Effects of ion concentration on elution pattern for the analysis of scopolamine which has tertiary amine and whose pKa is 7.6 is shown. When the ion concentration is lowered, non-specific adsorption is observed for ODS-A and sample is completely adsorbed at the ion concentration lower than 10 mM. This tendency is also observed even for ODS-C which is a polymer-coated ODS column and sample is completely adsorbed at 0 mM. To the contrary, Asahipak ODP columns are free from the non-specific adsorption problem at any ion concentration level. Then ODP columns are suitable for analysis with the ESI method (LC/MS) in which ionization of sample is often supressed under high-salt concentration.


Sample : 1.0 mg/mL Scopolamine , 50 μL

Columns      : Shodex Asahipak ODP-50 4D (4.6 mm I.D. x 150 mm),
               ODS-A, ODS-C (4.6 mm I.D. x 150 mm each)
Eluent       : Phosphate buffer (pH7)/CH3CN=60/40
Flow rate    : 0.6 mL/min
Detector     : UV (254 nm)
Column temp. : 30 °C