# Patent

## Title
Process and apparatus for providing a gaseous substance for the analysis of chemical elements or compounds

## Abstract

The invention relates to a process and to an apparatus for providing a gaseous substance for the analysis of chemical elements or compounds. In one embodiment, a starting substance is continuously admixed with a reagent substance. This results in a gaseous reaction product which contains information about the elements of the starting substance, and a residual substance. The gaseous reaction product is separated from the residual substance and removed for analysis. One application is the isotopic analysis of oxygen or hydrogen from water.

## Background
RELATED APPLICATIONS
This application claims priority to German Patent Applications Serial Number 102 16 974.8 and Serial Number 102 56 009.9, filed on Apr. 16, 2002 and Nov. 30, 2002, respectively, the disclosures of which are hereby incorporated by reference in their entireties.
FIELD OF THE INVENTION
The present invention relates generally to the field of chemical analysis. More specifically, the invention relates to a process and to an apparatus for providing a gaseous substance for the analysis of chemicals elements and/or compounds
BACKGROUND OF THE INVENTION
The mass spectrometry determination of elemental and of isotopic information are important analytical methods. The use of a mass spectrometer makes it possible to identify individual chemical elements or compounds. A significant application in this context is the determination of the isotopic ratios of individual elements in a starting substance, for example 18O/16O in water or the determination of different hydrogen isotopes. Since the variations of the isotopic ratios are minimal, extremely precise measurement apparatus and processes are required for the analysis. Therefore, importance attaches not only to the mass spectrometry itself, but also to the preparation of the chemical elements or compounds for the analysis to be carried out.
In an existing isotope analysis process, the oxygen of water is not analyzed directly. Rather, the isotopic information is transferred to carbon dioxide (CO2) by the method of equilibration. To this end, a small amount of the water to be analyzed is introduced into a vessel, as is an even smaller amount of CO2. The proportion of water is higher by a factor of about 103 than the proportion of CO2. The vessel is shaken and there is mixing of the isotopic information from the oxygen of the water and the CO2. Owing to the significantly greater proportion of water, the original isotopic information from the CO2 is virtually suppressed. The equilibrated CO2 then contains the isotopic information of the oxygen from the water and is removed directly or using a carrier gas and fed to an isotope mass spectrometer for analysis. The disadvantage of this system is the necessary provision of the vessels for equilibrating water and CO2, and also the residence time in the vessels required therefor. This is disadvantageous, especially in the context of relatively large sample sizes.
In this process, the CO2 added to the water has the function of a reagent substance. After the equilibration, the gaseous CO2 may be referred to as a reaction product, and the water as a residual substance. The reaction product is required for the analysis.
Further processes are conceivable in which a starting substance is not directly analyzed, but rather information is passed on therefrom to a gaseous reaction product. It is important that there is a means for rapid and reliable, precise implementation.
Accordingly, it is desirable to provide a process and an apparatus which allows chemical elements or compounds to be rapidly and precisely prepared for analysis.
SUMMARY OF THE INVENTION
It is one object of the present invention to provide a process and apparatus for the production of gaseous substances for the analysis of chemical elements or compounds.
One embodiment of the present invention provides a process for providing a gaseous substance for the analysis of chemical elements or compounds. In this process, the elements or compounds are contained in a starting substance. The starting substance is continuously admixed with a reagent substance. At least one gaseous reaction product and a residual substance are formed. The gaseous reaction product contains information about the elements or compounds of the starting substance. The gaseous reaction product is separated from said residual substance; and the reaction product is removed for an analysis.
In another embodiment of the present invention, an apparatus is provided for providing a gaseous substance for the analysis of chemical elements or compounds. This apparatus comprises a reaction unit for the reaction of a starting substance containing the chemical elements or compounds with a reagent substance. The apparatus also comprises a means for continuously feeding the starting substance and the reagent substance into the reaction unit as well as a separating unit that comprises means for separating a gaseous reaction product from a residual substance. The separating unit has a first outlet from for the residual substance and a second outlet for the reaction product. A means for passing the reaction product on from the separating unit to an analytical instrument is also provided.



BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become apparent upon reading the detailed description of the invention and the appended claims provided below, and upon reference to the drawings, in which:
FIG. 1 shows an overview of the individual constituents of the apparatus according to the invention and their combination for the provision of oxygen for isotopic analysis.
FIG. 2 shows an enlarged illustration of a degassing unit.
FIG. 3 shows a basic illustration of the apparatus for providing hydrogen for isotopic analysis.
FIG. 4 shows an overview of the individual constituents of an apparatus according to the invention for providing hydrogen for isotopic analysis.
FIGS. 5a to 5d show details of an equilibration unit for hydrogen, wherein FIG. 5a is a plan view of a lid of the equilibration unit, FIG. 5b is a side view of the lid of FIG. 5a, FIG. 5c is a plan view of a bottom of the equilibration unit, and FIG. 5d is a side view of the bottom of FIG. 5c. 
FIG. 6 is a schematic diagram of an apparatus according to the invention for providing CO2 for the analysis of the carbonate content of a water sample.
FIG. 7 is a schematic diagram of an apparatus according to the invention for providing air for the analysis of the air composition or of the isotopic composition of the air components.



DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed generally to system and method for providing a gaseous substance for analysis of chemical elements and/or compounds. In one embodiment, a process according to the invention includes the following features:

    
    
        a) the elements or compounds are contained in a starting substance,
        b) the starting substance is continuously admixed with a reagent substance,
        c) at least one gaseous reaction product is formed which contains information about the elements or compounds of the starting substance, and a residual substance,
        d) the reaction product is separated from the residual substance,
        e) the reaction product is finally removed for an analysis.
    
