New liquid-chromatographic method for measuring polyethylene glycol in urine

The various Mr fractions of polyethylene glycol (PEG) in human urine are quantified by "high-pressure" liquid chromatography. A simple preparation step involving lyophilization and chloroform extraction of the sample is required. Aliquots (10 microL) are chromatographed isocratically in equivolume mixtures of methanol and water on a column of styrene divinylbenzene and the refractive index of the effluent is measured. The results vary linearly with the concentrations of standards up to at least 10 g/L, and the six major fractions are clearly identifiable in injected samples containing 2 g or more of total PEG per liter. As little as 4 g/L can be precisely quantified, but for assessing the individual fractions, we recommend a minimum sample concentration of 7 g/L. Analytical recovery of PEG added to urine controls was 90%. Urines collected during 6 h from 11 human subjects after each had ingested 5.6 g of PEG showed no interference from endogenous compounds. We find this method to be a simple, labor-saving means of quantifying urinary PEG in the clinical laboratory.