Membrane filtration is an integral part of the 14C method of measuring primary productivity in natural waters. Polycarbonate, cellulose ester, and glass‐fiber filters retain about 0.0003, 0.09, and 0.24 mg water per mm2 surface area. The [14C]bicarbonate in this retained water must be eliminated before the filter is assayed for radioactivity. Air‐drying, desiccator‐drying in the presence or absence of a CO2 absorbant, and oven‐drying are only partially effective decontamination procedures; washing with pH 2 filtered lake water removes most of the contaminating activity. A plot (dpm·filter−1 vs. volume filtered) is used to diagnose the efficiency of decontamination. A simple and safe decontamination procedure is shown to eliminate effectively all residual [14C]bicarbonate activity. Membrane filters are placed in scintillation vials, 0.1–1.0 ml of 0.5 N HCl is added, and, after a 2–3‐h interval, the scintillation fluor is added.
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Lean et al. (1979) studied this question.