INFLUENCE OF METHOD FOR REMOVAL OF SESTON ON THE DISSOLVED ORGANIC MATTER. II. COBALAMINS

Area of Science:

• Environmental Science
• Analytical Chemistry
• Marine Biology

Background:

• Accurate measurement of cobalamins (vitamin B12) is crucial for aquatic ecosystem health assessments.
• Previous methods for preparing water samples for cobalamin analysis, including continuous flow centrifugation, Millipore® filtration, and biodialysis, have not been critically compared.

Purpose of the Study:

• To compare the effectiveness and identify potential errors associated with three common methods for removing seston from water samples prior to cobalamin analysis.
• To evaluate the reliability of these methods in determining soluble and total cobalamin concentrations.

Main Methods:

• Comparison of continuous flow centrifugation, Millipore® filtration, and biodialysis for seston removal.
• Analysis of water samples for cobalamins using the prepared samples.
• Assessment of discrepancies and potential error sources introduced by each method.

Main Results:

• Millipore® filtration showed unpredictable pore occlusion and irreversible cobalamin adsorption.
• Continuous flow centrifugation potentially caused cell injury and leakage of cobalamins.
• Discrepancies in soluble vitamin B12 measurements were observed between methods for certain water samples.
• Time-dependent fluctuations in soluble cobalamin levels were noted in one lake sample.

Conclusions:

• The methods used to render water samples seston-free introduce significant potential errors, impacting the accuracy of cobalamin determinations.
• The validity of distinguishing between total and sestonic cobalamin measurements is questionable due to methodological limitations.
• Further research is needed to develop reliable methods for seston removal and accurate cobalamin quantification in aquatic environments.