Traceable values for nitrate in water samples by isotope dilution analysis using a small thermionic quadrupole mass...

Area of Science:

• Analytical Chemistry
• Environmental Science

Background:

• Accurate nitrate determination in water is crucial for environmental monitoring and public health.
• Existing methods may have limitations in accuracy, traceability, or detection limits.

Purpose of the Study:

• To develop and validate an isotope dilution mass spectrometry (IDMS) procedure for precise nitrate quantification in diverse water matrices.
• To assess the accuracy and traceability of the developed IDMS method against certified reference materials and ion chromatography.

Main Methods:

• Utilized a 15N-enriched nitrate spike (IRMM-627) for isotope dilution mass spectrometry.
• Isolated nitrate by precipitation as nitron nitrate, followed by thermal ionization mass spectrometry using a quadrupole mass spectrometer.
• Employed negative thermal NO2- ions for optimal ion emission.

Main Results:

• Achieved excellent agreement (within 1%) between IDMS, ion chromatography, and certified values for nitrate in rainwater CRM 409, sparkling mineral water, and tap water.
• Demonstrated an expanded uncertainty (k=2) of 2-5% for nitrate determination.
• Established a low detection limit of 2 mumol kg-1 for nitrate in water samples.

Conclusions:

• The developed IDMS procedure provides an accurate, traceable, and sensitive method for nitrate determination in various water samples.
• This method offers a reliable alternative for water quality assessment and environmental monitoring.
• The use of a thermionic quadrupole mass spectrometer makes the technique accessible and cost-effective.