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We found lower concentrations for all doped elements when we used the 31 phosphorus line. But by taking as an internal standard one of the doped elements, our results became more accurate. Table I11 gives the corrected values for bismuth, cobalt, nickel, and boron where manganese was used as internal standard. Mass corrections for plate sensitivity were made for bismuth and boron. A further improvement in accuracy might have been obtained by correction for relative ionization efficiencies. The relative sensitivity coefficients for different elements in a spark source are not well known. We believe that they vary not only with electrical sparking conditions, which could easily be reproduced, but that they depend also on other parameters, such as the distance between electrodes, the temperature of the sample, etc. , , ,, and these parameters are different from one instrument to the other. This is the reason why we have not tried to use correction factors for ionization efficiencies proposed by other authors (8). Further work needs to be done in this field. However, Table 111 shows that quite good results can be obtained by this method even without relative ionization sensitivity correction. Analysis of Nitric Acid. The analysis of this acid was carried out in the same way as phosphoric acid. The quantitative analysis was made using 69Co as an internal standard. As we have already seen in the case of phosphoric acid, more accurate results are obtained with a known internal standard. Table IV shows our results compared with the results of spectrochemical analysis of a transistor grade nitric acid (J. T. Baker Chemical Co., Phillipsburg, N. J.), which has been doped with 50 ppm weight of cobalt. (8) B. Chakravarty, H. E. Duckworth. and V. S. Venkatasubramanian. “Advances in Mass Spectrometry,” Vol. 2, Pergamon, London, 1963, p. 128.
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Table IV. Analysis of Transistor Grade Nitric Acid (The impurities are expressed in ppm weight in relation with HNOJ SpectroBaker Impurity Spark source chemical“ specifications CO (standard) 50 ... ... cu 0.02 (0.01
