Concentrations of quinolinic acid in cerebrospinal fluid measured by gas chromatography and electron-impact ionisation mass spectrometry. Age-related changes in a paediatric reference population.

A simple method for the determination of the excitotoxin, quinolinic acid (QUIN) in cerebrospinal fluid (CSF) is described. QUIN, in lyophilized samples, was silylated by N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide in a single-step reaction at 65 to 70 degrees C to form a di-tert.-butyldimethylsilyl ester. Neither pre-purification of QUIN from CSF nor post-derivatisation sample clean-up was required. The derivatives were analysed by gas chromatography-electron impact mass spectrometry resulting in a prominent and characteristic [M-57]+ fragment ion which was used for quantitation. 2,6-Pyridine dicarboxylic acid, a structural analog of QUIN, was used as the internal standard. The detection limits for injected standards are in the femtomole range. CSF QUIN was found to be age-related and three preliminary reference ranges for CSF QUIN were found: 0 to 1 years, 31 +/- 15 nM QUIN (mean +/- standard deviation): 1.1 to 3 years, 26 +/- 15 nM; 3.1 to 14 years, 14 +/- 9 nM.