Determination of silicon, iron, and vanadium in petroleum coke by microwave digestion-microwave plasma torch atomic emission spectrometry

Using microwave plasma torch (MPT) as an excitation light source, argon as support gas, the sample solution was introduced into plasma by pneumatic nebulization system. The determination of silicon, iron, and vanadium in petroleum coke by microwave plasma torch atomic emission spectrometry (MPT-AES) was studied. The experimental conditions were optimized and chosen. The effects of coexistent ions on silicon, iron, and vanadium emission signal were investigated in detail. The detection limits for silicon, iron, and vanadium were 0.040 mu g/mL, 0.022 mu g/mL, and 0.052 mu g/mL, respectively. Linear dynamic ranges were 0.2-6 mu g/mL, 0.1-100 mu g/mL, and 0.2-100 mu g/mL, respectively. The addition recoveries were in the range of 95.8%-105.0%. Petroleum coke samples were digested in the sealed vessel by a microwave digestion system. The optimum parameters for microwave digestion were studied and selected. The method of microwave digestion is a useful, time-saving technique and can reduce total sample preparation time. The result shows that the method is effective in detecting silicon, iron, and vanadium in petroleum coke and has the advantages of accuracy, easy operation, high automation, and low operation cost.