Comparisons of pretreatment extraction methods for tree-ring radiocarbon analysis

An appropriate method for tree-ring pretreatment is essential to ensure the reliability of 14C data. This study compared three pretreatment methods for tree rings: acid-base-acid-bleaching (ABA-B), Jayme-Wise and an improved method proposed in this research. The improved method utilizes an ultrasonic bath instead of Soxhlet extraction in the Jayme-Wise method. We assessed the 14C results of the three methods using subfossil tree-ring samples from the Sixth International Radiocarbon Intercomparison and contemporary tree-ring samples from Shangdianzi. The 14C results showed that both the improved and the Jayme-Wise methods were effective for extracting alpha-cellulose from subfossil and modern tree-ring samples. The ABA-B method was sufficient only for subfossil wood, while unstable for the modern tree-ring samples when the heartwood-sapwood transition was presence. The Fourier-Transform Infrared spectroscopy results indicated that the purity of alpha-cellulose extracted by the improved method was similar to that of pure alpha-cellulose. In comparison to the Jayme-Wise method, the improved method reduced the extraction time and the amount of organic solvent, while increased batch processing capacity.