Determination of microgram amounts of platinum as dithizonate in the presence of palladium by second-derivative spectrophotometry

Abstract

A derivative spectrophotometric method, based on digitised secondśderivative absorption spectra, has been developed for the determination of trace amounts of platinum in the presence of palladium (<1 mg), using their dithizonates in carbon tetrachloride. Comparison of the first-, second- and third-derivative spectra revealed that the best conditions for the determination of Pt were obtained using second-derivative spectrophotometry in the range 20 000–19 000 cm^–1(500–526 nm). No interference from Pd in the determination of 0.1–2 µg of Pt at 19 510 cm^–1(513 nm) was observed when the zero-crossing measurement technique was applied. Good precision and increased sensitivity were attained by a suitable choice of instrument parameters (wavelength scale expansion, scanning speed and integration time) and also by smoothing and recording of multiple spectra. The method was applied to the determination of trace amounts of Pt (about 1 × 10^–4%) in preparations of palladium chloride (after preliminary separation of most of the Pd) with good precision and recovery.