Amostragem de sólidos em espectrometria de absorção atômica de fonte contínua com alta resolução: análise de plantas medicinais

• Autor(a) principal: Rêgo, Jardes Figuerêdo do [UNESP]
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/108493
• topic: Quimica analitica; Plantas medicinais; Contaminação; Medicinal plants

Phytotherapy has increased considerably during the last years. However, besides active compounds, products derived from medicinal plants may contain hazardous organic compounds or toxic metals. Thus, the goal of this work was to develop methods to determine As, Cd, Co, Pb, Se and Sn in medicinal plants by high-resolution continuum source atomic absorption spectrometry using solid sampling. The use of chemical modifiers allowed the determination of the analytes of interest using calibration with aqueous standard solutions. An additional air-assisted pyrolysis step at 600 °C was useful to remove carbonaceous residues and eliminate background signal. Spectral interferences due to structured background caused by diatomic molecules (PO and SiO) were observed on the analytical lines of As, Cd, Co and Sn. In this case, interferences were removed using least squares background correction algorithm (LSBC). In addition, interactive correction background algorithm (IBC) was used to remove spectral interferences caused by Al lines on the analytical line of As. Limits of detection were 28.7 ng g-1 (As), 0.15 ng g-1 (Cd), 3.2 ng g-1 (Co), 7.3 ng g-1 (Pb), 40.1 ng g-1 (Se) and 24.5 ng g-1 (Sn). Micro-homogeneity studies were performed after using knife or cryogenic mills in order to establish minimal sample mass and homogeneity. Most accurate and precise results were obtained for sample masses above 0.2 mg for samples ground using knife mill with 30 mesh sieve or cryogenic mill. Accuracy and precision were evaluated by analyzing plant certified reference materials and results were in agreement with certified values at a 95% confidence level (t test). The proposed methods were applied for the determination of analytes in eighteen medicinal plant samples. The concentration ranged from 3.2 to 287.2 ng g-1 (Cd), 14.7 to 1195.7 ng g-1 (Co), 124.2 to 1946.1 ng g-1 (Pb) and 142.8 to 342.6 ng g-1 (Sn). Results were in agreement at a 95% confidence level...