Separation and determination of chlorine as chloride in neodymium-praseodymium oxalate by pyrohydrolysis and ion chromatography

A method based on the pyrohydrolysis extraction of chlorine as chloride followed by its quantification with ion chromatography (IC) was proposed for Neodymium Praseodymium Oxalate (Nd-Pr-Ox). Optimum pyrohydrolysis conditions for separating chlorine from Nd-Pr-Ox were reported. Pyrohydrolysis was carried out with moist O₂ at 900℃ for 60 minutes and the recovery of chlorine was more than 95%. Chloride present in the pyrohydrolysis distillate was separated from other common anions on an anion exchange column using 8 mM bicarbonate mobile phase. Method was calibrated between 0.5 and 50 ppm of chloride with a linear coefficient value of 0.9997. LOD of chloride in IC method was 0.005 ppm whereas the detection limit for the pyrohydrolysis cum IC combined method was found to be 0.3 ppm. Reproducibility was better than 1% (RSD) at 0.1 ppm of chloride. (author)