    


One of the essential features of the novel process compared to the example illustrated at the outset is the continuous combination of the starting substance with the reagent substance. The gaseous reaction product is also formed continuously. Finally the separation of the reaction product from the residual substance likewise takes place continuously. The entire process is therefore continuous and can be carried out without breaks dictated by separate steps.
A preferred field of application is the isotopic or elemental analysis, and also the quantitative determination of elements or compounds in a starting substance. The information contained in the reaction products may therefore also be the elements or compounds themselves. For the sake of simplicity, unless otherwise stated, isotopic information and information on compounds is also referred to as elemental information.
As explained above, the reaction results in the reaction product and the residual substance. Further substances may be formed in addition which are removed. For later analysis, interest attaches to the gaseous reaction product which contains the information about the elements or compounds of the starting substance.
For the provision of oxygen on the one hand and hydrogen on the other hand, processes which differ in their detail may be used. For instance, for the provision of oxygen from water, the latter (in particular liquid water) and a suitable gas are equilibrated. The gas used is preferably CO2. The application of the inventive idea to the example mentioned at the outset of an isotopic analysis of the elements contained in water results in the following steps:

    
    
        a) oxygen and hydrogen are constituents of the water,
        b) the water is continuously admixed with CO2 or H2 as the reagent substance,
        c) at least gaseous CO2 or H2 are formed continuously as the reaction product and contain the isotopic information of hydrogen or oxygen of the starting substance, and water or steam are formed as the residual substance,
        d) CO2 or H2 are separated from the residual substance,
        e) CO2 or H2 are finally removed for analysis.
    
    


The process according to the invention provides for the first time the continuous equilibration of oxygen and/or hydrogen with a suitable gas. Continuous feeding of water is also possible for the first time.
The continuously fed water may be present in gaseous form as steam or in liquid form as a mixture of both phases. The separation of water and equilibration gas is preferably effected continuously, as is the feed of the equilibration gas to the isotopic analysis.
Advantageously, at least one of the elements H, O, C, S, P or N is present in the starting substance. The process according to the invention is preferably used for the preparation of the analysis of these elements or corresponding compounds.
For the provision of hydrogen for isotopic analysis, the water may be equilibrated as steam with a suitable gas. Preference is given to using hydrogen as the equilibration gas, though the use of other gases is envisioned within the scope of the present invention. In addition to steam, the water may also contain liquid water.
For the equilibration, preference is given to passing the mixture of water or steam and hydrogen over a catalyst and/or heating it. The catalyst contemplated is in particular platinum.
A carrier gas may be added to the water or hydrogen (or another equilibration gas) during or before the equilibration. The aim is to increase the gas stream after the equilibration by a factor of about 102.
Advantageously, the water (mainly in the form of steam) is separated from residual gases at a steam-permeable membrane. At this stage of the process, the water should be present as steam. The separation is effected using a NAFION tube known per se.
Generally speaking, the residual substance on separation of gaseous reaction product may be liquid, for example water or an aqueous solution. However, another state is also possible, for instance a gaseous residual substance such as steam. The liquid residual substance makes it possible to use special separating processes, for instance at a membrane which is gas-permeable and liquid-impermeable. When separating, it may be advantageous to entrain and remove the gaseous reaction product from a carrier gas stream on a gas side of the membrane. The residual substance then remains on the liquid side of the membrane. The separation is eased by a pressure differential between the water side and the gas side of the membrane. Preference is given to conducting helium as the carrier gas along the gas side. The pressure on the water side, for instance in the mixture of water and CO2, is about half an atmosphere above the pressure on the gas side (e.g. a mixture of carrier gas and CO2).
The starting substance may be a liquid, in particular an aqueous liquid, in which elements or compounds of interest are dissolved, e.g. drinks, in particular wine, mineral water, fruit juice. Useful liquids also include aqueous liquids or solutions such as blood or urine.
When liquid water is used as a starting substance or an aqueous liquid is used, the water may also be provided by continuously melting ice. For instance, it is possible by the process according to the invention to prepare drilled ice cores for an isotopic analysis. When water is continuously provided by constant melting of suitable amounts of ice, the melt water (in liquid form) is continuously aspirated by a pump and passed on for the reaction or equilibration. It is also possible to provide a sample in portions in combination with a continuous further feed. For instance, sample vessels containing liquid water may be connected to a pump. After the sample vessel is emptied, an automatic exchange takes place.
The reagent substance is preferably a gas. In this context, a gas mixture is a gas. However, liquids or solids are also possible.
Materials may be dissolved in the water (starting substance), such as carbonates, sulfates, nitrates, etc.
The invention further contemplates the reaction of at least one constituent of the reagent substance with at least one constituent of the starting substance, resulting in the gaseous reaction product.
As already stated above, the process according to the invention may be utilized in combination with an equilibration. In the equilibration, at least one constituent of the reagent substance equilibrates with at least one of the elements or compounds of the starting substance. This preferably results in isotopic information or other elemental information being transferred or taken up. The information is then present in the reaction product.
In a further alternative of the process according to the invention, the reagent substance changes the pH of the starting substance, which results in the gaseous reaction product being formed. An example of a useful reagent substance is an acid. Some of the reaction product may also already have been present before the reaction. The reaction then increases the proportion of the reaction product in the total amount of reaction product and residual substance.
The invention further contemplates the reaction product and the residual substance being in gaseous form and being separated from one another in this state.
It is also possible to heat at least one of the substances starting substance, reagent substance, reaction product and residual substance. This may effect a better reaction between starting substance and reagent substance or provide a better means of separating reaction product and residual substance. For the provision of oxygen from water, the mixture of water and CO2 is advantageously heated. This accelerates the equilibration or reaction. Temperatures of around 50° C. are desired.
A modification of the process according to the invention relates to applications in which the elements or compounds to be investigated are present as gases or as constituents of gases and are contained in a liquid starting substance in the widest sense (mixture, solution or the like). The starting substance (with the gases) is passed through a degassing unit. The gases are separated there from the liquid starting substance.
In the degassing unit is preferably disposed a membrane which is for separating a gas side from a liquid side and has a reduced pressure on the gas side.
After leaving the degassing unit, the gases are removed for the analysis. The individual steps are carried out continuously. The starting substance is preferably liquid water or at least one aqueous solution in the sense already described above. The elements or compounds present in the starting substance may be, for example, air or its constituents. The process is of particular interest for the isotopic or quantitative analysis, for instance of air constituents in water. The radon content of the dissolved air may also be determined by the analysis which follows.
In one embodiment of the present invention, the apparatus for preparing an analysis of chemical elements or compounds includes

