SPECIATION OF VITAMIN-B-12 ANALOGS BY LIQUID-CHROMATOGRAPHY WITH FLAME ATOMIC-ABSORPTION SPECTROMETRIC DETECTION

Vitamin B-12 analogues and aqueous cobalt are separated by liquid chro matography using a reversed-phase column (Spherisorb ODS-2) and a mobi le phase consisting of a linear gradient from a 25:75 (v/v) mixture of methanol and 0.085 M phosphoric acid solution buffered at pH 5.2 with triethanolamine to a 60:40 mixture over 5 min. The vitamins are selec tively detected by measuring cobalt with an atomic absorption spectrom eter directly interfaced to the chromatograph. A simple T-piece is use d to compensate with air the difference between the nebulizer uptake r ate and the chromatographic now-rate (1.5 mi min(-1)). Recoveries of t he components from spiked preparations ranged from 90.8 to 108%. The m ethod is applicable to the analysis of pharmaceuticals for cobalamins.