Quantification of nitrite and nitrate in seawater by triethyloxonium tetrafluoroborate derivatization-headspace SPME GC-MS

E Pagliano; M Onor; E Pitzalis; Z Mester; R E Sturgeon; A D'Ulivo

doi:10.1016/j.talanta.2011.07.098

Quantification of nitrite and nitrate in seawater by triethyloxonium tetrafluoroborate derivatization-headspace SPME GC-MS

Talanta. 2011 Oct 15;85(5):2511-6. doi: 10.1016/j.talanta.2011.07.098. Epub 2011 Aug 5.

Authors

E Pagliano¹, M Onor, E Pitzalis, Z Mester, R E Sturgeon, A D'Ulivo

Affiliation

¹ Scuola Normale Superiore, Piazza dei Cavalieri, 7, 56126, Pisa, Italy. e.pagliano@sns.it

PMID: 21962676
DOI: 10.1016/j.talanta.2011.07.098

Abstract

Triethyloxonium tetrafluoroborate derivatization combined with direct headspace (HS) or SPME-gas chromatography-mass spectrometry (GC-MS) is proposed here for the simultaneous determination of nitrite and nitrate in seawater at micromolar level after conversion to their corresponding volatile ethyl-esters (EtO-NO and EtO-NO(2)). Isotopically enriched nitrite [(15)N] and nitrate [(15)N] are employed as internal standards and for quantification purposes. HS-GC-MS provided instrumental detection limits of 0.07 μM NO(2)(-) and 2 μM NO(3)(-). Validation of the methodology was achieved by determination of nitrite and nitrate in MOOS-1 (Seawater Certified Reference Material for Nutrients, NRC Canada), yielding results in excellent agreement with certified values. All critical aspects connected with the potential inter-conversion between nitrite and nitrate (less than 10%) were evaluated and corrected for by the use of the isotopically enriched internal standard.