The spectral and differential pulse polarographic (DPP) behaviour of di-2-pyridyl ketone 2-thienoylhydrazone (DPKTH) has been investigated in 30% (v/v) ethanol-buffer mixtures over a wide range of pH (2.0-12.0). The spectral bands located at 325, 276. 230 and 208 nm of the DPKTH in ethanol are assigned to the possible electronic transitions of the molecule. The spectral data at various pH values indicates that the molecule characterized by the keto = enol tautomerization and the pK(a) value for the enolic form of the compound is determined in aqueous ethanol and was found to be 10.6. The effect of various operational parameters on the reduction current and the mechanism of the electrode reaction of DPKTH at the DME are discussed. The main reduction peaks are attributed to the reduction of C=N centre of both the keto and enol forms. This behaviour is compared with the DPP behaviour of the other related acid hydrazone compounds. The applicability of DPP technique for the trace determination of DPKTH was tested under the optimum experimental conditions and the detection limit is found to be 0.09 mu m.
Sensitive methods for the determination of trace amounts of cobalt and copper by complexation with 3-(2'-Thiazolylazo)-2,6- diaminopyridine (2,6-TADAP) are described. Copper forms a 1:2 violet complex with the reagent having a molar absorptivity of 1.00 times 104 L mol-1cm-1, Baer's law is obeyed over the range 0 -50.84 μg in the total volume of 10ml. Cobalt also forms a 1:1 green complex with a molar absorptivity of 1.07 times 104L mol-1cm-1 and obeying Beer's law over the range 0 -23.57 μg in the total volume of 10 ml. The procedure is simple and rapid without any tedious extraction steps for copper and without oxidation of cobalt (II) to cobalt (III).
The assignment of metal complexes to various regimes on the basis of their dissociation kinetics is one type of metal speciation study. The most common scheme, which involves column ion-exchange as a means of separating free metal ions and metals in the form of highly labile complexes from other forms of metals in the sample, is demonstrated to categorize incorrectly stable, charged complexes such as iron(II) and nickel(II) o-phenanthroline as labile. Donnan dialysis is an alternative ion-exchange method for metal speciation studies. Data are provided which demonstrate that the above complexes are correctly assigned by the Donnan dialysis method. The relative labilities of ethylenediamine and triethylenetetramine complexes of iron (II) and nickel (II) are also correctly determined by Donnan dialysis.
Sensitive methods for the determination of trace amounts of cobalt and copper by complexation with 3-(2′-Thiazolylazo)-2,6- diaminopyridine (2,6-TADAP) are described. Copper forms a 1:2 violet complex with the reagent having a molar absorptivity of 1.00 × 104 L mol−1cm−1, Baer's law is obeyed over the range 0 −50.84 μg in the total volume of 10ml. Cobalt also forms a 1:1 green complex with a molar absorptivity of 1.07 × 104L mol−1cm−1 and obeying Beer's law over the range 0 –23.57 μg in the total volume of 10 ml. The procedure is simple and rapid without any tedious extraction steps for copper and without oxidation of cobalt (II) to cobalt (III).