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Abstract
Unmodified silica columns used with non-aqueous, usually methanolic, eluents containing an ionic modifier provide simple, flexible systems for the HPLC analysis of a wide range of basic cardioactive drugs and some quaternary ammonium compounds. Retention and peak shape are influenced primarily by eluent pH and ionic strength although changes in eluent composition and in the stationary phase may also prove useful. Recently it has been found that chemically-bonded strong cation exchange materials provide enhanced retention for analytes which are poorly retained on silica alone. Solvent extracts and elution fractions from bonded-phase extraction tubes may be analysed directly and, in addition to low-wavelength UV and fluorescence, electrochemical oxidation detection may be used routinely for a wide range of analytes including secondary and tertiary aliphatic amines.