Spectrophotometric determination of vitamin E (alpha-tocopherol) using copper(II)-neocuproine reagent

The possibility of the utilization of the copper(II)-neocuproine spectrophotometric method, which has previously been shown to permit the determination of various reducing agents, to the determination of vitamin E was investigated. The molar absorptivity for vitamin E was found to be (2.1 +/- 0.1) x 10(4) 1 mol(-1) cm(-1) and Beer's law was obeyed between 2.4 x 10(-6) and 9.0 x 10(-5) M concentrations of alpha-tocopherol. The relative standard deviation of the slope of the absorbance vs. concentration plot was 2.1%. The results obtained by the copper(II)-neocuproine method were compared with those achieved by both the standard HPLC and the widely used iron(III)-bathophenanthroline method by means of a t-test which showed that the precision of the developed method was not essentially different from those of the others. The developed method was successfully applied to three commercial samples, two in dragee and one in ampoule form. The alpha-tocopheryl acetate contained in the samples, which did not respond directly to the Cu(II)-neocuproine reagent, was subjected to alkaline hydrolysis prior to the analysis of the hydrolysis product, i.e., alpha-tocopherol. The molar absorptivity due to Cu(I)-neocuproine at 450 nm against a reagent blank indicated a two-electron oxidation of vitamin E by Cu(II)-neocuproine, which may be slightly enhanced by solvent effects. Copper(II)-neocuproine is an oxidant of strength comparable to that of Fe(III)-bathophenanthroline. The developed method, although less sensitive, is easy to use in conventional laboratories, unlike the Fe(III)-bathophenanthroline method, which requires specially prepared reagents and solvents. The method is free from interferences from such common reductants as ascorbic acid and Fe(II) salts, found in pharmaceutical formulations, after washing the formulation with water and collecting vitamin E in the ether extract for subsequent analysis

Simultaneous derivative spectrophotometric determination of cobalt(II) and nickel(II) by dithizone without extraction

Dithizone (Dz), a common extractive-photometric ligand for Co(II) and Ni(II), has been dissolved in the water-miscible solvent tetrahydrofurane (THF) so as to constitute a reagent for both metals in aqueous phase without extraction. Complex formation was complete for both metals at pH 12.0 (adjusted by aqueous NH3) within 30 min, and the complexes were stable for at least 2 h. First-derivative spectra of the metal dithizonates (singly or as binary mixtures) were preferred to ordinary spectra, because working wavelength determination was more precise and spectral overlap was less. Two wavelengths at which the spectral overlap was minimum were selected as analytical wavelengths, i.e. 620 nm for Co and 740 nm for Ni, and the calibration curves drawn with zero-to-peak values as a function of concentration were linear for these wavelengths. Thus, the total D-1 values at 620 and 740 nm of the mixtures were used to determine Co and Ni concentrations. The relative standard deviation (R.S.D.) for the analysis of Co (3.0 mg l(-1)) individually was 3.5%, and for its admixture with Ni (3.5 mg l(-1)) was 3.5%. The R.S.D, for the analysis of Ni (5.9 mg l(-1)) individually and for its admixture with Co (1.8 mg l(-1)) were 5.5 and 5.8%, respectively. The linear range in D-1 evaluation was between 5.0 x 10(-6) and 1.0 x 10(-4) M for Co and 2.0 x 10(-5)-2.0 x 10(-4) M for Ni. Interference analysis was performed for individual metal (Co or Ni) determinations. Finally, the method has been applied to a Ni-Cr-based dental alloy (Wiron 99) successfully. (C) 2000 Elsevier Science B.V. All rights reserved

The accumulation levels in some tissues and the effect on lipid fractions in liver of dietary aluminum in broilers

In this study, the accumulation levels in serum, muscle and bone and the effect on lipid fractions in liver of dietary aluminum in broilers were examined