    
    
        a) a reaction unit for the reaction of a starting substance containing the elements or compounds with a reagent substance,
        b) a means for continuously feeding the starting substance and the reagent substance into the reaction unit,
        c) in a separating unit are provided means for separating a gaseous reaction product from a residual substance,
        d) the separating unit has a first outlet for the residual substance and a second outlet for the reaction product,
        e) a means for passing the reaction product on from the separating unit to an analytical instrument.

A conceivable reaction unit is a chamber provided with feeds which is otherwise closed, in which the reaction of the starting substance with the reagent substance takes place. The starting substance and the reagent substance are introduced into the reaction unit individually or together, for instance using pumps, or using an elevated pressure or pressure drop provided in another way. Preferred analytical instruments are mass spectrometers, isotope mass spectrometers and elemental analyzers. Other analytical instruments are also possible.

    
    


Reaction units and separating units are preferably spatially separated. Means for transferring the reaction product and the residual substance from the reaction unit into the separating unit are then provided.
The separating unit may have a membrane which is gas-permeable and at the same time liquid-impermeable. Alternatively, and taking into account the substances used and the states of matter present, the separating unit may have a membrane which is permeable to steam or certain gases, but impermeable to other gases.
The impermeabilities specified are dependent upon the quality of the particular membrane. In some cases, residues of the substance to be removed succeed in penetrating the membrane with the gases. Additional separating units may be provided to separate the residues mentioned.
In addition, heating equipment may be provided to heat at least one of the substances starting substance, reagent substance, reaction product and residual substance. The heating equipment may also be provided as part of the reaction unit.
In certain cases, the starting substance is present as a solid, for instance as ice. A melt unit for melting the solid starting substance is then advantageously provided. The starting substance is fed from the melt unit to the reaction unit or other units upstream thereof.
With regard to the equipment also, the invention independently contemplates the separation of liquid on the one hand and gas on the other hand. The separation is effected as a preparation for the analysis of chemical elements or compounds.
In an alternative embodiment of the present invention, the apparatus for providing the gaseous substance for the analysis of chemical elements or compounds includes

    
    
        a) a degassing unit having a liquid inlet, a liquid outlet and a gas outlet,
        b) in the degassing unit is disposed a gas permeable and liquid impermeable membrane which separates a liquid zone from a gas zone,
        c) the gas zone is coupled to the gas outlet, and the liquid inlet and liquid outlet are coupled to the liquid zone,
        d) from the gas outlet there is a connection to an instrument for the analysis of the elements or compounds.

The instrument contemplated for the analysis is preferably an isotope mass spectrometer (IRMS), an elemental analyzer or another analytical instrument. Downstream of the degassing unit, drying units and/or an open split for the exact metering of the gas may be provided. From there, a controlled fraction of the gas enters an ion source of the IRMS.

    
    


