Hydrophilic anions analysis using reversed phase chromatography coupled with evaporative lightscattering detection

A Liquid Chromatography (LC) method using volatile ion pairing agents and Evaporative Light Scattering Detector (ELSD) was developed. The separation of a series of three common inorganic anions (Cl-, NO3- and SO42-) and three organophosphonic anions (Methyl, ethyl and propylphosphonic acids) was achieved on a reversed-phase C-18 column with pentylammonium or heptylammonium formiate as ion pairing agent. This method provides good linearity of the calibration curve and enables a limit of detection to be reached of 4 mg/L and 3.12 mg/L for alkylphosphonic anions and inorganic anions respectively. The separation for methyl and ethylphosphonic acids, which are poorly resolved in the LC systems commonly used, was successfully achieved.