Highlighting the Biases Occurring in the Implementation of O-Dgt for the Sampling of 12 Hormones

Abstract

This work aimed to highlight the recommendations for Diffusive Gradients in Thin film (o-DGT) implementation through extension of the use to 12 natural and synthetic hormones belonging to three different families (estrogens, progestins and androgens). Since the adaptation of o-DGT in the laboratory can generate issues not only related to the analysis ( i.e. , presence of matrix effects) but also to the o-DGT configuration ( i.e. , undesirable sorption or desorption, lack of performance with insufficient elution or unreliable diffusion coefficient), a reliable strategy must be applied with the adaptation of o-DGT protocols. Thus, to avoid analytical issues due to the salts analysis, CaCl 2 exposure solutions, which result in fewer matrix effects, must be used on a lab-scale for hormones. In addition, due to the hormone’s sorption on several tested membranes, to the lower elution factors of the binding phases embedded in polyacrylamide gel and the greater variability of polyacrylamide gel diffusion coefficients, the selected o-DGT was composed of an Oasis® HLB binding gel and a diffusive gel in agarose, and a polycarbonate membrane. The elution factors of the binding gel were then from 0.79 ± 0.13 to 1.04 ± 0.13 (RSD < 15%) and the diffusion coefficients at 25 °C were from 4.07 ± 0.24 to 5.49 ± 0.28 x 10 6 cm 2 s -1 (RSD < 9%). A laboratory exposure to a synthetic solution containing hormones was performed to check the consistency with the DGT quantification model validating the calibration parameters for all hormones (except Ethinylestradiol with a quantification bias of 40%). Considering no risk of phase saturation, the o-DGT configuration is suitable for sampling hormones in the natural environment for a conventional deployment of 14 days with LOQ DGT ranging from 0.3 to 6.6 ng L -1 .

Keywords: Hormones, Passive sampling, o-DGT, Diffusion coefficients, Water monitoring