Possibilities for the automated determination of trace concentrations of uranium in water samples by adsorptive stripping voltammetry

The paper describes the development of two different techniques for the automated determination of uranium by adsorptive stripping voltammetry (AdSV). As a complex forming reagent 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid) is used. The automation was performed in one case using an auto-batch system and in the second case by means of a flow-through cell. Sensitivities, reproducibilities and the fields of application are evaluated. The auto-batch technique, with the automatic standard addition capability as well as its logical decision-making capacity for selecting the correct type of working electrode makes it highly suitable for the determination of varying uranium concentrations above 1 mu g/l. The dilution of the sample, required by the methodology, makes determinations of uranium concentrations less than 1 mg/l unattainable. The flow-through technique is more suited to determine uranium at the ultra trace concentration level (above 70 ng/l). Provided the matrix is reasonably constant, a pre-determined calibration curve can be used and, due to the higher slope of the calibration plot in the flow-through technique, the linear concentration range extends to a lower concentration compared to stationary conditions. Another advantage of the flow-through technique is the possibility of kinetic and mechanistic investigations of AdSV procedures.