Volume 46, Number 5  (September - October 2001)

Key words:  copper, iron, 2-hydroxy-1-naphthaldehyde benzoylhydrazone, first order derivative spectrophotometry, simultaneous determination

A very simple, highly sensitive and slective first derivative spectrophotometric method is proposed for the determination of copper(II) and iron(III) in microgram quantities. Copper(II) and iron(III) react with 2-hydroxy-1-naphthaldehyde benzoylhydrazone (OHNABH) in the pH range 3-7 forming greenish yellow and yellowish brown coloured solutions, respectively. The first order derivative spectra of these coloured solutions show maximum derivative amplitude at 443 nm for Cu(II) and at 450 nm and 540 nm for Fe(III). Beer's law is obeyed in the range 0.16-4.80 mg ml^-1 of Cu(II) at 443 nm and 0.14-4.20 mg ml^-1 of Fe(III) at 540 nm. Various statistical parameters are derived for the experimental data to show the accuracy of the method. The interference of many metal ions can be avoided in the derivative mode. The method is applied for the determination of copper in some copper based alloys and iron in some food materials. The first order derivative method is also employed for the selective simultaneous determination of copper and iron in some plant samples.