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Basic Drugs : Effects of Ion Concentration


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 10mM. This tendency is also observed even for ODS-C which is a polymer-coated ODS column and sample is completely adsorbed at 0mM. 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 : 1.0mg/mL Scopolamine , 50μL

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

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