Advantageously, the degassing unit has a gas inlet coupled to the gas zone. Carrier gas, in particular helium, flows through the gas inlet into the degassing unit to entrain the gas passing through the membrane.
Exemplary embodiments of the present invention are now described in greater detail with reference to the attached figures and drawings. The foregoing descriptions of these embodiments are intended to be merely illustrative and not limiting of the scope of the invention in any way.
An apparatus according to the invention for providing oxygen or hydrogen from water for isotopic analysis includes a water feed unit 10 (dashed), an equilibration unit 11 (dashed) and a degassing unit 12. In a water line 13 between the water feed unit 10 and the equilibration unit 11 is disposed a gas inlet 14. The equilibration unit 11 is connected to the degassing unit 12 via a line 15. Upstream of the water feed unit 10 is disposed a melt unit 16 for melting ice, which is maintained at a constant cold temperature by cooling equipment 17. Alternatively, for example, an upstream X-Y sampling tool (autosampler) may be provided for discrete water samples.
The degassing unit 12 has a water outlet 18, a gas outlet 19 and a gas inlet 20. Connected to the water outlet 18 are a pressure gauge 21 and a back pressure regulator 22. Downstream of the back pressure regulator 22 is disposed a waste line 23.
In the cooling equipment 17, an ice rod is provided, for instance from a glaciological drilling, and has a length of 50-100 cm and a cross section of 2×2 cm or the like. One end of the ice rod 24 is melted by the melt unit 16. The liquid water is pumped out via a drillhole (cross section=1 cm2) in the middle of a melt head 25. About 25% of the molten water thus enters an intake line 26 of a very uniformly operating pump 27. This is part of the water feed unit 10 and is in particular a peristaltic pump.
The water passes from the pump 27 via a pressure line 28 and a four-way valve or a six-way valve V1 into the water line 13.
A CO2 reservoir 29 is attached to the gas inlet 14. The CO2 passes through the gas inlet 14 into the water flowing through the water line 13. Specifically, the gas inlet 14 provided is a thin (35 μm), short (15 cm) pressure line (3 bar), from which the CO2 exits and enters the water line 13 in small bubbles. The gas inlet 14 may therefore be referred to as the bubble generator.
Subsequently, the mixture of water and CO2 is conducted through the equilibration unit 11. This has a narrow tube 30 or capillary of length 2 m and diameter 0.75 mm ( 1/16′′). The tube 30 is disposed in a water bath maintained at 50° C. for accelerating the desired equilibration. The flow rate is preferably set to about 1 ml per minute. This results in a transfer time of about 1 minute.
The equilibrated mixture of water and CO2 flows through the line 15 into the degassing unit 12. A tubular, gas-permeable membrane of length 5-10 cm and internal diameter 1.8 mm is disposed there in a Plexiglas tube of the same length (internal diameter 4.5 mm). Both tubes 31, 32 are accommodated in an aluminum casing 33 for sealing against the surrounding air. The CO2 contained in the mixture passes through the membrane into the Plexiglas tube 32 and is removed from there. To this end, a helium stream is conducted in parallel and in the same direction as (alternatively in the opposite direction to) the mixture of water and CO2 in the degassing unit 12. The gas inlet 20 is fed from a helium source (not shown). A mixture of helium and CO2 leaves the gas outlet 19.
The transfer of the CO2 into the Plexiglas tube 32 is dependent upon the pressure differential within and outside the tube 31. This pressure differential is about half an atmosphere. In other words, the pressure in the helium carrier gas is about 0.5 bar less than in the water within the tube 31. The pressure is determined by the cross sections of the lines in question, by the output of the pump 27 and the setting of the back pressure regulator 22. The pressure of the CO2 before entry into the water line 13 also has an influence.
The mixture of carrier gas and CO2 is fed from the gas outlet 19 through a first drying unit 34, a changeover valve 35 and a second drying unit 36 to an open split 37. From there, the carrier gas together with CO2 enters an isotope mass spectrometer (IRMS). Alternatively or additionally, helium may be fed or added in the open split, see feed 38. It is also possible to feed a reference gas.
The first drying unit 34 is designed as a water trap and freezes the water still remaining in the gas out. The cooling is effected by dry ice (−78° C.).
The second drying unit 36 is a NAFION tube having a helium counter stream. This drying principle is also known. The aim is to prevent any water content in the gas.
The valve 35 consists of two switching valves V2 and V3. In the arrangement shown in FIG. 1, the carrier gas together with CO2 passes from the first drying unit 34 to the second drying unit 36. When V2 and V3 are switched, the carrier gas together with CO2 is discharged, while exclusively carrier gas is fed to the second drying unit 36. This allows maintenance work to be carried out on the first drying unit 34 without interrupting the carrier gas stream into the mass spectrometer.
Parallel to pump 27 and line 28, a pump 39 with an intake line 40 and pressure line 41 is connected to the valve V1. Standard water can be fed to the apparatus via the intake line 40 as a comparative sample. In this manner, switching of the valve V1 allows rapid and simple switching between the sample to be analyzed and standard water. In FIG. 1, the valve V1 is switched for passing through the sample to be analyzed. The standard water is at the same time passed through the valve V1 into a waste stream 42.
In a simpler embodiment, the pressure line 28 is connected directly to the water line 13. The parts having the numbers 40, 39, 41 and 42 are then not provided.
According to FIG. 3, parts of the apparatus illustrated with the aid of FIGS. 1 and 2 are modified for the isotopic analysis of hydrogen. The gas inlet 14 is coupled to a hydrogen source. In addition to the thin tube, (similar to tube 30 in FIG. 1) which is not shown, an equilibration unit 43 has a stronger heater 44 which allows heating to above 100° C. (even evaporation). Also, a catalyst 45 is provided downstream of the heater 44, i.e. additionally thereto, which substantially accelerates the process of equilibration of the hydrogen from water with H2. The mixture of water (especially steam) and hydrogen (H2) leaving the equilibration unit 43 via line 15 contains a relatively large amount of water. The latter may be partially separated by an optionally provided condenser 46 upstream of the entrance into the degassing unit 12.
The degassing unit 12 may have exactly the same design as in the illustration of FIG. 2 and is only shown in simplified form in FIG. 3.
The equilibration unit 43 may also be a reaction chamber with a heater and be charged with a catalyst, in particular of platinum, uranium or zinc. The equilibration of the H2 is extremely temperature-sensitive. The heater 44 and the catalyst 45 are therefore arranged in very close spatial proximity, in order to be able to carry out the equilibration at a precisely defined temperature.
