Slurry Nebulization-Inductively Coupled Plasma Mass Spectrometry with Solution Calibration for Determination of Ultratrace Boron in High Pure Nuclear Graphite Powder
The method of slurry nebulization-inductively coupled plasma mass spectrometry ( SN-ICP-MS) was developed for the direct determination of trace boron in high purity graphite powders. The particle size was controlled <5 mu m after the graphite powders was ground and sifted. 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. About 0.1 mol/L 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 C-12 by peak tailing. Oxygen was added into the plasma at a flow rate of 60 mL/min, 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 for boron concentrations from 2 to 200 mu g/L was obtained with a detection limit (3s) of 0.095 mu g/g. As a practical application, with the advantage of simple, quick and low losing, the proposed method was applied to determine the trace boron 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%.