Comparison of Two Methods for Determining Heavy Metals by Touch-AnalysisAccording to the European Pharmacopoeia

Heavy metals are part of our daily lives, and in our everyday activities, they can be incorporated into products through catalysts, synthesis agents, or the manufacturing process itself. Heavy metal analysis according to the European Pharmacopoeia is a common semi-quantitative test performed in quality control laboratories. The objective of this work is to determine the sensitivity of each of the heavy metal determination methods: the spot test and the assay method according to the European Pharmacopoeia, and to study the interchangeability of these two methods in pharmaceutical quality control laboratories. The detection of heavy metals (Pb, Hg, Cd, Al) according to the European Pharmacopoeia is performed by comparing the color obtained to the color of a freshly prepared standard solution of well-defined concentration. Spot test, on the other hand, is a semi-quantitative method that uses reactions accompanied by a color change in the solution. The reactions are performed on filter paper. Based on the color, the presence or absence of the target ion in the solution being studied is determined at a given concentration by comparison to a standard solution of known concentration. The determination of heavy metals using both methods yielded comparable results with the same limit of detection for all metals tested (1 pbm). The results obtained with the touch-analysis led to the conclusion that this technique is specific, semi-quantitative, rapid, and less expensive than the method listed in the European Pharmacopoeia, with acceptable sensitivity (lead 2 pbm, mercury 2 pbm, cadmium 1 pbm, aluminum 1 pbm). It allows for the determination of the four main heavy metals, whereas the European Pharmacopoeia method is limited to lead. It therefore constitutes an alternative for the determination of heavy metals when reagents are unavailable and/or rapid results are required.