Assessment of matrix effects in quantitative GC-MS by using isotopologs

In quantitative analyses, thousands of compounds are extracted from a biological matrix in addition to the analytes of interest and can affect their quantification by many different effects. They are widely known as matrix effects (ME). A frequently used approach in LC-MS/MS to quantify ME is performing two series of analyses, that is 1) in the biological sample, and 2) in analyte solutions in water, organic solvents and/or in mixtures of them, and by comparing the slope values of the two standard curves. This article suggests a new approach for the quantification of ME in GC-MS using isotopologs, namely their specific peak area. The approach is exemplified for amino acids, representing an important group of physiological substances, for human serum and urine, two capital matrices in biological analysis.