The present application relates to a procedure for determining corrosive iron, that is to say, ferric and ferrous ions in the used lubricating compositions, particularly in compositions used lubricating engine, in particular marine engine. The present application also relates to a kit for implementing this method.

The engines, including marine engines, undergo significant stresses during operation, including coercion of friction, and are subject to corrosion, including, for example in the case of marine engines, due to the presence of sulfur in the fuel which is converted to sulfuric acid during combustion. Lubricating compositions are generally used to reduce these constraints.

Through these processes, including friction and corrosion, particles or metal contaminants, including particulate iron, ferric ions, and ferrous ions, are released into the lubricating compositions. These metal contaminants, if present in an excessively large amount, may cause a change in properties of said lubricating compositions and thus their performance and be harmful to the engine (including reduction in the duration of life). There is therefore an interest in the determination of such metal contaminants in the lubricating compositions to determine the state of degradation of these compositions and thus the optimal timing of change thereof. In addition, the dosage of these metal contaminants also determine the importance of these processes, including friction and corrosion, and to make decisions for the maintenance and preservation of lubricated equipment, including the adjustment of the amount lubricating composition to be introduced.

Laboratories propose to carry out analyzes of samples of used lubricating compositions to determine amounts of metal contaminants. However, this requires, sending samples, a significant implementation time and therefore delayed action.

There is therefore an interest in providing a method for determination of iron, particularly ferric and ferrous ions from corrosion in used lubricant compositions and a kit for the implementation of this method, which can be implemented on instead, that are fast and reliable.

Colorimetric tests, including the determination of iron concentration range is visually compared with the reference samples. However, these methods are unreliable.

It is also known from WO2006127098 a method for analyzing the amount of iron contained in a used lubricating composition. However, this method allows the determination of total iron content in said lubricating composition, that is to say as the particulate iron from the friction phenomena, ferric and ferrous ions from corrosion. It is not possible by this method to determine the real impact of each of these two phenomena separately and for operators, to act accordingly.

One objective of the present invention is therefore to provide an assay method "on site" iron ions, ferric and ferrous ions, in particular from the corrosion of metal parts of the engine, in the used lubricating compositions, especially recovered low engine cylinders.

Another object of the present invention is to provide such a method for which the sample preparation for the assay is quick and simple.

Yet another object of the present invention to provide such a method that is rapid implementation, preferably requiring less than 10 minutes, which is reliable and reproducible.

Another object of the present invention is to provide a method for a measurement accuracy of plus or minus 10 ppm and for a measure in the range 0-900 ppm.

Yet another object of the present invention is to provide a kit for implementing said method, which is simple and fast.

Other goals become apparent on reading the description of the invention that follows.

All these objectives are met by the present invention which provides a method for determining "on site" iron ions, such as ferric and ferrous ions in the lubricant compositions, including used lubricating compositions, eg recovered down engine cylinders , photochemical measurement after reaction of iron ions with a complexing agent for iron ions, the complexation reaction causing a color change which can be quantified spectrophotometrically.

The assay method of the iron ions including ferric and ferrous ions in the lubricating compositions according to the present invention comprises the following steps: a) Taking a sample of the lubricating composition to be analyzed, for example the bottom of the cylinder motor in a first container;

b) Removing the first vessel containing the sample to be analyzed on a magnet; c) Adding a second container:

o a first reagent composition (CR1) aqueous composition comprising at least one extractant ferric and ferrous ions of the oily phase to the aqueous phase;

o a second reactive composition (CR2) aqueous composition comprising at least one ferric ion reducing agent (Fe 3+ ) to ferrous ions (Fe 2+ ); o a third reagent composition (CR3) comprising at least an emulsion destabilizing agent; and

o a fourth reagent composition (CR4) in aqueous solution comprising a complexing agent for ferrous ions, characterized in that said agent changes color upon complexation with ferrous ions; and mixing;

d) Optionally, Photochemical measuring the absorbance of the mixture obtained in step c);

e) Taking a few drops of the lubricating composition contained in the first container held in place on the magnet, and adding these few drops into the second container comprising mixing the first, second, third and fourth reactive compositions obtained in step c);

f) Stirring mixture obtained in step e);

g) photochemical Measure the absorbance of the mixture obtained in step f);

h) Determination of the quantity of ferrous ions in the lubricating composition from the measurements obtained in steps d) and g).

It should be understood of step a) is that the collected sample which is introduced into a first container.

