METHOD AND AN APPARATUS FOR DETERMINING ISOTOPE RELATIONSHIPS

Abstract

The invention relates to a method and the device which is required for its performing for the determination of the isotope ratio of carbon and/or nitrogen in an aqueous mobile phase which contains a sample. The method comprises the following steps: introduction of the aqueous mobile phase into a reactor (i), heating of the aqueous mobile phase with addition of oxygen in the reactor to a temperature of higher than 600° C. for the formation of a water containing sample gas (ii), reduction of the nitrogen oxides being present in the sample gas as well as removal of the contained oxygen (iii), removal of water from the sample gas by chemical drying and/or membrane gas drying (iv) and introduction of the dried sample gas into an isotope mass spectrometer (v). It is essential for the present invention that the introduction in step (i) is realized by introducing the aqueous mobile phase in a capillary tube which leads into the reactor with a gas mixture of oxygen and at least one inert gas, wherein the mass flow of oxygen and inert gas is regulated or controlled by at least one mass flow controller which is upstream with respect to the introduction and that after step (iv) removed water is actively pumped off.

Claims

1. A method for the determination of the isotope ratio of carbon and/or nitrogen in an aqueous mobile phase containing a sample, comprising the following steps (i) introduction of the aqueous mobile phase into a reactor, (ii) heating of the aqueous mobile phase with addition of oxygen in the reactor to a temperature of higher than 600° C. for the formation of a water containing sample gas, (iii) reduction of the nitrogen oxides being present in the sample gas as well as removal of the contained oxygen, (iv) removal of the water from the sample gas by chemical drying and/or membrane gas drying, (v) introduction of the dried sample gas into an isotope mass spectrometer, wherein the introduction in step (i) is realized by introducing the aqueous mobile phase in a capillary tube which leads into the reactor with a gas mixture of oxygen and at least one inert gas, and wherein the mass flow of oxygen and inert gas is regulated or controlled by at least one mass flow controller which is upstream with respect to the introduction and that after step (iv) removed water is actively pumped off.

2. The method according to claim 1, wherein the step (iv) comprises a condenser and/or a membrane gas drying system which is downstream with respect to the condenser.

3. The method according to claim 3, wherein the condenser comprises a measuring device for the determination of the liquid level.

4. The method according to claim 4, wherein on the basis of the measured data of the liquid level the pumping is controlled or regulated.

5. The method according to claim 1, wherein for the membrane gas drying a perfluorinated copolymer containing a sulfo group as ionic group is used.

6. The method according to claim 1, wherein as inert gas helium is used.

7. The method according to claim 1, wherein via the addition of oxygen and/or inert gas into the atomizer the total mass flow in the system is controlled or regulated with at least one mass flow controller.

8. A device for the determination of the isotope ratio of carbon and/or nitrogen in an aqueous mobile phase containing a sample, comprising: an introduction device (100) for the introduction of the aqueous mobile phase into a reactor (10), the reactor (10) for heating the aqueous mobile phase to a temperature of higher than 600° C. for the formation of a sample gas, a reduction device (20) for the reduction of carbon and/or nitrogen compounds which are contained in the sample gas, at least one drying device (30, 40) for the removal of water and an isotope mass spectrometer (70), wherein the introduction device (100) is formed by at least one capillary tube (106) which is jacketed by a pipe (101), wherein through the capillary tube (106) the aqueous mobile phase and through the pipe (101) a gas mixture of oxygen and/or at least one inert gas are introduced.

9. The device according to claim 8, wherein the pipe (101) is at least partially jacketed by a cylinder (105).

10. The device according to claim 8, wherein through the purging region (103) between pipe (101) and cylinder (105) during operation a purging gas which is identical with or different from the atomizer gas mixture is guided.

11. The device according to claim 8, wherein the pipe (101) and/or the capillary tube (106) is/are manufactured from platinum.

12. The device according to claim 8, wherein the reactor (10) is filled with a silver wool.

13. The device according to claim 8, wherein a liquid chromatography is upstream with respect to the reactor (10).

Description

[0034] Further features, advantages and application possibilities of the invention also follow from the subsequent description of the figures. Here, all described and/or depicted features form on its own or in arbitrary combination the subject matter of the invention, independently of their summary in the patent claims or their back references.

