An ultra performance liquid chromatography-electrospray ionization-mass spectrometry method for the rapid analysis of nitrate in drinking water

Abstract

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 C₁₈ (50 mm × 2.1 mm i.d., 1.7 μm 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 μg L⁻¹; linearity (r² > 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 μg 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.