A method is described for the direct spectrophotometric determination of micro-amounts of tin, by extraction into a chloroform solution of 5,7-dichloroquinolin-8-ol from a solution containing sulphuric acid. The influence of the different experimental parameters on the formation and extraction of the complex were studied and optimum conditions for the determination of tin were established. The precision of the extraction-spectrophotometric procedure, expressed in terms of relative standard deviation, was 1.4%.
It is shown that two different complexes (with λmax. 403 or 390 nm) can be extracted into the chloroform, depending on the presence or absence of chloride and on the pH of the solution.
The method has been tested on six standard lead-based samples with tin contents ranging from 0.05 to 1%. The average relative error (mean error) of the results lies within the range ±1.4%, which shows that the accuracy is good and that systematic errors are absent.
