Determination of sulfur in coal using direct solid sampling and high-resolution continuum source molecular absorption spectrometry of the CS molecule in a graphite furnace

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.

Determination of sulfur in crude oil using high-resolution continuum source molecular absorption spectrometry of the SnS molecule in a graphite furnace

“…carbon-rich flame [13,14]. However, this molecule is not that promptly forming within a graphite furnace, depending on the type of sample, maybe due to the presence of oxidizing acids in the matrix or because of competitive reactions, such as the formation of the extremely volatile carbon disulfide CS 2 that can be volatilized in the pyrolysis stage before the measurement [18]. Because of these problems, it was considered important to find another molecule that is stable at high temperatures and the formation of which does not depend on carbon as moleculeforming reagent.…”

“…Resano and Flórez [17] investigated the potential of direct solid sample analysis for sulfur monitoring in different certified reference materials using Pd nanoparticles in combination with Ru as a permanent modifier. Mior et al [18] described a procedure for the determination of sulfur in coal with Ru as permanent modifier using direct solid sample analysis in a GF. Also for the same molecule, Nakadi et al [19] performed the determination of sulfur in coal and ash using slurry sampling without a chemical modifier, and in diesel [20] applying palladium nanoparticles as a chemical modifier.…”

Study on Quantitative Structure-Retention Relationships (QSRR) for Oxygen-Containing Organic Compounds Based on Gene Expression Programming (GEP)

“…The set of optimal parameter values were listed in Table 2 and the predicting results of test set on OV-1 and SE-54 were listed in Figures 1 and 2. It can be seen from the figures that the predictive values of gas chromatography retention index of oxygen-organic compounds applications of ANN have been adequately described elsewhere [7][8][9][10]. Extensive use of ANN, which has inherent ability to incorporate nonlinear and cross-product terms into the model and does not require prior knowledge of the mathematical function as well, largely rests on its flexibility and less sensitivity to collinearity among variables.…”

Determinação de metais por técnicas de espectrometria atômica em amostras de carvão mineral e cinzas utilizando metodologia de superfície de resposta

“…8,9 Além dessas possibilidades na decomposição de amostras sólidas (como carvão e cinzas), existem alternativas que também apresentam bons resultados, entre elas estão as extrações ácidas assistidas por ultrassom ou micro-ondas, 10,11 obtenção de suspensões, [12][13][14][15] ou determinação direta em amostragem sólida. 16,17 Porém, na maioria dos casos, com o uso das suspensões e amostragem sólida se faz necessário uma instrumentação apropriada para a introdução da amostra, com detectores e sistemas de correção de fundo de alta resolução, a fim de corrigir possíveis erros provocados por interferências associados à presença da matriz da amostra durante a análise.…”

“…8,9 Além dessas possibilidades na decomposição de amostras sólidas (como carvão e cinzas), existem alternativas que também apresentam bons resultados, entre elas estão as extrações ácidas assistidas por ultrassom ou micro-ondas, 10,11 obtenção de suspensões, 12-15 ou determinação direta em amostragem sólida. 16,17 Porém, na maioria dos casos, com o uso das suspensões e amostragem sólida se faz necessário uma instrumentação apropriada para a introdução da amostra, com detectores e sistemas de correção de fundo de alta resolução, a fim de corrigir possíveis erros provocados por interferências associados à presença da matriz da amostra durante a análise.De acordo com a American Society for Testing e Materials (ASTM), para a caracterização das amostras de carvão por técnicas de espectrometria atômica recomenda-se inicialmente uma etapa de calcinação seguida por digestão das cinzas resultantes com uma mistura de água régia e posterior dissolução em ácido nítrico ou o ácido fluorídrico. Em alguns casos, a amostra também pode ser dissolvida com ácido nítrico ou com uma mistura de ácido clorídrico/fluorídrico seguido do uso do ácido bórico.…”