Determination of urine melamine by validated isotopic ultra-performance liquid chromatography/tandem mass spectrometry.
Little is known about melamine (MEL) analysis in children's urine. In this study, an isotopic ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method was developed and systematically validated for the analysis of MEL in urine. The method is easily performed and comprises acidification, solid-phase extraction (SPE) and UPLC/MS/MS analysis. (13)C(3)N(3)((15)NH(2))(3) was used as the internal standard (IS) for calibration. Transition ions m/z 127 > 85 of MEL and m/z 133 > 89 of the IS were used for quantification and m/z 127 > 68 of MEL was used for quantitative confirmation. Recovery and precision were assessed to guarantee the applicability of the method. The limit of quantification (LOQ) was 0.01 microg/mL while the calculated method detection limit was 0.006 microg/mL. The mean recoveries ranged from 96-99%. The method was then applied to analyze urine samples from children who had potentially consumed MEL-tainted dairy products during screening in Taiwan. Ten nephrolithiasis cases and 20 age- and gender-matched controls were selected for this study. Three out of the 10 nephrolithiasis cases had elevated levels of MEL. Comparatively, twenty age- and gender-matched non-nephrolithiasis controls consuming Taiwan brand milk powder all showed MEL levels lower than the detection limit except for two children with background levels of 0.02 microg/mL. The background level in these children urine samples was established by UPLC/MS/MS analysis. Positive results of urine MEL tests might be associated with nephrolithiasis in these candidates. Measurement of urine MEL concentration can be helpful in confirming MEL-related nephrolithiasis, but its clinical application needs further clarification.
Cheng
Wei-Chih
WC
Bureau of Food and Drug Analysis, Department of Health, Taipei, Taiwan.
Chen
Shu-Kong
SK
Lin
Tien-Jen
TJ
Wang
I-Jen
IJ
Kao
Ya-Min
YM
Shih
Daniel Yang-Chih
DY
D000293:Adolescent; D002247:Carbon Isotopes / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009587:Nitrogen Isotopes / Q000032:analysis; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014227:Triazines / Q000652:urine*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014227:Triazines; C011907:melamine