The lubricant composition to be analyzed is preferably a lubricating composition harvester engine, preferably a marine engine lubricating composition, eg ship engine or hydroelectric power plant, etc. Preferably the lubricant composition is a lubricant composition for marine 2-stroke engine. Of

Preferably, the lubricating composition to be analyzed is a used lubricant composition recovered at the bottom of the engine cylinders.

The lubricating composition referred to in the present invention comprises at least one lubricating base oil. In general, lubricating base oils may be mineral oils of origin, synthetic or vegetable as well as mixtures thereof. Mineral or synthetic oils generally used belong to one of the groups I to V according to the classes defined in the API classification (or their equivalents according to ATIEL classification) as summarized below. API classification is defined in American Petroleum Institute 1509 "Engine Oil Licensing and Certification System" 17th Annual edition, September 2012. ATIEL classification is defined in "The ATIEL Code of Practice", Number 18, November 2012.

Group I mineral oils can be obtained by distillation of crude naphthenic or paraffinic selected and purification distillates obtained by methods such as solvent extraction, solvent dewaxing or catalytic, hydrotreating or hydrogenation. Oils of Groups II and III are obtained by more extensive purification methods, e.g., a combination of treatment selected from hydrotreating, hydrocracking, hydrogenation and catalytic dewaxing. Examples of synthetic base oils of Group IV and V include polyisobutenes, alkyl benzenes and poly-alpha olefins such as polybutenes or esters.

In lubricating compositions, lubricating base oils may be used alone or mixed. For example, mineral oil can be combined with a synthetic oil.

Oils cylinder two-stroke marine engines are generally characterized by a viscosimetric grade SAE 40 to SAE 60, SAE-50 generally equivalent to a kinematic viscosity at 100 ° C of between 16.3 and 21, 9 mm 2 / s measured according to ASTM D445. SAE-40 grade oils have a kinematic viscosity at 100 ° C

between 12.5 and 16.3 cSt measured according to ASTM D445. Oils of SAE 50 grade has a kinematic viscosity at 100 ° C of between 16.3 and 21, 9 cSt measured according to ASTM D445. SAE-60 grade oils have a kinematic viscosity at 100 ° C of between 21 9 and 26.1 cSt measured according to ASTM D445 standard. The lubricating compositions of the invention preferably have a kinematic viscosity measured according to ASTM D445 at 100 ° C of from 12.5 to 26.1 cSt, preferably 16.3 to 21, 9 cSt. To obtain such viscosity, the lubricating compositions of the invention may further comprise one or more additives. Typically, a conventional formulation of lubricating composition for marine engines, preferably two times, of SAE-40 grade SAE 60, SAE preferably-50 (according to SAE J300 classification) and comprises at least 40% by weight of oil lubricant based on mineral, synthetic or mixtures thereof, suitable for use in a marine engine. For example, a lubricating base oil group I, according to API classification, can be used in formulating a cylinder lubricant. The lubricating base oils of Group I have a Viscosity Index (VI) of from 80 to 120; the sulfur content is greater than 0.03% and the content of saturated hydrocarbon compounds is less than 90%.

The lubricating composition according to the invention may further comprise an additive selected from overbased detergents or neutral detergents. Detergents are typically anionic compounds comprising a lipophilic long hydrocarbon chain and a hydrophilic head, associated cation is typically a metal cation of an alkali metal or alkaline earth metal. Detergents are preferably selected from alkali metal salts or alkaline earth metal (particularly preferably calcium, magnesium, sodium or barium) salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and the salts. These metal salts may contain the metal in an approximately stoichiometric amount relative to (x) group (s) anion (s) of the detergent. In this case, we talk about non-overbased detergents or "neutral", although they also bring a certain basicity. These "neutral" detergents typically have a BN (Number Base or basicity index) measured according to ASTM D2896, less than 150 mg KOH / g, or less than 100 mg KOH / g, or less than 80 mg KOH / g detergent. This type of so-called neutral detergents can contribute in part to BN lubricant compositions. Are employed for example neutral detergents such carboxylates, sulfonates, salicylates, phenates, naphthenates of the alkali and alkaline earth metal, e.g. calcium, sodium,

