Glycol Detection In Oil

Abstract

A sample of engine oil is taken from a crankcase and introduced into an aqueous oxidizing solution. The mixture is shaken and allowed to separate into the oil and aqueous phases. A sample of the aqueous phase is then introduced onto a chromogenic aldehyde reagent adsorbed on a suitable supporting media. The sample and reagent are contacted and the presence or absence of glycol in the engine oil is observed by chromogenic determination. The method allows the observation of as little as several parts per million of glycol in oil.

Description

BACKGROUND OF THE INVENTION

The present invention relates to the indication of ethylene glycol antifreeze contamination in crankcase oil. More particularly, the invention discloses a method for the detection of ethylene glycol contaminates in small quantities in engine oils by a simple oxidation and an aldehyde chromogenic test.

The presence of contaminants in engine oil may have derogatory effects upon the performance of the engine and its internal parts. The cleanliness of internal parts of an engine depends upon the equilibrium between the oil-polluting substances and the remaining effective oil-lubricating molecules. Various methods are available for testing engine oils as to their effective lubrication and cleansing properties upon engine parts. Both laboratory and field tests have shown that ethylene glycol is one of the most hazardous contaminants which may enter engine oil. The ethylene glycol is derived from the antifreeze added to the engine's cooling system. Through abusive wear of the engine and failure of sealing members within the engine's parts, ethylene glycol may enter the crankcase and lubricating system of the engine and cause pasty emulsions which may plug oil filters, pump screens, oil feedlines and passages within the engine. The ethylene glycol also presents a problem in the engine combustion chamber where temperatures are high enough to convert the glycol into a varnishlike substance which causes valves to stay open, valve lifters to bend in their guides, and piston rings to stick in their grooves. Consequences of the above-mentioned malfunctions of the engine may result in extreme engine abuse, engine lifetime diminishment and eventual engine failure. The elimination of ethylene glycol in the crankcase oil is a matter of extreme importance in maintenance of the engine in that no engine oil additives are available on the market to combat the engine seizure properties of glycol.

The most common method used to combat ethylene glycol contamination in engine oil and subsequent varnishing of engine parts is to change the engine oil periodically so that the concentration of ethylene glycol never exceeds a minimal quantity which would damage the engine's moving members. What is required is an ethylene glycol testing method which will indicate the concentration of ethylene glycol after certain periodic intervals of engine-hour usage such that the engine may be serviced and the oil changed when ethylene glycol reaches the maximum tolerable concentration. This ethylene glycol test method must include a procedure by which servicing personnel may periodically check engine oil for glycol concentration without a rigorous analytical technique being required. The test must, therefore, be simple enough for layman's usage and also provide positive identification of the ethylene glycol content. To date, no suitable ethylene glycol test method is available for service station or industrial usage. Therefore, an ethylene glycol detection method which may be taught to untrained personnel, easily used, and which is not time consuming is desirable.

It is an object of the present invention to provide a method by which the ethylene glycol content in the crankcase oil of an internal combustion engine may be determined.

It is still another object of the present invention to provide a method by which the ethylene glycol content of the crankcase oil may be determined by usage of a simplified testing procedure which may be taught to untrained personnel.

It is still another object of the present invention to provide a method for ethylene glycol detection which utilizes stabilized chemical compounds which will have a long term usage and which will not deteriorate.

With these and other objects in mind, the present invention is hereinafter presented with particular reference to the following description.

