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A procedure using isotope dilution mass spectrometry (IDMS) was developed for the determination of nitrate in water. After the removal of nitrite with amidosulfuric acid, nitrate was isolated selectively from the matrix by precipitating it with nitron. The nitron-nitrate formed was used to produce NO(2) thermal ions from a double filament arrangement in the ion source of a small quadrupole thermionic mass spectrometer and from a triple filament arrangement in the source of a NBS type magnetic field thermionic mass spectrometer. Both measurement procedures are discussed and compared. The IDMS experiments were performed using the (15)N-enriched nitrate species-specific spike isotopic reference material, IRMM-629, which is traceable to the international SI unit system in the shortest possible way. The procedure developed was applied to the determination of nitrate in a certified reference material (simulated rainwater, CRM 409 from the Community Bureau of Reference), in tap, river and sparkling mineral water. It was shown how isotope dilution combined with negative thermal ionisation mass spectrometry yielded accurate and traceable values for nitrate along an unbroken chain of a transparent procedure. These values were in agreement with those obtained by using ion chromatography and with the certified value for CRM 409. Full orthodox uncertainty evaluation was done for each measurement.

Additional information

Authors: WOLFF J-C, JRC Geel (BE);TAYLOR P D P, JRC Geel (BE);DE BIEVRE P, JRC Geel (BE)
Bibliographic Reference: Paper presented: EUROANALYSIS IX, Bologna (IT) September 1-7, 1996
Availability: Available from (1) as Paper EN 40069 ORA
Record Number: 199611138 / Last updated on: 1996-10-28
Original language: en
Available languages: en