High-precision quadruple isotope dilution method for simultaneous determination of nitrite and nitrate in seawater by GCMS after derivatization with triethyloxonium tetrafluoroborate.
Quadruple isotope dilution mass spectrometry (ID(4)MS) has been applied for simultaneous determination of nitrite and nitrate in seawater. ID(4)MS allows high-precision measurements and entails the use of isotopic internal standards ((18)O-nitrite and (15)N-nitrate). We include a tutorial on ID(4)MS outlining optimal experimental design which generates results with low uncertainties and obviates the need for direct (separate) evaluation of the procedural blank. Nitrite and nitrate detection was achieved using a headspace GCMS procedure based on single-step aqueous derivatization with triethyloxonium tetrafluoroborate at room temperature. In this paper the sample preparation was revised and fundamental aspects of this chemistry are presented. The proposed method has detection limits in the low parts-per-billion for both analytes, is reliable, precise, and has been validated using a seawater certified reference material (MOOS-2). Simplicity of the experimental design, low detection limits, and the use of quadruple isotope dilution makes the present method superior to the state-of-the-art for determination of nitrite and nitrate, and an ideal candidate for reference measurements of these analytes in seawater.
National Research Council of Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada. Electronic address: enea.pagliano@nrc-cnrc.gc.ca.
Enea
E
Pagliano
National Research Council of Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada.
Juris
J
Meija
National Research Council of Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada.
Zoltán
Z
Mester
D001881:Borates / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D009566:Nitrates / Q000032:analysis* / Q000737:chemistry*; D009573:Nitrites / Q000032:analysis* / Q000737:chemistry*; D011865:Radioisotope Dilution Technique; D012623:Seawater / Q000737:chemistry*; D013997:Time Factors
D001881:Borates; D009566:Nitrates; D009573:Nitrites; C005142:triethyloxonium tetrafluoroborate
GCMS; High-precision; Nitrite and nitrate; Quadruple isotope dilution; Seawater; Triethyloxonium tetrafluoroborate derivatization