Determination of di(2-ethylhexyl) phthalate and four of its metabolites in blood plasma by gas chromatography-mass spectrometry.

A method using gas chromatography--chemical-ionization mass spectrometry has been developed for determination of the plasticizer di(2-ethylhexyl) phthalate (DEHP) in blood plasma. With selective monitoring of the protonated molecular ion, DEHP concentrations down to 75 ng per 500 microliters of human plasma can be measured. Methods using electron-impact mass spectrometry with single-ion monitoring have also been developed for determination of mono(2-ethylhexyl) phthalate (MEHP) in human blood plasma, and of MEHP and other DEHP-derived metabolites in rat plasma. After extraction and derivatization with pentafluoropropanol--pentafluoropropionic anhydride, the metabolites are monitored at m/z 281. The precision and sensitivity of these methods indicate that they will be valuable in studies of the pharmacokinetics of DEHP and its metabolites.