[0035] Shown are in:

[0036] FIG. 1 the schematic illustration of the measuring device according to the present invention and in

[0037] FIG. 2 the introduction device according to the present invention in detail.

[0038] Thus, FIG. 1 illustrates the interconnection of the different components of the measuring device. Via line 1 a liquid sample, preferably from an HPLC, in an aqueous mobile phase is loaded into a four-way valve 2. This one can either discard the liquid sample by an interconnection via lines 42 and 41 in a collecting container 40 or can guide the sample via line 3 to an introduction device 100 which is here not shown in detail.

[0039] In this introduction device the sample is mixed with an inert gas, preferably helium, which is guided via a line 11, a mass flow controller 5, a line 6 and/or with oxygen which is preferably guided via a line 7, a mass flow controller 8 in line 9. Optionally, inert gas and oxygen can also at least partially be introduced via a common line 11. In each case, the liquid sample exits line 3 and in atomized form enters a reactor 10.

[0040] From reactor 10 via a line 12 the completely evaporated, water containing sample is transferred in a reduction device 20 in which the contained components, especially the carbon and nitrogen compounds, are reduced.

[0041] Via a line 21 the so treated sample gas together with the water vapor is introduced into the condenser 30. This condenser 30 preferably comprises a liquid measuring sensor 31 which controls/regulates the liquid level in the condenser 30. So, condensed water is pumped off via the lines 32 and 38 as well as a pump 33 in a controlled or regulated manner. Via a bypass connection with the components 34, 35 and 37 this water can also be guided into the collecting container 40 so that it is guaranteed that also in the case of very large amounts of water this water does not remain in the system.

[0042] Then, via a line 51 the sample can be fed into a drying device 50 for complete drying which is particularly preferably conducted with Nafion®. In this case, via a line 54 an inert gas, also preferably helium, is introduced and is again removed via a line 56.

[0043] Finally, via a line 61 the so prepared sample gas is fed into a line 65 and then into a mass spectrometer 70. Via a line 66 it is also possible to discard the sample or to discharge redundant sample amount/carrier gas.

[0044] FIG. 2 shows in detail once again the introduction device 100 according to the present invention. The introduction device 100 comprises a first capillary tube 106 into which, preferably from above, via line 3 liquid sample in a mobile phase is introduced, the flow of which is favorably realized in a continuous manner.

[0045] This capillary tube 106 is jacketed by a pipe 101. Favorably, the pipe 101 extends beyond the length of the capillary tube 106. It is conceivable that the geometry of the pipe 106 in the region of the outlet opening of the capillary tube 106 changes in a manner which is not shown.

[0046] Via a line 11 at a connecting piece 102 which opens out into the pipe 101, for example in an orthogonal direction, oxygen and/or inert gas are admixed so that in the further course of capillary tube 106 and pipe 101 in the region of the outlet opening of the capillary tube 106 the sample is atomized.

[0047] Preferable is a design in which the pipe 106 is jacketed by a cylinder 105. So, a purging region 103 is formed around the pipe 101. The purging region 103 comprises a second connecting piece 104 which is preferably arranged in orthogonal direction and into which via line 11 or in an alternative via another source also oxygen and/or inert gas are fed.

LIST OF REFERENCE SIGNS

[0048] 1 line

[0049] 2 four-way valve

[0050] 3 line

[0051] 5 mass flow controller

[0052] 6, 7 line

[0053] 8 mass flow controller

[0054] 9 line

[0055] 10 reactor

[0056] 11, 12 line

[0057] 20 reduction device

[0058] 21 line

[0059] 30 condenser

[0060] 31 liquid level controller

[0061] 32 line

[0062] 33 pump

[0063] 34, 35 line

[0064] 37 valve

[0065] 38 line

[0066] 40 collecting container

[0067] 41, 42 line

[0068] 43 plug

[0069] 50 drying device

[0070] 51 line

[0071] 56 line

[0072] 57 valve

[0073] 58, 61 line

[0074] 65, 66 line

[0075] 70 mass spectrometer

[0076] 100 introduction device

[0077] 101 pipe

[0078] 102 connecting piece

[0079] 103 purging region

[0080] 104 connecting piece

[0081] 105 cylinder

[0082] 106 capillary tube