Análise de cádmio e chumbo em bijuterias por espectrometria de absorção atômica por chama (F AAS) e voltametria de pulso diferencial (VPD)

Abstract

The metal analysis of various types of samples, using atomic absorption spectrometry, is well described in the literature. It is the most popular technique for this type of analysis; however the development of electroanalytical techniques for the analysis of metals has been growing in recent years. The electroanalytical techniques have the advantages of be able to determine low concentrations of metals, allow the simultaneous determination of these and have low cost compared to spectrometric techniques. Due to the increased concern for quality of metals for the manufacture of jewelry, the metal analysis is extremely important since high concentrations of these metals in the body, in particular toxic metals such as cadmium and lead can bring irreversible harm to health. In this context, the aim of this study was to analyse cadmium and lead in jewelry samples by differential pulse voltammetry (DPV) with pre-concentration step and compare the results with atomic absorption spectrometry with flame (F AAS). The parameters used for the analysis by differential pulse voltammetry were: deposition potential = -0.9 V, deposition time = 120 s and the potential range from -0.9 to 0.1 V. Two types of samples digestion were tested: hot plate and microwave equipment. After digestions, the samples were analyzed by both techniques (DPV and F AAS). Digestion by microwave proved most suitable, as well as voltammetry results that showed good accuracy, which was evaluated by adding and recovery studies with results from 99 to 110% for cadmium and 99 to 105% for lead. Samples of jewelry and analysed by the DPV digested microwave contained the <LOD to 4.05 % w / w cadmium and 0.004 to 7.55 % w / w of lead. The limits of detection were 0.75 mg L-1 for cadmium and 0.07 mg L-1 for lead for atomic absorption technique and limits of detection for voltammetry was 0.02 mg L-1 for cadmium, and 2.26.10-3 mg L-1 for lead.