[Square-wave polarographic determination of tin in products of the food processing industry]

A square-wave polarographic method suitable for measuring tin in canned products and raw materials for food industry was examined. After wet digestion of the sample tin was directly determined from the acidic stock solution gained. If 10 ml of the stock solution was equivalent to 1 g sample,--varying sensitivity of the instrument--tin could be determined in the range of 5 micrograms/g--400 micrograms/g with +/- 5% relative error. By increasing sensitivity of the instrument this range could be extended to as little as 0,5 micrograms tin/g sample. The optimal quantity of hydrochloric acid to be added to the sulphuric acid solution of the digested sample before the instrumental measurement was determined by means of model solutions. Examinations concerning interference of lead were also performed. It is established, that if the ratio of Sn/Pb is at least 4/1, lead does not interfere with the polarographic tin determination. If the ratio of Sn/Pb is 2/1 or 1/1 tin content can be calculated after measuring the height of the peak of lead in sulphuric acid electrolyte. The method was applied for several canned products and comparative tests were performed with the spectrophotometric method given in the Hungarian standard MSZ 3612/7-77.