Improving elution strategies for Chelex®-DGT passive samplers

Abstract

Elution of Chelex® binding layers, commonly used for the diffusive gradients in thin films technique (DGT), is recognized as the most important contributor to the uncertainty of DGT measurements. Limiting uncertainty requires the use of optimized procedures and suitable elution recoveries (f ). This work therefore investigated elution robustness to propose improved strategies. A wide range of conditions were investigated for the main elution parameters (Chelex® particle size, elution time, Chelex® loading, and eluent concentration and volume) on Al(III), Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II). Results showed that the choice of elution conditions should be a compromise driven by study constrains in terms of accuracy, repeatability, sensitivity, and targeted elements. Using experimentally determined recoveries should improve accuracy by approximately 5 to 10% compared to the use of recoveries from the literature. Fast elution of 1 h can be achieved without significant loss of recovery and repeatability except for Cr(III) (8 h minimum). Elution recovery depended on Chelex® loading for Zn and Cr and introducing recoveries adapted to the loading could improve accuracy up to, respectively, 11 and 27%. When standard recoveries are used, a 0.85 f value would be more appropriate than the common value of 0.8 to minimize inaccuracy (except for Cr). Some flexibility can be applied to elution conditions without a significant change in recovery for most elements: HNO concentration of 1-15 M, volume of 1-2 mL, duration of 8-48 h. Cr(III) was unique in its sensitivity to elution condition variations; thus, choice is more restricted for this element. Graphical abstract Decisional tree for choosing elution procedure and recoveries for Chelex®-DGT.

Aluminum sampling by Chelex, titanium dioxide and zirconium oxide DGT: Influence of pH on accumulation behaviors

“…The Chelex and titanium dioxide binding gels were purchased from DGT Research Ltd. The zirconium oxide binding gels were prepared according to the protocol used by Devillers et al (2017). The DGT devices were assembled using plastic holders (DGT Research Ltd.) enclosing a binding gel, a polyacrylamide diffusive gel (0.78 mm thick, DGT Research Ltd.) and a polycarbonate filter membrane (0.4 µm pore diameter, 0.01 mm thick, Whatman).…”

“…An elution yield of 0.84 was used for the Chelex binding gels according to Panther et al (2012) and Devillers et al (2017). The elution yield for the titanium and zirconium oxide binding gels were determined since the protocols were adapted from Bennett et al (2010) and Ding et al (2016), respectively.…”

Evaluation of diffusive gradients in thin films (DGT) technique for speciation of trace metals in estuarine waters - A multimethodological approach

“…Effective diffusion coefficients (determined in separate controlled experiments; see next section) operational for brackish/seawater conditions were used for all calculations. According to Devillers et al (2017a) a common elution factor of 0.8 was found to be slightly underestimated and they recommended a value of 0.85 (Devillers et al, 2017a). However, in order to be comparable to other studies, a value of 0.8 was used.…”

Assessment of the DGT technique in digestate to fraction twelve trace elements

“…Then 150 the concentration of trace elements in the eluents (C e ) were quantified by the inductively coupled 151 plasma mass spectrometry (ICP-MS) or microwave plasma atomic emission spectroscopy (MP-152 AES) (see section 0). The accumulated mass is determined according to equation (1) [15]: 153 , Eq. (1) 154 where V e is the volume of the eluents (2 mL) and f e is the elution factor (values are reported in 155 Table S3).…”