Ultrasensitive and selective measurements of tin by adsorptive stripping voltammetry of the tin-tropolone complex

Trace levels of tin can be determined by voltammetry after controlled adsorptive preconcentration of the tin-tropolone complex on a hanging mercury drop electrode. The resulting adsorptive stripping procedure offers better sensitivity and selectivity than conventional stripping methods for tin. Optimal conditions include 4 x 10(-6)M tropolone in a stirred acetate buffer (pH 4.0), a preconcentration potential of -0.40 V, and differential-pulse stripping. For an 8-min preconcentration period, the detection limit is 2.3 x 10(-10)M (28 ng/l.). Linear calibration plots of i(p)vs. C are obtained at low concentrations, with linear plots of 1/i(p)vs. 1/C at high concentrations. The relative standard deviation (at the 6-mug/1. level) is 2.6%. The response is not affected by the presence of lead, cadmium, indium and thallium, which commonly interfere severely in analogous anodic stripping measurements. Results are reported for river and orange-juice samples.