Synthesis of Bis-Schiff Base Reagents and their Application in the Spectrophotometric Determination of Mesalazine via Azo Dye Formation
Abstract
Mesalazine (5-aminosalicylic acid) is an important first-line anti-inflammatory drug widely used in the management of inflammatory bowel diseases, particularly ulcerative colitis, making its reliable determination in pharmaceutical formulations important for routine quality control. In this study, bis-Schiff base reagents were synthesized by condensation of 4,4′-diaminoazobenzene with substituted aromatic aldehydes. Among the synthesized derivatives, 4,4′-bis[(4-hydroxybenzylidene)amino]azobenzene (SH1) was selected as the chromogenic reagent because it provided a superior analytical response compared with SH2. The novelty of the proposed method lies in the use of laboratory-synthesized SH1 as a coupling reagent for diazotized mesalazine, producing a color-stable azo product in alkaline medium with a maximum absorbance at 530 nm. The analytical procedure is simple and low-volume, employs a predominantly aqueous final reaction medium, and does not require chromatographic separation or solvent-extraction steps, thereby reducing solvent and instrumental requirements. Under optimized conditions, Beer’s law was obeyed over the concentration range of 2.0–20.0 μg/mL, with a molar absorptivity of 7.580 × 10³ L/mol/cm and Sandell’s sensitivity of 0.0202 μg cm⁻². The method showed recoveries of 99.20–100.83%, with RSD values of 0.70–0.80%, and a limit of detection of 0.1540 μg/mL. Good selectivity and robustness were observed, and the method was successfully applied to the determination of mesalazine in Pentasa® tablets. These findings support the applicability of the proposed SH1-based spectrophotometric method for routine pharmaceutical quality-control analysis.
Keywords
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References
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Details
Primary Language
English
Subjects
Analytical Spectrometry
Journal Section
Research Article
Authors
Publication Date
October 22, 2026
Submission Date
July 22, 2026
Acceptance Date
September 12, 2026
Published in Issue
Year 2026 Volume: 2026 Number: 2
