Agarose Cleaning Optimization for DGT Devices Specific for Cesium

Agarose gels commonly used in electrophoresis are regularly checked by its manufacturers for the absence of contaminating nucleases or residual sulfates. It is also tested for several metals and trace elements: Pb, Cd, Co, Cu, Zn, K, Ca, Cr Mg, Mn, Fe, Ni, Na, and Cl. However, no data are available for Cs-impurity measurements. A Diffusive Gradients in Thin films (DGT) device specific for cesium (Cs) is intended to be developed. Therefore, it is important to assess the impurity degree of agarose with Cs. Direct dissolution of agarose in 4 mol�L^-1 HNO<inf>3</inf> gives a concentration of 2.1?10^-8 mol�L^-1 of Cs, which is higher than that is found in natural environments (e.g. Cs<1?10^-8 mol�L^-1 in water). Two methods of Cs impurity removal have been tested, involving acidic cleaning with HCl and extraction by exchanger resin (KCuFC). Agarose powder was mixed with HCl in different concentrations, rinsed and dried. This method shows that the HCl-cleaning method is not quite efficient in removing the Cs impurity compared to untreated agarose gel. The second method, KCuFC resin was mixed with agarose powder in ultra-pure water, heated afterwards, and filtered. This method was able to reduce the amount of Cs by 99% compared to the untreated agarose gel. It appears that acceptable Cs levels (i.e. with respect to ambient Cs concentration in natural waters) are achievable by the removal of preexisting Cs in the agarose powder.