Performance characteristics of suspended particulate reagent iminodiacetate (SPR-IDA) as a binding agent for diffusive gradients in thin-films.

Warnken, Kent W. and Zhang, Hao and Davison, William (2004) Performance characteristics of suspended particulate reagent iminodiacetate (SPR-IDA) as a binding agent for diffusive gradients in thin-films. Analytica Chimica Acta, 508 (1). pp. 41-55. ISSN 0003-2670

Abstract

The performance characteristics of an alternative binding agent, suspended particulate reagent-iminodiacetate (SPR-IDA), for use with DGT methodology were investigated. The parameters investigated during this study included gel hydration, blank levels, elution factor (fe), capacity, the effects of pH on the binding of trace metals by DGT. The novel application of this resin for use as a quantitative standard for laser ablation ICP-MS was also evaluated. To further constrain the results for the SPR-IDA binding agent, parallel experiments were performed using resin gel containing Chelex 100, which has been widely reported in the literature. Hydration results showed that the SPR-IDA resin gel reached a stable dimension and weight within 30 min and was dimensionally stable for ≤6 months. The measured DGT blanks for the SPR-IDA resin were 0.0023, 0.15, 0.21, 0.0033 and 0.011 ng disc−1 for Co, Ni, Cu, Cd and Pb, respectively. The elution factor differed for the two resin types with the Chelex 100 recoveries slightly lower than previous reports and the SPR-IDA resin showing on average 5–9% better recoveries than DGT containing Chelex 100. The measured capacity of DGT discs containing the SPR-IDA binding agent was 0.26 mg Cd, similar to the calculated value of 0.29 mg Cd, indicating the entire resin layer was available for metal uptake. Both resin types performed equally well when deployed in 1 mM NaNO3 solutions with DGT measurements of 100% of direct solution measurements for Co, Ni and Cd. However, DGT measurements of Cu and Pb systematically decreased with increasing solution pH down to 50% of solution values at pH 8.0, due to artifacts resulting from colloid formation during the addition of the metals. This was remedied by adding the metals as dilute salt standards and addition of Mg(NO3)2 to eliminate adsorption to the container walls. In the latter experiments, DGT measured concentrations of Co, Ni, Cu, Cd and Pb were in agreement with solution concentrations. Deployment of DGT in solutions with increasing concentrations of trace metals yielded linear results, suggesting that quantitative analysis using simplified laser ablation techniques should be possible using this newly characterized SPR-IDA resin gel.