استخدام طريقة طيفية انتقائية لتقدير ايونات العناصر (Ⅱ)Co, (Ⅱ)Cd و(Ⅱ)Pb بواسطــــــة معقداتها مع ليكاندي شف (PTMH) و (MMPH)

The use of a selective spectroscopic method for the determination of ions of elements Co(Ⅱ),Cd(Ⅱ) and Pb(Ⅱ) by their complexes with ligand

Abstract
The study included the preparation and diagnosis of two new ligands from schiff base, to estimate the ions of the elements (Cobalt, cadmium , lead) using a selective spectral method. (PTMH) 1-phenyl-2-(thiophen-2-ylmethylene)hydrazine has been prepared by condensation reaction (phenylhydrazine) with (thiophene-2-carbaldehyde) .
As for (MMPH) 1-[(3-methylthiophen-2-yl)methylene]-2-phenylhydrazine has prepared by condensation reaction (phenylhydrazine) with (3-methylthiophene-2-carbaldehyde).
The ligands diagnosised with available spectrophotometric methods which is infrared (FT-IR) spectroscopy, 1H-NMR proton nuclear magnetic resonance spectrum ,13C-NMR spectrum of carbon isotopes , mass spectrum and UV-Visible Spectrum as well as melting point , prepared complexes with cobble, cadmium and lead ions .
The optimal conditions for the formation of complexes were determined, such as the effect of the concentration of the reagent solution , the acidity function, the time period for the stability of the formed complexes, the effect of temperature on the stability of the complexes and the order of addition , The ranges of concentrations that obey the Beer-Lambert law were also determined through calibration curves within the range (0.14-5.8) μg/mL for the cobalt(II) complex ,(0.28-11.2)µg/mL for the cadmium(II) complex and (0.51-20.7) μg/mL for the lead(II) complex for both ligands , from that , sandell´s sensitivity, molar absorption coefficient and correlation coefficient were determined for the spectrophotometric estimation method and for the first ligand (PTMH) the results were (8.2585×10-4µg/cm2 ،2.776×10-3µg/cm2 ، 8.9774×10-3µg/cm2) ، (7.136×104L.mol-1.cm-1،4.048×104 L.mol-1.cm-1 and 2.308×104 L.mol-1.cm-1 ) (0.9994، 0.999، 0.9995) for (cobalt، cadmium and lead) respectively .While the results of the second ligand(MMPH) were (9.8287×10-4µg/cm2، 2.16181×10-3µg/cm2، 1.0882×10-2µg/cm2)، (5.966×104 L.mol-1.cm-1، 5.2×104 L.mol-1.cm-1، 1.904×104 L.mol-1.cm-1)، (0.9993، 0.9989، 0.9998) for (cobalt ، cadmium and lead) respectively. The equivalence of the prepared complexes was also studied by finding the ratio of the metal ion to the detector (M:L) using the molar ratios method and the method of continuous changes. The results indicate that the ratio was ligand(2:1) metal for all the complexes and for both ligands. The stability constants were also calculated (2.0544×1010 L/mol ، 6.7640×109L/mol and 3.6150×109L/mol) for (cobalt , cadmium and lead ) complexes, respectively, for (PTMH) . While the results for (MMPH) were (4.9011×109L/mol ، 2.0032×1010L/mol and 2.2907×109 L/mol) for the same complexes in sequence . In addition, the thermodynamic functions (∆G°, ∆H°, ∆S°) were calculated for the prepared complexes under study at different temperatures (288-338)K, It was found that the stability constants of the complexes for both ligands decrease with increasing temperature, Because they are exothermic reactions, and the reactions of forming all complexes occur spontaneously, and this is what was observed through the values of change in free energy.
The reaction kinetics of each element were also studied using first-order and second-order pseudo-equivalences, and it was found that the second-order equation is the most applicable for (cobalt, cadmium and lead) and for both ligands, and the reaction rate constant and reaction rate were calculated for both ligands for the same complexes.
Also, the precision, accuracy and sensitivity of the spectroscopic analytical method used were determined by using standard solutions of the selected ions with standard solutions of ligands, From it, the standard deviation, the relative standard deviation and the percent relative error, whose limits did not exceed (±5), and the percentage recovery with three different concentrations, The spectral method used was characterized by being of good accuracy, selectivity and selectivity.