Comments on “Determination of total arsenic using a novel Zn-ferrite binding gel for DGT techniques: Application to the redox speciation of arsenic in river sediments” by Gorny et al.

Passive sampler measurements of inorganic arsenic species in environmental waters: A comparison between 3-mercapto-silica, ferrihydrite, Metsorb®, zinc ferrite, and zirconium dioxide binding gels

“…DGT techniques appear to be an interesting alternative for studying As speciation in river sediments compared to traditional ex situ approaches consisting in extracting porewater samples in several steps under nitrogen atmosphere. Bennett and co-workers [1] commented on our previous works describing a new DGT method using a zinc ferrite (ZnFe2O4) binding gel for the determination of total arsenic (As) at low concentration in the sediments of the Marque River, northern France [2]. In that study, the DGT performances of the ZnFe2O4 binding gel were compared to that of the ferrihydrite (Fh) and…”

“…Metsorb ® binding gels. Bennett and co-workers [1] pointed out several issues in the analytical development and in the validation of the new ZnFe2O4-DGT method.…”

“…We have also studied the possible interferences of the binding gels with carbonates, as Panther et al [10]had observed that this species interfered more with the accumulation of phosphates [chemical analogue of As(V)]on the FeOOH binding gel than on the Metsorb ® . As suggested by Bennett and co-workers [1], time-series accumulation experiments have now been performed to rule on the assumption that iron(III)-based binding gels are more susceptible to interference with carbonates, especially in sediment porewaters.…”

“…The amount of analyte adsorbed to the binding gel (%) is calculated from the initial mass of dissolved species in the deployment solution (Mi, µg), and the mass of dissolved species remaining in solution after the experiment (Mf, µg). Adsorption = M − M $ M Eqn 4In addition, investigations of the possible interactions with H3BO3were performed under similar experimental conditions than for the reduced species (except operations under nitrogen atmosphere).These batch experiments are performed to confirm whether or not the use of borate buffer could potentially reduce the accumulation performances of the binding gels as suggested in the comments of Bennett and co-workers[1].…”