magnesium, barium. When the metal is in excess (an amount greater than the stoichiometric amount relative to (x) groups (s) anion (s) of the detergent), we are dealing with so-called overbased detergents. Their BN is high, higher than 150 mg KOH / g of detergent, typically from 200 to 700 mg KOH / g of detergent, preferably from 250 to 450 mg KOH / g of detergent. The excess metal providing the character overbased detergent is in the form of insoluble metal salts in oil, for example carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate. In one overbased detergent, the metals of these insoluble salts can be the same as those soluble detergents in the oil or can be different. They are preferably selected from calcium, magnesium, sodium or barium. The overbased detergents are thus presented in the form of micelles composed of insoluble metallic salts maintained in suspension in the lubricating composition by detergents in the form of soluble metal salts in the oil. These micelles may contain one or more kinds of insoluble metal salts, stabilized by one or more types detergents. The overbased detergents comprising a single type of detergent-soluble metal salt will generally named according to the nature of the hydrophobic chain of the latter detergent. Thus, they will be called type phenate, salicylate, sulphonate, naphthenate claimed that this detergent is respectively a phenate, salicylate, sulphonate or naphthenate. The overbased detergents are called mixed type if the micelles comprise several types of detergents, different from each other by the nature of their hydrophobic chain. The overbased detergent and the neutral detergent may be selected from carboxylates, sulfonates, salicylates, naphthenates, phenates, and mixed detergents combining at least two of these types of detergents. The overbased detergent and the detergent include neutral compounds based on metals selected from calcium, magnesium, sodium or barium, preferably calcium or magnesium. The overbased detergent may be overbased metal insoluble salts selected from the group of carbonates of alkali and alkaline earth metals, preferably calcium carbonate. The lubricant composition can comprise at least one overbased detergent and at least one neutral detergent as defined above.

As mentioned above, in one embodiment of the invention, the lubricating composition has a BN determined according to ASTM D-2896 standard of at most 50, preferably at most 40, preferably at most 30 milligrams of potassium hydroxide per gram of the lubricating composition, in particular ranging from 10 to 30, preferably 15 to 30,

preferably 15 to 25 milligrams of potassium hydroxide per gram of the lubricating composition. In this embodiment of the invention, the lubricant composition may not comprise detergents based on alkali or alkaline earth metal overbased metal carbonate salts.

In another embodiment of the invention, the lubricating composition has a BN determined according to ASTM D-2896 standard of at least 50, preferably at least 60, more preferably at most 70, preferably 70 to 100.

The lubricating composition may also comprise at least one further additional additive selected from dispersants, anti-wear additives or any other functional additive. Dispersants are well known additives used in the formulation of lubricating composition, in particular for application in the marine field. Their primary role is to keep these particles suspended initially or appearing in the lubricant during its use in the engine. They prevent their agglomeration by adjusting the steric hindrance. They may also have a synergistic effect on neutralization. Dispersants used as lubricant additives typically contain a polar group, associated with a relatively long hydrocarbon chain, generally containing 50 to 400 carbon atoms. The polar group typically contains at least one element nitrogen, oxygen or phosphorus. Compounds derived from succinic acid are particularly used as dispersants lubricating additives. is used in particular succinimides obtained by condensation of succinic anhydrides and amines, succinic esters obtained by condensation of succinic anhydrides and alcohols or polyols. These compounds can then be treated with various compounds including sulfur, oxygen, formaldehyde, carboxylic acids and boron-containing compounds or zinc to produce e.g. succinimides borated succinimides or zinc-blocked. Mannich bases, obtained by polycondensation of phenols substituted with alkyl groups, formaldehyde and primary or secondary amines, are also compounds used as dispersants in lubricants. In one embodiment of the invention, the dispersant content may be greater than or equal to 0.1%, preferably 0.5 to 2%, preferably from 1 to 1 5% by weight relative to the total weight of the lubricant composition. Antiwear additives protect the formation by rubbing surfaces of a protective film adsorbed on these surfaces. The most commonly used is the di thiophosphate zinc or DTPZn. Also found in this category various phosphorus compounds, sulfur, nitrogen, chlorine and boron. There are a wide variety of anti-wear additives, but the most used category is additive

sulfur phospho alkylthiophosphates such as metal, in particular zinc alkylthiophosphates, more specifically zinc dialkyldithiophosphates or DTPZn. Preferred compounds are of the formula Zn ((SP (S) (OR) (OR 2 )) 2, or Ri and R 2 are alkyl groups, preferably having 1 to 18 carbon atoms. DTPZn is typically present at contents of the order of 0.1 to 2% by weight relative to the total weight of the lubricating composition. the amine phosphates, polysulfides, such as sulfurized olefins, are also anti-wear additives used commonly. We find also usually in lubricating compositions for marine engine anti-wear additives and extreme pressure nitrogen and sulfur type, such as for example, metal dithiocarbamates, particularly molybdenum dithiocarbamate. glycerol esters are also anti wear additives. One can include for example mono-, di- and trioleates, monopalmitates and monomyristates. in one embodiment, the amount of antiwear additives is from 0.01 to 6%, preferably from 0.1 to 4% by weight p ar relative to the total weight of the lubricating composition.

