A rapid method for measurement of ethylene glycol

Abstract

It has been reported that ethylene glycol produces a positive interference in the triglyceride assay on the DuPont aca discrete analyzer. The sensitivity of this method for ethylene glycol was exploited to develop a rapid and convenient method for detecting and quantitating ethylene glycol in serum by the use of a “triglyceride gap.” This method is based on the difference between two different enzymatic triglyceride measurements; the DuPont aca triglyceride measurement, which uses lipase and glycerol dehydrogenase, and a Boehringer Mannheim method, which uses lipase, glycerol kinase, glycerolphosphate oxidase, and peroxidase. Serum pools were spiked with increasing concentrations of ethylene glycol to construct a standard curve (linear to 25 mmol/L). Patient specimens and control sera were analyzed using a one point calibration. Within-run and between-run coefficients of variation (CV) of 1.5, 2.8, 5.8, and 3.2%; 3.4%; and 12.6% were obtained at ethylene glycol concentrations of 20.13, 8.37, and 2.18 mmol/L, respectively. The sensitivity of this method is 1.10 mmol/L. Methanol, ethanol, n-propanol, isopropanol, and acetone at 100 mmol/L; 20 mmol/L 1,3-propanediol; and 10 mmol/L glycolic acid, oxalic acid, glyxylic acid, and lactic acid did not interfere in the quantitation of ethylene glycol. High levels (10 mmol/L) of β-hydroxybutyrate and glycerol showed a slight positive interference on the quantitation of ethylene glycol, whereas 10 mmol/L glycoaldehyde caused a substantial overestimation of serum ethylene glycol. The presence of propylene glycol, at levels ranging from 5 to 50 mmol/L, resulted in an underestimation of serum ethylene glycol. Results obtained by our method showed excellent correlation with a gas chromatographic method ( n=56; y =1.05 x − 0.2; π 2=0.984). These results suggest that this method can provide a rapid and convenient alternative to measuring ethylene glycol concentrations by gas chromatography.