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Updated: Jun 28, 2026

A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
Published on: September 25, 2017
Colorimetric determination of theophylline and aminophylline with diazotized p-nitroaniline
S R El-Shabouri1, S A Hussein, S E Emara
1Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt.
Abstract:
The reactions of theophylline and aminophylline with diazotized p-nitroaniline in alkaline medium have been studied and developed into a sensitive assay for both drugs. The yellow azo-dyes formed with theophylline and aminophylline show maximum absorption at 440 and 410 nm respectively. Beer's law is valid within the concentration range 2-16 mug/ml for theophylline and 1-8 mug/ml for aminophylline. All variables which affect the reactions were studied and optimized. The proposed method has been successfully applied to determination of the drugs in their commercially available dosage forms. Statistical analysis of the results revealed that the proposed method is as precise and accurate as the official USP procedure.
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