Indirect Determination of Phosphate, Silicate, and Arsenate by HPLC-AES

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Abstract
The indirect determination of phosphate, silicate, and arsenate is performed by separation of their heteropoly acids by using ion-pair reverse-phase HPLC (IP-RPHPLC) and monitoring the molybdenum emission from a DCP with an echelle spectrometer and a charge-injection device (CID) detector. Limits of detection found for phosphate, silicate, and arsenate are 26, 31, and 52 ng/mL, respectively. The detection limit for arsenate is slightly degraded due to its proximity to the excess molybdate peak. These results represent an improvement in the determination for these nonmetals over results for direct aspiration into an emission source and show excellent linearity over three orders of magnitude.