Complex Formation of Nickel(11) with 5-Chloro-2-thiophenecarbaldehyde 2-Benzothiazolylhydrazone and Its Application to the Extraction Spectrophotometric Determination of Ni c k e r

Abstract

Nickel( II) ion reacts with 5-chloro-2-thiophenecarbaldehyde 2-benzothiazolylhydrazone (CTBH)to form a 1: 3 yellow complex (λmax=427 nm, ε = 7.4X 10⁴mol^-1 dm-³ecm^-1 in a micellar solution of Triton X-100, and Amax= 425 nm, v=8.7x 104m o1-' dm3. cm-' in isobutyl methyl ketone (MIBK) and an adduct complex (λmax= 435 nm, ε=5.2x 10⁴m ol^-1dm³cm^-1 in benzene) by the synergistic effect of pyridine base when it is present. The ratio of three components in the adduct complex is estimated to be nickel(III): CTBH: pyridine =1: 2: 2. On the basis of these results and the analysis of far infrared spectra, it is assumed that the nickel( 10complexes have the octahedral structure in the media studied. The complex, extracted into MIBK, was applied to the determination of trace amounts of nickel. The proposed procedure is as followsTake the sample solution containing up to 6 pg of nickelin in a 50 cm³ separatory funnel, add 1 cm3 of a 2.5 X 10^-3 mol. dm-8 CTBH solution in ethanol and 2 cm3 of ammonium buffer solution (pH 9.0), and dilute to about 30 cm³ with water. Then add 10.0cm³ of MIBK and extract the complex by shaking for 5 min. Measure the absorbance of the organic phase at 425 nm against a reagent blank. Beer's law was confirmed over a range of 0.2-6.2 pg Ni2+/10 c m³ MIBK and the sensitivity which gave the absorbance of 0.001 wa s 0.00079 μg Nicm-2. Among sixteen kinds of diverse metal ions tested, chromium (E) and vanadium(V)V ) ions seriously interfered with the determination of nickel. The procedure was applied to the determination of nickel in iron and steel. Satisfactory results were obtained.