The use of a polymer inclusion membrane for separation and preconcentration of orthophosphate in flow analysis

Abstract

A highly sensitive flow analysis system has been developed for the trace determination of reactive phosphate in natural waters, which uses a polymer inclusion membrane (PIM) with Aliquat 336 as the carrier for on-line analyte separation and preconcentration. The system operates under flow injection (FI) and continuous flow (CF) conditions. Under optimal FI conditions the system is characterised by a linear concentration range between 0.5 and 1000μgL−1P, a sampling rate of 10h−1, a limit of detection of 0.5μgL−1P and RSDs of 3.2% (n=10, 100μgL−1) and 7.7% (n=10, 10μgL−1). Under CF conditions with 10min stop-flow time and sample solution flow rate of 1.32mLmin−1 the flow system offers a limit of detection of 0.04μgL−1P, a sampling rate of 5h−1 and an RSD of 3.4% (n=5, 2.0μgL−1). Interference studies revealed that anions commonly found in natural waters did not interfere when in excess of at least one order of magnitude. The flow system, operating under CF conditions, was successfully applied to the analysis of natural water samples containing concentrations of phosphate in the low μgL−1P range, using the multipoint standard addition method.