Inductively coupled plasma atomic emission spectrometric determination of Gallium, phosphorus and other oxo-anion forming elements in geological materials

Abstract

A simple and rapid inductively coupled plasma atomic emission spectrometric method for the determination of Ga, P and other oxo-anion forming elements such as Mo, V, Cr, B and W in a variety of geological materials is described. The samples are fused with potassium hydroxide, iron carrier solution is added to act as a coagulant for the suspended particles, and after settling, the aqueous leachate is aspirated into the plasma for optical emission measurements. The method is accurate and precise, offering a relative standard deviation ranging from less than 1%(0.42% for WO₃ at the 1.30% level) to 5.26%(for Cr at the 10.4 ppm level) for all the elements studied. Interference studies were performed 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 other elements except for W. For W, two international reference standards, viz., CT-1 and GXR-4, together with some tungsten-mineralized and Nb/Ta-bearing tin slag samples, were analysed and the results are presented. The most probable Ga values are assigned to four international reference bauxite samples (NIST SRMs 69b, 696, 697 and 698) based on the present investigations. Further, a new set of experimental conditions are described for the determination of P in the presence of Cu-rich (up to 600 µg ml^–1 in the final solution) samples, after a thorough investigation. The method allows the determination of B down to 5 µg g^–1, Ga, Mo, V, Cr and W down to 10 µg g^–1 and P down to 100 µg g^–1 in the types of samples mentioned above.