Differential Contribution of Albumin and Lipids to the Hydrophobic Extraction of Bis-(2-ethylhexyl) Phthalate from Hemodialysis Tubing by Human Serum: Analysis by Gas Chromatography - Stable Isotope Dilution Mass Spectrometry

Abstract A method is presented which allows quantitative assignment of hydrophobic human serum components to the extraction of bis-(2-ethylhexyl) phthalate (DEHP) from medical tubing. Under optimized conditions (sample pH 5.5; fluid-fluid extraction with ethyl acetate + tert-butyl methyl ether 1 + 1 v/v; DEHP-ring-D4 as internal standard with ratios of endogenous (m/z = 149) and added deuterated DEHP (m/z = 153) adjusted to around 1.0; equilibration of added internal standard with the hydrophobic sample for 24 hours), a high precision can be achieved with an intra-assay coefficient of variation of 1.5% (n = 7) for sample DEHP quantification. Phthalate migration from hemodialysis tubing was quantified by use of a peristaltic pump and recirculation (200 minutes) of serum with different degrces of hypertriglyceridemia (range from 2.26 to 14.5 g/L) or solutions of human albumin (10 to 50 g/L). Only DEHP, but no other phthalates are detected in the extracts. There exist linear relations between DEHP extraction...