Determinação de boro em amostras de carbeto de silício utilizando piroidrólise e ICP-OES

Abstract

In this work a procedure for boron determination in samples of silicon carbide by pyrohydrolysis and detection by inductively coupled plasma optical emission spectrometry was developed. The silicon carbide samples were also decomposed by microwave assisted wet digestion in closed vessels and alkaline fusion. However, complete digestion was not observed under the conditions used for wet digestion and for fusion. Regarding the proposed pyrohydrolysis procedure important variables were initially investigated such as: oven temperature, air and water flow rate, sample mass, reaction time and use of accelerator. Spectral interference promoted by tungsten was observed during the studies and the selection of suitable emission lines for B determinations should be carried out. Sample mass of 200 mg, use of 200 mg of vanadium pentoxide (accelerator), reaction time of 15 minutes and a temperature of 1050 ° C were some of the optimized conditions wich were used for subsequent samples analysis. It was found that the spectral interference caused by W did not allowed the use of the main emission line to determine B. The absorbing solution used was distilled water and only the emission lines of 249.772, 208.889 and 182.639 nm could be used for the determination of boron. The accuracy of the proposed procedure was checked using certified reference material of silicon carbide (BAM S003) and agreement better than 96% were obtained using the three emission lines for boron. Coefficients of variation lower than 10% were obtained for the analysis (triplicate) of different samples of silicon carbide. Detection limits of 0.20, 0.90 and 2.0 mg-1 g were obtained for the emission lines of 249.772, 208.889 and 182.639 nm, respectively, using 200 mg of sample and a final volume of the absorbing solution equal to 30 mL.