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University of California
Stable Isotope Laboratory
Earth and Planetary Sciences
1156 High Street Santa Cruz, CA 95064

Lab: (831) 459-5751
Office: (831) 459-5857
Fax: (831) 459-3074


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Elemental Analyzer Overview

The Elemental Analyzer (EA) is a dumas (flash) combustion peripheral coupled to an isotope ratio mass spectrometer and used to measure:

  • δ15N and δ13C of a wide range of organic matter.
  • At UCSC, the EA is primarily used to simultaneously measure δ15N and δ13C of organic matter (e.g., muscle tissue, algae, kelp, collagen, hair). The facility has an EA dedicated to running 15N enriched samples primarily from samples collected on glass fiber filter (GFF) media.



    Elemental Analyzer Rates


    Continuous Flow: Elemental Analzer (EA) Analysis

    Elemental Analzer (EA)
      Isotope & Elemental
    Composition
    Phase Optimum
    Quantity
    Measurement
    Precision
    Cost per Sample
    Internal* External
    Elemental Analyzer δ13C, wt %C Solid 50 µg ± 0.2 ‰ $6.00 $9.24
    δ15N, wt. %N Solid 50 µg ± 0.2 ‰ $6.00 $9.24
    δ15N, δ13C, & wt. % Solid 50 µg N ± 0.2 ‰ $6.00 $9.24
    Sample Types: Organic solids, Oil, Some inorganic solids
    Examples: Plant matter, Bone, Animal tissue, δ15N and δ13C, Enriched samples, Ocean
    and Lacustrine Sediments
    δ15N, δ13C are typically measured simultaneously
    * An additional 54% University of California overhead (indirect) charge is automatically taken
    from UC based grants when paying for these samples..
    For samples that require sample processing above normal an additional assisted rate of
    $4.50/sample ($6.91/sample external) may be charged.



    Analysis


    Solid materials are analyzed for δ15N and δ13C isotopes using either a Carlo Erba 1108 or a CE Instruments NC2500 elemental analyzer interfaced to a ThermoFinningan Delta Plus XP isotope ratio mass spectrometer (IRMS). Tin (or silver) encapsulated samples are flash (Dumas) combusted at 1020°C in a quartz column containing chromium oxide (acting as an oxygen source to aid combustion) and silvered colbatous/cobaltic oxide (acting as a scrubber to "clean" the combustion products of sulfur bearing compounds and halides). Following combustion, excess oxygen and oxides of nitrogen are reduced in a reduction column (reduced copper at 650°C). Helium carrier flows through a water trap containing magnesium perchlorate. N2 and CO2 are separated on a Carbosieve GC column (45°C, 100 mL/min) before introduction to the IRMS.

    During analysis, calibrated in-house standards precede and are interspersed between samples to correct for linearity (size) effects and drift. A second calibrated laboratory standard is run "as-a-sample" to monitor quality control and long-term performance. These laboratory standards, which are selected to be compositionally similar to the samples being analyzed, have been previously calibrated against NIST Standard Reference Materials (IAEA-N2, IAEA-N3, IAEA-USGS25, and IAEA-USGS26 of δ15N and IAEA-CH7, and NBS-22 and IAEA-USGS25 for δ13C).

    Corrected delta values are expressed relative to international standards PDB (PeeDee Belemnite) for δ13C and Air for δ15N.


    Sample Preparation Guidelines


    Sample Size: The amount of sample required depends on the amount of carbon and nitrogen in the material. A sample should contain between 20-150µg N (60µg optimal size) and 200-2000µg C (60µg optimal). If the two of %N, %C and/or the carbon-to-nitrogen (C/N) ratio is know then you can use the tool below to guide the appropriate sample size for the instrumetation.


    Enter two of either the sample C:N ratio, weight % N, or weight % C in provided space:
    Entry 1: %N: %C: C:N ratio
    Entry 2: %N: %C: C:N ratio


    Acceptable range
    of sample weights
    Min. sample
    weight (mg)
    Optimal
    sample weight
    (mg)
    Max. sample
    weight (mg)
    Optimal sample
    contains: (µg)

    Run configuration: A Run Setup Tool is has been developed to aid in preparing standards for a run.

    Homogenization: Many samples, such as fish muscle, leaf disks, root sections, small insects, fish scales, etc., that meet the target weight can be encapsulated whole in tin capsules. Some samples (e.g., fish muscle) may need to be stripped of organic oils depending upon the scientific question. Heterogeneous samples such as leaves or coarse materials, such as soils or sediments requires homogenization by grinding using a mortar and pestle or automated grinder.

