Dissolved organic carbon contamination induced by filters and storage bottles

To optimize experimental protocol for marine dissolved organic carbon (DOC) studies in laboratory conditions, we examined the potential DOC releases f rom filters of different qualities as well as those from different types of bottles during 10 day-storage of Milli-Q water and 0.2 mu m-filtered seawa ter. The results showed that utilization of 47-mm circle filters including polycarbonate (0.2 and 1 mu m-pore size), polytetrafluoroethylene (PTFE: 0. 5 mu m-pore size) and aluminum oxide (0.2 and 0.02 mu m-pore size) may indu ce significant DOC contamination ranging from 12 to 41 mu M C for the first hundred milliliters of the filtrated solutions. However, filtrations of 2 to 41 of Milli-Q water decreased the DOC blank of the fillers to 2-5 mu M C . As expected, precombusted (450 degrees C, 6 h) glass fiber filters rinsed with 0.5-3 l of Milli-Q water produced very low blanks (1-4 mu M C). We fo und that 0 day-storage (15 degrees C, in the dark) of Milli-Q water and 0.2 mu m-filtered seawater (250 mi) into 11-polyethylene, polycarbonate and pe rfluoalkoxy (PFA)-Teflon bottles, initially cleaned with HCl 1% and abondan tly rinsed with copious amounts of Milli-Q water as well as in precombusted glass bottles (450 degrees C, 6 h) induced very low DOC contamination of t he solutions (0-5 mu M C). Although complete DOC-free contamination experim ent is difficult to reach particularly in shipboard conditions, these resul ts strongly suggest that appropriate cleaning procedure of the material is essential to reach blank level compatible with DOC studies in marine enviro nments. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.