Chapter 1 - Investigation of Multi-Component Drugs by NMR Spectroscopy

Abstract

This chapter examines the influence of a variation of parameters, which can be adjusted to achieve the optimal signal separation making it more reliable, and looks into the special case of the multicomponent drug codergocrine mesylate. Codergocrine mesylate is completely soluble in methanol, acetone, and DMSO only. In solvents such as water, acetonitrile, chloroform, dichloromethane, and benzene the analyte shows a poor solubility. To influence the signal separation, the kind of solvent or the pH value of the solution can be changed, different sample concentrations can be applied, or auxiliary reagents like cyclodextrins or shift reagents can be added. In NMR spectroscopy the chemical shift is directly related to the structure of the molecule. Thus, for compounds, which show only slight differences in their chemical structure, it can be difficult to separate signals in spite of suitable parameter settings. In some cases the temperature also influences the signal separation. In contrast to chromatographic methods such as HPLC, NMR spectroscopy offers only a few parameters, which can be optimized to achieve optimal signal separation. The primary advantage of NMR spectroscopy is its efficiency due to the lack of any preparation times.