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Determination of urinary S ‐sulphocysteine, xanthine and hypoxanthine by liquid chromatography–electrospray tandem mass spectrometry
Author(s) -
Rashed Mohamed S.,
Saadallah Amal A. A.,
Rahbeeni Zuhair,
Eyaid Wafaa,
Seidahmed Mohamed Z.,
AlShahwan Saad,
Salih Mustafa A. M.,
Osman Mohammad E.,
AlAmoudi Mohamed,
AlAhaidib Lujane,
Jacob Minnie
Publication year - 2005
Publication title -
biomedical chromatography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 65
eISSN - 1099-0801
pISSN - 0269-3879
DOI - 10.1002/bmc.439
Subject(s) - chemistry , hypoxanthine , chromatography , urine , xanthine oxidase , tandem mass spectrometry , isotope dilution , mass spectrometry , selected reaction monitoring , xanthine , molybdenum cofactor , cofactor , biochemistry , enzyme
Molybdenum cofactor and isolated sulphite oxidase deciencies are two related rare autosomal recessive diseases characterized by severe neurological abnormalities, dislocated lens and mental retardation. Determination of three biochemical markers S ‐sulphocysteine (SSC), xanthine (XAN) and hypoxanthine (HXAN) in urine is essential for a denitive diagnosis and identication of the exact defect. We developed a rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the analysis of SSC, XAN and HXAN in urine. The analysis was carried out in the negative‐ion selected‐reaction monitoring mode. The turnaround time for the assay was 7 min. Linear calibration curves for the three biomarkers were obtained in the range of 12–480 µmol/L. The intra‐ and inter‐day assay variations were <2.5%. Mean recoveries of SSC, XAN and HXAN added to urine at two signicantly different concentrations were in the range 94.3–107.3%. At a normal SSC urine excretion value of 3.2 µmol/mmol creatinine, the signal‐to‐noise ratio was 337:1. This stable isotope dilution LC‐MS/MS method is specic, rapid and simple, and provides denitive diagnosis for molybdenum cofactor and isolated sulphite oxidase deciencies in very small volumes of urine. We have identied seven new cases of isolated sulphite oxidase deciency from four Saudi families and one Sudanese family. Copyright © 2004 John Wiley & Sons, Ltd.