Effect of same surface active substances on the spectrophotometric determination of Th(IV) using some coumarin azo dyes

The complexes of Th(IV) with some 8-(Arylazo)-6,7-dihydroxy-4-methylcoumarin are investigated spectrophotometrically. The optimum conditions fur chelation, pH, sequence of addition, time, solvents and stoichiometry are critically evaluated. The studies reveal that 1:1 and 1:2 (M:L) complexes are formed. Beer's law is constructed for the spectrophotometric determination of Th(IV) in presence and absence of some surface active substances. The studies reveal that the use of surfactants increases the sensitivity of the methods of determination by raising the values of molar absorptivity (epsilon). The methods are precise as given by low standard deviations ranging from 0.0097 to 0.0448 and high correlation coefficient (r) ranging from 0.9884 to 0.9996. The values of molar absorpitivity epsilon (LM-1 cm(-1)), specific absorpitivity a (mL g(-1) cm(-1)) and Sandell sensitivity S (mu g cm(-2)) indicate the method to be quite sensitive compared to standard method using Thoron. The tolerance of interference of foreign ions is investigated in the presence and absence of surfactants. The photometric titration methods using EDTA and F- as titrant are given.