The generic method used in this application was developed to enable isocratic analysis of the fifteen most common counterions used in pharmaceuticals and dietary supplements within 35 minutes, using a carbonate-based eluent. A few coeluting anions were also injected to illustrate potential interferences.
Separation of pharmaceutical counterions on a Metrosep A Supp 10 column (250×4 mm) using an eluent containing 12 mM Na₂CO₃ and 24 mM NaHCO₃ in water pumped at 1.0 mL/min at 24 °C from an EQAX-B1 eluent bottle equipped with an EQAX-TC1 trap cartridge for carbon dioxide removal. Background reduced to ~38 µS/cm by XAMS suppressor with ASUREX-A200 automatic regenerator. Eluent pumping and conductivity detection by Metrohm 761 Compact IC. Injection of 20 µL of acetate (1), formate (2), mesylate (3), chloride (4), phosphate (5), succinate (6), malate (7), tartrate (8), maleate (9), sulfate (10), bromide (11), oxalate (12), nitrate (13), besylate (14), fumarate (15), tosylate (16), at 5 or 20 mg/L (inorganic ions and organic acids, respectively) in water, giving signals up to 6 µS/cm.
Diduco is a leading provider of professional services in high performance liquid chromatography and manufacturer of the Xenoic® XAMS chemical suppressor and ASUREX automatic regenerator for ion chromatography.
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