Principles and Overview - Reference Methods - LC/MS Methods - LC Methods

(See also: Bromate Methods)


Principles and Overview: Major Books, Reports & Review Papers on Oxyanion Analysis
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Reference Methods
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Khan, M.R., Alothman, Z.A., Khan, M.A., Busquets, R. and Alsohaimi, I.H. (2013) An ultra performance liquid chromatography-electrospray ionization-mass spectrometry method for the rapid analysis of nitrate in drinking water. Analytical Methods 5(5), 1225-1230.

Nitrate Excess of nutrient load can cause water eutrophication and be harmful to humans. While nitrogen is an important nutrient for crops, its introduction into the soil with fertilizers containing nitrate (NO3-) has been a major source of water pollution and monitoring NO3- has become necessary. In the present work, an ultra performance liquid chromatography-mass spectrometry method has been developed for the rapid quantification of NO3- in drinking water with reversed phase chromatography using a Waters Acquity BEH C-18 (50 mm x 2.1 mm i.d., 1.7 mu m particle size) column and a triple quadrupole mass spectrometer operating in Single Ion Recording mode. The quality parameters of the developed method were established, obtaining a limit of detection of 0.02 mu g L-1; linearity (r(2) > 0.999) over a concentration range covering 3 orders of magnitude; high precision, with repeatability and reproducibility lower than 3% (n = 5) in terms of relative standard deviation when analyzing a standard (0.05 mg NO3- L-1) and unspiked drinking water samples with levels of NO3- of 1 mg L-1 (metropolitan water) and 3 mg L-1 (bottled water). These quality parameters show that the proposed method improves the performance of conventional analytical methods used for the analysis of NO3-. This method has been applied successfully for determination of NO3- in metropolitan and bottled water from the Kingdom of Saudi Arabia; a total of 25 samples have been analyzed where NO3- was found to be present from levels below the limit of detection to 6.49 mg L-1.
Li, Y.T., Whitaker, J.S. and McCarty, C.L. (2011) Reversed-phase liquid chromatography/electrospray ionization/mass spectrometry with isotope dilution for the analysis of nitrate and nitrite in water. Journal of Chromatography A 1218(3), 476-483. Nitrate & nitrite A new method was developed for the analysis of nitrate and nitrite in a variety of water matrices by using reversed-phase liquid chromatography/electrospray ionization/mass spectrometry in the negative ion mode. For this direct analysis method, nitrate and nitrite anions were well separated under the optimized LC conditions, detected by monitoring m/z 62 and m/z 46 ions, and quantitated by using an isotope dilution technique that utilized the isotopically labeled analogs. The method sensitivity, accuracy, and precision were investigated, along with matrix effects resulting from common inorganic matrix anions. The isotope dilution technique, along with sample pretreatment using barium, silver, and hydrogen cartridges, effectively compensated for the ionization suppression caused by the major water matrix anions, including chloride, sulfate, phosphate, and carbonate. The method detection limits, based on seven reagent water replicates fortified at 0.01 mg N/L nitrate and 0.1 mg N/L nitrite, were 0.001 mg N/L for nitrate and 0.012-0.014 mg N/L for nitrite. The mean recoveries from the replicate fortified reagent water and lab water samples containing the major water matrix anions, were 92-103% for nitrate with an imprecision (relative standard deviation, RSD) of 0.4-2.1% and 92-110% for nitrite with an RSD of 1.1-4.4%. For the analysis of nitrate and nitrite in drinking water, surface water, and groundwater samples, the obtained results were generally consistent with those obtained from the reference methods. The mean recoveries from the replicate matrix spikes were 92-123% for nitrate with an RSD of 0.6-7.7% and 105-113% for nitrite with an RSD of 0.3-1.8%.



LC/MS Methods
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LC Methods
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Related Information: UMass LC/MS Instrument pages: Quattro Micro; Quattro Premier