Determination of trace metal contaminants in a wide range of varied chemicals by means of the Technicon AutoAnalyzer

Abstract

The Technicon AutoAnalyzer has been applied to the routine determination of iron, copper, lead and zinc, in the range 0 to 10 p.p.m., in a heterogeneous range of 230 substances used in the photographic industry. Conventional colorimetric methods are used. To enable the same calibration standards to be used for all samples, organic and inorganic, it was necessary to devise standard procedures for pre-preparation of samples before introduction into the AutoAnalyzer in solution form. All samples are finally present in the form of a 10 per cent. w/v salt solution; organic samples are ashed, the ash extracted with dilute hydrochloric acid and the extract finally adjusted with sodium chloride to 10 per cent. w/v salt content. Insoluble samples are extracted with dilute hydrochloric acid and the extract similarly adjusted to 10 per cent, with sodium chloride. The intermediate wash solution consists of a 10 per cent. w/v sodium chloride solution. In this manner, variations caused by salt effects are minimised. Reproducibility is ±1 per cent.