摘要
Two new sensitive spectrophotometric methods are reported for determination of tartrazine (Tz) (E102) in some commercial food samples. The first method involves two coupled reactions, the reduction of Cu(II) to Cu(I) by the analyte in acetate buffer medium (pH = 5.9) at 30°C and the complexation reaction between Cu(I) and Tz oxidized form to yield Cu-Tz complex (method I). The other method is based on oxidation of Tz by alkaline KMnO4. These reactions are monitored spectrophotometrically at maximum absorbances 332 and 610 nm for methods (I and II) respectively. Variables affecting these reactions are carefully studied and the conditions are optimized. The stability constants are calculated at 293, 303, 313 and 323 K. The thermodynamic parameters, Gibb’s free energy change (ΔG), entropy change (ΔS), and enthalpy change (ΔH) associated with the complexation reaction are calculated and discussed. Under optimized conditions the proposed methods (I, II) obey Beer’s law 10.69 - 85.50, 5.34 - 34.12 μg·ml<sup>-1</sup> of Tz respectively. The molar absorptivity, sandel sensitivity, detection and quantification limits are calculated. Matrix effects are also investigated. The methods are successfully applied to the quantification of Tz in different commercially food samples. The results obtained are in good agreement with those obtained by the reported methods at the 95% confidence level.
Two new sensitive spectrophotometric methods are reported for determination of tartrazine (Tz) (E102) in some commercial food samples. The first method involves two coupled reactions, the reduction of Cu(II) to Cu(I) by the analyte in acetate buffer medium (pH = 5.9) at 30°C and the complexation reaction between Cu(I) and Tz oxidized form to yield Cu-Tz complex (method I). The other method is based on oxidation of Tz by alkaline KMnO4. These reactions are monitored spectrophotometrically at maximum absorbances 332 and 610 nm for methods (I and II) respectively. Variables affecting these reactions are carefully studied and the conditions are optimized. The stability constants are calculated at 293, 303, 313 and 323 K. The thermodynamic parameters, Gibb’s free energy change (ΔG), entropy change (ΔS), and enthalpy change (ΔH) associated with the complexation reaction are calculated and discussed. Under optimized conditions the proposed methods (I, II) obey Beer’s law 10.69 - 85.50, 5.34 - 34.12 μg·ml<sup>-1</sup> of Tz respectively. The molar absorptivity, sandel sensitivity, detection and quantification limits are calculated. Matrix effects are also investigated. The methods are successfully applied to the quantification of Tz in different commercially food samples. The results obtained are in good agreement with those obtained by the reported methods at the 95% confidence level.