Other functional additives may be chosen from thickeners, defoamers to counter the effect of the detergents, which may be for example polar polymers such as polydimethylsiloxanes, polyacrylates, antioxidant additives and / or anti-rust, by example organo-metal detergents or thiadiazoles. These are known to the skilled person. These additives are generally present in a weight content of 0.1 to 5% based on the total weight of the lubricating composition.

Advantageously, in the method of the present invention, step b) allows to obtain a sediment at the bottom of the first container of the particulate iron possibly contained in the lubricant composition to be analyzed and a result of the friction of the engine parts. Particularly advantageously, the sampling step e) is carried out on the supernatant which allows only the dosage of ferric and ferrous ions and thus determine the importance of the only corrosion.

In the context of the present invention, the term "iron ion" refer to ferric ions and ferrous ions.

The lubricating compositions are generally composed of lubricating oils and additives and are viscous and generally colored. It is thus not easy to make the colorimetric determination of iron ions directly into the lubricating composition. The present invention thus proposes to increase the iron ions in aqueous phase. Of

way advantageous, the first reagent composition (CR1) of the method according to the present invention comprises an aqueous solution at least one extraction agent of ferric and ferrous ions in the oil phase of the lubricant composition to the aqueous phase. The extractant allows to pass all the ferric and ferrous ions in the oil phase of the lubricant composition to the aqueous phase, in particular water from the composition CR1, in which will be carried complexation with the complexing agent and dosage. This extractant is particularly chosen from solubilizing agents ferric and ferrous ions and being immiscible with the lubricating composition. Among these extracting agents there may be mentioned acids, preferably acids having a pKa of between -5 and +5, particularly sulfuric acid, nitric acid, Hydrochloric acid, phosphoric acid, alone or in admixture. Preferably, the acid has a pKa -3.

CR1 composition may further comprise other components, including additives assisting in the preparation of the composition and advantageously to increase the speed of analysis. Among these additives include co-solvents assisting in the solubilization of compounds of the reactive composition CR1, for example, alcohol type, for example ethanol, 1, 4-butanediol, preferably ethanol.

In the second reactive composition (CR2) of the present invention, the ferric ion reducing agent to ferrous ions is preferably selected from the following reducing agents: hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite, alone or in admixture . The reducing agent provides a solution containing only iron ions in only one form (entity) and therefore have a more reliable and accurate dosing.

CR2 composition may further comprise buffer solutions to maintain the pH substantially constant, preferably between 2 and 7, more preferably between 2 and 3. Among the buffer solutions include basic solutions or acid or a mixture thereof , for example solutions, in particular concentrated, preferably a weak acid and its conjugate base, salts, for example sodium salts such as sodium acetate, or a mixture thereof. Preferably, the buffer solution is preferably selected from sodium acetate and acid solutions, in particular acetic acid, glycine and solutions of hydrochloric acid, ethanoic acid and sodium ethanoate solutions or solutions citric acid and sodium phosphate.

Preferably, the first reactive composition according to the present invention preferably comprises from 1 to 10% by weight of extractant. Preferably, the second

Reactive composition according to the present invention comprises from 1 to 15% by weight of reducing agent.

