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Determination of prothipendyl by difference spectrophotometric method based on the absorption of its sulfoxide

Olena Mozgova, Mykola Blazheyevskiy, Liubomyr Kryskiw, Tetyana Kucher, Oksana Shliusar, and Valeriy Moroz

Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland



Received: 27 August 2023  Accepted: 10 December 2023


A new difference spectrophotometric method for the determination of prothipendyl hydrochloride in commercial pharmaceutical preparations has been proposed. The method includes oxidation of an aliquot of the drug solution with potassium caroate to form the corresponding sulfoxide (ε = (5.83 ± 0.07) × 103 L/mol cm) and subsequent measurement of the absorbance at 340 nm compared to that of the unoxidized drug solution of equal concentration. The graph of Beer’s law for prothipendyl hydrochloride shows that the ΔA values measured at the corresponding wavelength are proportional to the concentration of the drug in the concentration range of 1.5–70 µg/mL. The characteristics of the curve calibration curve of the linear regression equation were as follows: ΔA = (69.24 ± 1.78) × 10–4 C (where C in μg/mL). A new spectrophotometric technique has been developed and the possibility of quantitative determination of prothipendyl hydrochloride monohydrate in Dominal® tablets of 40 mg has been demonstrated. RSD ≤ 1.3%; (│δ│ < tα × RSD/\(\sqrt{n}\)), where µ is quantification data given in the Certificate of Quality, δ = (x̅-µ) 100%/µ. The resulting difference in absorption does not depend on the presence of excipients and possible API oxidation products in the composition.

Keywords: Difference spectrophotometry; Assay; Azaphenothiazine; Prothipendyl; S-oxidation; Oxone

Full paper is available at

DOI: 10.1007/s11696-023-03266-5


Chemical Papers 78 (4) 2613–2619 (2024)

Wednesday, June 19, 2024

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