Kaplan, L.A. 1994. Limnology and Oceanography 39(6):1470–1476.
I tested each step required to prepare freshwater samples for dissolved organic C (DOC) analysis, including collection, filtration, preservation, and storage. I placed particular emphasis on finding a protocol that was amenable for use at remote field sites as well as in the laboratory. A portable and manual syringe-type sample collection and filtration system was free of artifacts and yielded filter blanks of <5 µg C liter−1. Analysis of 5 yr of streamwater DOC data showed an average relative precision of 2% for the total procedure from sample collection through analysis by persulfate oxidation. Sample volumes of 100 liters or more were processed with a cartridge filtration system that gave results equivalent to syringe filtration. It is possible to store samples preserved with acids or biocides at room temperature for 2 weeks to 1.5 yr with only a 1–11% reduction in accuracy.