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Determination of Ethylene Glycol in

Used Engine Oil by Headspace-Gas Chromatography

Authors:
Timothy D. Ruppel
Gerald Hail 

PerkinElmer Life and
Analytical Sciences
710 Bridgeport Avenue
Shelton, CT 06484

Introduction
The presence of ethylene glycol in used motor oil is an indication of antifreeze coolant leakage into the crank case of an internal combustion engine, thus predicting engine-wear problems. Several options for the determination of glycols currently exist, including colorimetric tests which are easy to perform, but subjective in interpretation and not particularly sensitive, fast or cost effective. Gas chromatography (GCJ) can also be used for analysis, but the ethylene glycol is difficult to detect and quantify due to its low molecular weight, low volatility and high polarity. Ethylene glycol chromatographic peak shape is often difficult to control and carryover can be a problem.

Injecting used engine oil directly into a gas chromatograph for the determination of ethylene glycol introduces high- molecular-weight oil and non-volatile components into the injector and the column, consequently the chromatography is very long, the column lifetime is shortened and the sample throughput is low, since high boiling components from the oil matrix must elute before the next injection.

ASTM Method 04291-98 specifies diluting the oil sample with hexane, extracting the glycol into water and analysis by GC. This is a very labor intensive sample preparation procedure and an unforgiving chromatographic method, whereby water and the polar analyte are injected on-column.

An alternative to ASTM Method 04291-98 is investigated here, which involves a very simple in-situ derivatization technique that allows the glycols to be made more volatile and less polar. Headspace extraction is used to isolate the glycols from the complex sample matrix and inject into a gas chromatograph for rapid separation and quantification without the oil matrix. The result is a rapid, high-throughput method capable of analyzing hundreds of samples per day for ethylene glycol and propylene glycol in motor oil.

For further information on these methods visit www.perkinelmer.com

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