2-Hydroxy-1-naphthaldehyde-p-hydroxybenzoic hydrazone as a spectropho-tometric reagent for the determination of lanthanum (III)

Abstract

A new chromophore, 2-hydroxy-1-naphthaldehyde-p-hydroxybenzoic hydrazone has been used for the determination of lanthanum (III). The reagent reacts with lanthanum (III) in aque-ous dimethyl formamide in wide pH range forming brownish yellow coloured 2:3 (M:L) soluble complex with max at 415 nm. The colour intensity further increases in the cetyl trimethyl am-monium bromide micellar medium (0.1%) at room temperature. Beer’s law is obeyed in the range 0.277-8.334 μg mL⁻¹ and 0.008-2.639 μg mL⁻¹ of La(III) in direct and derivative methods, respectively. The molar absorptivity, Sandell’s sensitivity, detec-tion limit, determination limit and relative standard deviation are found to be: 2.3810⁴ L mol⁻¹ cm⁻¹, 0.006 μg cm⁻², 0.035 μg mL⁻¹, 0.106 μg mL⁻¹ and 0.42%, respectively. The second order derivative spectrophotometric method developed for the determi-nation of lanthanum (III) shows greater sensitivity and selectivity. The proposed direct and derivative methods are applied for the determination of lanthanum in standard lanthanum samples.