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A Validated Quantification of Benzocaine in Lozenges Using TLC and a Flatbed Scanner

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Abstract

We present a video-densitometric quantification method for benzocaine in lozenges. The quantification is based on a derivatisation reaction with 4-dimethylaminobenzaldehyde. Measurements were carried out using a 16-bit flatbed scanner. Benzocaine was separated to a distance of 50 mm in a vertical developing chamber without vapour saturation. We present an RP-18 phase separation on a cyanopropyl plate (Merck, Darmstadt, Germany) using water, CH3CN, dioxane, ethanol, and NH3 (25 %) (8 + 2 + 1 + 1 + 0.05, v/v) as the mobile phase. We also separated benzocaine in a normal phase system on silica gel 60 LiChrospere® plates (Merck, Darmstadt, Germany) with the mobile phase MTBE/cyclohexane (1 + 1, v/v). The calibration functions for benzocaine in both separations were linear in the range from 1 to 1,000 ng per spot. The range of linearity covers two magnitudes of power because the Kubelka–Munk expression was used for data transformation. In the cyanopropyl-system, the benzocaine amount was quantified as 242.5 ± 18.2 ng in a spot or 6.86 ± 0.52 mg in a single lozenge. The amount of 7.0 mg benzocaine per lozenge was labelled. The combined uncertainty of sample and calibration measurements was statistically calculated using a significance level of α = 0.05 to a total relative uncertainty of 7.49 %. The separation method is inexpensive, fast and reliable.

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Acknowledgments

The authors express their appreciation to Merck-Company (Darmstadt, Germany), BioStep (Jahnsdorf, Germany) and DESAGA GmbH (Wiesloch, Germany) for their kind support.

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Authors and Affiliations

  1. Institute of Process Engineering, University of Offenburg, Badstrasse 24, 77652, Offenburg, Germany

    Barbara Milz & Bernd Spangenberg

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  1. Barbara Milz
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  2. Bernd Spangenberg
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Correspondence to Bernd Spangenberg.

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Published in the topical collection Miniaturized and New Featured Planar Chromatography and Related Techniques with guest editor Paweł K. Zarzycki.

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Milz, B., Spangenberg, B. A Validated Quantification of Benzocaine in Lozenges Using TLC and a Flatbed Scanner. Chromatographia 76, 1307–1313 (2013). https://doi.org/10.1007/s10337-013-2436-4

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  • DOI: https://doi.org/10.1007/s10337-013-2436-4

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