Particularly advantageously, the first and second reagent compositions can be mixed in one aqueous reagent composition (CR1 ') then comprising at least one extraction agent of ferric and ferrous ions of the oily phase to the aqueous phase, water in particular from the composition CR1 ', and at least one ferric ion reducing agent (Fe 3+ ) to ferrous ions (Fe 2+ ). Preferably, the reactive composition CR1 'comprises from 1 to 15% by weight of reducing agent and 1 to 10% by weight of extractant. This reactive composition (CR1 ') may further comprise other components, including additives assisting in the preparation of the composition and advantageously to increase the speed of analysis. Among these additives include co-solvents assisting in the solubilization of compounds of the reactive composition CR1 ', e.g., alcohol type, for example ethanol or 1, 4-butanediol, preferably ethanol and / or buffer solutions to maintain substantially stable pH, preferably between 2 and 7, more preferably between 2 and 3, among buffer solutions include basic solutions or acid or mixture thereof, for example solutions, in particular a concentrated acid low and its conjugate base, salts, for example sodium salts such as sodium acetate, or a mixture thereof. Preferably, the buffer solution is preferably selected from sodium acetate and acid solutions, in particular acetic acid, glycine and solutions of hydrochloric acid, ethanoic acid and sodium ethanoate solutions or solutions citric acid and sodium phosphate.

Preferably, the reactive composition (CR1 ') of the invention comprises ethanol or 1, 4-butanediol (preferably ethanol), sulfuric acid, hydroxylamine hydrochloride and sodium acetate solution in water.

The third reagent composition (CR3) of the method according to the invention comprises at least one destabilizing agent emulsion. The first, second and fourth reactive compositions and the reactive composition CR1 'are aqueous compositions. Mixed with the lubricating composition such aqueous compositions may form an emulsion. The third reagent composition allows advantageously to break the emulsion thus obtained and consequently allowing greater phase shift. Thus, the third reagent composition of the method according to the invention advantageously allows to facilitate and expedite the passage of ferric and ferrous ions in the oil phase of the lubricant composition to the aqueous phase caused by the first, second and fourth reactive compositions or the reactive composition CR1. Advantageously, the destabilizing agent is non-miscible compound The water destabilizing agent of the invention is preferably selected from primary or secondary alcohols (C4 to C10), individually or in combination. Preferably the destabilizing agent of the invention is selected from isoamyl alcohol, octan-1-ol, octan-2-ol, 1 -heptanol, 2-ethyl-hexanol, 2-ethyl- butanol, alone or in admixture, preferably the isoamyl alcohol, octan-1-ol, octan-2-ol, either alone or in admixture, preferably isoamyl alcohol, 1 -heptanol, 2-ethyl hexanol, 2-ethyl-butanol, alone or in admixture, preferably the isoamyl alcohol.

Preferably, the third reagent composition according to the method of the present invention comprises 20 to 100% by weight of an emulsion destabilizing agent.

The third reagent composition of the present invention may further comprise additives, for example when the destabilizing agent has a too high flash point, the third reagent composition according to the invention may include co-solvents to reduce the flash point of the composition. Among these co-solvents, there may for example be made of light distillates Any oil comprising less than 2% aromatics, such as for example hydrocarbons, preferably C9-C16, for example n-alkane C9-C16 , isoalkane C9 to C16 cyclic hydrocarbons C9-C16.

The fourth reagent composition (CR4) of the method according to the present invention comprises a complexing agent for ferrous ions. This complexing agent is chosen from complexing agents including ferrous ions and complexation is to cause a color change that can be detected by measuring the absorbance of the solution obtained by a spectrophotometer. The measured absorbance may then be connected to the ferrous ion content, and therefore, iron ions, of the analyzed sample, expressed in ppm. Preferably, the complexing agent is selected from ferrozine, the Ferene, the phenanthroline and its derivatives, e.g. bathophenantroline, bipyridine, thioglycolic acid, R-nitroso salt (sodium salt of 3-hydroxy-4 -nitroso-2,7-disulfonate), potassium ferricyanurate (hexacyanoferrate (III) potassium), 2,4,6-tripirydyl-s-triazine (TPTZ). Preferably, the complexing agent is selected from the TPTZ, potassium ferricyanurate or R-nitroso salt. Preferably, the complexing agent is R-nitroso salt.

Preferably, the fourth reactive composition comprises 0.5 to 5% by weight of the complexing agent. Preferably, the reactive composition comprises 1% by weight of the complexing agent.

The assay method of the present invention is a colorimetric assay method employing a measurement of the absorbance of the solution obtained by complexing of the complexing agent with ferrous ions by UV-Vis spectrometry, using of a spectrophotometer, preferably an electronic spectrophotometer. Thus, the absorbance measurements of steps d) and g) are performed using a spectrophotometer, preferably an electronic spectrophotometer.

