β Scribed by G.R. Watson; J.P. Williams
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Assay of %-labeled solid organic material by liquid scintillation counting (LSC) may be carried out (a) as a finely powdered suspension in a suitable gel mixture, (5) by dissolving in an appropriate solvent and subsequent treatment as a liquid sample, or (c) by combustion to a gas soluble in a liquid amenable to LSC (1, 2). Complete oxidation and combustion has the advantages of improving l*C recovery and reducing quenching in the LSC assay.
Jeffay (3) and Ragland (4) have reviewed the advantages and disadvantages of the oxidation and combustion techniques available. The procedure of Van Slyke and Folch (5, 6) is most generally used because of its rapidity and the completeness of combustion of the compounds found in biological materials. This method, modified in the collection of the 14C0., produeed, has been used for the preparation of barium carbonate precipitates for Geiger-Miiller or proportional counting. Stiller (7) used a modified Stutz and Burris apparatus (8) for collection of Ba14C0, with good results, but the procedure requires 45 min per sample. Kuyper, Cortese, and Aghdashi (9) designed a wet-combustion method for **C analysis which utilized forced circulation in a closed system and required 14 min per sample. The absorbed CO, is quantitized and counted as barium carbonate. Roy (10) used essentially a similar system on a macro scale and counted an aliquot of the sodium hydroxide absorbent.
Previous methods for collecting '"CO, from various sources for LSC required long periods for diffusion and absorption (11-13)) and were time-consuming and tedious in their administration (14,15). They often necessitated the transfer of absorbent-laden filter paper strips and rinsings, or aliquots of absorbent to scintillation vials (16-18). Weyman et al. (19) described a system accessory to the Van Slyke-Neil1 blood gas apparatus in which 14C0, is absorbed directly in a scintillation vial immediately after manometric determination. Baggiolini and
π SIMILAR VOLUMES
The organic samples triply labeled with 3H, 14C, and 35S were combusted in a flow-type combustion flask under a continuous oxygen flow. The oxygen gas containing the combustion products, which were mainly 3H2O, 14CO2, and 35SO2, was introduced into successive 0.5 M H2O2 and Oxisorb (2-methoxyethylam