Cremated bones are a commonly preserved material and often found in burial environments where unburned bone may not be preserved. As such direct radiocarbon dating of cremated bone could be essential in determining the chronology of an event. Pretreatment of cremated bone exploits the structural carbonate component of the bone which survives cremation. However, due to the low abundance (ca. 0.1%) of this component, the extraction of an amount of endogenous carbon sufficient for radiocarbon dating may represent a challenge. Here we investigate two modifications to the phosphoric acid digestion protocol used during the preparation of cremated bones at the Oxford Radiocarbon Accelerator Unit (ORAU). The first of these was to use ultrasonication to release evolved CO2 from the viscous phosphoric acid and cremated bone mixture that is formed during digestion. The second was to double the amount of time during which evolved CO2 was removed from the reaction vessel by transfer into a cryogenically cooled ampoule. Ultrasonication of the digestion mixture failed to produce a significantly higher carbon yield, while double-time collection resulted in an average 21.5±13.8% increase of C yield without affecting the measured age. Extending the collection time can better enable reliable dating of small (less than 1 g) samples.

Radiocarbon (14C) dating of sediment deposition around Antarctica is often challenging due to heterogeneity in sources and ages of organic carbon in the sediment. Chemical and thermochemical techniques have been used to separate organic carbon when microfossils are not present. These techniques generally improve on bulk sediment dates, but they necessitate assumptions about the age spectra of specific molecules or compound classes and about the chemical heterogeneity of thermochemical separations. To address this, the Rafter Radiocarbon Laboratory has established parallel ramped pyrolysis oxidation (RPO) and ramped pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) systems to thermochemically separate distinct carbon fractions, diagnose the chemical composition of each fraction, and target suitable RPO fractions for radiocarbon dating. Three case studies of sediment taken from locations around Antarctica are presented to demonstrate the implementation of combined RPO-AMS and Py-GC-MS to provide more robust age determination in detrital sediment stratigraphy. These three depositional environments are good examples of analytical and interpretive challenges related to oceanographic conditions, carbon sources, and other factors. Using parallel RPO-AMS and Py-GC-MS analyses, we reduce the number of radiocarbon measurements required, minimize run times, provide context for unexpected 14C ages, and better support interpretations of radiocarbon measurements in the context of environmental reconstruction.

This work presents the integration of an elemental analyzer (EA) and an isotope ratio mass spectrometer (IRMS) into the 6 MV AMS system at the Institute for Nuclear Physics, University of Cologne. The AMS measurement of δ13C values for IAEA-C6 reference material resulted in –11.39(226)‰, compared to –10.28(32)‰ obtained by IRMS. The EA-IRMS system was also tested with IAEA-C3, IAEA-C5, and IAEA-C7 reference materials, yielding –24.79(9), –25.18(15), and –14.76(18)‰ respectively. Compared to the IAEA information values given as –24.91(49), –25.49(72) and –14.48(21)‰ respectively. To investigate an observed sample mass dependency, environmental samples from Spitzbergen were examined, showing δ13C values of –25.17(55), –25.80(31), and –26.17‰ in Cologne, while Hamburg recorded –24.8(1), –25.5(1), and –26.2(13)‰. In summary, this new setup could enable online analysis and quasi-simultaneous measurements of 14C, δ13C, and δ15N for ultra-small samples, utilizing precise δ13C values from IRMS for fractionation correction of the 14C/14C isotopic ratio.

Accurate radiocarbon (14C) analysis depends on a successful carbon separation relevant to the studied object. The process of 14C dating involves the following steps: characterization and sample choice, sample treatment, measurements, and evaluation of the results. Here, we provide an overview of conventional approaches to macromolecular samples and address specific issues such as detecting and removing contamination with roots, dolomite, and conservation products. We discuss the application of elemental analysis (%N, %C) in the preparation of bones and the infrared analysis in monitoring the contamination of samples. Our observations provide the basis for the discussions of the existing results and for planning the future sampling.

The Laboratoire des Sciences du Climat et de l’Environnement (LSCE) has operated a radiocarbon dating laboratory for almost 70 years. It has evolved from a traditional ß-decay counting to an accelerator mass spectrometry facility. In 2015, the LSCE received a major upgrade with the installation of a MICADAS. This evolution required adjustments in sample preparation to match the new capability to date samples as small as a few tens of µgC. We summarize here the sample cleaning procedures and the chemical purification or extraction treatment that we apply to the samples. We also report values of blank and reference materials of different matrices that match the large diversity of samples handled at LSCE.

