Direct and derivative spectrophotometric determination of La(III) using 2- hydroxy-3-methoxy benzaldehyde-p-hydroxybenzoic hydrazone

La (III) reacts with 2-hydroxy-3-methoxy benzaldehyde-p-hydroxybenzoic hydrazone (HMBAHBH) in alkaline buffer solutions (pH 7.5-9.0) forming an intense lemon yellow coloured stable complex with a λmax at 390nm. The colour reaction is highly sensitive with an ε, 1.93 ´ 104 Lmol-1 cm-1 , detection limit 0.038 μg mL-1 obeying Beer’s law in the range 0.14 – 9.72 μg mL-1. The correlation coefficient (0.9999) and relative standard derivation (0.06%) indicate the good linearity for the regression curve and precision respectively. The method is reasonably selective as number of diverse ions are tolerable in large quantities in the presence of some masking agents. Stoichiometry and formation constant of the complex are determined as 2:3 (M:L) and 3.39 ´ 1018 respectively. The proposed method was applied for the determination of lanthanum in some standard lanthanum samples. Second, third and fourth order derivative spectrophotometric methods are also proposed for the determination of lanthanum. All the derivative methods are found to be more sensitive and the second derivative method is more selective than the zero order method. The second derivative method was also applied for the determination of lanthanum in standard samples

Author(s): S. Satyasree, V. Krishna Reddy and P. Raveendra Reddy

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