Radiocarbon dating samples Radiocarbon dating samples Samples used for radiocarbon dating must be handled carefully to avoid contamination. Not all material can be dated by this method; only samples containing organic matter can be tested: the date found will be the date of death of the plants or animals from which the sample originally came. Samples for dating need to be converted into a form suitable for measuring the content; this can mean conversion to gaseous, liquid, or solid form, depending on the measurement technique to be used. Before this can be done, however, the sample must be treated to remove any contamination
Stable-isotope probing Stable-isotope probing Stable-isotope probing (SIP) is a technique in microbial ecology for tracing fluxes of nutrients in biogeochemical cycling by microorganisms. A substrate is enriched with a heavier stable isotope that is consumed by the organisms to be studied. Biomarkers with the heavier isotope incorporated into them can be separated from biomarkers containing the more naturally abundant lighter isotope by isopycnic centrifugation. For example, CO can be used to find out which organisms are actively photosynthesizing or consuming new photosynthate. As the biomarker, DNA with C is then separated from DNA with C by centrifugation. Sequencing the DNA identifies which