The absorbance measurement by the spectrophotometer is based on Beer's law. Incident light intensity I0 passes through the aqueous solution to be analyzed, a part of this light is absorbed by the solution, the resulting current I is passed through the solution. The absorbance (A) of the solution is then determined by the following relationship:

A = log (y)

It is possible to connect the absorbance to the concentration of ferrous ions in the solution with the aid of a calibration curve showing a straight line joining the absorbance at the ferrous ion concentration in solution of known concentration. E spectrophotometer is previously calibrated with this calibration curve and the absorbance measured to determine the amount of ferrous ions in ppm in the test sample.

In a first embodiment, a blank measurement of the absorbance can be performed on a container comprising the mixture of the four reagent compositions defined above. This blank measurement is then considered as a reference in the spectrophotometer and each of the measures taken on the compositions obtained in step (f) will be compared to the blank value to give the actual value of the absorbance as explained below.

In a second embodiment of the invention, and in order to obtain a reliable value and just the absorbance and thus indirectly of the concentration of ferrous ions, white is made to account for the influence of the second container and first, second, third and fourth reactive compositions on the measurement of absorbance. For this, a step d) of measuring the absorbance is carried out on the mixture obtained in step c) in the second container. The difference between the absorbance obtained in step g) and that obtained in step c) obtaining the actual absorbance of the solution obtained in step f), and can thus determine the corresponding amount of iron ions. Particularly advantageously, the electronic spectrophotometer is programmed to make the difference between the absorbances measured in steps d) and g) and then the corresponding iron ion concentration in the solution to be analyzed in ppm.

During step g), the second container is placed in the spectrophotometer so that the incident light emission only through the aqueous phase. As will be seen below, the present spectrophotometer preferably a receiving region of the adapted sample, preferably with a suitable angle so that the incident light emission only through the aqueous phase.

Particularly advantageously, all of these steps d), g) and h) are implemented directly by the electronic spectrophotometer which is programmed for this.

Preferably, the agitation of step f) is performed by turning the container at least 5 times, for example 10 times. After stirring, the vessel is directly introduced into the spectrophotometer. Advantageously, the agitation is gentle agitation.

Preferably, the measurement in step g) is performed within 10 minutes after introduction of the container into the spectrophotometer, preferably, the measurement is performed 5 minutes after the introduction of the container in the spectrophotometer, this time representing the time required for the complexing reaction of the complexing agent with the ferrous ions.

Preferably, the first, second, third and fourth reactive compositions are each introduced at a rate of 5 to 10 ml in the second container. Preferably, the first, second, third and fourth reactive compositions are introduced each in an amount of 5 ml into the second container.

Preferably, the third and fourth reactive compositions and the composition CR1 'are each introduced at a rate of 5 to 10 ml in the second container. Preferably, the third and fourth reactive compositions and the composition CR1 'are each introduced at a rate of 5 ml into the second container.

In another embodiment, the first, second and third reagent compositions may be contained in a single reagent composition (CR) prepared previously.

Preferably 1 to 10 drops, preferably 3 drops or about 100 or 0,075g μΙ, of lubricating composition to be analyzed are introduced in step e) in the second container.

The method of the present invention can be repeated as many times as we have samples for analysis. In this case, there will be as many first and second container as lubricating compositions to analyze. Particularly advantageously, if step d) is implemented, it will be necessary to do the steps d) and g) for each sample to be analyzed one after the other and not to steps d) to each sample to be analyzed then steps g) for each sample to be analyzed, in fact, the spectrophotometer is preferably configured to compare each of the mixtures obtained in steps c) and f).

Particularly advantageously, the method according to the present invention is reliable, it is for the determination of 0 to 900 ppm of iron in the samples, preferably 50 to 700 ppm.

Advantageously, the method according to the invention is quick and easy and requires no special knowledge of the operator. Advantageously, the method according to the invention allows to obtain a result on the amount of iron ions in a lubricant composition Used in less than 10 minutes and with an accuracy of about plus or minus 10 ppm.

Particularly advantageously, the method of the present invention does not require heating the samples to be analyzed, nor the digestion of particulate iron.

