Quantitation of blood and plasma amino acids using isotope dilution electron impact gas chromatography/mass spectrometry with U-C-13 amino acids as internal standards

A method to quantitate blood and plasma amino acids by isotope dilution gas chromatography/mass spectrometry (GC/MS) is described, Samples were spiked with U-C-13 amino acids as internal standards and the tert-butyldimethylsi lyl derivatives (tBDMS) separated by capillary column gas chromatography. L inear regression curves, generated for individual amino acids, gave correla tion coefficients of 0.9999. The reproducibility of the method was assessed from the analysis of 10 replicate blood and plasma samples. For most amino acids a coefficient of variance (CV) of less than or equal to 1% was obtai ned with the exception of aspartate which gave a value of 1.8%. This was pr obably due to the low concentration of this amino acid in the samples analy sed, Recovery of amino acids added to plasma was between 96 and 103%. The u se of electron impact ionization (EI) allows the method to be used in labor atories where only the more basic GC/MS is available and reduces the time s pent on instrument maintenance. The method should prove useful in areas of work where accurate and precise amino acid concentrations are required. Cop yright (C) 1999 John Wiley & Sons, Ltd.