Desenvolvimento e aplicação de um sistema de geração fotoquímica de vapor para a determinação de Hg, Mn e Pb em bijuterias por ICP-OES

Abstract

Analytical techniques for identifying contaminants in imitation jewelry are a current and important issue, in addition to being a challenge due to the complexity of the sample matrix (composed mainly of metals in high concentration). Photochemical vapor generation (PVG) coupled to inductively coupled plasma optical emission spectrometry (ICP-OES) is a straightforward approach that can be applied for the determination of trace-elements in matrices such as those of imitation jewelry. Thus, an analytical method for the determination of Hg, Mn, and Pb in imitation jewelry samples. Our results demonstrated the formation of vapor from Hg and Pb, while Mn was determined by aerosol formation in the system. The PVG system was built with two UV-C germicidal lamps (15 W, 254 nm), a quartz capillary with 250 cm length, 2.5 mm internal diameter, 4 mm external diameter, and 11 mL internal volume, and a glass gas-liquid separator (GLS). The levels of the factors acetic acid concentration and UV exposure time were optimized using a central composite design (CCD) for the PVG system, as well as the carrier gas flow rate and the radiofrequency (RF) power for the ICP-OES. The optimum conditions were obtained at 30% v/v acetic acid, 60 s radiation exposure time, 0.02 L min-1 carrier gas flow rate, and 1200 W for RF power. The influence of the inorganic matrix of the sample was studied, where it was found that the presence of the major constituents in imitation jewelry may cause the suppression of the analytical signal for the analytes, probably due to the suppression of the formation of volatile species. To circumvent this effect, chemical modifiers were studied. The accuracy of the proposed method was evaluated by recovery tests, which ranged from 88 to 102%. The detection limits ranged from 1 to 3 mg g-1.