Radiocarbon carbon advantages

All of the above particulate investigations were based on mini-radiocarbon measurement techniques, with sample masses typically in the range of 5-10 mg-carbon. This constituted a major advantage, because it was practicable to select special samples (given region, source impact, sediment depth) and to further subject such samples to physical (size) or chemical separation before 14C measurement. This type of "serial selectivity" provides maximum information content about the samples and in fact it is essential when information is sought for the sources or atmospheric distributions of pure chemical species, such as methane or elemental carbon. 

UPLC offers advantages over HPLC for AMS quantitation. The delivery of compound (parent or metabolite) occurs in a small volume. For example, a 12 s peak at a flow rate of 600 pL per minute is contained with an eluent volume of only 120 pL. This provides compatibility with automated well plate collection, a minimal amount of extraneous solvent carbon, and an optimum compound-to-eluent ratio. Second, UPLC column recovery is generally better than for HPLC, and it is often possible to get 95-100% of the radiocarbon through the column. This is difficult to compare to HPLC separation, as this parameter is often not assessed or reported, but our experience indicates an 80—90% recovery to be realistic for HPLC. Quantified high column recovery assures that no unknown metabolites have been lost in separation. The high throughput available from short elution times of UPLC is not accompanied by a loss peak resolution, as seen in the next section. 

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