A simple and sensitive spectrophotometric method is developed for the determination of zinc in aqueous solutions. The metal ion forms a greenish-yellow colored complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range of 4-10. The complex shows maximum absorbance at 390 nm and in the pH range of 6-8. Beer's law is obeyed in the range 0.10-1.50 µ g/mL of Zn(II). The molar absorptivity and Sandell's sensitivity are 3.55 × 10 4 mol -1 cm -1 and 0.0016 µ g/cm 2 , respectively. The composition of the complex is 1 : 1. The effect of interfering ions has been studied, and the method was applied to the determination of zinc(II) in potable water and pharmaceutical samples. A fast derivative spectrophotometry method is also proposed for the determination of zinc in the range 0.06-1.60 µ g/mL, which is more sensitive than the zero order method.

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Abstract:The quantification of copper in water, vegetables, foodstuffs, human hair and pharmaceutical samples was determined by a simple more sensitive and selective spectrophotometric method. Cu(II) forms an orange -red color complex with 5-{ά -methyl-3-hydroxy benzylidene} rhodanine [5M, 3H-BR], at pH 5.5 in sodium acetate and acetic acid buffer. The maximum absorbance was measured at 430 nm. The Beer's law is obeyed in the range of (0.05 µg -13 µg/mL). The molar absorptivity (ε) and the Sandell's sensitivity of the complex were 0.6027× 10 4 mol -1 cm -1 and 0.01054 µg cm -2 respectively. First, second and third derivative spectrophotometry were also proposed and employed successfully for the determination of copper in the supra. The performance of the present method was also evaluated in terms of RMSEP, REP and RSD, students t-test. This indicates the greater importance of the method than other methods reported in the literature.

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