DETERMINATION OF IMPURITIES IN HIGHLY PURIFIED HYDROFLUORIC-ACID BY ICP-MS

The determination by ICP-MS of sub ppb level impurities in highly purified hydrofluoric acid has been investigated for routine analysis of factory products. Boron determination: mannitol of 4 mg was added to 100 g of the sample and the sample was evaporated to dryness on a water bath. The residue was dissolved by adding 1.2 ml of nitric acid (1 + 2). The final solution was made up to 10 ml with water and the boron content was determined by ICP-MS. Arsenic determination: nitric acid of 3 ml, saturated bromine water of 5 ml, and sulfuric acid (1 +99) of 1 ml were added to 90 g of the sample and the above procedures were repeated to determine arsenic content. Gold determination: 100 g of the sample was evaporated to dryness on a water bath, and the residue was dissolved by adding 0.4 ml of aqua regia. The sample was evaporated to dryness on a water bath again. This residue was again dissolved by adding 0.4 ml of aqua regia, and made up to 10 ml with water to determine Au. Niobium and Tantalum determination: The sample of 100 g was evaporated to dryness on a water bath and the residue was dissolved by adding 0.4 ml of hydrofluoric acid. The sample was made up to 10 ml with water to determine Ta and Nb. Determination of other impurities: The sample of 100 g (1000 g for the determination of Th and U) was evaporated to dryness on a water bath, and the residue was dissolved by adding 1.2 ml of nitric acid (1 + 2). The solution was made up to 10 ml with water to determine Li, Be, Na, Mg, Al, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, Ge, Sr, Zr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, Pb, Bi, Th and U. The recovery of each element was greater than about 90%. Analytical results of these impurities in highly purified hydrofluoric acid were sub ppb level concentration. The concentration of U and Th, were 0.03 ppt and 1 ppt, respectively.