treatment methods applied to sample preparations for
TRANSCRIPT
Treatment Methods Applied to
Sample Preparations for Carbon-14 Determinations
Dr Sophie CERSOY
Muséum national d’Histoire naturelle, Paris (France)
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Plan of the seminar
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
1
2
3
4
5
6
Principle of 14C dating
Sample contamination
Sample treatment methods
Effect of burial environnment
Collagen characterization
Data processing
Pr. Willard F. Libby (right), the physical chemist
who conceived of 14C dating(University of Chicago Library)
Pr. Hessel de VRIES, "the unsung hero of radiocarbon dating"
(Université de Gröningen)
Principle of 14C dating
Carbon (C) = a chemical elements, with more than one type of atom, called isotopes.
98.99 % 1.11 % 0.000000000001 % Content on earth
UNSTABLESTABLESTABLE
Carbon-12 (12C)
Carbon-13 (13C)
Carbon-14 (14C)
protons
neutrons
electrons
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
1
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
14N + 1 neutron 14C + 1 proton
Carbon-14 production
Cosmic rays
In the upper atmosphere (stratosphere) :
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Carbon incorporation into living organisms
Photosynthesis
Feeding
Troposphère
CO2
Breathing
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
After death….
End of CO2
exchanges
The amount of 14C decreases over time: it is a natural process
called radioactive decay
CO2
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Radioactive decay of carbon-14
Date of death
14C 14N + 1 electron + 1 anti-neutrino
14C12C
Time elapsedsince death
« Cambridge half-life »of radiocarbon
Regular math law !
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Radioactive decay of carbon-14
Regular math law !
Date of death
14C 14N + 1 electron + 1 anti-neutrino
14C12C
Time elapsedsince death
VALID IF the amount of 14C in the atmosphere (t=0)is constant over time !!
« Cambridge half-life »of radiocarbon
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Need for calibration
IntCal 13 radiocarbon
calibration curve
The quantity of carbon-14 in the atmosphere is NOT constant over time, in particular because of the activity of the sun and fossil fuel combustion
From : https://c14.arch.ox.ac.uk/oxcal/OxCal.html.
Result of the measurementin year "Before
Present“(BP = before 1950)
Calibrated date = calendar age
(in calBC or calAD)
Without calibration
Principle of 14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Which archaeological materials can be dated ?
First requirement : Carbon-containing materials
Bone, ivory, sinew, antlers, teeth Shell, coral, otholith Horn, feather, nails, beak, claws
Hair, textiles like silk, wool, fur, leather, parchment, paper
Insects Wood, charcoal
Seeds, plant remains,
…
and all objects made of these materials!
Fats, peat, wax, lead white,
carbon black…
Second requirement : Materials less than 50,000 years old
Principle of 14C dating
Which archaeological materials can be dated ?
-50 000 -40 000-30 000 -20 000-10 000 0
Neolith
ic
AN
TIQ
UITY
Homo Sapiens in
Europe
Pleistocene Holocene
Time
14C dating
Lascaux Cave
First burials
Paleolithic
PREHISTORY
MID
DLE
AG
ES
, M
OD
ER
N
an
d C
ON
TEM
PO
RA
RY
ER
A
Dendrochronology
Uranium-Thorium dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Second requirement : Materials less than 50,000 years old
Principle of 14C dating
Which archaeological materials can be dated ?
14C dating
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Representativeness You date what you have chosen to sample !
Archaeological interpretationYou date the death of the living organism and not the date of use of the object.
Association of the sample dated with the archaeological event of interest ?
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
2
Main issue : Dating carbon that was present in the living organism
valid if all exogenous sources of carbon are removed !
From : (Wood, 2015)
80 14C yroverestimation
Effect of contamination on
a radiocarbon date
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Main issue : Dating carbon that was present in the living organism
valid if all exogenous sources of carbon are removed !
Effect of contamination on
a radiocarbon date
From : (Wood, 2015)
80 14C yroverestimation
14 500 14C yrunderestimation
5 14C yrunderestimation
For accurate dates, contamination needs to be reduced to 0.1%
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Main issue : Dating carbon that was present in the living organism
valid if all exogenous sources of carbon are removed !
