The simultaneous determination by selected ion monitoring of the levels of homovanillic, isohomovanillic, 3,4-dihydroxyphenylacetic and 3-methoxy-4-hydroxymandelic acids in single biological samples.

Methods for the determination and quantitation of homovanillic, isohomovanillic, 3,4-dihydroxyphenylacetic and 3-methoxy-4-hydroxymandelic acids in single samples of biological material by gas chromatography, gas chromatographic mass spectrometry and selected ion monitoring during gas chromatographic mass spectrometry are described. Examples of the levels of these four acid metabolites of catecholamines in serum and CSF of untreated dog, cat and human, in urine of parkinsonian subjects treated with varying doses of L-DOPA and in CSF of dogs which had received 1 g of L-DOPA per day for 7 weeks are presented.