A fundamental study was performed to establish a method of quantitative analysis by mass chromatography using direct inlet system in chemical ionization mass spectrometry. The samples of human serum which were obtained by venipuncture from healthy man volunteer treated orally with 5-(4'-chloro-n-butyl)-picolinic acid (CBPA). CBPA-d5 was used as internal standard. Direct probe-mass chromatography was performed by an on-line system of the Shimadzu LKB-9000 B and the GC-MSPAC 300. It can be concluded that this method is applicable to the quantitative determination of medicines in biological fluids.