Challenging
From : (Wood, 2015)
PleistoceneHolocene
Effect of contamination on
a radiocarbon date
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
What are the sources of contamination?
Soil organic matters, bacterial contamination
Aromatics
Alkanes/alkenes
Cholestanes
Alcohols/ketones
Bone sample from the Neolithic site of Bercy, France Chemical analysis of the composition of humic acids
(Py-GCxGC/MS)
From : (Cersoy, 2018)
• Buried material• Humification process (from plants mainly)• Dark coloured humic substances (humic acid, fulvic acid and humin)
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
What are the sources of contamination?
Exogeneous carbonate
• Secondary carbonaceous material (diagenetic and non-biogenic)• Deposited on or in the material to be dated, after its fossilization
Atmospheric CO2
DissolvedCO2
E.g. : Leaching of bones by groundwater
Precipitation of « modern » calcite in the pores of the bone
Isotope exchange between the bone's carbonate and the dissolved carbon
Dissolution/reprecipitation of apatite
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
What are the sources of contamination?
Carbon-based exogeneous products (anthropogenic)
Preparation or decoration of the material for its use
Preservation/restoration additives
Organic dyes
Plant residues in mummy hair
From : (Fresnais, 2015)
Bone preservatives recommendedby archaeologists since 1904
From : (Johnson, 1994)
Sample contamination
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
What are the sources of contamination?
Lab/ modern contamination
Filters and ultrafilters
= Keratin (from hair, woolen clothing, eyelashes, eyebrows), fats (on fingers)
= with organic membranes
Archaeologists and lab staff
© R. Barrois
© N. Goepfert
3 Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
From sampling to measurement
Sampleselection
Mechanicalcleaning
Chemical treatments / purification
Carbon isolation (combustion and graphitization)
Counting the number 14C atoms
(AMS)
Sample Cleanedsample
Endogenouscarbon phase
CO2 then C (graphite target)
Uncalibrateddate
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
From sampling to measurement
Sampleselection
Mechanicalcleaning
Chemical treatments / purification
Carbon isolation (combustion and graphitization)
Counting the number 14C atoms
(AMS)
Sample Cleanedsample
Endogenouscarbon phase
CO2 then C (graphite target)
Uncalibrateddate
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Conventional AAA treatment
• Widespread• Effective for most samples (e.g. charcoal) • Basis of more complex treatments
Acid step
(A)
Alkali step
(A)
Acid step
(A)
Removeexogenous
carbonates and some fulvic acids
Removehumic acids
Effect : Remove somefulvic acids
and dissolvedC02
Variations between
protocols :
Choice of acid, concentration and duration
Optional Choice of pH, temperature and duration
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Conventional AAA treatment
Tips and practical precautions
• Wear lab coat, nitrile gloves, safety goggles, closed shoes and outfit covering the legs
• Use dedicated glasswares baked out at 450-500°C for a minimum of 3 hours
• Carefully rinse between each wash (at least 3 times and ideally with ultrapure water)
• Separated soluble and insoluble phases by centrifugation, decanting or using pre-
cleaned filters (e.g. Ezee filters from Elkay, Millipore nitrocellulose filters, glass filters)
• Monitor the pretreatment to adjust the protocol if necessary (duration)
• Treat the samples in batches with known-age standards and/or similar material for
quality controls and to improve data correctionKnown age VIRI E mammouth sample
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of charcoal : MNHN protocol
Acid step
(A)
Alkali step
(A)
Acid step
(A)
Hydrochloric acid(HCl) 1 M
20°C1h at least
(Several times)
Sodium hydroxyde (NaOH) 0,0005M - 0,03M
20 °C10 to 30 minutes
Several rinseuntil pH 7
Several rinseuntil pH 7
Hydrochloric acid(HCl) 1 M
20°C30 minutes
1) Sorting :Isolate charcoal samples
from sediment, plant remains and rootlets
2) Weighing :Weigh at least 10-20 mg of sample
4) DryingAt 50-70°C , one night
3) Chemical treatment :
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Bleaching : for wood, parchment and plant remains
Bleaching
Sodium chlorite (NaClO2) pH 3
2.5–5.0% w/v70 to 80 °C
Up to 30 min
• Remove lignins, waxes, and resins• Concentration, temperature and duration MUST be
adjusted depending on the fragility of each sample !