The present invention also relates to a kit for implementing the method described above. This kit includes:

- a first reagent composition (CR1) aqueous composition comprising at least one extractant ferric and ferrous ions in the oil phase of the lubricant composition to the aqueous phase;

- a second reactive composition (CR2) aqueous composition comprising at least one ferric ion reducing agent (Fe3 +) to ferrous ions (Fe2 +);

- a third reagent composition (CR3) comprising at least an emulsion destabilizing agent;

- a fourth reagent composition (CR4) in aqueous solution comprising a complexing agent for ferrous ions characterized in that said agent changes color upon complexation with ferrous ions;

- a spectrophotometer, preferably an electronic spectrophotometer;

- optionally at least one first container;

- at least one second vessel;

- optionally at least one device (D1) for sampling the lubricating composition to be analyzed;

- a device (D2) for each of the samples of the first, second, third and fourth reactive compositions;

- a magnetic support;

- at least one device (D3) for the removal of a few drops of the lubricating composition to be analyzed in step e).

CR1, CR2, CR3 and CR4 are as defined above.

The spectrophotometer, preferably electronic spectrophotometer comprises a light emitting device, for example a light emitting diode; a photoelectric sensor; a receiving area of ​​the second container; a data processor for conversion of the absorbance in concentration of ferrous ions in ppm. Preferably, the second container receiving area is positioned between 10 and 50 mm, preferably between 15 and 30 mm, eg 24 mm from the bottom of the second container and oriented with an angle of 35 to 75 °, preferably 50 at 70 °, eg 60 ° to allow a measurement of the absorbance only in the aqueous phase of the mixture obtained in step f) is located in the colored complex formed between the complexing agent and ferrous ions.

Preferably, the first container is made of plastic or glass, preferably plastic. It optionally comprises a plug. Preferably, the kit comprises at least as many first container that samples of lubricating composition to be analyzed. Indeed, the engines include between 4 and 14 cylinders, so there is at least between 4 and 14 samples of lubricating composition to be analyzed at the same time (a sample of lubricant composition per cylinder). Preferably, there is at least a first container, preferably there are between one and 50 first containers, for example between 5 and 40 first containers.

Preferably the second container is a container in the form of tube with a stopper, preferably a test tube with a stopper. It can be plastic or glass, preferably glass. Preferably, the kit comprises as many second vessel that samples of lubricant compositions to analyze. The kit therefore comprises between 1 100 and second containers, for example between 10 and 80 second containers, for example 50 second containers.

The first and second containers may be of glass or plastic, which may be disposable or cleanable. Preferably, in the context of the invention the first and second containers are disposable.

Preferably, the device (D1) for sampling the lubricating composition to be analyzed is a syringe, preferably in disposable plastics material. The kit may comprise as many device (D1) as lubricating compositions to be analyzed, preferably the kit comprises 1 to 100 devices (D1), preferably from 10 to 80, for example 50.

Preferably, each of the devices (D2) are syringes, preferably disposable plastic. The kit may comprise from 3 to 18 devices (D2), preferably 3 to to 6 devices (D2).

Preferably, the magnetic carrier is a carrier for receiving the first container comprising the lubricating composition to be analyzed and including a magnet at its bottom. Preferably, the magnetic carrier is a rack comprising from 1 to 50, preferably 7 slots for receiving the first container. Preferably, the magnetic support is in two parts, a lower part comprising the slots for receipt of first containers, each of the locations comprising a magnet, and an upper part comprising slots for the second containers, the locations of the lower part and the locations of the upper portion preferably being positioned one opposite the other in order to quickly and easily identify the lubricating compositions to be analyzed.

Preferably, the device (D3) for the removal of a few drops of the lubricating composition to be analyzed in step e) is a pipette, preferably disposable plastic micropipette or a positive displacement, for example 100 μΙ, e.g. Gilson Microman type or Transferpettor Brand. There may be at least as device (D3) as lubricating compositions to analyze. For example, the kit may comprise from 1 to 50 devices (D3), preferably 50 devices (D3).

Particularly advantageously, the kit of the invention may be stored in a trunk or suitcase and is therefore easily transportable.

Figure (1) shows a kit according to the invention.

Figure (2) shows a magnetic support according to the invention.

