Chemiluminescence flow sensor for the determination of vitamin B12

A novel chemiluminescence (CL) sensor for vitamin B12 combined with flow-injection analysis is presented in this paper. It is based on the catalytic effect of cobalt(II), liberated from vitamin B12 by acidification, on the CL reaction between luminol, immobilized electrostatically on an anion-exchange column, and hydrogen peroxide electrochemically generated on-line via a negatively-biased electrode from dissolved oxygen in the flow cell. The sensor responds linearly to vitamin B12 concentration in the 1.0 × 10−3–10 mg l−1 range, and the detection limit is 3.5 × 10−4 mg l−1 vitamin B12. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of < 3.5%. The system is stable for over 500 determinations and has been applied successfully to the determination of vitamin B12 in pharmaceutical preparations.