Acid step
(A)
Alkali step
(A)
Acid step
(A)
Hydrochloric acid(HCl) 0,5 to 1 M20°C to 80 °C20 minutes
Sodium hydroxyde (NaOH) 0,2 M20 °C to 80 °C
20 minutes
Hydrochloric acid(HCl) 0,5 to 1 M20°C to 80 °C
1 h
From : (Brock, 2010)
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of keratin samples : hair, wool, horn, nails, claws
Idea: extract keratin from the inner part of the hair (cortex)
Keratinextraction
Dithiothreitol (DTT), 10% in sodium
dodecylsulphate (SDS), and
Tris–HCl buffer50 °C5 – 7 d
Acid step
(A)
Alkali step
(A)
Acid step
(A)
Hydrochloric acid(HCl) 0,5 to 1 M60°C to 80 °C
20 minutes – 1h
Sodium hydroxyde (NaOH) 0,005 – 0,1 M
20 °C to 60 °C20 minutes – 1h
Hydrochloric acid(HCl) 0,5 to 1 M60°C to 80 °C
1 h
• Wear hairnet (to avoid modern hair contamination !)• 50- 100 mg of sample for hair
From : (Richardin, 2011)
Keratinprecipitation
Dichloroacetic acid (DCO), 2 %20°C
15 minThen trichloroacetic acid (TCA)
1hThen acetone
15 min
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of collagen samples
What’s in a bone ?
80 % Mineral phase
- Hydroxylapatite
- Carbonates
Collagen17 to 18% of the material
20 % Organic phase
- 88% collagen (type I) = a protein
- 8% glycoproteins
- 3% non-collagenic proteins(osteocalcin, osteonectin)
- 1% lipids and sialoproteins
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of collagen samples : protocols for bone, teeth, ivory
Purification
• Dating the organic phase of bone is more reliable• About 20 protocols for this phase proposed over the last 50 years
Demineralization
(A)
Contaminant removal
(A)
Gelatinization
(A)
Removeexogenous
carbonates and some fulvic acids+ remove the
mineral part of bone
Removehumic acids
Remove somefulvic acids
and dissolvedC02
+ collagensolubilization
Isolate pure collagenpeptides
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of collagen samples : protocols for bone, teeth, ivory
PurificationDemineralization
(A)
Contaminant removal
(A)
Gelatinization
(A)
Removeexogenous
carbonates and some fulvic acids+ remove the
mineral part of bone
Removehumic acids
Remove somefulvic acids
and dissolvedC02
+ collagensolubilization
Isolate pure collagenpeptides
Hydrochloric acid(HCl) 0,2 to 2 M
4°C, 20°C or 80 °C20 minutes – 2 days
EDTA20°C
Several days/weeks
or
Sodium hydroxide(NaOH) 0,1 M
20°C 0 minutes – 1 night
Hydrochloric acid(HCl) pH 1 to 558 °C to 100 °C
50 minutes – 17 h
Macro (10-100 μm), micro (0,1-10 μm)
and/or ultrafiltration (0,001-0,1 μm)
From : (Cersoy, 2017)
Sample treatment methods
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Case of collagen samples : difficult samples
Consolidants, preservatives, chemical contaminants
Highly contaminatedsamples
Microsamples (< 60 mg)e.g. small vertebrates, precious objects
Solventextraction
Acetone 40°C, 30-60 min
+ Methanol 40-50 °C,
30-60 min+
Chloroform 20°C, 30- 60 min
(ultrasonication)
« Soft » protocol
1. Demineralization : HCl 0.2 M, 4°C, 2- 4 d
2. Contaminant removal : NaOH 0,1M, 4°C, 2-4 d
3. Solubilization :pH 1, 1h, 90 °C
4. Purification : glass microfilters
From : (Cersoy, 2017)
Single aminoacid dating
Idea : isolatinghydroxyproline,
an amino acid foundmostly in collagen
preparative high performance liquid chromatography (HPLC)
From : (Brock, 2018) From : (McCullagh, 2010)
© J Rofes
Effect of burial environnment
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Contamination
4
• Cross-linking between collagen and organic acids from the soil (within hours)
• Difficult to study
• Uptake until circa 20 %
• « Complexes » partly dissolved during gelatinization and basic washes
From : (van Klinken, 1995)
Effect of burial environnment
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Collagen diagenesis
Collagen denaturation
The mineral matrix may protect collagen from degradation in the burial environment BUT
Hydrolysis with preferential loss of some amino acids
Collagen polypeptide chains
Breaking of weak bonds
Breaking of peptide bonds
Free amino acids(possibly modified e.g. deamidated asparagine or glutamine)
Degradation process favoured in hot and humid environments
Collagen characterization
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Quality control of extracted collagen
5
Yield
Carbon content and C/N ratio
Is the extracted collagen suitable for 14C measurement ?
