Separation of oxyanions of phosphorus by single column ion chromatography

Separation of mixtures containing hypophosphite, phosphite, orthophosphate, chloride, nitrate and sulphate ions has been achieved using a Vydac 300 IC 405 column, refractive index detection and eluents which were 2mM in p-hydroxy benzoic acid or 4mM in p-amino benzoic acid (adjusted to ph 5.5). Calibration curves were linear over the concentration range 3 to 30 mg P/l.; and the precision (RSD for peak heights in mixtures) was < +/- 10%. Using p-hydroxy benzoic acid, detection of eluted peaks by indirect UV absorption was equally satisfactory. In an initial survey, the elution behaviour of nine oxyanions of phosphorus (simple ions and condensed species) was examined, using eluents containing different organic carboxylic acids (six aliphatic and nine aromatic), present at levels of 1 to 5m(M); with the pH adjusted to values between 3 and 8.6. No suitable conditions for separating mixtures containing condensed phosphates were identified.