Leibniz laboratory for radiometric dating and isotope research
The resulting graphite-iron powder is pressed into aluminium target holders for the ion sputter source with the help of a pneumatic press. Based on our experience, samples can be easily contaminated by radiocarbon used in tracer studies, e.g. As tracer concentrations are typically a millionfold natural, minute quantities suffice to seriously contaminate samples with natural radiocarbon levels.
Those quantities may remain for years in equipment, e.g.
* Sample and sample pretreatment should be documented, if possible a picture should show the quality of the prepared sample.
** To establish the quality of the sample preparation outside our laboratory these samples should be accompanied by • at least two background samples • one or two standard samples (e.g. These samples have to be prepared in the same laboratory in substantially the same way as the unknown samples and will be charged as regular samples.
C dating service is for samples yielding at least 0.5 mg of carbon after chemical pretreatment (often acid-alkali-acid treatment of organic material).
The AAA extraction often produces two fractions: (i) the alkali residue (humin), free of the mobile contaminants, which (often) will yield a reliable sample age upon radiocarbon dating and (ii) the humic acid fraction, which may contain contaminating, soluble organic components.Repeated magnetic and electrostatic filtering reduces interfering ions to a level where can be measured.Schematic of the AMS system: the symbols indicate L a lens, Y-S one pair, XY-S two pairs of steerers (horizontal and vertical), BPM a beam profile monitor, FC faraday cups, SL vertical slits, and A aperture (drawing by M.-J. Approximate sample sizes required for the AMS Please contact us before sending these samples.* Sample size of dry peat; more material is required if the mineral content is high or the peat is decomposed. The precision of radiocarbon dates for recent samples (younger than 2000 years) of “normal” sample size (1-2 mg of carbon) is better than 0.5% (typically 0.3 - 0.4%) which equals /-40 years (25 - 30 years) for the 1-σ statistical uncertainty of the measured age.