Simultaneous analysis of catecholamine acidic metabolites by single ion monitoring and manual control of the magnetic field.

A method for multicomponent analysis by single ion monitoring is presented. This method involves monitoring of one ion per selected compound in a GC run. To focus sequentially on each ion, the magnetic field strength of the mass spectrometer is manually reset to the proper value during the intervals between eluting peaks. Stationary phase bleeding provides a suitable reference background for rapid location of selected ions. This technique has been applied to the simultaneous analysis of 3,4-dihydroxyphenylacetic acid (DOPAC), vanillylmandelic acid (VMA) and homovanillic acid (HVA) in urine samples. Quantitative data for DOPAC and HVA are presented using 3,4-dihydroxyphenylpropionic acid (DHPPA) as an internal standard.