate the amount of the ethanol in the petroleum sample. In an embodiment, at least about 10 mL of petroleum sample is contacted with the dye suspension. In another embodiment, at least about 50 microliters of the dye suspension is contacted with the petroleum sample.
[0035] In still another aspect, the present disclosure relates to an ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit including (a) a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; (b) a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) a computing device configured to take an image of the color of the petroleum sample and analyze the color to estimate the amount of the ethanol in the petroleum sample.
[0036] An embodiment of the present disclosure provides a dye suspension for use in qualitative and quantitative estimation of an amount of alcohol (preferably ethanol) in a petroleum sample. In an embodiment, the dye suspension can include dispersion of one or more finely divided water soluble dye(s), known to a person skilled in the art, in paraffin oil. In a preferred embodiment, finely divided crystal violet dye can be dispersed in paraffin oil to produce a dye suspension. In an embodiment, about 0.1 gram to 1 gram of finely divided crystal violet dye can be dispersed in 100 mL of paraffin oil. In a preferred embodiment, about 0.25 gram to 0.75 gram of finely divided crystal violet dye can be dispersed in 100 mL of paraffin oil. In a most preferred embodiment, about 0.5 gram of finely divided crystal violet dye can be dispersed in 100 mL of paraffin oil. In accordance with embodiments of the present disclosure, a water soluble dye of appropriate particle size can be selected that can allow for its uniform dispersion in paraffin oil to produce a dye suspension. Preferably, the dye(s) should be dried using any methods known to a person skilled in the art to remove any residual moisture before its dispersion in paraffin oil. In an embodiment, a mass (powder, granules, lump or any other solid form) of dye(s) can be heated at 110°C to remove any residual moisture followed by its size reduction to obtain a smooth powder. It would be appreciated that any method known to a person skilled in the art can be followed for size reduction of the selected dye(s). Alternatively, commercially available dried and finely divided dye powder(s) can directly be utilized to produce a dye suspension.
[0037] An embodiment of the present disclosure relates to a method of preparing a dye suspension for use in qualitative and quantitative estimation of an amount of alcohol (preferably ethanol) in a petroleum sample. In an embodiment, an appropriate amount of water soluble dye(s) is firstly heated at an appropriate temperature for appropriate time duration to remove any residual moisture followed by its size reduction, using any method known to a person skilled in the art, to produce a smooth powder. An appropriate quantity of the dye powder thus obtained can then be dispersed in an appropriate amount of paraffin oil to prepare a dye suspension. In accordance with an embodiment of the present disclosure, an appropriate amount of commercially available crystal violet dye can be heated at 110°C for 15-20 minutes for removing any residual moisture. Then, the heated dye can be crushed using mortar and pestle to obtain a smooth powder. A weighed quantity (preferably about 0.5 gram) of smooth powder of crystal violet dye can then be mixed with a measured volume (preferably 100 mL) of paraffin oil to produce a dispersion. The dispersion can be shaken vigorously for an appropriate time (preferably for 10-15 minutes) either continuously or intermittently to produce a uniform suspension of crystal violet dye in paraffin oil.
[0038] In an aspect, the present disclosure relates to a method for quantitative estimation of an amount of alcohol (preferably ethanol) in a petroleum (or EBMS) sample, said method including the steps of: (a) contacting an appropriate amount of the petroleum (or EBMS) sample with an appropriate amount of a dye suspension, wherein the dye suspension includes about 0.5% crystal violet dye dispersed in paraffin oil; (b) obtaining a color based on a reaction between the petroleum (or EBMS) sample and the dye suspension after a pre-defined time interval, wherein the obtained color is proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) estimating the amount of the alcohol (preferably ethanol) based on the obtained color. In an aspect, the amount of the alcohol can be estimated based on one or a combination of visual chart, a computing means and a spectroscopy. In another aspect, the computing means can involve any or a combination of a mobile phone, a smartphone, an optical reader device, and an image capturing device, wherein camera of the computing means is configured to take an image of the color and enable processing of the image for estimating the amount of the alcohol.
