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ABSTRACT
Schiff bases are compounds containing azomethine group (-HC=N-); they are condensation products of ketones or aldehydes with primary amines. Schiff bases played important role in the development of coordination chemistry because of their remarkable versatility, good solubility in common solvents and formation of stable complexes with most metals. The spectrophotometric determination of metals using Schiff base metal complex is very important in analytical chemistry. In this study, Schiff base ligand was synthesized using benzaldehyde and aniline to form a metal complex with the target analyte (Ni2+). Characterization of the synthesized ligand and its nickel complex was carried out using nuclear magnetic resonance (NMR), melting point determination, electrical conductivity, IR, AAS, GC-MS and UV-VIS spectroscopic techniques and the stoichiometry of the Schiff base nickel (SB-Ni) complex was established using Job’s method of continuous variation, mole- ratio and slope-ratio methods. The proposed method (SB-Ni system) was applied to the determination of Ni2+ in digested soil sample, ground water and waste water. This new method was juxtaposed with a known method of Ni2+ determination such as atomic absorption spectroscopy (AAS).
The melting point and molar conductivity of the synthesized nickel complex were 175.6oC and 8.4x10-6 Ώ-1cm-1respectively and the maximum absorbance at 360 nm was 0.60. The peak in FT-IR spectra at 1625.2 cm-1 confirmed the (C=N) stretching vibration. The 13C and 1H NMR spectra showed 193.8 and 10.0 ppm of (CH=N) which was assigned to the azomethine carbon atom. The stoichiometry of the Schiff base nickel (SB-Ni) complex was 1:2. The result of the AAS and the proposed method for the determination of Ni+2 in sediment samples were respectively 2.014 and 1.971 µg/ml while that of the waste water samples were 0.401 and 0.393 µg/ml. The level of nickel in ground water was not within the detection limit of both AAS and the proposed method.
The GC-MS analysis revealed a plausible structure of the complex (Nickel N-benzylidene aniline). The stoichiometry of Schiff base nickel complex was established as NiSB2. The result of the developed method and that of AAS are in good agreement
