Quantitative EPMA of ultra-light elements : strategies and pitfalls

The electron probe microanal. (EPMA) of B,C, and O using wavelength dispersive techniques requires complicated exptl. procedures. A major phys. problem in the quantification of B, C, N, and O using matrix correction procedures is the uncertainty in the mass absorption coeffs. (mac's). Two different EPMA procedures were used to obtain better consistent mac values. Both methods are based upon the use of a reliable correction program. The first method required the knowledge of the compn. of the specimen, and the measured k-ratios must be compared with values calcd. by the correction program in conjunction with a specific sets of mac's. Increasing discrepancies between measurements and calcns. with increasing accelerating voltage point to inconsistent mac's. A slight disadvantage of this method is that the compn. of the specimen has to be known accurately. In the alternative procedure the relative intensity of emitted radiation was measured as a function of accelerating voltage and subsequently compared with the calcns. made with a good j(rz) correction program, using a variety of mac values. [on SciFinder (R)]