As a result, the invention enables a rapid and precise feed of hydrogen and/or oxygen isotopes from a water sample or from an ice sample for isotopic ratio determination in a mass spectrometer provided therefor.
FIG. 4 relates to the isotopic analysis of the hydrogen contained in the water. Liquid water may be fed as illustrated in FIG. 1. Alternatively, FIG. 4 shows the provision of a water sample in a vessel 47, consisting in particular of glass, which is sealed in a vapor-tight manner by a rubber membrane 48. The vessel 47 and the rubber membrane 48 are pierced by a hollow needle 49, through which the water passes into the intake line 26. It is also possible to evaporate the water (not shown) before entry into the equilibration unit 43, or equally to feed a vaporous sample.
In this case, the equilibration unit 43 has a special design. As already illustrated with the aid of FIG. 3, heater and catalyst material are integrated. The equilibration unit 43 is a chamber with line 13 as the inlet, a separate hydrogen inlet 50, a carrier gas inlet 51 and line 15 as the outlet for a mixture of carrier gas, steam and hydrogen. For the feed into the equilibration unit 43, the hydrogen is taken from a hydrogen reservoir 52.
The catalyst charge 53 consists of platinum-coated catalyst spheres of approximately 1 millimeter diameter. The carrier gas provided is helium which flows into the equilibration unit 43 at 20 ml/min. In comparison, hydrogen is fed in a stream of 0.1 to 0.2 ml/min. The liquid water in line 13 flows at about 1 to 2 microliters/minute. A gaseous mixture leaves the equilibration unit 43 at a flow rate of about 22 ml/min.
The equilibration unit 43 is also referred to as a deuterium chamber and in the present case is designed in two sections with a bottom 54 and a lid 55 which form a cavity 56 of about 2 to 5 ml between them.
Bottom 54 and lid 55 each have two heating cartridges 57, 58 for heating and evaporating, so that there is a total heating output of about 400 watt.
The catalyst charge 53 (about 50 to 100 HOKO beads), or alternatively uranium or zinc, are arranged in a basket of fine stainless steel mesh in the middle of the cavity 56 (not shown).
Lid 55 and bottom 54 are held together by four screws and are sealed against each other by an indium wire (not shown).
Downstream of the equilibration unit 43, along line 15, is disposed a NAFION tube. NAFION refers to a special material which is gas-impermeable but water-permeable, especially to steam. The NAFION tube 59 serves in this case as a degassing or drying unit and removes the majority of the water from the mixture of carrier gas, hydrogen and steam. As is customary, a carrier gas counter stream is conducted in the NAFION tube 59, and there is a carrier gas inlet 60 an outlet 61 for the mixture of stream and carrier gas, in particular helium.
Downstream of the gas outlet 19 of the NAFION tube 59 are provided further apparatus parts in accordance with FIG. 1, such as a cold trap as a drying unit 34, the changeover valve 35, a NAFION tube as a further drying unit 36 and the open split 37. A degassing unit for separating liquid as in FIGS. 1 to 3 is not provided in this case.
In this case, the equilibration unit 43 and the cavity 56 are heated to 100° C. The water entering via line 13 immediately evaporates completely. When the hydrogen is fed continuously (inlet 50), an average residence time (exchange time) in the cavity 56 of about 6 seconds at a volume of 2 ml and about 15 seconds at a volume of 5 ml is achieved. Complete HD equilibration is the consequence.
The helium entering via inlet 51 continuously purges the cavity 56 and transports the mixture (helium, hydrogen, steam) into the NAFION tube 59. In this case, line 15 is heated to about 40-50° C. The NAFION tube 59 has a length of about 60 centimeters. The first quarter of it is heated to 60° C. This temperature is about 10 to 20° C. above the dew point of the gas. The helium counter stream in the NAFION tube 59 flows at about three times the rate of the entering gas stream (steam, hydrogen and helium) and is about 60 to 70 ml/min. Pressures and temperatures in this case are preferably selected in such a way that no condensate occurs in the region of the NAFION tube 59.
Downstream of the NAFION tube 59, steam still present is efficiently removed in the cold trap 34. The coolant is preferably liquid nitrogen at a temperature of −196° C.
One of the features of the implementation example of FIG. 4 is that the mixture of residual substance and reaction product is present exclusively in gaseous form and thus no degassing unit is used. Only steam is removed. It may also be contemplated to feed steam as the starting substance.
EXAMPLES
The following detailed examples are provided to demonstrate the present invention. The examples are provided herein for illustration purposes only and are in no way intended to limit the scope of the invention.
In Table 1 and Table 2, a plurality of examples are in each case systematically listed for the application of the invention in the context of isotopic analyses (Table 1) and elemental analyses (Table 2). The diagrams of FIGS. 6 and 7 also refer thereto. FIG. 6 relates in particular to Example 1, Table 2 and Example 3, Table 1. FIG. 7 relates in particular to Example 5, Table 2 and Example 6, Table 1. Importance also attaches to the footnotes given under each of the tables.
Example No. 1 of Table 2 relates to the analysis of carbonate-containing water. The carbonate may be present as calcium carbonate, magnesium carbonate or potassium carbonate. The carbonate is present in ionic form, i.e. as carbonate CO3 (2−), as bicarbonate HCO2(−) and also as CO2. In neutral water (pH 7), the carbonate:bicarbonate:CO2 ratio is 90:9:1. The water is continuously conducted by a water pump to a mixing unit in which it is continuously admixed with acid. This changes the pH and forces the equilibrium completely to the CO2 side in the course of the reaction zone. In the downstream degassing unit, the CO2 is separated from the water and conducted with a helium stream into a CO2 analyzer. The CO2 analysis results in a quantitative carbonate content determination, since the CO2 content is proportional to the carbonate content.
When the CO2 analyzer is replaced by a mass spectrometer, the carbon isotope content of the carbonate (δ13C) and also the oxygen isotope content of the water may be determined, see Table 1, Example 3.
The apparatus shown in FIG. 6 may also be used solely as a degassing unit, see FIG. 7. The apparatus may be used in this form as an isotopic or elemental analysis unit for ground water, ice water, etc., see in particular Table 2, Example 5 and Table 1, Example 6.
Example 1 in Table 1 relates to FIG. 1; the examples 2a, 2b in Table 1 relate to FIGS. 3 and 4.
In the Table 1 and Table 2, the starting substance is water or at least an aqueous solution. This also includes blood, urine, etc., and also all further medicinal or pharmaceutical areas of application.
Exemplary Embodiments
The following descriptions of exemplary embodiments of the invention are provided for illustration purposes. They are not intended to limit the scope of the invention in any way.
