SIMULTANEOUS DETERMINATION OF ALUMINUM AND IRON IN GLASSES, PHOSPHATEROCKS AND CEMENT USING FIRST-DERIVATIVE AND 2ND-DERIVATIVE SPECTROPHOTOMETRY

First- and second-derivative spectrophotometric methods for the simult aneous determination of aluminium and iron in their mixtures are descr ibed. The methods are based on the colored complexes formed by alumini um and iron with hematoxylin in the presence of cetyltrimethylammonium bromide as a surfactant. The zero-crossing method has been utilized t o measure the first- and second-derivative value of the derivative spe ctrum. Aluminium (0.05-1 mu g ml(-1)) could be determined in the prese nce of iron (0.09-1.6 mu g ml(-1)) and vice versa. The detection limit s of aluminium and iron are 0.01 and 0.09 mu g ml(-1), respectively in the first-derivative mode and 0.014 and 0.1 mu g ml(-1) in the second -derivative mode. The proposed method has been applied to the simultan eous determination of aluminium and iron in glasses, phosphate rocks, cement and magnesite alloy.