Sealed Tube Combustion Method with MnO2 for AMS 14C Measurement

Abstract

ABSTRACTAn effective sealed tube combustion method was designed with an MnO2 oxidant for accelerator mass spectrometry radiocarbon (AMS 14C) measurements. Different types of materials (oxalic acid, cellulose, sucrose, wood, collagen, graphite, and humic acid) were used to test the method. A normal borosilicate glass tube was used instead of quartz and the combustion was done at 550ºC. The yield of the combustion is above 98% even in the case of the less combustible material such as graphite. The MnO2 reagent does not introduce detectable carbon contamination. The typical background is 0.29±0.20 pMC in the case of 200 µg carbon, measured as solid graphite target. With direct measurement of the CO2 by gas ion source AMS, the method is applicable up to 50 µg of carbon with an acceptable (~1 pMC) 14C background. A new type of tube cracker was developed for a quick chipless method of tube cracking and sample changing. In this way, the gas handling process takes only 5–6 min/sample.