Ephedrine alkaloids are used for the treatment of asthma and nasal congestion. There are numerous drugs containing pseudoephedrine hydrochloride in combination with paracetamol and other ingredients.

¹H NMR spectroscopy in solution application for quantitative determination of the alkaloids from Ephedra species: (-)-ephedrine, (+)-pseudoephedrine, and (+/-)-norephedrine, either singly or in mixtures with each other was reported. The method was specific and accurate.

However, there are a number of situations when it is necessary to determine the concentrations of components in solid-state mixtures without dissolving the sample. Therefore, an attempt was made to quantify pseudoephedrine in a solid formulation with microcrystalline cellulose.

Samples with different fractions (from 5.09 to 95.97 % g/g) were prepared by mixing pure (3S,2S)-(+)-pseudoephedrine hydrochloride and pure microcellulose (Avicel-105), one of the most commonly used excipients. To obtain homogeneous physical mixtures, the components were mixed for 5 minutes using an electric mixer.

Cross-polarization (CP) magic angle spinning (MAS) solid-state ¹³C NMR spectra were recorded. The CP parameters were used as optimized for experiments with pure (3S,2S)-(+)-pseudoephedrine hydrochloride.

Variable contact time experiments were necessary in order to find “perfect” contact time which ensures quantitation for all carbons of interest (outside the region overlapped by the resonances of cellulose). The peaks chosen for the analysis are these of methyl carbons and quaternary carbon.

¹³C CPMAS NMR spectra of pseudoephedrine/cellulose mixtures with various compositions were recorded. For statistical reasons, each measurement was repeated three times. A plot was constructed with composition of pseudoephedrine mixtures versus the measured ratio of peak areas. As a next step, the MAS NMR spectra of three drugs containing pseudoephedrine were recorded: Sudafed, Ibuprom-zatoki and Gripex in order to determine, if the content of pseudoephedrine can be determined in the solid commercial formulations.

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