Oxidative pyrolysis combined with the microwave-assisted extraction method for the multi-elemental analysis of boron carbide powders by inductively coupled plasma optical emission spectrometry (ICP-OES)

A method based on oxidative pyrolysis (OP) using an in-house quartz chamber in combination with microwave-assisted extraction (MAE) was developed as a new sample preparation approach for the determination of metallic impurities in boron carbide powders. Initially, a known amount of boron carbide powder (100–400 mg) was weighed into a quartz boat, which was inserted in the pyrolysis chamber. The chamber was heated to ∼500 °C by means of a Bunsen burner in the presence of an oxygen stream. The heating was continued until the burning process was completed. After this step, the chamber was allowed to cool to room temperature and the boat was taken out. Subsequently MAE was applied with an extractant mixture of 10 mL of 30% HNO3 + 10% HCl + 5% HF using the optimized microwave program (microwave power: 1200 W, ramp: 10 min, temperature: 200 ± 5 °C, hold: 10 min). After completion of the extraction process, the supernatant was separated from the undissolved residues by centrifugation for 4 min at 5000 rpm. A known volume of the clear supernatant was transferred to another pre-cleaned tube and diluted to the required volume for subsequent step of analysis of W, Si, Pb, Ni, Fe, Ca, Mg, Ti and Al by an inductively coupled plasma optical emission spectrometer (ICP-OES). Parameters affecting the recoveries of the metals of interest with the proposed combined approach were investigated. The sodium carbonate fusion method was adopted for cross-validation of the results of the proposed OP–MAE method. The detection limits obtained were significantly lower than those of the fusion method. The results obtained have proven the suitability of the developed combined approach as a sensitive sample preparation methodology for the determination of metallic impurities in boron carbide powder samples.