UPLC-ESI/MS analysis of disinfection by-products (perchlorate, bromate, nitrate, nitrite and sulfite) in micro-filtered drinking water obtained from spring, well and tap water (desalinated) sources

Abstract

Objectives: In the current study, an analytical technique has been optimized for the analysis of disinfection by-products (perchlorate (ClO4−), bromate (BrO3−), nitrate (NO3−), nitrite and sulfite (SO32–) in drinking water obtained from spring, well and tap water (desalinated) sources. Methods: The ultra-performance liquid chromatography-electrospray ionization mass spectrometry (UPLC-ESI/MS) conditions have been optimized for oxyhalides ClO4− (isotopes, 37ClO4− and 35ClO4−) and BrO3− (isotopes, 81BrO3− and 79BrO3−), and inorganic anions NO3−, NO2− and SO32–. Separation was achieved by BEH C18 column with methanol (75%) and water (24.99%, HCOOH 0.01%) mobile phase at flow rate 0.2 mL/min. Results: The analysis was carried out in <1 min with excellent coefficient of determination, (R2 > 0.995–0.999), limit of detection (0.016–0.043 µg/L), limit of quantification (0.051–0.104 µg/L) and precision (repeatability, 1.54–2.28% and reproducibility, 3.13–4.08%) in terms of RSD%. The method was successfully applied, and the amounts of 35ClO4− (5.33–22.64 µg/L), 81BrO3− (7.52–16.73 µg/L), NO3− (5.42–12.14 mg/L), NO2− (1.08–4.37 mg/L) and SO32– (6.84–32.45 mg/L) were identified in spring water, whereas well and tap water contained 35ClO4− (4.20–21.33 µg/L), 81BrO3− (8.05–15.13 µg/L), NO3− (1.27–16.11 mg/L), NO2− (0.43–10.77 mg/L) and SO32– (7.14–36.10 mg/L), and 35ClO4− (0.89–7.37 µg/L), 81BrO3− (5.15–14.68 µg/L), NO3− (1.12–6.33 mg/L), NO2− (0.67–3.95 mg/L) and SO32– (5.40–23.26 mg/L), respectively. Conclusions: The levels of 35ClO4−, 81BrO3−, NO3−, NO2− and SO32– were found beyond the maximum contaminant levels and drinking water equivalent levels regulated by the Environmental Protection Agency, respectively. The outcomes also revealed that comparatively tap water produced lower levels of these contaminants especially in the cities with low population densities. In addition, the geographical site would be helpful to categorize the tap water samples.