Development of a microwave-assisted digestion method for the rapid determination of chloride and fluoride in nuclear-grade boron carbide powders

Abstract

A simple and efficient microwave-assisted digestion (MAD) method for the rapid determination of chloride and fluoride in nuclear-grade boron carbide powders has been developed using a closed microwave-vessel (G30, Anton Parr) and a domestic microwave oven. Parameters optimized to get quantitative recoveries of chloride and fluoride were extractant concentration, microwave power, irradiation time and amount of the sample. The optimized MAD conditions for quantitative recovery of chloride and fluoride were obtained by irradiating ∼0.5 g of sample in 10 mL of 10% HNO₃ (v/v) for about 30 s at a microwave power of 480 W. After completion of the extraction process, the sample mixture was centrifuged and then a known volume of the sample extract (clear supernatant) was transferred to another pre-cleaned tube for subsequent analyses of Cl and F using an ion-selective electrode (ISE). A pyro-hydrolysis method was used for validation of the results of the proposed MAD method. The LOD values for chloride and fluoride in conjunction with the proposed MAD were found to be 1.9 μg g⁻¹ and 1.2 μg g⁻¹ respectively with a relative standard deviation (RSD) of less than 10%. The studies have demonstrated that the proposed microwave-based approach constitutes a good alternative sample preparation methodology for the determination of chloride and fluoride in nuclear-grade boron carbide powder samples.