Studies of cosmogenic in-situ ¹⁴CO and ¹⁴CO₂ produced in terrestrial and extraterrestrial samples: experimental procedures and applications

We have developed an experimental procedure for quantitative extraction of cosmogenic in-situ ¹⁴C produced in terrestrial and extraterrestrial samples, in the two chemical forms ¹⁴CO and ¹⁴CO₂ in which it is found to be present in these samples. The technique is based on wet digestion of the sample in vacuo with hydrofluoric acid at 60-80°C in a Kel-F® vessel. Kel-F is a homo-polymer (chlortrifluorethylene). The procedures and the digestion vessel sizes used allow convenient extraction of ¹⁴C activity from samples of 50 mg to 50 g weight. Procedure blanks were reduced considerably by the experience gained with the system, and can be reduced further. We determined that most of the in-situ ¹⁴C activity was present in the CO phase (> 60%) in the case of both terrestrial quartz and in bulk samples of meteorites, analogous to the case of in-situ production of ¹⁴C in ice. Some results of measurements of ¹⁴C activities in meteorites and in terrestrial samples are presented. The latter include several samples which have been studied earlier for in-situ ¹⁰Be (and ²⁶Al) concentrations, and allow us to determine relative ¹⁴C and ¹⁰Be production rates in quartz.