The analysis of geological samples for trace elements by direct-reading emission spectrometry

The experimental work is described that led to the development of a rapid and convenient method for the determination of a number of trace elements in geological samples by use of a direct-reading spectrometer. The technique involves the diluting of a sample in the ratio of 1 part of sample to 3 parts of a buffer consisting of graphite containing 20% lithium fluoride and 0.03% germanium oxide as a reference element. The mixture is loaded into a special electrode and is excited in a d.c. arc at 12 A for 80 ± 2 seconds. The excitation takes place in an inert atmosphere that is provided by a “double flow” gas-stabilizing jet. The resulting digital-voltmeter readings for the various elements are read against previously prepared calibration graphs, and the concentrations of the elements in the sample are derived. The elements determined in the direct-reader programme are Co, Cr, Cu, Mn, Mo, Ni, Pb, Sn, V, Zn and Zr. A photographic spectrographic variant of the method, developed at the same time, is also described. It permits the determination of a number of trace elements not in the direct-reader programme. The relative standard deviation for the method is 10–15%, and the accuracy is of the same order.