Soil/Sediment/Rock Sample Decarbonation – Organic 13C

Requirements

  • Samples must be sent ground up as well as possible, with no chunks present.
  • Roots must be thoroughly removed.
  • The decarbonation process requires a minimum of 2 grams of sample; however, we suggest you send at least twice that amount for rock-based carbonate samples.
  • Samples can be sent in vials/bags of your choice.
  • Received samples deemed too coarse (non-homogenized) will be ground via mortar and pestle at the client’s expense on an hourly rate (see Pricing, Billing, and Payment).

Methodology

Samples are processed 24 at a time in graduated 50 mL falcon tubes (Fisher Scientific # 22-171-717) by acidifying 2 grams of the sample with 40 mL of 0.5 N hydrochloric acid. The acidification process is done a minimum of two times over two days, with regular agitation of the vials done several times per day. Tubes are centrifuged at 4,000 RPM for 5 minutes between acidification steps and the acid is decanted. Vials are capped tightly overnight, and any residual pressure upon undoing the cap merits an additional acidification process. This is repeated until no residual pressure is heard or felt. Acid is decanted and the samples are rinsed twice with deionized water or until a pH of 5 to 7 is reached. Again, tubes are centrifuged and the supernatant is discarded between rinse steps. At the end of the final rinse, the supernatant is decanted and the tubes are placed in a drying oven at 46 °C for a week. Dried samples are then crushed by mortar and pestle into a fine powder and stored in 2 dram vials (Fisher Scientific # 14-955-326) until ready for analysis of δ13Corg.

Turnaround Time

  • ≤ 25 samples: 4-5 weeks to process.
  • > 25 samples: 6-8 weeks to process.