Showing papers by "Joanna Karpińska published in 2003"

Derivative Spectrophotometry as a Tool for Determination of Stability Constants of Some 4-2(-Pyridylazo)-resorcinol Complexes with Divalent Metal Ions

Abstract: The suitability of derivative spectrophotometry for examination of complexation equilibria was elaborated by the determination of stability constants of Zn-PAR and Pd-PAR complexes. Derivatization minimized the influence of an excess of a colored reagent on the absorbance of the complex and allowed the direct measurement of its true value. The stability constants determined using two different methods were compared with available published data. In the case of the Zn(PAR)2 complex the error of determination did not exceed ± 5%.

Analytical studies and application of reaction of promazine and thioridazine hydrochlorides with some oxidants.

Abstract: The run and analytical application of oxidation reaction of promazine (PM) and thioridazine (TR) hydrochlorides with iron(III) and ferrocyanide(III) are described. The coloured products of oxidation absorb at 512 nm for promazine and 634 nm for thioridazine. This property is a basis of a rapid, accurate and sensitive spectrophotometric method for determination of these phenothiazines. The elaborated methods allow to determine 3-28 microgPM/ml in Fe(III)-PM and 2-11 microgPM/ml in [Fe(CN)6](3-)-PM systems, 2.5-22 microgTR/ml in the Fe(III)-TR and 4-16 microgTR/ml in [Fe(CN)6](3-)-TR systems.

UV Derivative Spectrophotometric Study of the Photochemical Degradation of Thioridazine Hydrochloride

Abstract: A rapid, selective, and accurate method, based on derivative spectra is proposed for the quantification of thioridazine hydrochloride in the presence of its main degradation product—thioridazine sulphoxide, and vice versa. The determination of thioridazine hydrochloride was made using the second order of derivative (Δλ = 22 nm, third polynomial degree) at 280 nm, while the determination of its sulphoxide is possible by applying the first order derivative spectra (Δλ = 22 nm, second polynomial degree) based on measurements of derivative height at 312 nm. The calibration graphs were linear up to 30 and 50 µg/mL for thioridazine and its sulphoxide, respectively. The limits of detection were 2.91 and 0.77 µg/mL. The elaborated method was applied successfully for determination of the photostability of thioridazine hydrochloride in aqueous solution and in solid phase.