A Sensitive Extractive Spectrophotometric Determination of Cobalt(II) in Real Samples Using Pyridoxal-4-phenyl-3-thiosemicarbozone

Abstract

Pyridoxal-4-phenyl-3-thiosemicarbozone(PPT) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of cobalt(II). Cobalt(II) forms a reddish brown colored complex with PPT, which is extracted into n-butanol, under optimum conditions. The maximum absorption of the n-butanol extract is measured at 450 nm. The Beer's law is applied in the range 0.5–6.0 ppm of cobalt(II), with a relative standard deviation of 1.45 percent. The molar absorptivity and Sandell's sensitivity of the complex is calculated as 1.4 × 10⁴ L mol⁻¹ cm⁻¹ and 0.004209 µg cm⁻², respectively. An excellent linearity with a correlation coefficient value of 0.99 is obtained for the Co(II)-PPT complex. The instability constant of the complex, calculated from Edmond and Birnbaum's method is 2.7467 × 10⁻⁸ and that of Asmus' method is 2.6822 × 10⁻⁸, at room temperature. The method is successfully employed for the determination of cobalt(II) in real samples, such as biological, soil and pharmaceutical samples. The reliability of the method is assured by analyzing the standard alloy samples, such as High speed tool samples (BCS 484 and 485), Alloy steel samples (BCS 233 and 266) and by an inter-comparison of the experimental values, using atomic absorption spectrometer(AAS).

Keywords:

• Pyridoxal-4-phenyl-3-thiosemicarbazone
• Cobalt(II)
• Extractive spectrophotometry
• Real samples