Device and method for continuous analysis of the concentration of dissolved inorganic carbon (DIC) and of the isotopic carbon and oxygen compositions thereof

Abstract

The present invention relates to a novel analysis device and method for obtaining the concentration of dissolved inorganic carbon (DIC) and isotopic carbon and oxygen concentration thereof, continuously from a liquid sample.

Claims

1. A device for continuous analysis of a concentration of dissolved inorganic carbon (DIC) and/or of isotopic carbon and oxygen compositions thereof in a liquid sample, said device comprising: a plurality of reservoirs, each comprising a fluid; an assembly of tubes, each connected to one of the plurality of reservoirs, each containing a fluid, and connected to a pump positioned downstream of said tubes; a mixing chamber positioned downstream of the pump and wherein the fluids conveyed to the pump are dynamically mixed; a reaction loop positioned downstream of the mixing chamber, said reaction loop making it possible to convert the DIC into CO.sub.2 gas according to an acid-base reaction; a separation chamber positioned downstream of the reaction loop, said separation chamber also being connected to a vector-gas cylinder containing CO.sub.2-free vector gas; a pressure regulator and a control unit positioned between the vector-gas cylinder and the separation chamber and which control a flow of CO2-free vector gas sent from the vector-gas cylinder into the separation chamber for capturing the CO.sub.2 gas produced in the reaction loop; a waste reservoir positioned downstream of the separation chamber for recovering, via the pump, a residual fluid; a water- and particle-trap positioned downstream of the separation chamber; optionally, an open-split positioned between the separation chamber and the water- and particle-trap in order to adjust a flow of CO.sub.2-loaded vector gas; and a detection system positioned downstream of the water- and particle-trap.

2. The device as claimed in claim 1, wherein the separation chamber comprises a wall with an extended and treated surface for optimizing degassing.

3. The device as claimed in claim 2, wherein the wall of the separation chamber is made of frosted glass.

4. The device as claimed in claim 1, wherein the plurality of reservoirs comprise a first reservoir containing the liquid sample and a second reservoir containing an acidifying reagent.

5. The device as claimed in claim 1, wherein the detection system is an analyzer of infrared laser spectrometry type, of cavity ring-down type, or of isotope-ratio infrared spectrometer type.

6. The device as claimed in claim 1, wherein the CO.sub.2-free vector gas is chosen from helium and CO.sub.2-free synthetic air.

7. A method for continuous analysis of the concentration of dissolved inorganic carbon (DIC) and/or of the isotopic carbon and oxygen compositions thereof in a liquid sample, said method comprising: a) conveying the liquid sample to be analyzed and an acidifying reagent to a pump with constant flows F1 and F2, respectively; b) injecting and mixing the liquid sample and the acidifying agent in a mixing chamber; c) conveying the mixture of fluids obtained in step b) to a reaction loop wherein an acid-base reaction makes it possible to totally or partially convert the DIC into CO.sub.2 gas; d) conveying a mixture of gas and liquid obtained in step c) into a separation chamber; e) injecting a flow of vector gas devoid of CO.sub.2 into the separation chamber in order to capture the CO.sub.2 gas produced during step c) and released in the separation chamber; f) conveying the flow of vector gas containing the CO.sub.2, captured in step e), through a water- and particle-trap, optionally after a passage through an open-split for a flow adjustment; g) conveying a residual fluid composed of the acidifying reagent and of the degassed sample into a waste reservoir; h) conveying the flow of vector gas containing the CO.sub.2, captured in step e), into a detection system; i) determining the concentration of the DIC and/or the isotopic carbon and oxygen compositions thereof by means of said detection system.

8. The method as claimed in claim 7, wherein step a) is carried out under constant flows F1 of liquid sample and F2 of acidifying reagent of the order of 750 μl/min and 190 μl/min, respectively.

9. The method as claimed in claim 7, wherein step e) is carried out with a reaction loop of which the length ranges from 0.5 to 4.5 ml as a function of the liquid sample to be analyzed.

10. The method as claimed in claim 7, wherein step e) uses a vector gas chosen from helium and CO.sub.2-free synthetic air.

11. The method as claimed in claim 7, wherein the flow of CO.sub.2-free vector gas is controlled by a pressure regulator and a control unit in order to optimize an amount of CO.sub.2 gas arriving at the detection system.

12. The method as claimed in claim 7, wherein step a) is carried out with an acidifying reagent which is an anhydric acid.

