Novel and rapid NH4HF2 assisted KH2PO4 fusion of pegmatite ores bearing refractory minerals for multi-element determination by atomic spectrometry

Abstract

Sample digestion and complete dissolution are prerequisites for the precise and accurate elemental analysis of ores and minerals by instrumental analytical methods. Pegmatite ores containing refractory mineral phases are not effectively attacked and dissolved by the low boiling HF–HCl/HNO₃ mixture. A novel, rapid, and efficient NH₄HF₂-assisted KH₂PO₄ fusion has been standardized for multi-elemental determination of geological samples containing refractory mineral phases. Critical parameters, such as the sample-to-flux ratio, digestion temperature, and contact time of the ore with ammonium bi-fluoride (ABF), were optimized and reported. The novel fusion method has been demonstrated to be effective for the quantitative recovery of all the analytes, including Ti, W, and, especially, Sn. The repeatability of the method was estimated analyzing a control sample. The relative standard deviaiton among replicates for all the analytes were below 3%. The accuracy was established using certified reference materials (IGS-26, IGS-33, and BH-1). All the target analytes were recovered at more than 95% in CRMs. Other validation parameters, such as robustness, selectivity, and LOD/LOQ are also described. This method can be routinely and safely used for the determination of Li, Rb, Nb, Ta, Ti, Mn, Sn, and W in addition to Fe, Ca, Mg, and Al in pegmatite ores.