Proton Magnetic Resonance Spectroscopic Determination of Bethanechol Chloride in Tablets

A simple and reliable proton magnetic resonance spectroscopic method was developed for the assay of bethanechol chloride in tablets. The proposed method entails a minimum of procedural steps and reagents. The recovery of bethanechol chloride from synthetic formulations was 99.9 ± 0.4% (n = 15), CV = 0.4%. Mean assay values for 25 and 10 mg commercial tablets were 100.5% (n = 8) and 99.7% (» = 7) of declared, respectively. A detailed interpretation of the proton magnetic resonance spectrum is also presented.

Proton magnetic resonance spectrum of cellulose triacetate. Temperature effects, the rotational conformation of the 6-acetoxymethyl group, and computer modelling of methyl 4,6-di-O-acetyl-β-glucopyranoside

Pronounced narrowing of the resonance signals in the 400-MHz 1H nmr spectrum of cellulose triacetate in CDCl3 between 25 and 50 °C, as well as shielding and deshielding changes in 1H chemical shifts, suggest that thermal disruption of intermolecular aggregates is accompanied by a conformational modification. Analysis of the spin–spin coupling patterns clearly evident at 50 °C indicates that although there is a reversal in the chemical shifts of H-6R and H-6S relative to those for acetylated D-glucopyranose derivatives, the rotational conformations of the exocyclic 6-acetoxymethyl groups of the polymer and the model compounds all favor RHS and RCS rotameric forms. Supporting evidence for this conclusion is obtained from the 2-dimensional 1H spectrum of a trisaccharide, O-β-D-glucopyranosyl-(1 → 3)-O-β-D-glucopyranosyl-(1→ 4)-O-β-D-glucopyranose undecaacetate. Computer-generated models of methyl 4,6-di-O-acetyl-β-glucopyranoside are examined in relation to the stereochemistry of 6-acetoxymethyl groups.