title: Quantification of nitrite and nitrate in seawater by triethyloxonium tetrafluoroborate derivatization-headspace SPME GC-MS.
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.
authors.affiliation: Scuola Normale Superiore, Piazza dei Cavalieri, 7, 56126, Pisa, Italy. e.pagliano@sns.it
authors.forename: E
authors.initials: E
authors.lastname: Pagliano
authors.forename: M
authors.initials: M
authors.lastname: Onor
authors.forename: E
authors.initials: E
authors.lastname: Pitzalis
authors.forename: Z
authors.initials: Z
authors.lastname: Mester
authors.forename: R E
authors.initials: RE
authors.lastname: Sturgeon
authors.forename: A
authors.initials: A
authors.lastname: D'Ulivo