GC-MS profiling of urinary organic acids evaluated as a quantitative method.
We assessed the quantitative performances of a classical method for profiling urinary organic acids: ethyl acetate extraction/oxime-trimethylsilyl derivatization/GC-MS. Twenty-seven acids were quantified on the basis of specific ions in both scan and selected-ion monitoring modes. We found that the tuning of the mass detector severely affects the calibration factors, being critical to achieve quantitative results, and we propose a practical procedure for reproducible tuning. Of seven compounds tested, tropic acid was retained as the internal standard suitable for most of the acids of clinical interest; a second internal standard, 2-ketocaproic acid, was used in quantifying keto-acids. The within-day and total relative standard deviations (CVs), estimated from scan-mode analyses of urine, ranged from 2.6% to 12.7% and from 4.2% to 11.8%, respectively. Curvilinear relationships between analytical response and concentration were observed for most of the acids investigated.
Duez
P
P
Laboratoire de Biochimie médicale, Institut de Pharmacie, Université Libre de Bruxelles (ULB), Brussels, Belgium.
Kumps
A
A
Mardens
Y
Y
D002208:Caproates; D002264:Carboxylic Acids / Q000652:urine*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D006801:Humans; D010666:Phenylpropionates; D015203:Reproducibility of Results
D002208:Caproates; D002264:Carboxylic Acids; D010666:Phenylpropionates; C001916:alpha-ketocaproic acid; C011377:tropic acid