DETERMINATION OF SELENIUM IN URINE BY ISOTOPE-DILUTION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY USING 4-NITRO-ORTHO-PHENYLENEDIAMINE, 3,5-DIBROMO-ORTHO-PHENYLENEDIAMINE, AND 4-TRIFLUOROMETHYL-ORTHO-PHENYLENEDIAMINE AS DERIVATIZING REAGENTS

An isotope dilution gas chromatography-mass spectrometry method for selenium determination in urine using 76Se as an internal standard is described. Three different derivatizing reagents, 4-nitro-o-phenylenediamine (NPD), 3,5-dibromo-o-phenylenediamine (DBPD), and 4-trifluoromethyl-o-phenylenediamine (TFMPD) were investigated for their gas chromatographic behavior including memory and precision and accuracy of isotope ratio measurements. By these criteria, the performance of these reagents was TFMPD > DBPD > NPD. Overall precision values of 1 to 7% were observed in determining Se isotope ratios at the 10-ng level, with no significant difference in using any of the three reagents. Memory effect was observed in the order NPD > DBPD > TFMPD with TFMPD showing no measurable memory effect. Accuracy of the GC-MS method was verified by quantitation of selenium in the NIST freeze-dried urine reference material SRM 2670. © 1992.