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

Abstract

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 × 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 μg 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.

Sampling of ammonium ion in water samples by using the diffusive-gradients-in-thin-films technique (DGT) and a zeolite based binding phase

“…Binding layer is the most important part of DGT technique. Many kinds of sorbent were developed as the binding layer, such as Chelex 100 for 24 elements [9], ferrihydrite for 6 oxoanions [10,11], Sodium polyacrylate and polymer-bound Schiff base for Cu 2+ and Cd 2+ [12,13], molecularly imprinted polymer for 4-chlorophenol [8], polyquaternary ammonium salt for phosphorus [14], and so on. However, there has been little focus on DGT-measurement for nitrogen nutrition (ammonium).…”

Diffusive gradients in thin films: devices, materials and applications

“…In addition, Fe 3 O 4 nanoparticle aqueous suspensions (Fe 3 O 4 NPs) have been applied as liquid binding phases in DGT measurement of DRP concentrations and As species (Liu et al 2016;Zhang et al 2018a). Furthermore, polyquaternary ammonium salt (PQAS) aqueous solutions have also been applied as the liquid binding phase in DGT systems, to monitor the concentration of DRP in water, with effective performance within pH range of 3-10 and at ionic strengths of 10 −4 -1 M (Chen et al 2014b). Qin et al (2018) used Zr-based metal-organic frameworks (MOFs, UiO-66) as liquid binding agent for DGT measurement of P (UiO-66 DGT), and good agreements were obtained between the concentrations measured by DGT and in waters (C DGT /C sol : 0.9-1.1).…”

Effect of Biofilm on Passive Sampling of Dissolved Orthophosphate Using the Diffusive Gradients in Thin Films Technique

“…Therefore, orthophosphate is preferably determined by the in situ passive sampling device–diffusive gradients in thin films technique (DGT). To date, four kinds of binding agents, ferrihydrite, titanium dioxide (Metsorb), zirconium oxide (Zr oxide), and polyquaternary ammonium salt (PQAS), have been used to accumulate orthophosphate. However, along with soluble orthophosphate, several organic P compounds and long-chain polyphosphates were misidentified as dissolved orthophosphates using the ferrihydrite-based DGT device and Zr oxide-based DGT device, which caused over estimation of orthophosphate. , …”