13. The method as claimed in claim 7, wherein step i) is carried out by means of an analyzer of isotope-ratio infrared laser spectrometer type.

14. The device as claimed in claim 4, wherein the acidifying agent of the second reservoir is an anhydric acid or an orthophosphoric acid.

15. The method as claimed in claim 12, wherein the acidifying reagent is an orthophosphoric acid.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 represents a simplified diagram of an embodiment of an exemplary version of a device of the present invention.

(2) FIG. 2 represents an exemplary prototype of a device of the present invention.

(3) FIG. 3 represents the results of measurement of the carbon (D13C) and oxygen (D18O) isotope ratios of the DIC of various liquid samples obtained by a conventional analysis method with equilibration and the analysis method according to the present invention. (A) graph of comparison of the results obtained for the two methods (conventional method and continuous method) for the carbon isotopes. (B) graph of comparison of the results obtained for the two methods (conventional method and continuous method) for the oxygen isotopes.

(4) FIG. 4 represents the effects of the concentration on the carbon (D13C) and oxygen (D18O) isotopic values of various liquid samples: (A) in Na.sub.2CO.sub.3, (B) in NaHCO.sub.3.

(5) FIG. 5 represents the effects of the pump speed on the CO.sub.2 concentration of the DIC (A) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3, and the isotopic carbon values of the DIC (B) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3 and isotopic oxygen values of the DIC (C) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3.

(6) FIG. 6 represents the effects of the length of the reaction or mixing loop on the CO.sub.2 concentrations of the DIC (A) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3, and the isotopic carbon values of the DIC (B) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3, and isotopic oxygen values of the DIC (C) in Plancoët mineral water, Na.sub.2CO.sub.3 and NaHCO.sub.3.

(7) FIG. 7 presents a graph showing a linear relationship between the DIC concentrations read on mineral water bottles and the concentrations deduced from our analyses.

EXAMPLES

Example 1: Comparison of the Isotopic Carbon and Oxygen Compositions of the Dic of Liquid Samples Obtained by a Conventional Analysis Method with Equilibration and by the Analysis Method of the Invention

(8) For this experiment, 7 mineral waters and a seawater were measured for δ.sup.13C and δ.sup.18O in order to compare the measurements obtained with the hydride generator used according to the present invention and with the conventional equilibration method (Smajgl et al. 2017 19th EGU General Assembly, EGU2017, proceedings from the conference held Apr. 23-28, 2017 in Vienna, Austria., p. 9793) [6]. The 2 types of measurements were carried out on a Delta Ray instrument. The straight lines of correlation between the methods have correlation coefficients of 0.99.

(9) For this experiment, the default parameters are the following: pump speed: 40 rpm loop size: 0.5 ml gas flow: 80 ml/min

(10) The results are presented in FIGS. 3A and 3B.

(11) The results for each sample tested are detailed in the tables below of FIGS. 3A and 3B.

Example 2: Effects of the Concentration on the Isotopic Carbon and Oxygen Values of the Dic of Liquid Samples

(12) For this example, two standards (Merck Na.sub.2CO.sub.3 for analysis and Merck NaHCO.sub.3 for analysis) were prepared. The standards were dissolved in distilled water in order to obtain 5 different concentrations: 150; 300; 600; 800 and 1000 ppm; this made it possible to determine the influence of the CO.sub.2 concentration in the solution on the measurement of the δ.sup.13C and of the δ.sup.18O with the hydride generator used according to the present invention. For this experiment, the loop size was fixed at 500 μl and the pump speed at 40 rpm.

(13) The results are presented in FIG. 4.

Example 3: Effects of the Pump Speed on the Concentration and the Isotopic Carbon and Oxygen Values of the Dic of Liquid Samples

(14) For this example wherein the hydride generator was used according to the present invention, 5 peristaltic pump speeds were tested: 10; 20; 40; 60 and 80 rpm. For this experiment, the loop size was fixed at 500 μl and 3 samples were measured: a Plancoët mineral water, Na.sub.2CO.sub.3 (1000 ppm) and NaHCO.sub.3 (1000 ppm). It appears that the more the pump speed increases, the higher the CO.sub.2 concentration; the exchange between the acid and the sample appears to be more efficient, on the other hand the δ.sup.13C value measured is relatively stable. The δ.sup.18O, for low pump speeds, shows a certain variability, probably due to the low CO.sub.2 concentrations produced.

(15) The results are presented in FIG. 5.

