Spectrophotometric determination of copper (II) by using 2-pyridinealdehyde-4, 4'-diphenylsemicarbazone

2-Pyridinealdehyde-4, 4'-diphenylsemicarbazone is a condensation product of 2-pyridinealdehyde and 4, 4'-diphenylsemicarbazide. The reagent reacts with copper (II) to form a water soluble yellowish green complex at pH 4.06.5 within 10 min. The complex has an absorption maximum at 380 nm. The reagent solution does not show any absorbance in wavelength range of 350 nm500 nm. The absorbance of the mixture of copper (II) and the reagent is stable for at least 5 h and constant in the pH range of 4.06.5 and at the reagent-copper (II) molar ratio range of 2 : 14 : 1. At pH 4.04.5, the effect of nickel (II), cobalt (II), and iron (III) on the absorbance can be ignored. The molar ratio of the copper (II) to the reagent is estimated to be 1 : 1 by the continuous variation method and molar ratio method. The copper (II) was determined as follows : alcoholic solution of the reagent 24 times as much as copper (II), was added to the sample solution and pH was adjusted to 45. After the mixture was allowed to stand for 10 min20 min at room temperature, the absorbance of the solution was measured at 380 nm. Beer's law obeyed over the range of 0.14 mg/l2.88 mg/l of copper (II). The apparent molar absorption coefficient of the complex at 380 nm was 1.8 × 104 mol-1 cm-1 dm3. The effect of 1 l diverse cations were examined. Among them, 3 hold amount of nickel (II) and cobalt (II) and 10 hold amount of iron (III) in molar ratio interfered with the determination of copper (II). Other ions of zinc (II), lead (II), cadmium(II), manganese(II), strontium(II), calcium(II), barium(II), and aluminum (III) were tolerated up to 20 hold amount of copper (II) in molar ratio.