A fluorometric method for the determination of micro amounts of gallium with 2-hydroxy-4-methylbenzaldehyde-semicarbazone (HMBS) was established and applied to the analysis of aluminium and aluminium alloy. To a sample solution containing less than 5.0 μg of gallium, were added 0.1% sodium fluoride solution (Ga 05.0μg : 0.05 ml, Ga 01.0μg : 0.02 ml, Ga 00.1μg : 0.01 ml), 2 ml of HMBS solution in DMF (Ga 0 5.0 μg : 0.03%, Ga 00.1μg : 0.01%, Ga 00.1μg : 0.01%), and 0.5 ml of 2 w/v% ammonium acetate solution. The pH of the solution was adjusted to 3.2±0.1 with hydrochloric acid or ammonia solution, and the solution was diluted to 25 ml with water. The fluorescence intensity was measured at 440 nm (λex : 365 nm) against the standard quinine sulfate solution (0.2 μg/ml, 0.02 μg/ml, and 0.01μg/ml). This method was applicable to the determination of gallium above 0.1 ppm in practical samples with satisfactory results, where the gallium was separated from interfering elements by isopropyl ether extraction procedure before the determination.