SUMMARY OF THE INVENTION

The objects of the present invention are achieved by a method for the detection of ethylene glycol in oil. The method involves introducing a sample of the oil to be tested into an aqueous solution of water and an oxidizer which preferentially oxidizes ethylene glycol to formaldehyde. The oil and aqueous solution containing the oxidizer are thoroughly mixed and the mixed solution is allowed to separate into the aqueous and oil phases. Some of the aqueous phase is then mixed with a chromogenic formaldehyde reagent adsorbed on a suitable supporting media to determine the presence of formaldehyde and thereby indicate the presence of ethylene glycol in the original oil. Suitable oxidizers include sodium periodate, potassium periodate, hydrogen peroxide, sodium perborate, ceric nitrate, lead tetra-acetate and ceric sulfate. Suitable chromogenic formaldehyde reagents include 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate, salicylalhydrazone, p-nitrobenzalhydrazone,2-hydrazinobenzothiazole, 2-hydrozinobenzothiazole-4-nitrobenzenediazonium fluoborate, etc., adsorbed on supporting media which may be any suitable material, such as silica gel, anhydrous alumina, diatomaceous earth, or firebrick or polymeric material. Suitable polymeric material includes polyethyline, nylon, etc. and is preferably present in particulate form such as chips or powder.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a method for the detection of ethylene glycol trace contamination in engine oils. The method comprises an analytical technique for chromogenically determining the presence of ethylene glycol in the engine oil. The method consists of sampling the engine oil and mixing the sample of engine oil with an aqueous solution containing an ethylene glycol oxidizer. After the mixing step, the aqueous and oil phases are allowed to separate such that the aqueous phase may be sampled and introduced into a chromogenic formaldehyde reagent absorbed on a supporting media.

Most oxidizers which will transform glycols into aldehydes may be used in the present invention, however, the oxidizer must have the characteristic of not tainting the aqueous solution such that the colormetric determination may not be used. Therefore, standard oxidizers such as potassium permanganate and ferric sulfate would not be suitable for the present invention as they would leave a distinct color in the aqueous phase which would conceal the color change of the colormetric formaldehyde indicator. Suitable oxidizers for use in practicing the invention include sodium periodate, potassium periodate, hydrogen peroxide, sodium perborate, ceric nitrate, ceric sulfate and lead tetra-acetate. In particular, the sodium and potassium periodates are preferred oxidizers which selectively oxidize ethylene glycol to the formaldehyde without the presence of byproduct reactions which form other oxidized compounds. In most cases, the oxidizer, in particular the periodate solution, will be about 0.01 to 1.0 molar concentration. By this procedure, an economic quantity of the oxidizer is utilized and strong oxidation does not take place. In most instances, between about 1 and about 10 milliliters of oxidizing solution per milliliter of oil sample will be sufficient to fully oxidize the ethylene glycol contained in an oil sample withdrawn from an engine crankcase.

In the field application of a preferred embodiment of the present invention generally 5 to 10 milliliter oil samples are withdrawn from the engine oil by use of a piece of tubing or by a syringe-type instrument introduced into the crankcase through the dip tube. The engine oil is withdrawn and dropped into the solution of oxidizer held in a container. The container is then sealed and vigorously shaken. After the mixing has occurred, the solution is allowed to separate into a lower aqueous phase and an upper oil phase. The aqueous phase contains the oxidized ethylene glycol or the resultant formaldehyde which may be withdrawn to test the amount of aldehyde present.

Many chromogenic formaldehyde reagents exist, but the reagent used must be highly specific for formaldehyde or other aldehydes and not be influenced by other substances which may be oxidized or may be contained as additives or original components of the engine oil. Many aldehyde reagents, which are specific to aldehyde indication, may be utilized in accordance with the present invention such as 3-methyl-2-benzothiazolinone hydrazine hydrochloride monohydrate, salicylalhydrazone, p-nitrobenzalhydrazone, 2-hydrazinobenzothiazole, 2-hydrazinobenzothiazole-4-nitrobenzenediazonium fluoborate, etc. Oil samples tested in accordance with the present invention, especially crankcase oils, are usually acidic by nature. The aldehyde reagent used must therefore be able to respond to the presence of formaldehyde in an acidic media when testing these acidic oils. This criterion eliminates a number of excellent aldehyde reagents as they will not perform under acidic conditions. Indicators such as 2-hydrazinobenzothiazole and 2-hydrazinobenzothiazole-4 -nitrobenzenediazonium fluoborate are excellent for the detection of aliphatic, aromatic, and heterocyclic aldehydes; however, these indicators require an alkaline media and are not suitable for practicing the preferred embodiment of the invention wherein the oil sample tested in an acidic crankcase oil.

