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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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How to Prepare Water Samples for Inorganic Carbon Analysis

Please keep the samples refrigerated . If the samples are refrigerated and analysed rapidly (holding time can be many months).

  • Filter sample with a 0.2micron filter into 40 ml vial
  • Fill the vials completely (i.e. with no headspace).
  • There is no need for preservative such as HgCl.
  • Refrigerate, do not freeze.
  • Vial Preparation:

  • Vials should be triple rinsed in DI water and dried in a carbonate particle-free atmosphere (Pre-cleaned EPA-VOA vials are available)
  • Optional: Add about 5-10 mg of blue copper sulfate solid to the vials prior to sample collection. The copper sulfate acts as a hindrance to microbial activity to preserve the dissolved CO2 in the sample.

    TraceClean EPA vials. Precleaned, 40 ml, amber borosilicate, 0.125" with silicone-teflon septa. (Quality Assurance is not necessary)
  • At VWR cat# 15900-024 (72 per case)
  • At Fisher cat# 0333827A (144 per case) NOTE: these vials will NOT hold the additional septa.
  • At Fisher cat# 03340120 VL NOTE: these vials are NOT pre-cleaned.
  • PLEASE ORDER EARLY; there is often a couple of months backorder.

    Septa for 13CDIC (2 options):

    Please note: The silicone-teflon septa provided with the EPA vials are permeable, in particular the inorganic carbon; therefore, for storage of more than a day or two, use an additional septum underneath the silicone-teflon septum, rubber or butyl side facing the water in the vial:

  • At Chromatographic Specialties Inc, rubber-teflon, #C8850522C
  • Or you can make your own septa with parts from McMaster-Carr (www.mcmaster.com> 1/8" thick butyl rubber sheets and a hole punch.
  • 12" 12" 8609K35 $10.49 Each
  • Cut-to-length (per foot) 36" 8609K67 23.78 per Ft.
  • Round Hole Arch Punches (e.g.: 3/4" 3427A19 14.65, need to determine hole size, this is likely incorrect)
  • Syringe and Filter

  • 40 mL syringe
  • Syringe filters (or filter disks) Recommended type: 0.2 mm Polysulfone GD/X Syringe Filters
  • Low protein binding filter for aqueous samples. Units include two prefilters [graded density Multigrade GMF 150 (10:1Ám) and Grade GF/F (0.7Ám)] that allow filtration of even the most difficult samples with minimal hand force. Choose the 13mm (0.51") size for samples up to 10mL or the 25mm (0.98") size for samples greater than 10mL.

    Collecting the DIC samples:

    1) pull sample water into a 40 mL syringe and empty 2-3 times to rinse syringe with fresh sample.
    2) SLOWLY pull sample for collection into the syringe (try to avoid entraining excess sediment and air bubbles)
    3) remove bubbles/headspace from syringe by tilting syringe upwards and expelling excess air
    4) attach syringe filter
    5) flush filter with approximately 10 mL (to rinse filter).
    6) SLOWLY push sample water into the vial. Vials need to be COMPLETELY FULL with a positive (convex upward) miniscus forms over the vial opening.
    7) screw the cap on firmly (some spillage will occur) until the septa slightly pops up into the cap opening, but dont overtighten cap. If the septa is off-center, the vial may leak and the sample will be compromised.
    8) keep the vials chilled until analysis. DO NOT FREEZE VIALS! Freezing will cause the water to expand and crack the vials!