New extraction procedure and high-performance liquid chromatographic method for analyzing polyethylene glycol-400 in...

We describe a new, highly efficient method for extracting polyethylene glycol-400 from urine and for its analysis by isocratic reversed-phase high-performance liquid chromatography. This method is an improvement over previously published methods in that it does not require the use of ion-exchange resins and lyophilization prior to extraction, nor does it require the separation and analysis of the individual polymers of polyethylene glycol. The procedure described in this report entails extraction with a salt-solvent combination of ammonium sulfate and dichloromethane and analysis by reversed-phase high-performance liquid chromatography. The lower limit of detection was approximately 0.25 g/l with a 2-ml urine sample. Analytical recoveries of polyethylene glycol-400 added to urine at 2.5 and 5.0 g/l averaged 97 and 96%, respectively (n = 10). Within- and between-day coefficients of variation were less than 5% at 2.5 and 5.0 g/l. Studies of various urine samples from patients receiving polyethylene glycol-400 revealed no interferences from other urine substances.