A Simple Spectrophotometric Method for the Determination of Aluminum in Some Environmental, Biological, Soil and Pharmaceutical Samples Using 2-Hydroxynaphthaldehydebenzoylhydrazone

A simple ultra-trace, and highly selective non-extractive spectrophotometric method is presented for the rapid determination of aluminum at trace levels using 2-hydroxynaphthaldehydebenzoylhydrazone (HNPBH) as a new spectrophotometric reagent (lambda max = 412 nm) in slightly acidic solution (1.5×10^-5-1.25×10^-4 mol L^-1 H2SO4) in 50% N,N-dimethylformamide (DMF) medium. The reaction is instantaneous and absorbance remains stable for over 24 h. The color system obeys Beer’s law from 0.01-2.0 mg L^-1 having detection limit of 1 μg L^-1 and RSD 0-2%. The average molar absorptivity and Sandell’s sensitivity were found to be 2.21times10^4 L mol^-1 cm^-1 and 6 ng cm^-2, respectively. The stoichiometric composition of the chelate is 2:3. The interference from over 50 cations, anions, and complexing agents (tartrate, oxalate, citrate, EDTA, DMG, 1.10 phenanthrolin, oxine, phosphate, thiourea, SCN^-) has been studied at 1 mg L^-1 of Al. The method was successfully applied to some certified reference materials (alloys and steels), environmental waters (inland and surface), biological samples (human blood, urine and gallstone), soils, pharmaceutical samples (entacyd and almasil) and complex synthetic mixtures. The method has high precision and accuracy (s = ±0.01 for 0.5 mg L^-1).