The analysis of diagnostic markers of genetic disorders in human blood and urine using tandem mass spectrometry with liquid secondary ion mass spectrometry

Abstract

A method has been developed for the rapid diagnosis of metabolic diseases based on the analysis of characteristic metabolites in body fluids by fast atom bombardment or liquid secondary ion tandem mass spectrometry (FAB-MS—MS or LSIMS—MS). Acylcarnitine profiles were obtained from 100 μl urine. 200 μl plasma or 25 μl whole blood spotted onto filter paper by simple solvent extraction, esterification and analysis using a precursor ion scan function on a triple quadrupole mass spectrometer. Specificity and sensitivity were improved by adding a small percentage of sodium octyl sulfate to the liquid matrix, which forms ion pairs with acylcarnitine esters. Acylglycines in urine were specifically detected as a group using a different precursor ion scan function. By forming methyl esters, metabolic profiles of both acylcarnitines and acylglycines were achieved in the same sample loading by application of alternating scan functions. Quantitative analysis of selected metabolites was achieved by use of stable isotope-labeled internal standards. Amino acid profiles were obtained from 100 μl plasma and 25 μl whole blood spots using butyl esters and a neutral loss scan function. The quantitative analysis of phenylalanine and tyrosine was achieved in these samples using stable isotope dilution. This capability will facilitate the diagnosis of phenylketonuria and other amino acidemias. These new methods have the requirements of speed, accuracy and capability for automation necessary for large-scale neonatal screening of inborn errors of matabolism.