Slurry Nebulization-Inductively Coupled Plasma Mass Spectrometry with Solution Calibration for Determination of Ultratrace Boron in High Pure Nuclear Graphite Powder

Slurry nebulization-inductively coupled plasma mass spectrometry (ICP-MS) was developed for the direct determination of trace boron (B) in high-purity graphite powders. After the graphite powders were ground and sifted, the particle size of graphite was collected less than 5 μm. Polyvinylpyrrolidone (PVP) was used as the dispersant in slurry preparation. The optimal mass ratio of PVP to the graphite was found to be 0.5. Well-proportioned and stable slurry solution was obtained by magnetic stirrer. 0.1 M NH4OH as the aqueous medium could provide the optimal pH of 10 for the stable slurry and eliminate the memory effect of B. ICP-MS was operated in a higher resolution mode (0.6 amu) to eliminate the interference with the matrix 12C by peak tailing. Oxygen was added into the plasma at a flow rate of 60 mL min−1 to resolve carbon deposition on the sampler and skimmer cones and accelerate particle dissociation in the plasma. External calibration with aqueous solution standards was established for quantification. Beryllium was chosen as the internal standard to evaluate the efficiency of matrix effect correction. A correlation coefficient of 0.9995 was obtained for B concentration ranging 2–200 μg L−1. The detection limit (3S) of B was 0.095 μg g−1. As a practical application, the proposed method was used for the determination of trace B in four nuclear graphite samples (claimed 99.999% purity), with the satisfactory recoveries for the spike tests in the range of 97.2%–103.1%.