Example 4: Effects of the Length of the Reaction Loop on the CO.SUB.2 .Concentrations and the Isotopic Carbon and Oxygen Values of the Dic of Liquid Samples

(16) For this example wherein the hydride generator was used according to the present invention, 4 loop lengths were tested; 0.5; 2; 3 and 4.5 ml. For this experiment, the pump speed was set at 40 rpm and 3 samples were tested: a Plancoët mineral water, Na.sub.2CO.sub.3 (1000 ppm) and NaHCO.sub.3 (1000 ppm). It appears that the greater the loop size, the more the CO.sub.2 concentration decreases; the exchange between the acid and the sample is possibly less efficient.

(17) The results are presented in FIG. 6.

Example 5: Calculation of the Residence Time Under Various Experimental Conditions (Pump Speed, Chamber Volume, Vector-Gas Flow Rate)

(18) For this example, the hydride generator was also used according to the present invention and the characteristics of table (a) below. (a) Gas-liquid separator configuration used

(19) TABLE-US-00001 Internal diameter of the tubes for the liquids (mm) 0.3 Gas flow rate (ml/s) (80 ml/min for Delta Ray) 1.33 Chamber volume (ml, estimate) 8 Pump speed (rpm) 40

(20) The results are presented in the tables below. (b) Calculation of the residence time (RT) of the CO.sub.2 by the known continuous method (seconds)
Total RT=total volume/(total volume×seconds.sup.−1)
Gas RT=total volume/(gas volume×seconds.sup.−1)
Total volume=liquid volume+gas volume (c) Calculation of the residence time (RT) for various pump speeds, in typical configuration

(21) TABLE-US-00002 Pump Vector-gas Total speed Liquid flow flow rate Total flow RT (s) Gas RT (rpm) rate (μl/s) (μl/s) rate (pl/s) 5.98 6.00 10 4.0 1333.3 1337.3 5.96 6.00 20 7.9 1333.3 1341.2 5.95 6.00 30 11.9 1333.3 1345.2 5.93 6.00 40 15.8 1333.3 1349.1 5.91 6.00 50 19.8 1333.3 1353.1 5.90 6.00 60 23.7 1333.3 1357.0 5.88 6.00 70 27.7 1333.3 1361.0 (d) Calculation of the residence time (RT) for various chamber volumes in typical configuration

(22) TABLE-US-00003 Vector-gas Total Chamber Liquid flow flow rate Total flow RT (s) Gas RT volume (ml) rate (μl/s) (μl/s) rate (μl/s) 0.37 0.38 0.5 15.8 1333.3 1349.1 0.74 0.75 1 15.8 1333.3 1349.1 1.48 1.50 2 15.8 1333.3 1349.1 2.96 3.00 4 15.8 1333.3 1349.1 5.93 6.00 8 15.8 1333.3 1349.1 11.86 12.00 16 15.8 1333.3 1349.1 23.72 24.00 32 15.8 1333.3 1349.1 (e) Calculation of the residence time (RT) for various vector-gas flow rates

(23) TABLE-US-00004 Total Liquid flow Vector-gas Total flow RT (s) Gas RT rate (μl/s) flow rate (μl/s) rate (μl/s) 69.08 80.00 15.8 100.0 115.8 37.07 40.00 15.8 200.0 215.8 19.24 20.00 15.8 400.0 415.8 9.81 10.00 15.8 800.0 815.8 4.95 5.00 15.8 1600.0 1615.8 2.49 2.50 15.8 3200.0 3215.8 1.25 1.25 15.8 6400.0 6415.8

(24) The results show that the total average residence time using this type of assembly is calculated at approximately 6 s. It is possible to decrease this time to 1 s by decreasing the volume of the separation chamber.

REFERENCE LIST

(25) 1. Method 4500-CO2 in Rice E W, Bridgewater L, Association APH, Association AWW, Federation WE«Standard Methods for the Exalination of Water and Wastewater», Am. Public Health Assn., 2012

(26) 2. Assayag et al., Rapid Communications in Mass Spectrometry, 20: 2243-2251, 2006

(27) 3. Bass et al., Rapid Communications in Mass Spectrometry, 26: 639-644, 2012

(28) 4. Patent application US 2010/0212406

(29) 5. Using Isotope Ratio Infrared Spectrometer to determine 513C and δ18O of carbonate samples

(30) 6. Smajgl et al. 2017, 19th EGU General Assembly, EGU2017, proceedings from the conference held Apr. 23-28, 2017 in Vienna, Austria., p. 9793