Microdetermination of 2-ketoglutaric acid in plasma and cerebrospinal fluid by capillary gas chromatography mass spectrometry; application to pediatrics

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Abstract
Quantification of 2‐ketoglutaric acid in plasma and cerebrospinal fluid as its O‐trimethylsilyl‐quinoxalinol derivative by gas chromatography chemical ionization mass spectrometry is described with benzoylformic acid as internal standard. This technique, with ammonia as reactant gas, only detects the protonated molecular ions. The recovery of 2‐ketoglutarate from perchloric‐deproteinized plasmas is 99.7±1.2%. The normal value of 2‐ketoglutarate in children is 8.6±2.6 μmol I−1 (Mean ± standard deviation) in plasma (n =25) and 4.8±1.4 μmol I−1 in cerebrospinal fluid (n 20). The plasma level of 2‐ketoglutarte is correlated with urea concentration (r = 0.96; p < 0.001) in healthy subjects and in patients with chronic renal insufficiency. Increased values are found in one case of pyruvate carboxylase deficiency, and inconstantly in diabetes; physiological variations are described during tasting and after an oral glucose load.