Analytical Services - δ13C of Dissolved Inorganic Carbon (DIC) in natural waters
The SPA lab does not routinely analyze δ13C of dissolved inorganic carbon (DIC) in natural waters; we have a very limited track record. However we have the capability to analyze DIC isotopes using a Gas Bench II coupled to a MAT-253 IRMS. Water samples are injected into helium flushed 12 ml Labco exetainer vials containing 0.5 ml of 85% phosphoric acid. After 18 hours of reaction time, DIC derived CO2 evolves from the acidified water into the headspace and is passed on to a MAT-253 IRMS.
Calibrated in-house NaHCO3 standards that are interspersed between samples to correct for linearity effects and drift. A second calibrated laboratory standard is run "as-a-sample" to monitor quality control and long term performance. Standards are prepared by dissolving NaHCO3 in water that has been stripped of DIC by sonicating under a weak vacuum for 1 hour. The in-house NaHCO3 powders have been previously calibrated against international Standard Reference Materials (NBS-19 and LSVEC) using a two-point linear normalization approach. Normalized values are expressed relative to VPDB for δ13C.
DIC δ13C Rates
|δ13C||Liquid||20-50 µg||± 0.1 ‰||$8||$12|
Sample Types: natural waters
Sample requirements: Because we do not routinely analyze δ13C of DIC, please contact the SPA lab prior
to submission. Typically, 1-5 ml of natural waters is required for analysis; most
samples can be run using 1 ml, though samples very low in DIC will need the higher
5 ml amount. Water should be ﬁltered through a binder-free 0.7 µm glass ﬁber syringe
ﬁlter, placed in glass vials vials, ﬁlled until a positive meniscus forms,and then
tightly capped so that no headspace or bubbles remains. Often waters are poisoned
with HgCl2 to stop bacterial transformations. Alternatively, you may filter with
with a 0.2 µm polysulfone syringe ﬁlters to remove bacteria and avoid the use of mercury
(Doctor et al. 2008). Vials should be kept dark and refrigerated; provide shipping
tracking information so we may be on hand to accept samples and keep them refrigerated.