Determination of isomeric acid dopamine metabolites in human cerebrospinal fluid by mass fragmentography

A method for the quantitative determination of the isomers 4-hydroxy-3-methoxyphenylacetic acid (HVA) and 3-hydroxy-4-methoxyphenylacetic acid (iso-HVA) in cerebrospinal fluid (CSF) by mass fragmentography has been developed. The heptafluorobutyryl methyl ester derivations of the two compounds could not be separated by gas chromatography. The relative intensity of the base peak (m/e 333) and the molecular ion (m/e 392) in the mass spectra were, however, quite different and allowed a separate determination. Contradictory to a previous report, it was found that the concentration of iso-HVA was less than 2% of the HVA level in the investigated 12 CSF samples from patients with different diseases.