DoE-based development and validation of an ion chromatography method for anion determination in drinking water

This research reports the development, optimization, and validation of a high-performance ion chromatography (IC) method for the simultaneous determination of fluoride, chloride, sulfate, and phosphate in drinking water. The study comparatively evaluated two anion-exchange columns (Dionex AS-20 and AS-09). Optimization was achieved through a 2^k factorial design, identifying the ideal conditions for mobile phase concentration, flow rate, and injection volume. To address the low concentrations typically found in potable water and enhance method sensitivity, a thermal preconcentration step was implemented at 90 °C, reducing detection limits (LOD) to 0.017-0.024 mg L^-1 and quantification limits (LOQ) to 0.058-0.081 mg L^-1. Analytical figures of merit demonstrated excellent linearity (r > 0.997) and high accuracy, with recovery rates ranging from 90% to 107% for both systems. The AS-09 column was selected for sample analysis due to its capacity for larger injection volumes. The method's applicability was successfully verified using real drinking water samples from different urban and domestic purification systems. The standard addition method confirmed the absence of significant matrix effects, with relative errors below 5%. This optimized IC method provides a robust, precise, and highly sensitive tool for monitoring inorganic anions, ensuring compliance with international water quality standards (WHO and COVENIN) and protecting public health against risks such as fluorosis or gastrointestinal disorders.