Sequential injection determination of orthophosphate as ion associate of 12-molybdophosphate with Astra Phloxine
Abstract
A simple and fast reaction between 12-molybdophosphate heteropoly anion and the polymethine dye Astra Phloxine was used for the development of a new SIA method for the determination of orthophosphate. The suggested method has higher sensitivity and a broader calibration range than existing SIA methods.
It can be used to detect phosphate in the range from 0.2 to 10 mu mol L(-1) with a detection limit of 0.1 mu mol L(-1) and an acceptable throughput of 20 samples h(-1). The comparably low molybdate (5.6 mmol L(-1)) and dye (0.1 mmol L(-1)) concentrations led to an improvement in the stability of the base line.
Inter-day reproducibility was better than 5%, while the intra-day RSD was in the range 0.8-3.5%. The method was used for the analysis of natural water samples and phosphorus-containing chemicals having a low content of orthophosphate.