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Stable Isotope Facility

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Please note: This research Programme is no longer active


 

The Facility
The development in the early 1980’s of mass spectrometers more suited to the analysis of biological material, and the subsequent rise in the demand for analyses, led to the establishment in 1984 of the 15N facility at Merlewood. Located at Grange-over-Sands in Cumbria, the stable isotope facility is now based at the CEH Lancaster site and carries out stable isotope analyses directed toward the terrestrial and freshwater scientific communities. In addition to 15N analyses, the Facility’s remit was extended to include analysis of the heavy stable isotope of carbon, namely carbon-13 (13C).

Analytical Equipment
The Stable Isotope Facility currently has 3 mass spectrometers as follows:

  • An ANCA Roboprep/Tracermass instrument manufactured by Europa Scientific. This is a combined on-line, continuous-flow elemental analyser and single-inlet mass spectrometer for the automated analysis of solid samples. It is used for enriched 15N analysis and natural abundance 15N in addition to 13C analyses.

  • A Carlo Erba NA1500 elemental analyser coupled to a Denis Leigh Technology mass spectrometer. In addition to handling service work at busy periods, it is also used by visitors to the laboratory and by Facility staff in the development of techniques and personal research. One such future development may be the analysis of d34S in organic materials.

  • Recently the Facility has been equipped with state-of-the-art instrumentation to enable compound specific (GC-C-IRMS, irm-GC-MS) d13C and d15N analyses. This consists of a fully automated (100 sample capacity carousel) Hewlett Packard 6890 gas chromatograph (GC) interfaced to a Micromass Isoprime mass spectrometer via an on-line furnace. The Isoprime can also be interfaced to our trace gas pre-concentrator for the analysis of CO2, N20 and CH4.

Analyses

  • Bulk analysis: Total % N and d15N at enriched and natural abundance levels in solid material. Precision at natural abundance better than 0.3 ‰.

  • Bulk analysis: Total % C and d13C at enriched and natural abundance levels in solid material. Precision at natural abundance better than 0.2 ‰.

  • 15N in N2 and 13C in CO2 by manual injection of gases

  • 13C in methane in air: the analysis of 100 ml air containing 1.7 ppm CH4 shall give an external precision of < 0.5 ‰ (SD 1 s and n = 10).

  • 13C in carbon dioxide in air: the analysis of 100 ml air containing 360 ppm CO2 shall give an external precision of < 0.2 ‰ (SD 1 s and n = 10).

  • Compound specific 13C: an accuracy < 0.3 ‰ with an external precision < 0.2 ‰ (SD of 1 s and n = 5) following injection of 1 nmole carbon onto the GC. The linearity shall be < 0.2 ‰ over the range 1 – 10 nA at mass 44.

  • Compound specific 15N: injection onto the column of 2 nmole N gives an external precision < 0.5 ‰ (SD 1 s and n = 10).

  • 15N in nitrous oxide: the analysis of 100 ml air containing 0.33 ppm N2O shall give an external precision of < 0.5 ‰ (SD 1 s and n = 10).

  • 18O in nitrous oxide: the analysis of 100 ml air containing 0.33 ppm N2O shall give an external precision of < 1.0 ‰ (SD 1 s and n = 10).

Sample preparation
The Facility operates two liquid nitrogen impact grinders (freezer/mills, Glen Creston) for thorough homogenisation of bulk samples prior to isotopic analysis. The combined movement of the impactor under liquid nitrogen permits ultra-fine grinding of materials that are often difficult to grind at normal room temperature. If grinding is required, the weight of the sample to be submitted should ideally fall between the range 80 mgs and 2 g dry weight. A place micro balance is utilised for obtaining sample weights prior to automated analyses.

Samples
Preferably the size of the sample should be sufficient to contain:

  • 100 mg nitrogen for 15N by automated analysis

  • 1.5 mg nitrogen for high precision determinations

  • 100 mg carbon for natural abundance and enriched

Examples of samples analysed
The experience of the facility is mainly of plant and soil samples, but has analysed freeze-dried animal tissues. Typical samples the SIF has analysed in the past include foliage, roots, soil fauna, fungi, zooplankton, feathers, fish etc. Water and gas samples are accepted according to circumstances, as they may require special treatment.

User Access
The SIF is available to carry out analyses in support of research within HEI’s and component and grant aided Institutions of NERC. A request for an analyses application form should be made to the facility either via e-mail or by telephone or facsimile. The facility requests that all applicants complete their application forms in typed format. On its completion, the form should be forwarded to the facility with accompanying information relevant to the project in question. The proposal is assessed for scientific merit by a small Steering Committee Applications to the Facility can be made at any time of the year as the Committee holds its meeting by post and not at fixed times. Successful applicants will then be notified. Funding arrangements will be agreed centrally by NSS and the Steering Committee of the Soil Biodiversity Programme.

Further information can be obtained from:
Dr. Andy W. Stott,
Stable Isotope Facility,
Centre for Ecology & Hydrology, Lancaster
Lancaster Environment Centre
Library Avenue
Bailrigg
Lancaster
LA1 4AP
 
Tel: 01524 595801
Fax: 01524 61536

e-mail: astott@ceh.ac.uk