Alternative Methods for Cellulose Preparation for AMS Measurement

Abstract

ABSTRACT.The main methods applied to clean plant material for radiocarbon dating are not compound-specific and generally remove only the easily exchangeable components by an acid-base-acid sequence and additional optional steps like Soxhlet extraction to remove resins and oxidative bleaching with NaClO 2 . The products are normally clean enough for standard 14 C measurement, but in some cases it is desirable to have pure cellulose, which remains unchanged and immobile over longer time ranges, better representing the original plant material. In this work, 2 more compound-specific but still simple methods were tested to separate the cellulose from wood. The viscose method is based on the xanthification process used in the textile industry, where the alkali-cellulose with CS 2 forms a soluble cellulose xanthate, which is then extracted and cellulose is recovered. The second procedure is based on the wood/cellulose dissolution in ionic liquid 1-butyl-3-methylimidazolium chloride [BMIM]Cl, when the dissolved cellulose could be precipitated again by simply adding a water-acetone mixture. This process was recently reported, but still not used in sample preparation procedures for 14 C dating.

Radiocarbon Determination of Past Growth Rates of Living Acacia tortilis Trees from Two Arid Sites in Eastern Sahara

“…A total of 78 samples from these 10 cores were submitted for 14 C dating to satisfy the requirements for optimizing the calendar chronologies of the cores. 14 C measurements in these samples were performed on alpha-cellulose extracted from wood (Nemec et al 2010). Results (Table 2) revealed post-bomb 14 C concentrations (Hua and Barbetti 2004;Levin et al 2010) in the outer parts of the tree trunks, while the inner parts almost exclusively yielded 14 C dates between ~100 and 200 14 C BP, in agreement with the range of the wiggly part of the 14 C calibration curve between AD 1650 and 1950 (Reimer et al 2009).…”

MICADAS: Routine and High-Precision Radiocarbon Dating

“…The wood samples for high-precision measurements as shown below were cleaned with a base-acidbase-acid bleaching procedure (NÏmec et al 2010) and then graphitized on a recently developed system that is fully automated (Wacker et al 2010b). The graphitization system is directly coupled to an elemental analyzer (EA) and runs without any user interaction after the samples are loaded into the EA and the iron catalyst is inserted into individual reactors.…”

“…We do not know if the offset originates from systematic effects of our measurement procedures. Some of the wood samples presented were also treated with a simple acid-base-acid procedure for comparison and do not show the 26-yr offset (NÏmec et al 2010). The applied rigorous pretreatment with baseacid-base-acid-bleaching could therefore be responsible for the observed offset.…”

Evidence of 11-year solar cycles in tree rings from 1010 to 1110 AD – Progress on high precision AMS measurements

“…It remained open whether the offset originates from a systematic error during 14 C measurement or if the base-acid-base-acid-bleaching (BABAB) method [7] can be responsible for the observed offset.…”