Isotope Ratio Mass Spectrometry

Stable Isotope Ratios

• Service Provided: Stable isotope ratios for hydrogen, carbon, nitrogen, oxygen, and sulfur

• Techniques Used: Stable isotope ratio mass spectrometers combined with periphals allowing the introduction of gas, liquid, and solid samples

• Species Determined: d2H, d13C, d15N, d18O, and d34S

• Sample Types/Characteristics: Plant and animal tissues, soils, sediments, particulate organic matter trapped on glass fiber filters, aqueous and organic liquids, gasses

Specific sample preparation, storage, and shipping considerations

(Also see general sample submission information.)

Samples for isotope ratio determination fall into three major categories:

Biological Materials

Samples must be thoroughly dried and finely ground (powdered). Screw-cap glass vials are the preferred containers. If sample amounts are not severely limited, a sample size of 20-100 mg is convenient for us to work with. We normally use 1 - 2mg of sample per analysis. For materials with unusually low organic content (<10% carbon), a larger amount of material can be analyzed to provide optimal results. We will return unused samples, if so requested.

Geological Materials

Geological samples, such as marine sediments, must be thoroughly dried and finely ground (powdered). Up to 20mg of sample is weighed into a sample capsule for analysis. If inorganic carbon (carbonate) is expected to be greater than 1-2% of total carbon, then the samples should be pre-treated with acid. About 5 - 10 times the expected analysis weight should be provided, if possible. Screw-cap glass vials are the preferred sample containers.

Glass Fiber Filters

Before collecting samples, filters must be pre-combusted at 450C for 30 min. (Greater times and/or temperatures may alter the filters' properties.) We have found that Watman filters, either GFC or GFF, provide low background contamination and are easy to handle (they don't crumble when being loaded into analysis capsules), and are highly preferred. Our instrument will handle filters up to 25 mm in diameter. Filters must be dried, and should contain no more than 2 mg of organic material. Glass or plastic scintillation-type vials are the preferred containers; plastic petri dishes (with lids) or glassine envelopes work well also. Wrapping in aluminum foil is acceptable as long as the filters do not stick to the foil during drying.