HR-ICP-MS Determination of 4 Key Impurity Elements of As, P, B and Zn in Hydrofluoric Acid of Electronic Grade

HR-ICP-MS was used for determination of As, P, Zn and B as key impurities in electronic grade hydrofluoric acid. The ICP-MS instrument is fitted with adjustable device for choosing of resolution at 3 gradings, i.e. high, medium and low, for solution of various interferences which may be encountered in the analysis. For instance, in the determination of As, MS interference of diatomic moleculrs of ³⁸Ar³⁷Cl and ⁴⁰Ar³⁵Cl was overcome by setting MS resolution at 12 000; in the determination of P and Zn, resolution modes of 4 000 and 5 500 were selected respectively to overcome interferences of diatiomic molecule of ¹⁵N¹⁶O and bicharged ⁶²Ni²⁺ (for P) and interference of ²⁸Si³⁸Ar (for Zn); and in the determination of B, taking ¹¹B as the analyte, almost no interference was found, and the determination can be carried out at the resolution mode of 500. However, a new source of interference, i.e. B as impurity present in pure water 1ed to positive and unstable errors. It was eliminated by strict controlling the BEC at a low level and by washing with blank solution until attaining to stable values of measurements before making normal determination. For analysis of sample, hydrofluoric acid sample was diluted 50 time with pure water and used for analysis according to the instrumental working conditions. Standard working curves were prepared by standard addition method. Linear relationships between values of intensities of response signals and mass concentrations of the 4 elements were found in the same range of 10 to 200 ng·L^-1, with detection limits less than 5.00 ng·L^-1. Values of BEC were controlled at less than 16.00 ng·L^-1. Recovery was tested by standard addition method, giving results in the range of 90.5% to 103%. Values of RSDs (n=11) found were less than 11%.