Metodologia para a determinação de cádmio, cromo e chumbo em tinturas fitoterápicas por análise direta em gf aas

Abstract

In this work, herbal tinctures from Cynara scolymus L, Rhamnus purshiana DC, Maytenus officinalis Mabb and Mikania glomerata Spreng, (Artichoke, Cascara Buckthorn, Espinheira Santa and Guaco, respectively) prescribed by the Brazilian public health system (SUS), had their levels of Cd, Cr and Pb determined through direct analysis by graphite furnace atomic absorption spectrometry (GF AAS). Acid digestion assisted by microwave radiation was used as sample preparation to evaluate the proposed method efficiency, which showed no significant differences between the proposed and reference methods. Figures of merit were obtained to both methods and the values found were in agreement with literature. The accuracy for direct analysis were evaluated and the recovery levels obtained were suitable (102 and 109% to Cr, 104 and 112% to Cd, 92 and 111% to Pb), as well as the precision in terms of repeatability (with relative standard deviation under 10% to the three analytes). The proposed method also showed appropriate limits of detection for trace elements analysis, with values (in µg Kg-1 ) of 0.5, 1.3 and 1.6 to Cd, Cr and Pb, respectively. No significant matrix effect were observed and, therefore, external calibration was used for purposes of prevision, which constitutes an important advantage of the developed method, considering routine applications. Through herbal tinctures preparation from the correspondent medicinal plants, the transference of these inorganic contaminants were also evaluated, with Cd transferring up to 120%, Cr up to 19% and Pb up to 88% of the metal present in the raw material until the final product. Twenty-one herbal tinctures commercial samples were evaluated, being possible to detect the presences of Cd, Cr and Pb in some of them. The levels varied from 0.76 to 40.80 µg Kg1, from 4.45 to 21.40 µg Kg-1 and from 22.26 to 88.47 µg Kg-1 to Cd, Cr and Pb, respectively. The levels of these contaminants, considered toxic to human being, were under the maximum allowed limit by World Health Organization (WHO). Direct analysis had favorable results for the determination of inorganic contaminants by GF AAS, showing great analycitcal frequency, and decreased use of chemical reagents and energy.