Fast 14C Sample Preparation of Organic Material

Abstract

A fast 14C sample preparation technique for organic material in conventional 14C counting is described. The basic difference from conventional preparation is oxidation of the organic substances in a closed system under an oxygen pressure of ca 10 bars. After the explosion-like combustion, the reaction products SO2 and NO2 are oxidized immediately to SO4 2-and NO3 − and precipitated on the wall of the reaction vessel. The residual gas mixture is passed first through a cold trap at −78° to remove water vapor and then through an activated charcoal column at 0° for purification. CO2 is removed from the remaining O2−CO2 gas mixture in a LN2 trap at a pressure of ≃ 100mbar. With this method sample preparation time is reduced from ca 10 hr to ca 1 hr. The efficiency and reproducibility of the procedure is shown with 14C and 13C measurements of a sugar-carbon standard. The results obtained by the new technique agree well with conventionally prepared wood and bone samples.