In a first (E1) embodiment of the present invention, a process is provided for generating a gaseous substance for the analysis of chemical elements or compounds. In this process, the elements or compounds are contained in a starting substance, the starting substance is continuously admixed with a reagent substance, at least one gaseous reaction product is formed which contains information about the elements or compounds of the starting substance and a residual substance, the gaseous reaction product is separated from the residual substance, and the reaction product is finally removed for an analysis.
In a second (E2) embodiment of the present invention, a process is provided as in embodiment E1 further characterized in that at least one of the elements H, O, C, S, P or N is contained in the starting substance.
In a third (E3) embodiment of the present invention, a process is provided as in embodiments E1 or E2, further characterized in that the residual substance is liquid on separation from the gaseous reaction product.
In a fourth (E4) embodiment of the present invention, a process is provided as in embodiment E3, further characterized in that the separation of the reaction product from the residual substance is carried out at a membrane which is gas-permeable and liquid-impermeable.
In a fifth (E5) embodiment of the present invention, a process is provided as in embodiment E4, further characterized in that the gaseous reaction product is entrained and removed by a carrier gas stream on a gas side of the membrane.
In a sixth (E6) embodiment of the present invention, a process is provided as in any of embodiment E1 to E5, further characterized in that the starting substance is a liquid.
In a seventh (E7) embodiment of the present invention, a process is provided as in embodiment E6, further characterized in that the starting substance is an aqueous liquid.
In an eighth (E8) embodiment of the present invention, a process is provided as in embodiment E6, further characterized in that ice is melted continuously to provide the liquid water or aqueous liquid.
In a ninth (E9) embodiment of the present invention, a process is provided as in any of embodiments E1 to E8, further characterized in that the reagent substance is a gas.
In a tenth (E10) embodiment of the present invention, a process is provided as in any of embodiments E1 to E9, further characterized in that at least one constituent of the reagent substance equilibrates with at least one of the elements of the starting substance or at least partially takes on its elemental or isotopic information.
In an eleventh (E11) embodiment of the present invention, a process is provided as in any of embodiments E1 to E10, further characterized in that at least one constituent of the reagent substance reacts with at least one constituent of the starting substance and thus forms the gaseous reaction product.
In an twelfth (E12) embodiment of the present invention, a process is provided as in any of embodiments E1 to E11, further characterized in that the reagent substance changes the pH of the starting substance, and in that this results in the gaseous reaction product being formed.
In an thirteenth (E13) embodiment of the present invention, a process is provided as in any of embodiments E1 to E12, further characterized in that the reaction product and the residual substance are present in gaseous form and are separated from one another in gaseous form.
In an fourteenth (E14) embodiment of the present invention, a process is provided as in embodiment E1, further characterized in that the starting substance is present in gaseous form and is admixed thus with the reagent substance.
In an fifteenth (E15) embodiment of the present invention, a process is provided as in embodiment E1, further characterized in that at least one of the substances starting substance, reagent substance, reaction product and residual substance is heated.
In a sixteenth (E16) embodiment of the present invention, a process is provided for generating a gaseous substance for the analysis of chemical elements or compounds. In this process, the elements or compounds are contained in a liquid starting substance as gases or as constituents of gases, the starting substance is passed through a degassing unit, in the degassing unit, the gases are separated from the liquid starting substance, after leaving the degassing unit, the gases are removed for analysis.
In an seventeenth (E17) embodiment of the present invention, a process is provided as in embodiment E16, further characterized in that the starting substance is liquid water or at least an aqueous solution.
In an eighteenth (E18) embodiment of the present invention, an apparatus is provided for the analysis of chemical elements or compounds. This apparatus comprises a reaction unit for the reaction of a starting substance containing the elements or compounds with a reagent substance, a means for continuously feeding the starting substance and the reagent substance into the reaction unit, and a separating unit further comprising means for separating a gaseous reaction product from a residual substance. The separating unit has a first outlet for the residual substance and a second outlet for the reaction product. Also provided are a means for passing the reaction product on from the separating unit to an analytical instrument.
In an nineteenth (E19) embodiment of the present invention, an apparatus is provided according to embodiment E18, further characterized in that the separating unit has a membrane which is gas-permeable and at the same time liquid-impermeable.
In an twentieth (E20) embodiment of the present invention, an apparatus is provided according to embodiment E18 or E19, further characterized by heating equipment for heating at least one of the substances starting substance, reagent substance, reaction product and residual substance.
In an twenty-first (E21) embodiment of the present invention, an apparatus is provided according to embodiment E18, further comprising a melt unit for melting solid starting substances.
In an twenty-second (E22) embodiment of the present invention, an apparatus is provided for generating a gaseous substance for the analysis of chemical elements or compounds. The apparatus comprises a degassing unit (12) having a liquid inlet, a liquid outlet and a gas outlet (19). In the degassing unit (12) is disposed a gas permeable and liquid impermeable membrane which separates a liquid zone from a gas zone. The gas zone is coupled to the gas outlet (19), and liquid inlet and liquid outlet are coupled to the liquid zone. From the gas outlet (19) there is a connection to an instrument for the analysis of the elements or compounds.
In an twenty-third (E23) embodiment of the present invention, an apparatus is provided according to embodiment E22, further characterized in that the degassing unit (12) has a gas inlet (20) coupled to the gas zone.
The foregoing description of specific embodiments and examples of the invention have been presented for the purpose of illustration and description, and although the invention has been illustrated by certain of the preceding examples, it is not to be construed as being limited thereby. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications, embodiments, and variations are possible in light of the above teaching. It is intended that the scope of the invention encompass the generic area as herein disclosed, and by the claims appended hereto and their equivalents.







