Determination of zinc (II) in lubricant oils by stripping chronopotentiometry

A method for the determination of zinc (Il) in lubricant oils by stripping chronopotentiometry is described. The only necessary sample pretreatment was the extraction of zinc (II) from the corresponding alkyl derivatives by hot concentrated hydrochloric acid in a suitable extractor. The metal ions were concentrated as the corresponding metals on a glassy carbon working electrode and then stripped by a suitable oxidant. Quantitative analysis was carried out by the method of standard additions; a good linearity was obtained in the range of concentrations examined. Recoveries of 94 % were obtained from a lubricant oil spiked at different levels. The detection limit was 0.02 mg g-1 and the coefficient of variation (mean of nine deterrninations) was 5.2%. Results obtained on commercial lubricant oils were not significantly different from those obtained by atomic absorption spectrometry.