- Weigh the cleaned bone before extraction- Weigh the "collagen" extracted after drying. -Calculate the ratio of the two
< 1 % : unsuitable !
%C <30 % or %C >50% of the weight of the collagen : unsuitable !C/N <2,9 : too degraded or C/N > 3,5 : contaminated : unsuitable !
Isotopic ratio mass spectrometry (IRMS)
Collagen characterization
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Quality control of extracted collagen
Proteomics
Py – GCxGC /MS
Is the extracted collagen suitable for 14C measurement ?
Soft ionization mass spectrometry techniques (MALDI-MS or LC-MS/MS)
If no endogenouspeptides detected:
unsuitable !
Pyrolysis 2-dimensional gas chromatography coupledwith mass spectrometry If contaminants
identified/ if collagen fingerprint
is missing : unsuitable !
Collagen characterization
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Upstream quantity control
ATR- FTIR
FTIR : Fourier TransformInfra-Red (spectroscopy)
ATR : Attenuated Total Reflectance
Estimation of the preservation of the organic phaseFrom 1 mg of crushed bone sample !
From : (Lebon, 2016) and (Rofes, 2020)
Mineralband
Organicband
amide I/PO4 α % collagen in the bone !
Collagen characterization
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Upstream quantity control
Collagen preservation (%)
1 mg of C
Estimation of the minimum quantity of bone to be sampled
From : (Rofes, 2020)
Well-preservedBadly
preserved
Data processing
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Measurements presentation
6
To allow further comparison and quality control, please provide on publication/reports :
• Yield and C/N ratio
• Collagen amount and carbon mass
• Raw result = 14C age (BP) : to allow the date to be recalibrated in the future
with a more accurate calibration curve
• Lab code = traceability which allows to go back to details about pretreatment
Data processing
IAEA seminar - TC Project RAS1025 - Enhancing the Capabilities of Radiocarbon Dating in Archaeological Applications (ARASIA) – 3rd Sept 2020
Calibration
6
Result of the measurement in year "Before Present" (BP = before 1950) with an associated margin of imprecision (±).
Exemple 1Measure : 22 920 ± 80 BP
After calibration : the age of the dated mammoth has a 95.4% chance of being
between 25 521 and 25 116 B.C.
OxCal program can be found here : https://c14.arch.ox.ac.uk/oxcal.html
Calibration curve Calibrated date
Plateau
Exemple 2Measure : 2500 ± 30 BP
After calibration : the age of the datedhuman has a 95,4% chance of being
between 788 and 537 B.C.
ReferencesStuiver, M. (1961), Variations in radiocarbon concentration and sunspot activity, J. Geophys. Res., 66( 1), 273– 276
Suess, H.E. (1955). Radiocarbon Concentration in Modern Wood. Science, 122(3166), 415-417.
Reimer, P., et al. (2013). IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP. Radiocarbon, 55(4), 1869-1887.
Waterbolk, H.T. (1971). Working with radiocarbon dates. Proc. Prehist. Soc. 37, 15e33.