TABLE 1







Examples of Isotopic Analyses
















Equilibration

Residual liquid substance 



Example
Starting substance
Elements of
substance added
Equilibration
to be removed from 



No.
gaseous/liquid
interest
gaseous/liquid
gas to be removed
the equilibration gas
Information





1
Water*
O
Gaseous CO2
CO2
Water
δ18O of H2O



Liquid







2a+
a) Water*
a) H
a) Gaseous H2
a) H2
a) Water
δD of H2O



liquid







2b&
b) Water*
b) H
b) Gaseous H2
b) H2
b) Steam
δD of H2O



liquid







2c°
B) Water*
b) H
b) Gaseous H2
b) H2
b) Steam
δD of H2O



gaseous







3
Carbonate-
C
Acid (e.g.
CO2 formed by
Water containing Mg(2+)
δ13C of



containing water*

orthophosphoric acid
the reaction
K(2+)
carbonate



(MgCO3 or K2CO3

H3O4P)

Ca(2+)
plus δ18O of



or CaCO3 + HCO3(−) +




H2O



CO3(2−) + . . .)







4
Sulfate-containing
S
Acid (e.g.
SO2 formed by the
Water containing
δ18S of



water*

orthophosphoric acid
reaction
Ca(2+)
sulfur plus



(CaSO4 or MgSO4

H3O4P)

Mg(2+)
possibly



or K2SO4 etc.)



K(2+)
δ18O of H2O


5
Nitrate-containing
N
pH-dependent
Nox (NO, NO2, N2O,
Water
δ13N



water*

reaction
NH3)





(NaNO3)







6
Ice, ground water*
All isotopes
none
Air components
Water
Isotopic




in air



composition








of the air








components





+With reference to FIG. 3.


&: No degassing unit is used here, since only gaseous substances are present. However, these gaseous substances are conducted through a drying unit (NAFION tube) before analysis, see FIG. 4.


°: According to FIG. 4, when the samples have also been fed in gaseous form. For example, gaseous feed of water vapor in air.


In Examples 3-5, salts of the corresponding elements are usually dissolved in water (present as ions) and may partly be released as gas by changing the pH.


*: The term water also covers all aqueous solutions such as blood, urine, etc.













TABLE 2







Examples of Elemental Analyses
















Gaseous/liquid
Reaction
Residual liquid substance 



Example
Starting substance
Elements of
substance added
product to
to be removed from 



No.
gaseous/liquid
interest
gaseous/liquid
be removed
the reaction product
Information





1
Carbonate-containing
C, or sum of
Acid (e.g.
CO2 formed by
Water containing
Carbonate



water*
(CO3(2−),
orthophosphoric acid
the reaction
Mg(2+)
content



(MgCO3 or K2CO3 or
HCO3(−),
H3O4P)

K(2+)




CaCO3 + HCO3(−) +
CO2)


Ca(2+)




CO3(2−) + . . .)







2
Sulfate-containing water*
S
Acid (e.g.
SO2 formed by 
Water
Sulfate content



(CaSO4 or MgSO4 or

orthophosphoric acid
the reaction





K2SO4 etc.)

H3O4P)





3
Phosphide-containing
P
pH-dependent
PH3 formed by 
Water containing Ca(2+)
Phosphorus



water*

reaction
the reaction
Mg(2+)
content



(Ca3P2)



K(2+)



4
Nitride-containing
N
PH-dependent
NOx (NO, NO2,
Water
Nitrate content



water*

reaction
N2O, NH3)





(NaNO3)







5
Ice, ground water*
All elements
none
Air components
Water
Air




in air



composition


6
Water*
Rn#
None
Radon gas
Water
Radon content





+With reference to FIG. 3


#Radon as a radioactive noble gas, analytical instrument (α-detector)


*The term water also covers all aqueous solutions such as blood, urine, etc.
















Reference Numeral List


















10
Water feed unit
36
Second drying unit (Nafion tube)


11
Equilibration column
37
Open split


12
Degassing unit
38
Helium feed


13
Water line
39
Pump (tubing pump)


14
Gas inlet (bubble generator)
40
Intake line


15
Line
41
Pressure line


16
Melt unit
42
Waste stream


17
Cooling equipment
43
Equilibration unit


18
Water outlet
44
Heater


19
Gas outlet
45
Catalyst


20
Gas inlet
46
Condenser


21
Pressure gauge
47
Vessel


22
Back pressure regulator
48
Rubber membrane


23
Waste stream
49
Needle


24
Ice rod
50
Hydrogen inlet


25
Melt head
51
Carrier gas inlet


26
Intake line
52
Hydrogen reservoir


27
Pump (tubing pump)
53
Catalyst charge


28
Pressure line
54
Bottom


29
CO2 reservoir
55
Lid


30
Tube
56
Cavity


31
Tube
57
Heating cartridges


32
Plexiglas tube
58
Heating cartridges


33
Casing
59
Nafion tube


34
First drying unit (water trap)
60
Inlet


35
Changeover valve
61
Outlet

## Claims

1. A continuous process for providing a gaseous substance for the isotopic or elemental analysis of chemical elements or compounds, comprising the steps of:
a) providing a liquid starting substance containing the chemical elements or compounds;
b) continuously mixing a stream of said liquid starting substance with a stream of a reagent substance, forming a mixture;
c) continuously reacting at least one constituent of said liquid starting substance with at least one constituent of said reagent substance in said mixture resulting in the formation of at least one gaseous reaction product and a liquid residual substance, wherein said gaseous reaction product contains information about the chemical elements or compounds of said liquid starting substance;
d) continuously separating said gaseous reaction product from said liquid residual substance thereby resulting in the formation of a stream of said liquid residual substance and a separate stream of said gaseous reaction product; and
e) using the stream of said gaseous reaction product for said isotopic or elemental analysis of the chemical elements or compounds.

