Method for determining content of red light impurities in paracetamol bulk drug

By using a UV-Vis spectrophotometer under alkaline conditions and specific detection conditions, the accuracy problem of determining the content of indophenol, a red light impurity in paracetamol, was solved, achieving rapid and accurate quantitative detection, which is suitable for the quality control of paracetamol raw materials.

CN121540653APending Publication Date: 2026-02-17JIANGSU OCEAN UNIV
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Patent Information

Application Number
CN202511710777.1
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-11-20
Publication Date
2026-02-17

AI Technical Summary

Technical Problem

Existing technologies are insufficient to accurately determine the content of the red-light impurity indophenol in acetaminophen, especially since HPLC is unstable under alkaline conditions, leading to inaccurate test results.

Method used

The content of red light impurity indophenol was determined by ultraviolet-visible spectrophotometer under alkaline conditions (pH 11~14). By setting specific detection conditions (spectral scanning range, slit width, integration time, etc.) and using sodium hydroxide or potassium hydroxide as diluent, the maximum absorption wavelength of indophenol was ensured to be at 629 nm±3 nm for quantitative detection.

Benefits of technology

It enables rapid, accurate, and stable quantitative detection of indophenol, a red-light impurity in paracetamol, with high sensitivity and good repeatability, and is suitable for controlling impurity formation during the preparation process.

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Abstract

The invention discloses a method for determining the content of red light impurities in a paracetamol raw material medicine. The method comprises the following steps: (1) preparing a solution: (1.1) preparing a diluent with the pH value of 11-14 from alkali and pure water; (1.2) preparing a contrast solution of the red light impurity indophenol by using a diluent; (1.3) preparing a test solution by using a diluent; (2) setting detection conditions: detecting by adopting an ultraviolet and visible spectrophotometer; the spectrum scanning range is that spectrum scanning is carried out in the range of 200-800 nm, and the maximum absorption wavelength of indophenol is 629 nm + / -3 nm; (3) respectively measuring the contrast solution and the test solution under the spectrum condition in the step (2) to obtain absorbance values of the contrast solution and the test solution; and (4) calculating the content of the red light impurity indophenol in the test sample through a reference substance comparison method. The method disclosed by the invention can be used for rapidly, accurately and stably measuring the content of the red light impurity indophenol in paracetamol.
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