Determination of 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl)-1-nitrosourea in plasma by negative chemical ionization mass spectrometry

A sensitive and specific method for the quantitative determination of a new antitumor agent, 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl)-1-nitrosourea, (PCNU) has been developed for the analysis of plasma. This assay involves extraction of the plasma sample, separation of the drug by thin-layer chromatography and mass spectrometric detection of the negative ions derived from the unchanged drug and its 2H4-labeled analog. Ion current profile peaks are obtained when drug samples are introduced into the heated source using a desorption chemical ionization probe. Detection limits are below 1.0 ng ml-1 of plasma. This method has been applied to determine the in vitro rate of decomposition of PCNU in plasma and the plasma clearance of this drug from a cancer patient.