A new micromethod for the quantification of low molecular weight oligomers of polyethylene glycol

We describe a gas-liquid chromatographic technique for quantifying the low molecular weight (Mr 106-634) oligomers of polyethylene glycol (PEG) in clinical specimens. The deionized sample, containing tetra-ethylene glycol as an internal standard, is applied on column. This technique readily quantifies as little as 2.5 micrograms of an individual oligomer; with such a quantity, the coefficient of variation is +/- 2.5 percent (N = 25 analyses). Small volumes (250 microliter) of urine are conveniently analyzed, and a single column can be utilized for the analysis of approximately three hundred specimens. We have analyzed timed urine specimens from humans who received 0.15 g of PEG 400 per kilogram. Individuals varied markedly with regard to the total amount of PEG excreted into the urine; each subject, however, consistently excretes a uniform percentage of the ingested dose. The urinary oligomeric profile of PEG does not vary from subject to subject nor from hour to hour, during the first six hours following oral administration, so that a random urine obtained during this period provides a reliable clinical specimen. This technique should facilitate clinical studies that utilize polyethylene glycol 400 as an index of passive intestinal transport.