A low-blank photochemical extraction system for concentration and isotopic analyses of marine dissolved organic carbon

We report the development of a modified, low blank, ultraviolet oxidation and vacuum line system to convert marine dissolved organic carbon into carbon dioxide for concentration,Delta C-14, and delta C-13 analyses. The system performs quantitatively and precisely with preservation of isotopic signatures ( +/- 3%) based on additions of pure International Atomic Energy Agency standards. Analytical blank reduction from < 1.5 mu M to 0.2 mu M enabled a decreased detection limit from a sample size of similar to 650 mL to 30 mL using a simple dilution technique. Combined with advances in analyses of ultra- small ( 2 mu gC) samples using accelerator mass spectrometry, the technique provides a means for measuring Delta C-14 values in samples that were previously not analyzable.