التقدير الطيفي لأيونات الكادميوم Cd(II) والزئبقHg(II) باستعمال كواشف عضوية آزو- آزوشف مشتقة من الاميدازول

Spectrophotometric determination of Cadmium Cd(II) and Mercury Hg(II) ions Using Azo – Azo Schiff organic reagent derived from Imidazole

The study included the preparation and diagnosis of two reagents and complexes of metal ions Cd(II) and Hg(II), and the reagents were prepared by the traditional nitrogenous method and the first reagent was prepared in two steps, the first step included the reaction of (P-aminoacetophenone) with (P-nitroaniline) (Schiff base preparation), and the second step was the reaction of the product with (4,5-diphenylimidazole) to give the reagent [ 1-(4-(((4,5-dimethyl-1H-imidazol-2-yl)diazenyl)methyl)phenyl)-N-(4-nitrobenzyl)ethan-1-imine(DMIPNI)], As for the second reagent, it was prepared by nitrogen reaction from the reaction of (sulphadiazine) with (imidazole) to give the reagent [ 4-((imidazole-2-yl)diazenyl)-N-(pyrimidin-2yl) benzenesulfonamide (IDPBS)].
Diagnostics reagents and complexes by infrared (FT-IR) spectroscopy as well as 1H-NMR proton nuclear magnetic resonance spectrum, Some physical properties of complexes such as solubility, melting point, electrical conductivity and magnetic sensitivity were studied
The optimal conditions for the formation of complexes were determined, such as the effect of the concentration of the reagent solution, the pH, 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 (0.056-1.120)µg/mL for the cadmium(II) complex and (0.1-2.0)µg/mL for the mercury(II) complex for both reagents, form it, sandell´s function , molar absorption coefficient and correlation coefficient were determined for the spectrophotometric estimation method.
The equivalence of the prepared complexes was also studied by finding the ratio of the metal ion to the reagent (M:R) using the molar ratios method and the method of continuous changes. The results indicate that the ratio was reagent (2:1) metal for all the complexes and for both reagents, the stability constants were also calculated(4.1216×109 L.mol-1 , 2.7368×109 L.mol-1) for cadmium(II) and mercury(II) complexes respectively with reagent(DMIPNI) and (4.8272×108 L.mol-1 , 2.2071×109 L.mol-1) for cadmium(II) and mercury(II) complexes respectively with reagent (IDPBS).
In addition, the thermodynamic functions (∆G, ∆H, ∆S) were calculated for the prepared complexes under study at a range of temperatures (15-65)C˚, It was found that the stability constants of the complexes for both reagents 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 charge of the dissolved complexes was determined using the electrical conductivity and magnetic sensitivity device, and the result was that all the complexes are uncharged, from which we conclude that the complexes formed are octahedral.
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 reagents, 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, and from it we conclude that the spectral method used is of good accuracy, precision and sensitivity.
This spectrophotometric method was applied in laboratory prepared models for the determination of cadmium and mercury using reagents (DMIPNI)and(IDPBS) on laboratory samples with different concentrations, the results were very close and good, which indicates that the proposed method in the study is fast, economical, highly sensitive and selective.