An Investigation of Three Methods for the Determination of Sub-Micromolar Ion Concentrations in Water.

摘要

Two methods were studied for the sampling,concentration,or determination of trace metal ions at submicromolar levels. (1) Trace ions in a sample donor solution are concentrated by loading upon a pellicular ion exchanger,and these are eluted or stripped into an acceptor solution at an enhanced concentration level so that they can be more easily measured. In studies with Cu(II),enhancements up to 64-fold have been obtained that are in accord with the theoretical Donnan enhancement. Times required are reasonable,being about a half hour for the loading step and about five minutes for the stripping step. Equipment and procedure are being designed to permit estimations of copper ion concentration or activity (speciation) in the field. (2) With sample solution flowing through two tubular electrodes in series,trace metal ions may be deposited cathodically at the upstream electrode,and then stripped off by scanning the upstream electrode toward anodic potentials. With the proper control of conditions,and with the downstream electrode maintained at a constant cathodic potential,collector currents due to metal ions stripped from the upstream electrode can be measured at the downstream electrodes and used for estimating the trace metal ion concentration in the original sample solution.