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Soil Sample Carbon-13 Analysis by Isotope-Ratio Mass Spectrometry

Last revised July 22, 1997

Page contents: (click to skip down)

* [Overview of technique]
* [Sample prep considerations]

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Overview of technique
Isotope-ratio analysis for carbon-13 in solid-phase samples such as soil starts with transformation to gas phase by extremely rapid and complete flash combustion of the sample material. Ionized combustion product (carbon dioxide) is mass-analyzed by means of differing mass/charge ratios among the various isotopic species of CO2. A great many more details of the process are available in the [Process Overview] and [Practical Considerations] documents.

Sample prep considerations
Soil samples must be oven-dried, ball-milled to less than 250 um particle size, and weighed (25-30 mg, with ug digits significant) into 5 x 5 mm tin capsules before combustion. Poor precision can often be traced to inadequate grinding that leaves visible granules in the sample. Sample prep for soil 13C analysis is set out in excruciating detail in the [Sample Collection] instructions.

Clients may send us unprocessed soil samples, or may provide any of the above processing themselves at a major reduction in price. Please refer to the [Fee Schedule] page.

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