This paper compares various wood pretreatment methods for highly degraded, and problematic fossil wood extracted from the opencast Szczerców site of the Bełchatów Lignite Mine in Central Poland. The study evaluates the pretreatment methods using both large samples (55–255 g, referred to as series A) and small samples (36–150 mg, referred to as series B). Additionally, all preparation methods were applied to medium-sized samples (approximately 3 g, referred to as series C) with solvent washes in the Soxhlet apparatus. Radiocarbon dating was conducted using the LSC technique (subseries A1) and the AMS technique (subseries A2, series B, and C). The effectiveness and utility of each pretreatment protocol were compared based on 14C measurements and FTIR analysis. Through the conducted research and a multi-criteria analysis, the most effective method for preparing old fossil wood was identified. Our experience indicates that an extended, multistage preparation of highly degraded fossil wood samples, with a 14C concentration near the detection limit of the radiocarbon method, may result in a significant increase in 14C content.

Obtaining accurate radiocarbon (14C) results from wood samples requires the extraction of cellulose. In the past, this has been done using different combinations of methods including acidified bleaching, acid-base-acid, and strong bases. This often becomes a time-consuming task in most analyses, especially when single ring isotope chronologies are needed from wood samples. Using 14C and Fourier-transform infrared spectroscopy (FTIR), we tested four different pretreatment methods to determine their ability to produce high quality cellulose. We then adjusted the best methods to determine a method for pretreating wood laths of multiple rings. A sequence of base-acid-base-acid-bleach + strong base (BABAB+) and BABAB produced the most accurate results when compared to the Bomb20 Northern Hemisphere Zone 1 curve with an average difference in Δ14C of 1.3‰ and 5.8‰ respectively. These methods were adjusted to pretreat an entire wood lath and a comparison of the FTIR results suggest that our adjusted BABAB+ and BABAB produced high quality cellulose comparable to that of an individually pretreated ring. The possibility to pretreat wood lath samples has the potential to more than double the number of tree rings which can be pretreated in a week. This is a significant reduction in time when creating long tree ring chronologies.

Shipping radiocarbon samples from the scientist to the laboratories involves packaging and wrapping them with all sorts of bags and materials to make sure the samples arrive safely. Over the years a variety of possible and impossible package materials have arrived at our laboratory, causing problems occasionally but often being the highlight of the day cheering up the people involved. The reality of excavating important, occasionally unexpected, samples during field work sometimes includes taking samples when time is short or package materials could not be prepared. At this point, any kind of package becomes useful. Things like cigarette packets, reused office packets, tissue boxes, or medical packaging can become handy. But sometimes samples are taken, wrapped in aluminum foil, and forgotten in the desks. This article celebrates creativity, giving an overview of the many ways samples can be packed. However, using some of the less-than-ideal choices, drawbacks will be shown and possible problems explained.

Accelerator mass spectrometry (AMS) radiocarbon (14C) dating is central to the development of robust chronologies in archaeological and paleoenvironmental contexts spanning the last 50,000 years. For dates to be accurate, samples must be free of exogenous carbon contamination. At the Oxford Radiocarbon Accelerator Unit (ORAU), considerable advancements in the dating of bone collagen have been made through the development of a high performance liquid chromatography (HPLC) method for the dating of the amino acid hydroxyproline, which can mitigate the effects of carbon contamination. However, recent changes in ligand manufacturing methods for the mixed-mode column used in the ORAU protocol (Primesep A, SIELC Technologies; IL, USA) have resulted in unacceptably high analytical backgrounds. Prior to the manufacturing change, backgrounds of > 50k BP were achievable. Since the manufacturing change, a mean background of 32.5k BP has been measured. Due to column bleed, the Primesep A is therefore no longer suitable for 14C measurement of hydroxyproline from older material. Here, we present background data and the chromatography conditions used to isolate hydroxyproline using an alternative column, a preparative-scale Newcrom AH, which shows promising potential as an alternative for the routine isolation and AMS dating of hydroxyproline—especially approaching the age and mass limits of the method.

CH4 is the second most important anthropogenic greenhouse gas and originates from different sources. The use of radiocarbon (14C) analysis of CH4 opens up the possibility to differentiate geological and agricultural origin. At the CologneAMS facility, the demand for 14C analysis of CH4 required the development of a sample handling routine and a vacuum system that converts CH4 to CO2 for direct injection of CO2 into the AMS. We evaluated the processing of CH4 using several series of gas mixtures of 14C-free and modern standards as well as biogas with sample sizes ranging from 10 to 50 µg C. The results revealed a CH4 to CO2 conversion efficiency of 94–97% and blank values comparable to blank values achieved with our routinely used vacuum system for processing CO2 samples. The tests with a near modern CH4:CO2 biogas mixture gave reproducible results with a near modern 14C content of 0.967–1.000 F14C, after applying the background correction.