The kit of the figure (1) comprises:

- a magnetic support (1) comprising slots (2) each including a magnet and adapted to receive the first container (3) and points (4) for receiving the second containers (5);

- the first container (3);

- second containers (5);

- a reagent composition (CR1 ') (6);

- a reagent composition (CR3) (7);

- a reagent composition (CR4) (8);

- an electronic spectrophotometer (9) comprising a location (10) for receiving the second containers, preferably, this location makes an angle of 35-75 °, preferably 50 to 70 °, eg 60 ° relative to body of the spectrophotometer;

- at least one device (D3) (1 1); and

- at least three devices (D2) (12)

CLAIMS

1 .- ion assay method iron, including ferrous and ferric ions, in lubricating compositions, comprising the steps of:

a) Collecting a sample of the lubricating composition to be analyzed in a first container;

b) Removing the first vessel containing the sample to be analyzed on a magnet; c) Adding a second container:

o a first reagent composition (CR1) aqueous composition comprising at least one extractant ferric and ferrous ions of the oily phase to the aqueous phase;

o a second reactive composition (CR2) aqueous composition comprising at least one ferric ion reducing agent (Fe 3+ ) to ferrous ions (Fe 2+ ); o a third reagent composition (CR3) comprising at least an emulsion destabilizing agent; and

o a fourth reagent composition (CR4) in aqueous solution comprising a complexing agent for ferrous ions, characterized in that said agent changes color upon complexation with ferrous ions; and mixing;

d) optionally, photochemical measurement of the absorbance of the mixture obtained in step c);

e) Taking a few drops of the lubricating composition contained in the first container held in place on the magnet, and adding these few drops into the second container comprising mixing the first, second, third and fourth reactive compositions obtained in step c);

f) Stirring mixture obtained in step e);

g) photochemical Measure the absorbance of the mixture obtained in step f);

h) Determination of the quantity of ferrous ions in the lubricating composition from the measurements obtained in steps d) and g).

2.- Method according to claim 1, wherein the extractant is selected from the solubilizing agents ferric and ferrous ions and being immiscible with the lubricant composition, such as acid, in particular sulfuric acid, nitric acid, Hydrochloric acid , phosphoric acid, alone or in admixture.

3.- Method according to claim 2, wherein the extracting agent is sulfuric acid.

4.- Method according to any one of claims 1 to 3, wherein the agent for reducing ferric ions to ferrous ions is selected from hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite, alone or in admixture.

5. - Method according to claim 4, wherein the ferric ion reducing agent to ferrous ions is hydroxylamine hydrochloride.

6. - Method according to any one of claims 1 to 5, wherein the destabilizing agent is selected from primary or secondary alcohols (C4 -C10) non-miscible with water, alone or in admixture.

7. - Method according to claim 6, wherein the destabilizing agent is isoamyl alcohol, octan-1-ol, octan-2-ol, 1 -heptanol, 2-ethyl-hexanol, 2-ethyl- butanol.

8 - Method according to any one of claims 1 to 7, wherein the complexing agent is chosen from complexing agents including ferrous ions and complexation is to cause a color change that can be detected by measuring the absorbance of the solution obtained by a spectrophotometer, preferably the complexing agent is selected from ferrozine, the Ferene, the phenanthroline and its derivatives, e.g. bathophenantroline, bipyridine, thioglycolic acid, R-nitroso salt (sodium salt of 3-hydroxy-4-nitroso-2,7-disulfonate), potassium ferricyanurate (hexacyanoferrate (III) potassium), 2,4,6-tripirydyl-s-triazine (TPTZ) .

9. - A method according to claim 8, wherein the complexing agent is R-nitroso salt.

10. - Method according to any one of claims 1 to 9, wherein the first and second reagent composition are included in an aqueous reagent composition CR1.

1 1 .- kit for the implementation of the method according to any one of claims 1 to 10 comprising:

- a first reagent composition (CR1) aqueous composition comprising at least one extractant ferric and ferrous ions in the oil phase of the lubricant composition to the aqueous phase as defined in claims 1 to 3;

- a second reactive composition (CR2) aqueous composition comprising at least one ferric ion reducing agent (Fe3 +) to ferrous ions (Fe2 +) as defined in claims 1, 4 and 5;

- a third reagent composition (CR3) comprising at least one emulsion destabilizing agent as defined in claims 1, 6 and 7;

- a fourth reagent composition (CR4) in aqueous solution comprising a complexing agent for ferrous ions, as defined in revdendications 1, 8 and 9, characterized in that said agent changes color upon complexation with ferrous ions;

- a spectrophotometer, preferably an electronic spectrophotometer;

- optionally at least one first container;

- at least one second vessel;

- optionally at least one device (D1) for sampling the lubricating composition to be analyzed;

- a device (D2) for each of the samples of the first, second, third and fourth reactive compositions;

- a magnetic support;

- at least one device (D3) for the removal of a few drops of the lubricating composition to be analyzed in step e).