2024, Volume 70(74), Issue 2 (June), pp. 65 - 76

 Spectrophotometric Characteristics of Rifaximin Aqueous Solution and The Consequences for Quantitative Analysis

ELENA FASNIUC-PEREU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environment Protection, Department of Environmental Engineering and Management, Iaşi, Romania
ANDREI-EUGEN BULGARIU, Emergency Hospital “Professor Doctor Nicolae Oblu” of Iaşi, Romania
LAURA BULGARIU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environment Protection, Department of Environmental Engineering and Management, Iaşi, Romania, lbulg@ch.tuiasi.ro

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DOI: 10.5281/zenodo.13308277
Abstract
Rifaximin is known as an oral antibiotic that can be used in a wide range of digestive diseases, but not only. Chemically, rifaximin is a yellow solid powder that can be relatively easily dissolved in methanol and which, because of its color, can be analyzed spectrophotometric. To be able to use such a simple method in the quantitative analysis of rifaximin, the most important spectrophotometric characteristics are required. In this study, these spectrophotometric characteristics (maximum wavelength (λmax, nm), spectral band width (Δλ1/2, nm), molar absorption coefficient (ε, L·mol-1·cm-1) are determined from VIS molecular spectra, recorded for aqueous solution containing a known concentration of rifaximin (4.22–16.88 mg·L-1) and different pH (1.0–7.0). Based on the obtained experimental results, the optimal conditions for the spectrophotometric analysis of rifaximin were established, namely: pH = 7.0 (distilled water or phosphate buffer) and λmax = 444 nm. These conditions are suitable for the quantitative analysis of rifaximin with a detection limit of 0.0125-0.0179 mg·L-1 and a precision of 2.12-2.43%. The very good agreement between theoretical and experimental values for rifaximin concentration in tap and sea water samples shows that this method is valid and can be used in quantitative analysis.
Keywords: rifaximin, spectrophotometric characteristics, aqueous solution, qualitative and quantitative analysis