We constructed a laser ablation (LA) system using a diode laser for the accelerator mass spectrometry radiocarbon (AMS 14C) measurement of organic materials. The system could extract adequate CO2 to analyze small masses (0.1 mg C) at a resolution of 250 µm by a 5.5 W diode laser. The LA system was assessed using standard materials (IAEA-C1, IAEA-C2, IAEA-C3, IAEA-C6, and Ox II) and applied to natural tree ring samples. For the LA sampling of organic samples, which generally results in incomplete combustion, tungsten (VI) oxide was used as an oxidant to achieve complete burning. The results of the measurement of standard materials showed a low 14C background of F14C 0.0085 ± 0.0005 and reasonable reproduction of 14C values. Finally, we applied this system to a single-year analysis of tree-ringed spruce timber in Alaska. It was observed to have a detectable background for the 14C bomb peak.

Analysis of the chronological data and observation of a lagoonal sediment core reveal sand washover events between around 2.4 to 2.5 cal. ky BP in the Isumi River lowland. We conducted radiocarbon dating with AMS and constructed an age-depth model using the latest calibration curve and appropriate model routine. In the middle to lower part of the core, dark-gray sand layers are repeatedly deposited. Sand layers may exhibit an erosional surface at the base with fining upward grading. The overwash layers are composed of well-rounded sand with occasional gravel, indicative of transportation. overwash sediment characteristics are consistent with proximal marine deposits, suggesting an ocean origin (though riverine sediment is also similar in character). The age-depth model indicates very high sediment accumulation rates associated with overwash deposits. Based on the amount of accumulated sediment, relatively large-scale redeposition events occurred during this period but more information is needed to constrain the mechanism(s) causing the events. We also present a local reservoir age correction compatible with the Marine20 calibration curve.

The AMS Golden Valley laboratory is equipped with two accelerator mass spectrometers: the AMS facility from the Budker Institute of Nuclear Physics (BINP) and the Mini Carbon Dating System (MICADAS-28) from Ionplus AG and two graphitization systems: the Automated Graphitization Equipment (AGE-3) from Ionplus AG and the Absorption-catalytic setup (ACS) developed at the Boreskov Institute of Catalysis (BIC). The ACS was designed for graphite preparation from labeled biomedical samples, dissolved organics, and dissolved or gaseous carbon dioxide but has proven to be suitable for the traditional dating of objects no older than 35,000 years. Here we present two series of AMS data for the samples from Glasgow International Radiocarbon Inter-comparison (GIRI), prepared using AGE-3 and ACS, and then measured on MICADAS-28. The mean value of the background F14C was 0.0024 ± 0.0009 and 0.012 ± 0.003 for AGE-3 and ACS, respectively, and both methods gave reproducible results for the OXI.

The AMS Golden Valley radiocarbon analysis laboratory is equipped with two accelerator mass spectrometers: AMS facility from Budker Institute of Nuclear Physics (BINP AMS) and MIni CArbon DAting System (MICADAS-28) from Ionplus AG and two graphitization systems: Automated Graphitization Equipment (AGE-3) from Ionplus AG and Absorption-catalytic setup developed in Boreskov Institute of Catalysis (ACS BIC). The laboratory provides routine 14C analyses of various samples: collagen, cellulose, humic acids, carbonates from sediments, etc. The main focus of the laboratory is to determine the age of archaeological artifacts by radiocarbon dating. This work presents a comprehensive description of the BINP AMS facility, with its operation compared with that of MICADAS in the same laboratory. In 2022, the AMS Golden Valley laboratory participated for the first time in the Glasgow International Radiocarbon Inter-comparison (GIRI). The samples were graphitized on the AGE-3 and subsequently measured in both AMS facilities. A comparison of the results of the two series of experiments, namely AGE-3 + MICADAS-28 and AGE-3 + BINP AMS, is given.

A newly developed compact AMS, LEA (Low Energy Accelerator), is tested and compared with a state-of-the-art AMS system MICADAS (Mini Carbon Dating System), which has a precision performance of better than 1‰ for modern 14C. The main difference between these two systems is the acceleration voltage, which has been reduced from 200 kV with the MICADAS system to 50 kV with the LEA system. In order to execute the final performance tests, exactly same samples (2 sets consisting of 7 standards, 4 blanks, 26 wood samples) are measured on both systems successively. The results show that the LEA system is fully operational, and the performance is entirely comparable with that of the MICADAS system.

