Spent coffee grounds (SCG) immobilized in agarose gel are proposed as a novel binding agent for application in the Diffusive Gradients in Thin films (DGT) technique for the determination of Cd, Cu, Ni, Pb and Zn in waters. The SCG-agarose gel was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry and Porosimetry by nitrogen adsorption. Elution of analytes from the binding agent was effectively performed with 2 mol L−1 HCl. The effects of key DGT parameters (e.g. immersion time, ionic strength and pH) were evaluated with a deployment of DGT devices (DGT-SCG) in synthetic solutions with ionic strengths between 0.005 mol L−1 and 0.1 mol L−1 and within a pH range of 3.5–8.0. The results were in excellent agreement with the predicted theoretical curve for mass uptake. Consistent results were found for solutions with ionic strengths between 0.005 mol L−1 and 0.1 mol L−1 and within a pH range of 3.5–8.0. The DGT-SCG performance was also evaluated in two spiked river water samples (Corumbataí and Piracicaba river) with satisfactory uptake values (CDGT-SCG/Csol) between 0.74 and 1.53. The proposed DGT-SCG opens opportunities for using residual biomass as binding phase in the DGT technique, showing low costs in production and complying with “green” technology approaches.
Yabuki, L. N. M., Menegário, A. A., Gemeiner, H., Rolisola, A. M. C. M., Gastmans, D., & Williams, P. N. (2019). Residual biomass of coffee as a binding agent in diffusive gradients in thin-films technique for Cd, Cu, Ni, Pb and Zn measurement in waters. Talanta. https://doi.org/10.1016/j.talanta.2019.120148