Determination of trace amount of copper (Cu) using UV - VIS spectrophotometric method

Abstract

Trace amount of Copper has determined by spectrophotometric technique using 1-(2-pyridylazo)-2-naphthal, as a new spectrophotometric reagent. 1-(2- pyridylazo)-2-naphthal reacts in highly acidic solution at pH 2.45 to 2.55 with Copper to give a pink chelate which has an absorption maximum at 550 nm. The reaction is instantaneous and absorbance remains stable for over 48 hrs. The average molar absorption co-efficient was found to be 2.05×104 L mol-1 cm-1. Linear calibration graphs were obtained for 0.1-2.5 μg mL-1 of Cu. The stoichiometric composition of the chelate is 1: 2 [Cu: 1-(2-pyridylazo)-2- naphthal]. Large excess of over 50 cations, anions, and some common complexing agents (e.g, oxalate, phosphate, tartarate, thio-urea) do not interfere in the determination. The method was successfully used in the determination of Copper in Several Standard Reference Materials (alloys, steels and water) as well as in some environmental and industrial waste water. The method has high precision and accuracy.