Some Practical Aspects of Measuring DOC:
Sampling Artifacts and Analytical Problems with Marine Samples

E. T. Peltzer
Marine Chemistry and Geochemistry Department
Woods Hole Oceanographic Institutiton
Woods Hole, MA 02543

P. G. Brewer
Monterey Bay Aquarium Research Institute
Pacific Grove, CA 93950

Marine Chemistry (1993) 41: 243-252.

Received: 8 July 1991.
Accepted: 5 December 1991.
Published: Juanuary 1993.

ABSTRACT

Efforts to reproduce the high-temperature catalytic oxidation technique for the determination of dissolved organic carbon (DOC) in marine samples are described and details of the construction of a home-made DOC analyzer are presented. Calibration of this instrument is compared with that of a commercial analyzer. Various problems relating to the determination of the instrument blank, instrument calibration, sample collection, preservation and processing are presented. Several hypotheses explaining the observed analytical artifacts are proposed and possible implications of these artifacts are discussed.

Acknowledgements

The authors thank M. Altabet for the seawater samples from Bermuda; S. Fitzwater for the frozen DOC samples; R. Benner and G. Tien for their samples of ultra-low carbon distilled water; C. Goyet for the use of the Li-Cor NDIR; Ionics, Inc. for the loan of the Model 555 Carbon Analyzer; and the captains and crews of the R/Vs Oceanus, Atlantis II and Alpha-Helix. We would especially like to acknowledge the help and advice of Dr. Yoshimi Suzuki in the early stages of this work. This work was supported by US National Science Foundation grants OCE-8701461 and OCE-8814393 to PGB and OCE-8716954 to ETP. This is contribution 7775 from the Woods Hole Oceanographic Institution.

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