Novel, Rapid, and\nSimple Isocratic UPLC-UV Method\nfor Estimating Nitrate and Nitrite Contents in Environmental Water\nSamples Using an Analytical Quality by Design Approach

In this study, we\nreported a novel reverse-phase UPLC\nmethod for\nthe simultaneous estimation of nitrite and nitrate ions using a Quality\nby Design (QbD) approach. Nitrite and nitrate ions were separated\non an ACQUITY CSH Fluoro-Phenyl column (100 × 2.1 mm, 1.7 μm)\n in isocratic mode with a mobile phase composition of solvent A and\nsolvent B in a ratio of 980:20 v/v. Solvent A consisted of 100% Milli-Q\nwater, while solvent B comprised 0.5 mL of formic acid in 1000 mL\nof methanol. The column temperature was maintained at 40 °C,\nand the flow rate was 0.6 mL/min. Detection was carried out at 214\nnm with an injection volume of 5.0 μL. The method was developed\nand validated in accordance with ICH Q2 (R2) guidelines Validation\nparameters, including system suitability, sensitivity, precision,\nlinearity, and accuracy, were within acceptable ranges. These findings\nsuggest that the developed RP-UPLC method is highly sensitive and\nsuitable for the estimation of nitrite and nitrate ions in various\nenvironmental water samples.