    Inorganic carbon removal from soils and sediments (2 methods): Sample containing both organic and inorganic carbon, generally inorganic carbonates, will combine to yield a mixed organic and inorganic δ13C value, if inorganic carbon is not removed prior to analysis. Inorganic carbon is often a component of ocean or lacustrine sediment and soils. Removal techniques are sample dependent. Please consult the literature for the standard protocols for your samples. Here we generally use one of two techniques.


    Supplies:

    Company Part Number Item Qnty. Cost
    Costech Analytical 41060 Tin capsules, 3.5x5 mm 100/pk $13.00
    Costech Analytical 41061 Tin capsules, 5x9 mm 100/pk $13.00
    Costech Analytical 41074 Tin capsules, 3.5x5 mm 250/pk $26.00
    Costech Analytical 41077 Tin capsules, 5x9 mm 250/pk $26.00
    Costech Analytical 41070 Tin capsules, 4x6 mm 250/pk $26.00
    Costech Analytical 41073 Tin capsules for large samples, 9x10 mm 100/pk $13.00
    Costech Analytical 41066 Silver capsules, 3.5x5 mm 100/pk $25
    Costech Analytical 41072 Silver capsules, 4x6 mm 250/pk $50
    Costech Analytical 41067 Silver capsules, 5x9 mm 100/pk $25
    Electron Microscopy Sciences 70437-R1 96-Well Plate, Round-Bottom, With Lid 10/pk $58.00
    Electron Microscopy Sciences 70437-R5 96-Well Plate, Round-Bottom, With Lid 50/cs $206.00

    Preparing samples:

    Samples must be dried, ground, and weighed prior to isotope analysis.

  • Analysis of a suite of wet samples can lead to poor analytical performance, and can potentially be damaging to the instrumentation. Therefore, all samples must be dried to constant weight prior to submission.
  • Drying of samples (plants, animals, soils and sediments) can be accomplished using a drying oven at 50-60C for 24-48 h, or a freeze drier.
  • Homogenization can be achieved by grinding with a mortar and pestle, a ball-mill grinder, a mixer mill, etc. The goal is to improve sample homogeneity (i.e., isotopic homogeneity). Grind the sample into a fine powder or flour with a consistent particle size.
  • Following sample drying and grinding, samples need to be weighed into small tin (or in some cases silver) capsules prior to isotope analysis. Choose a capsule size appropriate for your sample weight.

    For best results, samples should be weighted to &plusmin;1µg. Samples weighted to a lower precision can somewhat compromise the quality of %C, %N and C/N ratio data.

    Weighing and crushing:
    On a micorbalance tare an empty capusle and then add your sample. Once your sample is weighted, record the weight and shape the sample into a compact form for analysis.
    For small samples (ca. <5 mg), use a pair of forceps to articulate and crush the capsule. Crush the samples such that the capsule is compact and roundish (low aspect ratio), does not have spurious edges, and does not have sample spilling out of it.
    For large samples (ca. >5 mg), shape the sample into a cylinder using a homemade press. Make a press by drilling an approimately 5 mm hole in a 1/2" thick block of material (e.g., aluminum, or plastic), and making a piston of slightly smaller diamter (i.e., slightly less than 5 mm diameter).
    Do not handle the casules with your hands because hand oils will contaminate your sample.


    Sample Submission and Tray Preparation:

    Shipping Info:

    UCSC - Earth and Planetary Sciences
    Stable Isotope Laboratory
    1156 High Street, E&MS C512
    Santa Cruz, CA 95064

    Securing 96-well trays for shipping:

    For secure sample shipment, encapsulate samples in 5x9 tin capsules and store in a 96-well sample tray. Secure the tray tightly with 2 to 4 small pieces of lab tape. Multiple trays may be stacked. Wrap the tray or stack of strays in bubble wrap and tape tightly. DO NOT allow parafilm to contact your samples due to likely contamination.

    In cases where small (<5x9 mm) capsules are to be shipped caution is advised. It is not uncommon for crushed capsules to be liberated from their well positions during transport or shipping. 96-well tray design vary with vendor and some trays are not optimal for small capsule containment during transit. Ensuring that samples remain in thier positions it is the shippers responsibility and should be thoughtfully considered. Covering the wells with aluminum foil, prior to firmly securing the lid may help hold samples in place. Avoid organic material (paper, wax, etc..) coming in contact with your wrapped samples.