No abstract

An analytical method has been developed for the determination of sulfur in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry (HR-CS GF MAS). The molecular absorbance of the carbon monosulfide molecule (CS), which is formed in the vaporization stage, has been measured using the rotational line at 258.033 nm. Several chemical modifiers were tested and Ru, applied as permanent modifier was chosen, because it exhibited the best performance. The optimum pyrolysis and vaporization temperatures were found to be 500 °C and 2200 °C, respectively. Aqueous standard solutions prepared from l-cysteine were used for calibration, as the linear regression obtained for this standard was not significantly different from that for a certified coal reference material (CRM) according to a Student t-test. The results obtained for sulfur in three coal CRM and six additional samples also showed no significant difference for the two calibration techniques according to the same statistical test. The sulfur concentration in the coal samples was found between 3.5 mg g(-1) and 33.7 mg g(-1) with a typical repeatability around 10%. The limit of detection for the direct analysis of solid coal samples was better than 0.1 μg S.

IntroduçãoO níquel é um elemento natural muito abundante no meio ambiente e pode ser combinado com outros metais, tais como ferro, cobre, cromo e zinco, para formar ligas [1]. A importância da determinação de íons de elementos de transição, tais como Ni(II), em amostras ambientais, é bastante enfatizada devido a sérios riscos que esses elementos causam ao sistema biológico. As principais fontes de Ni(II) em sistemas aquáticos são provenientes da dissolução das rochas e solos, ciclos biológicos, e especialmente de processos industriais [2]. Sabe-se que a inalação de compostos que Esses metais encontram-se, em geral, em concentrações-traço e por isso é necessário o desenvolvimento de métodos analíticos que possibilitem suas determinações quantitativas de acordo com os crescentes níveis de exigência das organizações governamentais.A espectrometria de absorção atômica em chama (F AAS) é uma das técnicas mais uti-

Recebido em 13/7/12; aceito em 18/2/13; publicado na web em 15/4/13 DEVELOPMENT OF AN ANALYTICAL METHOD FOR THE DETERMINATION OF HEXAVALENT CHROMIUM IN WATER SAMPLES BASED ON LIQUID-LIQUID MICROEXTRACTION WITH DETECTION BY FLAME ATOMIC ABSORPTION SPECTROMETRY. In this study, a method for determination of hexavalent chromium in aqueous samples using liquid-liquid microextraction (LLME) and detection by Flame Atomic Absorption Spectrometry (F AAS) was developed. The LLME procedure was based on the extraction of Cr (VI) by acetone at a sample pH of 1.2. The use of saturated ammonium sulphate solution allowed effective separation of the aqueous and organic phases and acetone extracted chromium. The sample pH, acetone volume and stirring time were optimized by a full factorial design.

Aluminum has been determined in body lotions after mixing with dilute nitric acid using graphite furnace AAS and Zr as a permanent modifier.