INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRIC DETERMINATION OF GALLIUM, PHOSPHORUS AND OTHER OXO-ANION FORMING ELEMENTS IN GEOLOGICAL-MATERIALS

A simple and rapid inductively coupled plasma atomic emission spectrom etric method for the determination of Ga, P and other oxo-anion formin g elements such as Mo, V, Cr, B and W in a variety of geological mater ials is described. The samples are fused with potassium hydroxide, iro n carrier solution is added to act as a coagulant for the suspended pa rticles, and after settling, the aqueous leachate is aspirated into th e plasma for optical emission measurements. The method is accurate and precise, offering a relative standard deviation ranging from less tha n 1% (0.42% for WO3 at the 1.30% level) to 5.26% (for Cr at the 10.4 p pm level) for all the elements studied. Interference studies were perf ormed for the four most sensitive lines and the most suitable analyte( s) lines selected. The method was applied to a number of international reference standards, viz., SY-2, SY-3, MRG-1, G-2, DR-N, SO-1, SO-2, SO-4, ASK-1, ASK-2, NIST SRMs NBS 69b, 696, 697 and 698, for Ga and ot her elements except for W. For W, two international reference standard s, viz., CT-1 and GXR-4, together with some tungsten-mineralized and N b/Ta-bearing tin slag samples, were analysed and the results are prese nted. The most probable Ga values are assigned to four international r eference bauxite samples (NIST SRMs 69b, 696, 697 and 698) based on th e present investigations. Further, a new set of experimental condition s are described for the determination of P in the presence of Cu-rich (up to 600 mu g ml(-1) in the final solution) samples, after a thoroug h investigation. The method allows the determination of B down to 5 mu g g(-1), Ga, Mo, V, Cr and W down to 10 mu g g(-1) and P down to 100 mu g g(-1) in the types of samples mentioned above.