Analysis of mineral suspensions by d.c. plasma emission spectrometry

Dilute aqueous suspensions of sub-sieve fractions of various minerals are analyzed for their major constituents by d.c. plasma emission spectrometry. In favourable cases (e.g., determination of zinc in sphalerite or smithsonite powders below 5 μm), the suspensions may be analyzed quantitatively simply by comparison with standard solutions, and with a relative error less than 10%. In other cases (e.g., determination of beryllium in beryl powders), the required element is so poorly atomized that the analysis is impossible, even when very fine-grained suspensions are used. As expected, the atomization efficiency for a particular element decreases with increasing particle size, and with increasing free energy of formation of its oxide at high temperatures. The region extending along the vertical branch of the plasma is a convenient excitation zone for suspensions containing elements that are difficult to atomize but the high background in this region limits the analytical possibilities.