Wood, R. (2015). From revolution to convention: the past, present and future of radiocarbon dating. JAS, 56, 61-72.
Klinken, G. J. Van et al. (1995) Experiments on Collagen-Humic Interactions: Speed of Humic Uptake, and Effects of Diverse Chemical Treatments. J. Archaeol. Sci., 22, 263–270
Cersoy, S., et al. (2018). Pyrolysis comprehensive gas chromatography and mass spectrometry: A new tool to assessthe purity of ancient collagen prior to radiocarbon dating. Analytica chimica acta, 1041, 131–145.
Stevenson, F.J. 1982. Humus chemistry genesis, composition, reactions. Willey Inter science, New York.
Zazzo, A., Saliège, J.-F. (2011). Radiocarbon dating of biological apatites: A review. Pal., Pal., Pal., 310 (1–2), 52-61.
Fresnais, M. et al. (2015). Recent advances in the characterization of hair of mummies from the Chilean Andean coast. Forensic Science International, 249, 25-34.
Johnson, J.S. (1994). Consolidation of Archaeological Bone: A Conservation Perspective. Journal of Field Archaeology, 21(2), 221-233.
Huls, C., et al.(2009). Ultrafiltration: Boon or Bane?. Radiocarbon, 51(2), 613-625.
References
Brock, F., et al. (2010). Current Pretreatment Methods for AMS Radiocarbon Dating at the Oxford RadiocarbonAccelerator Unit (Orau). Radiocarbon, 52(1), 103-112.
Richardin, P., et al. (2011). A new protocol for radiocarbon dating of hair and keratin type samples—application to an Andean mummy from the National Museum of Natural History in Paris. Archaeol Anthropol Sci 3, 379–384.
Cersoy, S., et al.(2017). Collagen Extraction and Stable Isotope Analysis of Small Vertebrate Bones: A Comparative Approach. Radiocarbon, 59(3), 679-694.
Cersoy, S., et al. (2017) Radiocarbon dating minute amounts of bone (3–60 mg) with ECHoMICADAS. Sci Rep 7, 7141.
Fewlass, H., et al. (2019). Pretreatment and gaseous radiocarbon dating of 40–100 mg archaeological bone. Sci Rep9, 5342 (2019)
Brock, F., et al. (2013). Analysis of Bone “Collagen” Extraction Products for Radiocarbon Dating. Radiocarbon, 55(2), 445-463.
van Klinken, GJ. (1999). Bone collagen quality indicators for palaeodietary and radiocarbon measurements. JAS26(6):687–95.
Lebon, M., et al. (2016). Rapid Quantification of Bone Collagen Content by ATR-FTIR Spectroscopy. Radiocarbon, 58(1), 131-145.
Rofes, J., et al. (2020), Detecting stratigraphical issues using direct radiocarbon dating from small‐mammal remains. J. Quaternary Sci, 35: 505-513.
Questions about quality assurance procedures
• Organised by SUERC/Glasgow University • Long-running program of inter-laboratory quality
control exercises undertaken by the 14C community (e.g. TIRI, FIRI, VIRI, SIRI in 2003; 2010 and 2017)
• Liquid scintillation (LS) and gas counting (GC) laboratories, as well as AMS laboratories
• Results analysed and published by E. Marian Scott (School of Mathematics and Statistics, University of Glasgow) and colleagues
International intercalibration studies
MNHN procedure
• Including know-age references samples in batches : same material, sameage, if possible international intercalibration samples, prepared the sameway as the real samples
• Including blank (14C free) in the batches : e.g. Phtalic anhydride• Including standard (modern 14C) in the batches : e.g. oxalic acid II NIST• Handle blanks and standards with dedicated tools (no contact with samples
or solvents)• Treatment of samples, weighing and handling on clean benches, covered
with aluminum foil like glasswares
Reference bone samples from the FifthRadiocarbon Inter-comparison (VIRI) :
Pleistocene mammoth bone from the Yukon Territory, Canada (VIRI E, 38772± 2532 BP). Consensus values for the ages made on 40
measurements (42 laboratories)