Another criteria for preferred aldehyde indicators is the stabilization of the coloring test after introduction of the formaldehyde into the chromogenic formaldehyde reagent. The color should remain stable for several minutes so that the operator may observe the reagent color against predetermined charts or a blank for a quantitative determination of the amount of ethylene glycol present in the original sample. A study has been made by Sawicki, et al. Analytical Chemistry, Vol. 33, No. 1, Jan. 1961, p. 93, and has indicated that 3-methyl-2-benzo-thiazolinone hydrazine hydrochloride monohydrate (MBTH) is an excellent reagent for the determination of formaldehyde and this is a preferred reagent in practicing the present invention. We have found in particular that the application of the above-mentioned reagent adsorbed on silica gel, polyethylene chips, or other chromatographic supports has proven to be a stable reagent which may be kept for a long period of time and ultimately used in the field. Silica gels of wide mesh sizes may be used. In particular, the mesh size range of 28 to 200 mesh has proven favorable. Polyethylene in chipped or powered form gives an excellent support. Other chromatographic supports which may be used in the present invention may be selected from the group consisting of silica gel, anhydrous alumina, diatomaceous earth, and firebrick. Although it is preferred to use silica gel, or polyethylene chips the other chromatographic supports have proven satisfactory. As with the oxidizing agents, the chromatographic supports used to adsorb the formaldehyde reagent thereto should be translucent or opaque, such that any color imparted from the support will not interfere with the chromogenic test. Therefore, it is a necessary criterion of the chromogenic support that it not have an interfering background color which would interfere with the color test.

In the preparation of a chromogenic reagent, which would generally be unstable on exposure to air and unsuitable for the determination of aldehydes contained in samples, the chromogenic reagent generally is dissolved in a solvent. In most applications, the solvent used for the solution makeup would be deionized or distilled water. After the solution is formed it is introduced onto a suitable support medium which will adsorb the chromogenic reagent. An inert atmosphere is maintained about the support medium during the adsorption process so that no oxidation of the chromogenic reagent will occur during its preparation. The adsorbing step may be enhanced by simultaneously drying the chromogenic reagent on the support medium to strip off the solvent. This drying process may take from 5 minutes to an hour depending on the amount of solution introduced onto the adsorbing medium. As mentioned, a preferred reagent to be used is 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate. The MBTH solution in deionized water would generally be a 0.5 to 5 percent solution.

The inert atmosphere is maintained by introducing an inert gas such as nitrogen into the column of support medium with the MBTH adsorbed thereon and the solvent thereabout. The column may consist of a graduated cylinder or buret. A nitrogen containing cylinder may be connected to the column and nitrogen transferred therethrough so that inert atmosphere is continuously in contact with the MBTH and support medium. The drying procedure utilizes temperatures below about 100.degree. C. so that no destructive degradation of the MBTH takes place during the adhesion process. The MBTH in effect forms a complex with the support material so that after it is adsorbed on the active surfaces of the silica gel, polyethylene chips, or other support medium used, it will remain stable and will not be subject to attack by oxygen in the atmosphere about it. It has been found that 0.01 to 10 grams of chromogenic formaldehyde reagent adsorbed for each 10 grams of support material such as silica gel, preferably 0.005 to 1 gram per gram, provides sufficient reagent to give the results desired.

In a preferred embodiment of the present invention, chromogenic reagent contained on the support is introduced into a container such as a hypodermic syringe. It has been found that about 2 milliliters in a 5 milliliter syringe is an appropriate quantity. A sample of the aqueous phase is withdrawn from the container holding the oil and aqueous phases onto the chromogenic reagent in the syringe by means of the syringe plunger. Generally, from about 0.5 to about 2.0 milliliters of aqueous phase are used per milliliter of chromogenic reagent. The reagent will turn blue within 15 minutes if ethylene glycol is present in the oil.

