THERMOSPRAY MASS-SPECTROMETER AS A QUANTITATIVE SPECIFIC, SENSITIVE, DETECTOR FOR LIQUID-CHROMATOGRAPHY - ITS APPLICATION TO THE ANALYSIS OF PYRIDOSTIGMINE IN HUMAN PLASMA

A thermospray interface between a HPLC system and a mass spectrometer has been used to develop an assay for pyridostigmine bromide measuring plasma concentrations down to 1 ng ml-1 on a routine basis. Plasma is loaded onto an AASP reversed-phase cartridge, injected onto a HPLC system connected to a Finnigan 4500 mass spectrometer via a thermospray interface and the molecular ion monitored. A deuterated internal standard is used, but calculations with and without the internal standard show its use does not materially improve the quantitation. The precision and accuracy at the limit of quantitation is < +/- 5% and 95-105%, respectively. The method is used to analyse samples from a bioavailability study by fully automated unattended overnight sample analysis.