Determination of homocitrulline in urine of patients with HHH syndrome by liquid chromatography tandem mass spectrometry |
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Authors: | Osama Y Al-Dirbashi Zuhair N Al-Hassnan Mohamed S Rashed |
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Institution: | (1) National Laboratory for Newborn Screening, King Faisal Specialist Hospital and Research Center, P.O. Box 3354, Riyadh, 11211, Saudi Arabia;(2) Department of Medical Genetics, King Faisal Specialist Hospital and Research Center, P.O. Box 3354, Riyadh, 11211, Saudi Arabia |
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Abstract: | A liquid chromatography tandem mass spectrometric method is described for the analysis of homocitrulline in human urine, a
key metabolite in the differential diagnosis of hyperammonemia, hyperornithinemia, homocitrullinuria (HHH) syndrome. Urine
samples were prepared by mere five-fold dilution with a mixture of internal standards (2H2-citrulline and 2H3-creatinine) used for the simultaneous quantification of creatinine. Analytes were separated on a cyano column and eluted
isocratically within seven min. Detection was achieved by monitoring transitions of 190 > 84 and 190 > 127 for homocitrulline,
178 > 115 for 2H2-citrulline, 114 > 44 for creatinine and 117 > 47 for 2H3-creatinine. Calibration curves were linear up to 100 micromol/L. Intraday (n = 7) and interday (n = 6) variations were less than 10%. In urine samples from three siblings confirmed to have HHH syndrome, homocitrulline levels
were at 13.3 (74), 21.1 (50) and 108.2 (103) mmol/mol creatinine (micromol/L). Control values were 0–9 mmol/mol creatinine
(n = 120). The current method solves specificity issues in homocitrulline determination often encountered with some ninhydrin-based
systems (coelution with methionine) and some o-phthalaldehyde-based ones (coelution with taurine), and presents an attractive alternative with a relatively high throughput. |
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Keywords: | Homocitrulline Homocitrullinuria HHH syndrome LC– MS/MS |
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