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Pyrohydrolysis was proposed as an eco-friendly sample preparation method for silicon carbide (SiC) and subsequent determination of W by ICP-MS. The use of water and compressed air was not enough to ensure the quantitative recovery of W (only 18% recovery of W) during the pyrohydrolysis reaction of SiC. The replacement of water and compressed air by H2O2 and oxygen, respectively, ensured a significant increase in recovery of W. The optimized conditions with a flow-rate of 1.2 mL min−1 of 50% H2O2 and oxygen flow-rate adjusted at 0.1 L min−1 allowed the quantitative recovery of W when compared with results obtained for sample previously analyzed by instrumental neutron activation analysis (INAA, 19700 ± 800 µg g−1 of W). The additional amount of oxygen provided by the use of 50% H2O2 (as pyrohydrolysis reagent) and oxygen (as carrier gas) allowed the conversion of WC present in the sample into volatile species of W. The temperature, time of reaction and absorbing solution were 1000 °C, 60 min and only water, respectively. Comparison of results for W using the pyrohydrolysis method, alkaline fusion and INAA for the six samples did not present significant differences. The limit of detection was 1 µg g−1 using sample mass of 200 mg and ICP-MS for W determination. The proposed method can be considered as eco-friendly method in agreement with Green Analytical Chemistry recommendations, because no toxic reagent was used during pyrohydrolysis reaction, lead to minimum waste generation and the main products of H2O2 thermal decomposition were water and oxygen. |
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