Aqueous Infrared Pharmaceutical Analysis of Two Choline Compounds by Flow Injection Analysis Using the CIRCLE Cell

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Abstract
The advent of the cylindrical internal reflectance (CIRCLE) cell has solved the difficult problem of quantitation of solutes in aqueous solutions by infrared spectroscopy. By a combination of flow injection analysis (FIA) and Fourier transform infrared (FT-IR) spectroscopy with the CIRCLE cell, a fast, reproducible technique suited for the determination of two choline compounds of pharmaceutical interest—succinylcholine chloride and bethanechol chloride—was developed. Quantitation was carried out with the use of either the ester band at 1075 cm−1 for bethanechol or the trimethyl quaternary ammonium band at 953 cm−1 for succinylcholine. Linearity of standard solutions was achieved from about 0.5 to at least 50 ppt for both compounds, and detection limits of 0.02% w/v were possible. A sample throughput of 60 samples/h was estimated. Analysis of pharmaceutical preparations was performed after minor sample clean-up, which was necessary only in the case of the bethanechol chloride tablets.