L-Carnitine is often formulated with tartrate as counterion which in this application would have been coeluting with the structurally similar compound maleate, but fortunately that anion is not present in formulations of carnitine. The generic method used in this application was developed to enable analysis of the fifteen most common counterions used in pharmaceuticals and dietary supplements within 35 minutes, using an isocratic carbonate-based eluent.
Ion chromatographic analysis of carnitine dietary supplement 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 carnitine capsules dissolved and diluted in mobile phase 1:10000 and filtered (0.45 µm), giving signals up to 3.6 µS/cm.
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