Determination of lead (pb ) in trace amount using Ultraviolet - visible spectrophotometric method

Abstract

Trace amount of Lead (Pb) has been determined by spectrophotometric technique using 1-(2-pyridylazo)-2-naphthol [PAN], as a new spectrophotometric reagent. 1-(2-pyridylazo)-2-naphthol reacts in slightly acidic solution at pH 4.5 with Pb to give a pink chelate that has an absorption maximum at 548 nm. The reaction is instantaneous and absorbance remains stable for over 48 hrs. The average molar absorption co-efficient was found to be 6.32×104 L mol-1 cm-1. Linear calibration graphs were obtained for 0.1 – 3.0 ppm of Pb. The stoichiometric composition of the chelate is 1: 2 (Pb: PAN). Large excess of over 20 cations, anions, and some common complexing agents (e.g, oxalate, phosphate, tartarate, thio-urea) have been studied. The method was successfully used in the determination of Pb in some environmental and industrial waste water and made a comparison with those obtained by Atomic Absorption Spectrophotometer (AAS).