[0039] In still another aspect, the present disclosure relates to an ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit including (a) a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; (b) a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and (c) a computing device configured to take an image of the color of the petroleum sample and analyze the color to estimate the amount of the ethanol in the petroleum sample. A smartphone, tablet, camera, computer, PDA or any other computing device known to a person skilled in the art can be used as a computing device. Further, an application/program/software can be developed and installed on any of the computing device(s) known to a person skilled in the art to confer image processing and alcohol estimation capabilities. Alternatively, a separate image capturing device can be used which can be operatively coupled to a computing device to input image(s) captured by an image capturing device to a computing device for further processing. In case a separate image capturing device and a separate computing device are used, the image(s) captured by the image capturing device can then be fed to the computing device for further processing of the images. The computing device converts RGB values (color) to HSV values (HSV color space) as known to a person skilled in the art, wherein the HSV space has three variables for expressing a color, which are hue (H), saturation (S), and brightness (V) instead of R, G, and B. Even though H, S, and V are needed to fully express a color, only H is needed to discriminate the colors of specific frequencies because H represents the primary colors or combinations of them and distinguishes one color family from another. The H value can be calculated through known algorithms with appropriate equations (Anal. Chem. 2000, 72(7), 282 A-288 A). The computing device correlates and output the amount of alcohol present in the sample (EBMS or petroleum samples) based on the calculated H values using a calibration graph(s) or correlation table(s) or correlation chart(s) stored in the computing device.
[0040] It is to be appreciated that although most of the embodiments of the present disclosure have been explained with reference to ethanol, being a constituent present in EBMS, a person ordinarily skilled in the art would understand that the proposed techniques, methods, and kits can be used for qualitative and quantitative estimation of any other alcohols including but not limited to methanol, propanol, butanol, isopropanol and the like in any hydrocarbon based liquids or fuels and hence, use of ethanol and EBMS are only exemplary illustrations for explaining various aspects of the present invention.
[0041] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES
Example 1: Preparation of a dye suspension
[0042] In a study, a dispersion containing crystal violet dye in paraffin oil was prepared. Commercially available crystal violet dye (5 gram) was firstly heated at 110°C for 20 minutes for removing any residual moisture. Then, the dye was crushed using mortar and pestle to make a smooth powder. About 0.5 gram of dye powder prepared above was dispersed in 100 mL of paraffin oil. The dispersion was shaken vigorously for 15 minutes. The dispersion was then kept on a plain surface for 10 minutes. The dispersion was then again shaken vigorously for 15 minutes to prepare the dye suspension.
Example 2: Experiment depicting linearity of detection of ethanol over an ethanol concentration ranging from 6% to 10% in EBMS sample.
[0043] In this study, a series of standards with known concentration of ethanol in EBMS samples (6%, 7%, 8%, 9% and 10%) were prepared and kept in separate reaction chambers. A drop (about 50 microliter) of dye suspension prepared in example 1 was added via a dropper to each of the standards and reaction mixtures were shaken well for about 10-30 seconds and kept for 15-20 seconds to allow for development of violet color. The intensity of the developed violet color varies significantly from each other (between standards containing 6%, 7%, 8%, 9% and 10% of ethanol) and can allow for quick differentiation between different concentrations using naked eye as can be seen from figure 1. Further, each reaction mixture was subjected to UV-Visible spectrophotometer to measure absorbance values (at wavelength - 590 nm). The measured absorbance values are as shown below in table 1. The measured absorbance values were then plotted as illustrated in figure 2, where X-axis values represents sample ID (1 through 5) with known amount of ethanol concentration. It can be inferred from the plot that the method exhibits linearity of detection over an ethanol concentration ranging from 6% to 10% in contrast to prior art reported methods which fails to exhibit utility in quantitative estimation of ethanol when its concentration is more than 5% in EBMS or petroleum samples. The plot as illustrated in figure 2 was then utilized as calibration curve for quantitative estimation of ethanol in test samples (EBMS or petroleum samples) in subsequent experiments.
Table 1: Absorbance value corresponding to each ethanol concentration
Sample Id Ethanol concentration Absorbance
1 6% 0.274
2 7% 0.444
3 8% 0.521
4 9% 0.654
5 10% 0.778