In practicing the invention using sodium periodate oxidizer and MBTH reagent, the reactions occurring may be summarized as follows. Sodium periodate oxidizes the ethylene glycol to formaldehyde. The aldehyde then contained in the aqueous phase is withdrawn and placed on the MBTH chromogenic reagent. The aldehyde reacts with the MBTH to form the azine. In addition, some MBTH is oxidized to a reactive cation which combines with the azine to form a blue dye. Therefore, a normally translucent chromogenic formaldehyde reagent contained on a support will turn a dark blue if ethylene glycol is present. A blank solution may be run by taking an uncontaminated sample of the oil, mixing it with periodate solution, and then introducing the aqueous phase, which is separated, onto the chromogenic formaldehyde reagent. The reagent turns green when absorbed on silica gel or red when absorbed on polyethylene to give a blank test to indicate that no ethylene glycol is present. Shades of color between the blank color and blue indicate increased concentration of ethylene glycol. A color chart may be presented to quantitatively show the relative amount of ethylene glycol in parts per million which was contained in the engine oil. With this method the operator knows at any time in the ethylene glycol contamination process what the ethylene glycol concentration is and when the oil must be changed. Each time the oil is checked the reading is recorded until a maximum allowable concentration of ethylene glycol in the engine oil is experienced. The oil is then changed and the process repeated. The procedure is formulated below for the reaction of formaldehyde with 3-methyl-2-benzothiazolinone hydrazone , to form the azine, ; oxidation of to a reactive cation, , and formation of the blue cation, . ##SPC1##

A preferred embodiment of the present invention is a method whereby the oil sample for a given test is withdrawn in a ratio in accordance with the stated quantities from the crankcase by means of a plastic syringe, of about 10-milliliter capacity, equipped with a suitable length of small bore plastic tubing. In this method, about 7 milliliters of oil sample is discharged into the container, for example a 1 -ounce vial, containing about 10 milliliters of a 0.1 molar aqueous sodium periodate solution. A plastic closure tip is removed from the discharge end of the syringe which contains a chromogenic formaldehyde reagent such as MBTH on silica gel or particulate polyethylene. The tip of the syringe is introduced into the aqueous phase of the periodate solution after it has been shaken and the oil and water phases have separated. About 2 to 5 milliliters of the aqueous solution are withdrawn onto about 2 milliliter chromogenic formaldehyde reagent adsorbed on silica gel or particulate polyethylene. As in the previous preferred embodiment of the invention, the chromatographic support is prepared by placing about 0.5 grams of MBTH on 100 grams of 28 to 200 mesh silica gel or particulate polyethylene. Therefore, as the aqueous solution is drawn up onto the silica gel or particulate polyethylene to saturate them, the chromogenic check will be made by observing whether green or dark blue or intermediate color indication is given.

To further understand the application of the present invention the following example and data are presented.

