[en] Niobium (Nb) and Tantalum (Ta) are rare metals and they present in the rock samples at trace levels and their variation in rock samples is used as an indicator for certain geochemical process within the crust-mantle system. The Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) determination of Nb and Ta at trace levels in geological samples suffers from spectral and non-spectral interferences due to matrix elements. Therefore, a selective quantitative separation of both Nb and Ta from rock samples matrix is necessary for their accurate determination. In the present report a simple, selective hydroxide precipitation separation of both Nb and Ta present in the geological samples is developed. Rock samples are treated with a mixture hydrochloric acid and hydrofluoric acid initially, and finally with perchloric acid. The sample solution is prepared in 5% (v/v) hydrochloric acid. Then hydroxide precipitation of both Nb and Ta is carried out using dilute ammonia solution in the presence of ammonium EDTA and Sn (IV) as carrier. The precipitate after filtration is re-dissolved in a hydrochloric acid, oxalic acid and hydrogen peroxide solution. The Nb and Ta are determined by ICP-AES using emission lines at 316.340 nm for Nb, and 240.063 nm for Ta respectively. Accuracy of the method was checked using Standard Reference Materials, niobium ore CANMET OKA-1, tantalum ore CANMET TAN-1, and syenite CANMET SY-3. The values obtained are in close agreement with the recommended values. The reproducibility is characterized by a relative standard deviation (RSD) of 1 to 6% (n=4). The present method was applied to determine Nb and Ta above 10 μg g"-"1 in the mineralized rock samples. (author)

[en] During the mineral exploration for strategic Tin-Tungsten minerals, a large number of geological samples are to be chemically characterized for their major, minor and trace constituents. Tin mineral, Cassiterite and Tungsten minerals Wolframite (Fe, MnWO₄) and ferberite (FeWO₄) are resistant to acid attack and demand NaF/KHF₂ or KHSO₄ fusion for complete dissolution, a pre-requisite for ICP-OES/ AAS analysis. An effective, rapid, economic and green sample dissolution method for Tin-Tungsten ores using molten ammonium bifluoride (ABF) is described here. Results obtained for samples agreed well with those obtained using established NaF/KHF₂ fusion method. The obtained values (OV) are in close agreement with the Certified values (CV) in reference materials (CRMs). A few advantages of the proposed method is that the reagent, ABF, is completely removed while the sample is digested. A single solution containing all the desired elements including refractory elements is obtained. As the fusion/ digestion is done at 300°C, the method is energy efficient. No matrix elements are added during the digestion and therefore, Na & K can also be analysed. The reproducibility of the method is found to be better than 95% in samples and the CRM analyzed. Therefore, the proposed sample digestion method for determination of major, minor and trace elements in tin-tungsten ores is rapid, safe, green and equipment-friendly compared to the acid-digestion fusion route

[en] Determination of rare earth elements by ICP-AES has been attempted after their preconcentration on Chitin, a biopolymer and also on Sawdust. Various adsorption desorption parameters are optimised. REE's are sorbed at pH 4 and recovered by heating with 5% HNO₃. The possible mechanism of sorption is surface adsorption. The method is applied on selected rock samples like barytes, calcites and water samples. (author)