Example 3: Qualitative estimation for testing presence of ethanol in a petroleum sample
[0044] In a study, 10 ml of EBMS sample to be tested for the presence of ethanol was taken in a reaction chamber. 1 drop (about 50 microliter) of dye suspension prepared in example 1 was added to the reaction chamber containing petroleum sample. The reaction mixture containing petroleum sample and dye suspension was shaken well for about 10-30 seconds and kept for 15-20 seconds. As illustrated in figure 1, the development of violet color suggests presence of ethanol in the petroleum sample.
Example 4: Quantitative estimation of an amount of ethanol present in an EBMS sample
[0045] In the study, 10 ml of EBMS sample to be tested for the presence of ethanol was taken in a reaction chamber. 1 drop (about 50 microliter) of dye suspension prepared in example 1 was added to the reaction chamber containing EBMS sample. The reaction mixture containing EBMS sample and dye suspension was shaken well for about 10-30 seconds and kept for 15-20 seconds. The intensity of developed violet color was then compared to the color charts to detect amount of ethanol present in the EBMS sample.

ADVANTAGES OF THE PRESENT INVENTION
[0046] The present disclosure provides for methods and kits that allow for detection of ethanol content in petroleum or Ethanol Blended Motor Sprit (EBMS).
[0047] The present disclosure provides for a kit that allows for quantitative estimation of ethanol content in petroleum or Ethanol Blended Motor Sprit (EBMS) over a wide range of concentrations.
[0048] The present disclosure provides for a kit that allows for qualitative determination of ethanol in petroleum.
[0049] The present disclosure provides for a simple and quick test method for testing ethanol content in Ethanol Blended Motor Spirit at TLF gantry during dispatch of EBMS tank lorries at supply locations.
[0050] The present disclosure provides for a simple and quick test method for checking the ethanol content at installation site itself without using any sophisticated instrument or calibrated glassware.
[0051] The present disclosure provides for a kit that allows for better control of Ethanol doping system in MS in addition to current test methods.
[0052] The present disclosure provides for a kit that can allow for quantitative estimation of ethanol content ranging from 6% to 10% in Ethanol Blended Motor Sprit (EBMS).
[0053] The present disclosure provides for a color chart for quantitative estimation of ethanol content ranging in Ethanol Blended Motor Sprit (EBMS).

Claims:1. A method for quantitative estimation of an amount of ethanol in a petroleum sample, said method comprising the steps of:
contacting an appropriate amount of the petroleum sample with an appropriate amount of a dye suspension, wherein the dye suspension comprises about 0.5% crystal violet dye dispersed in paraffin oil;
obtaining a color, based on a reaction between the petroleum sample and the dye suspension after a pre-defined time interval, wherein the obtained color is proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and
estimating the amount of the ethanol based on the obtained color.

2. The method of claim 1, wherein at least about 10 mL of the petroleum sample is contacted with the dye suspension.

3. The method of claims 1, wherein at least about 50 microliters of the dye suspension is contacted with the petroleum sample.

4. The method of claim 1, wherein the amount of the ethanol is estimated based on one or a combination of visual chart, a computing means and a spectroscopy means.

5. The method of claim 4, wherein the computing means is configured to take an image of the obtained color and analyze the color to estimate the amount of the ethanol.

6. An ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit comprising
a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; and
a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and
a chart configured to enable comparison of the color of the petroleum sample with colors present in the chart to estimate the amount of the ethanol in the petroleum sample.

7. An ethanol detecting kit for quantitative estimation of an amount of ethanol in a petroleum sample, said kit comprising
a suspension comprising about 0.5% crystal violet dye dispersed in paraffin oil; and
a reaction chamber for holding an appropriate amount of the petroleum sample, wherein the petroleum sample upon contact with the suspension produces a color proportional to the amount of ethanol in the petroleum sample over an ethanol concentration ranging from 6% to 10%; and
a computing device configured to take an image of the color of the petroleum sample and analyze the color to estimate the amount of the ethanol in the petroleum sample.

8. The ethanol detecting kit of claim 6 or claim 7, wherein at least about 10 mL of the petroleum sample is contacted with the suspension.

9. The ethanol detecting kit of claim 6 or claim 7, wherein at least about 50 microliters of the suspension is contacted with the petroleum sample.