EXAMPLE

Five experiments were run with 30 SAE motor oil. Measured quantities of ethylene glycol were added to each of the five motor oil samples so that a precise indication of the effectiveness of the chromogenic-ethylene glycol detection method could be determined. Each 5-milliliter sample was placed in a 1-ounce vial containing 10 milliliters of an aqueous 0.1 molar solution of sodium periodate. The vial was sealed with a cap and shaken vigorously for 2 minutes to ensure complete oxidation of the ethylene glycol contained in the oil. The cap was then removed and the vial set on a flat surface in an upright position for 3 minutes so as to allow the oil and aqueous liquid phases to separate. A second 1-ounce vial contained granular material which consisted of 0.5 grams of the chromogenic formaldehyde color reagent MBTH adsorbed on 100 grams of 28 to 200 mesh silica gel. An eye dropper was inserted into the lower aqueous phase of the 1-ounce vial containing the aqueous and oil phases. A sample of the aqueous phase was removed by squeezing and releasing the rubber bulb upon insertion so that the clear liquid was raised into the dropper until 10 milliliters of liquid had been withdrawn. The eye dropper was wiped and the liquid added to the granular material in the other 1-ounce vial. The vial was stoppered and shaken vigorously for approximately 5 seconds. The vial was then placed on a flat surface. Color indication for each test was noted as shown in the following table. The color became apparent to be either a green, dark blue, or an intermediate color within a 15 minute period. No glycol was indicated by a negative response with a green color formed and glycol presence was indicated by different shades of blue color formation. As can be seen, the sensitivity to the silica gel based MBTH test for ethylene glycol was effective and stable down to 30 parts per million of ethylene glycol in the motor oil, therefore giving a positive test for ethylene glycol content in motor oil. More than about 50 p.p.m. glycol in motor oil is generally considered to be excessive and requires an oil change. --------------------------------------------------------------------------- TABLE

Sensitivity of Silica Gel Based MBTH Test for Glycol

Motor oil Blue color 30 SAE Formation __________________________________________________________________________ 1000 p.p.m. glycol Positive 100 Positive 60 Positive 30 Positive 0 Negative __________________________________________________________________________

It can be seen by use of the present invention that the ethylene glycol content in motor oils may be specifically determined by testing the crankcase motor oil with the present invention. The invention then enhances the ability of service attendants to remove the hazards of ethylene glycol varnish deposits which cause valves to stay open, valve lifters to bend in their guides, and piston rings to stick in their grooves. The method provides the ability to warn of ethylene glycol leakage into the engine crank case and avoid severe damage therefrom.

While the present invention has been described above with respect to certain embodiments thereof it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as set forth herein.

Claims

Therefore, we claim:

1. A method for the detection of glycol in oil comprising the steps of:

a. introducing a sample of the oil to be tested into an aqueous solution of an oxidizer which preferentially oxidizes glycol to an aldehyde;

b. mixing the oil and aqueous solution containing the oxidizer;

c. separating the resulting aqueous and oil phases; and

d. contacting a sample of the resulting aqueous phase with a chromogenic aldehyde reagent selected from the group consisting of 3-methyl-2-benzothiazolinone hydrazine hydrochloride monohydrate, salicyhalhydrazone, p-nitrobenzalhydrazone, 2-hydrazinobenzothiazole, and 2-hydrazinobenzothiazole-4-nitrobenzenediazonium fluoborate, said reagent being adsorbed on a support medium.

2. The method of claim 1 in which the oil is acidic.

3. The method of claim 2 in which the chromogenic aldehyde reagent is 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate.

4. The method of claim 3 in which

a. the oxidizer is selected from the group consisting of sodium periodate, potassium periodate, hydrogen peroxide, sodium perborate, ceric nitrate, ceric sulfate; and lead tetra-acetate.

5. The method of claim 4 in which the aldehyde reagent support media is selected from the group consisting of silica gel, anhydrous alumina, diatomaceous earth, firebrick and polymeric material.

6. The method of claim 4 in which:

a. the oxidizer is about a 0.01 to 1.0 molar aqueous solution of sodium periodate;

b. the aldehyde reagent support media is particulate polyethylene; and

c. the chromogenic aldehyde reagent is prepared by adsorbing 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate on polyethylene.

7. The process of claim 6 in which:

a. the oil sample and aqueous phase are mixed for about 1 to about 2 minutes;

b. the aqueous phase and chromogenic aldehyde reagent are mixed for about 5 to about 10 seconds; and

c. the color is allowed to develop for 15 minutes.

8. The process of claim 7 in which the glycol is ethylene glycol.

9. The process of claim 7 whereby the detection takes place in a syringe which contains the chromogenic aldehyde reagent MBTH on particulate polyethylene.