We are building a flow-through system for 13C-CO2 analysis in water. We use acid to convert bicarbonate in water samples into CO2. Are there any catalyzes that could speed up the release of CO2 from water sample upon acidification?
Mechanical agitation
Sonication
High surface acid-compatible (inert) solid
etc....Much depends upon your specific application setup
Carbon isotope fractionation during gas-water exchange and dissolution of CO2
Author : J.Zhang P.D.Quay D.O.Wilbur
Geochimica et Cosmochimica Acta Volume 59, Issue 1, January 1995, Pages 107-114
Abstract
The kinetic and equilibrium fractionation effects for 13C during CO2 gas transfer (εk and εag−g) have been measured in acidified distilled water. The equilibrium fractionation effects between bicarbonate and carbonate and gaseous C02 (εHCO3−g and εCO3−g) have been measured in NaHC03 and NaHC03 + Na2C03 solutions, respectively, from 5° to 25°C. The measured fractionations, except εCO3−g, agreed with earlier work to within 0.2‰. εCO3−g was about 2‰ smaller than most values previously reported. The temperature dependence of the fractionation for 13C between bicarbonate and carbonate and gaseous CO2 was found to be εHCO3−g = −(0.141 ± 0.003) T(°C) + 0.05) ‰ and εCO3−g = −(0.052 ± 0.03) T(°C)E+ (7.22 ± 0.46)‰ respectively. The fractionation during gas dissolution was εCO3−g = −0.03) T(°C) + (1.31 ± 0.06%. and the kinetic effect during gas transfer, εk, was −0.81 ± 0.16‰ at 21°C and −0.95 ± 0.20‰ at 5°C.
The equilibrium fractionation between total DIC in seawater and CO2 in air (εDIC−g) was measured and compared with that calculated from the concentration of aqueous CO2, HC03− and CO3= and individual fractionations between the three C species and CO2 gas. The measured and calculated results showed a significant difference of up to 0.2‰. We hypothesize that carbonate ion complexes likely complicate the calculation of εDIC−g from individual C species. We obtain the following empirical function of εDIC−g in seawater vs. temperature and the carbonate fraction (fCO3), εDIC−g = (0.014 ± 0.01) TfCO3 − (0.105 ± 0.002) T + (10.53 ± 0.05) %., when 0.05 < fCO3 < 0.20and5°C< T < 25°C.
On-line technique for preparing and measuring stable carbon isotope
of total dissolved inorganic carbon in water samples (δ 13CTDIC)
Giorgio Capasso, Rocco Favara, Fausto Grassa, Salvatore Inguaggiato and Manfredi Longo
ANNALS OF GEOPHYSICS, VOL. 48, N. 1, February 2005
Abstract
A fast and completely automated procedure is proposed for the preparation and determination of δ 13C of total inorganic carbon dissolved in water (δ 13CTDIC). This method is based on the acidification of water samples transforming
the whole dissolved inorganic carbon species into CO2. Water samples are directly injected by syringe into 5.9 ml vials with screw caps which have a pierciable rubber septum. An Analytical Precision «Carbonate Prep System» was used both to flush pure helium into the vials and to automatically dispense a fixed amount of H3PO4. Full-equilibrium conditions between produced CO2 and water are reached at a temperature of 70°C (± 0.1°C) in less than 24 h. Carbon isotope ratios (13C/ 12C) were measured on an AP 2003 continuous flow mass
spectrometer, connected on-line with the injection system. The precision and reproducibility of the proposed method was tested both on aqueous standard solutions prepared using Na2CO3 with δ 13C=−10.78 per mil versus
PDB (1σ = 0.08, n = 11), and at five different concentrations (2, 3, 4, 5 and 20 mmol/l) and on more than thirty natural samples. Mean δ 13C TDIC on standard solution samples is –10.89 < per mil versus PDB (1σ = 0.18, n = 50), thus revealing both a good analytical precision and reproducibility. A comparison between average δ 13C TDIC values on a quadruplicate set of natural samples and those obtained following the chemical and physical stripping method highlights a good agreement between the two analytical methods.
