Measurement of Dissolved Reactive Phosphorus in Water with Polyquaternary Ammonium Salt as a Binding Agent in Diffusive Gradients in Thin-Films Technique

Diffusive gradients in thin-films (DGT) sampler with a polyquaternary ammonium salt (PQAS) aqueous solution as a binding phase and a dialysis membrane as a diffusive phase (PQAS DGT) was developed for the measurement of dissolved reactive phosphorus (DRP) in water. The performance of PQAS DGT was not dependent upon pH 3-10 and ionic strength from 1 x 10(-4) to 1 mol L-1. The effective binding capacity of PQAS DGT containing 2.0 mL of 0.050 mol L-1 PQAS solution was estimated as 9.9 mu g cm(-2). The measurement of DRP in a synthetic solution by PQAS DGT over a 48 h deployment period demonstrated high consistency with the concentration of DRP in the synthetic solution measured directly by the ammonium molybdate spectrophotometric method. Field deployments of PQAS DGT samplers allowed for accurate measurement of the DRP concentration in situ. The advantages of PQAS DGT include no requirement of the elution steps and direct concentration measurements of the binding phase.