A simple and highly reproducible technique to extract the 14CO2 resulting from respiration of 14C-labeled seawater samples
Résumé
Production of 14CO2 from water samples amended with 14C-labeled molecules allows estimation of the mineralization rates of a variety of organic compounds. Diverse protocols have been already proposed for 14CO2 extraction and trapping. Yet, efficiency of carbon dioxide recovery greatly varies and, despite the application of operators, data from duplicate samples are often divergent. In order to propose a standardized protocol and to avoid the main source of artifacts, we suggest keeping the trapping agent for 14CO2 directly into a 20 ml scintillation vial hanging in the degassing bottle. To validate this protocol, we plotted the radioactivity (disintegration per minute) due to 14CO2 recovered after acidification of 42 seawater samples supplemended with sodium (14C)-bicarbonate (NaH14CO3) against the actual radioactivity of the corresponding added bicarbonate solutions. Efficiency of this protocol results satisfactory; as for these 42 assays the percentage of recovery is equal to 99% with a very low variability (±1%, p ¼ 0.05).