INFLUENCE OF METHOD FOR REMOVAL OF SESTON ON THE DISSOLVED ORGANIC MATTER. II. COBALAMINS.
Comparisons of the 3 previously used methods (continuous flow centrifugation, Millipore®filtration, and biodialysis) for making water samples seston-free before analysis for cobalamins point to several likely sources of error: (a) unpredictable occlusion of pores in Millipore®membranes during filtration; (b) irreversible adsorption of cobalamins by Millipore®membranes; (c) probable cell injury and leakage by centrifugation. Some water samples gave good agreement on soluble vitamin B12 by all 3 methods, while other samples had appreciable discrepancies. The validity of total vs. sestonic cobalamin determinations therefore is questioned. One lake had time-dependent fluctuation in soluble cobalamin.
Department of Botany, Washington University, St. Louis, Missouri 63130.
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Parker