Eight atmospheric carbon dioxide samples (as calcium carbonate—CaCO3—precipitates) from Lindesnes site (58ºN, 7ºE), belonging to 1963 and 1980 (four samples from each year) and stored at the National Laboratory for Age Determination (NTNU), have been reevaluated through radiocarbon (14C) analysis. Previous 14C results indicated the presence of a contaminant, which was not removed through different chemical cleansing procedures (e.g., hydrochloric acid—HCl and/or hydrogen peroxide—H2O2). Here, we present a follow up investigation using 14C step-combustion and Fourier-transform infrared spectroscopy (FTIR) analysis. Results from 14C data indicate unsuccessful removal of the contaminant, while further FTIR analysis displayed the presence of moisture. This finding alludes to the possibility that the contaminant is of ambient air-CO2 deeply embedded in CaCO3 powders (within clogged CaCO3 pores and/or bonded to the lattice). Samples were found exposed to air-CO2 and humidity. These conditions may have lasted for years, possibly even decades, leading to the 14C offsets detected here.

GIRI (Glasgow International Radiocarbon Intercomparison) was designed to meet a number of objectives, including to provide an independent assessment of the analytical quality of the laboratory/measurement and an opportunity for a laboratory to participate and improve (if needed). The principles in the design of GIRI were to provide the following: (a) a series of unrelated individual samples, spanning the dating age range, (b) linked samples to earlier intercomparisons to allow traceability, (c) known age samples, to allow independent accuracy checks, (d) a small number of duplicates, to allow independent estimation of laboratory uncertainty, and (e) two categories of samples—bulk and individual—to support laboratory investigation of variability. All of the GIRI samples are natural (wood, peat, and grain), some are known age, and overall their age spans approx. >40,000 years BP to modern. The complete list of sample materials includes humic acid, whalebone, grain, single ring dendro-dated samples, dendro-dated wood samples spanning a number of rings (e.g., 10 rings), background and near background samples of bone and wood. We present an overview of the results received and preliminary consensus values for the samples supporting a more in-depth evaluation of laboratory performance and variability.

A new vacuum line to extract CO2 from carbonate and dissolved inorganic carbon (DIC) in water was established at Guangxi Normal University. The vacuum line consisted of two main components: a CO2 bubble circulation region and a CO2 purification collection region, both of which were made of quartz glass and metal pipelines. To validate its reliability, a series of carbonate samples were prepared using this system. The total recovery rate of CO2 extraction and graphitization exceeded 80%. Furthermore, the carbon content in calcium carbonate exhibited a linear relationship with the CO2 pressure within the system, demonstrating its stability and reliability. The system was also employed to prepare and analyze various samples, including calcium carbonate blanks, foraminiferal, shell, groundwater, and subsurface oil-water samples. The accelerator mass spectrometry (AMS) results indicated that the average beam current for 12C- in the samples exceeded 40 μA. Additionally, the contamination introduced during the liquid sample preparation process was approximately (1.77 ± 0.57) × 10−14. Overall, the graphitized preparation system for carbonate and DIC in water exhibited high efficiency and recovery, meeting the requirements for samples dating back to approximately 30,000 years.

As a required sample preparation method for 14C graphite, the Zn-Fe reduction method has been widely used in various laboratories. However, there is still insufficient research to improve the efficiency of graphite synthesis, reduce modern carbon contamination, and test other condition methodologies at Guangxi Normal University (GXNU). In this work, the experimental parameters, such as the reduction temperature, reaction time, reagent dose, Fe powder pretreatment, and other factors, in the Zn-Fe flame sealing reduction method for 14C graphite samples were explored and determined. The background induced by the sample preparation process was (2.06 ± 0.55) × 10–15, while the 12C– beam current were better than 40μA. The results provide essential instructions for preparing 14C graphite of ∼1 mg at the GXNU lab and technical support for the development of 14C dating and tracing, contributing to biology and environmental science.

A single-stage accelerator mass spectrometer (GXNU-AMS) developed for radiocarbon and tritium measurements was installed and commissioned at Guangxi Normal University in 2017. After several years of operational and methodological upgrades, its performance has been continuously improved and applied in multidisciplinary fields. Currently, the measurement sensitivity for radiocarbon and tritium is 14C/12C ∼ (3.14 ± 0.05) ×10–15 and 3H/1H ∼ (1.23 ± 0.17)×10–16, respectively, and the measurement accuracy is ∼0.6%, which can meet the measurement requirements in the nuclear, earth, environmental and life science fields. This study presents the performance characteristics of GXNU-AMS and several interesting application studies.