2. The process according to claim 1, wherein at least one of the elements H, O, C, S, P and N is contained in said starting substance, is present in the gaseous reaction product for said isotopic or elemental analysis, and is the chemical element for which the isotopic or chemical analysis is conducted.

3. The process according to claim 1 or claim 2, wherein said liquid residual substance is still a liquid after being separated from said gaseous reaction product.

4. The process according to claim 3, wherein said continuous separation of said gaseous reaction product from said liquid residual substance is carried out at a membrane, said membrane being gas-permeable and liquid-impermeable.

5. The process according to claim 4, wherein said gaseous reaction product is entrained and removed by a carrier gas stream on a gas side of said membrane.

6. The process according to claim 1, wherein said starting substance is an aqueous liquid.

7. The process according to claim 6, wherein ice is melted continuously to provide said liquid.

8. The process according to claim 1, wherein said reagent substance is a gas.

9. The process according to claim 1, wherein at least one constituent of said reagent substance equilibrates with at least one of the chemical elements of said starting substance.

10. The process according to claim 1, wherein the reagent substance changes the pH of the starting substance, and in that this change in pH results in the gaseous reaction product being formed.

11. The process according to claim 1, wherein at least one of said starting substance, said reagent substance, said reaction product, and said residual substance is heated.

12. The process according to claim 1, wherein said analysis is conducted with a mass spectrometer.

13. The process according to claim 1, wherein at least one constituent of said reagent substance at least partially takes on the elemental or isotopic information of said starting substance.

14. The process according to claim 1, wherein step d) is carried out at a temperature at which water is a liquid.

15. The process according to claim 1, wherein in steps c) or d) liquid water is present.

16. The process according to claim 1, wherein said starting substance is present in gaseous and liquid state during step c).

17. The process according to claim 1, wherein after step d) residual water is removed from the gaseous reaction product.

18. The process according to claim 17, wherein the water removal is done through a gas impermeable but water, including steam, permeable membrane.

19. A continuous process for providing a gaseous substance for the isotopic or elemental analysis of chemical elements or compounds, the process comprising the steps of:
a) providing a liquid starting substance containing the chemical elements or compounds;
b) continuously mixing a stream of said liquid starting substance with a stream of a reagent substance, forming a mixture, and continuously feeding the mixture of the starting substance and the reagent substance into a reaction unit;
c) continuously reacting at least one constituent of said liquid starting substance with at least one constituent of said reagent substance in said mixture resulting in the formation of at least one gaseous reaction product and a liquid residual substance, and wherein said gaseous reaction product contains information about the chemical elements or compounds of said liquid starting substance;
d) continuously separating said gaseous reaction product from said liquid residual substance thereby resulting in the formation of a stream of said liquid residual substance and a separate stream of said gaseous reaction product, wherein said liquid residual substance is still a liquid after being separated from said gaseous reaction product; and
e) using the stream of said gaseous reaction product for said isotopic or elemental analysis of the chemical elements or compounds.

20. The process according to claim 19, wherein at least one of the elements H, O, C, S, P and N is contained in said starting substance, is present in the gaseous reaction product for said isotopic or elemental analysis, and is the chemical element for which the isotopic or chemical analysis is conducted.

21. The process according to claim 19, wherein said continuous separation of said gaseous reaction product from said liquid residual substance is carried out at a membrane, said membrane being gas-permeable and liquid-impermeable, and wherein said gaseous reaction product is entrained and removed by a carrier gas stream on a gas side of said membrane.

22. The process according to claim 19, wherein at least one constituent of said reagent substance equilibrates with at least one of the chemical elements of said liquid starting substance.

23. The process according to claim 19, wherein at least one of said liquid starting substance, said gaseous reagent substance, said reaction product, and said residual substance is heated.

24. The process according to claim 19, wherein step d) is carried out at a temperature at which water is a liquid.

25. The process according to claim 19, wherein in steps c) or d) liquid water is present.

26. The process according to claim 19, wherein said starting substance is present in gaseous and liquid state during step c).

27. The process according to claim 19, wherein after step d) residual water is removed from the gaseous reaction product.

28. The process according to claim 27, wherein the water removal is done through a gas impermeable but water, including steam, permeable membrane.

29. A continuous process for providing a gaseous substance for the isotopic or elemental analysis of chemical elements or compounds, comprising the steps of:
a) providing a liquid starting substance containing the chemical elements or compounds;
b) continuously mixing a stream of said liquid starting substance with a stream of a reagent substance, forming a mixture, and continuously feeding the mixture of the starting substance and the reagent substance into a reaction unit;
c) continuously reacting at least one constituent of said liquid starting substance with at least one constituent of said reagent substance in said mixture resulting in the formation of at least one gaseous reaction product and a liquid residual substance, wherein the reagent substance changes the pH of the liquid starting substance, and in that this change in pH results in the gaseous reaction product being formed, and wherein said gaseous reaction product contains information about the chemical elements or compounds of said liquid starting substance;
d) continuously separating said gaseous reaction product from said liquid residual substance thereby resulting in the formation of a stream of said liquid residual substance and a separate stream of said gaseous reaction product, wherein said liquid residual substance is still a liquid after being separated from said gaseous reaction product; and
e) using the stream of said gaseous reaction product for said isotopic or elemental analysis of the chemical elements or compounds.

30. The process according to claim 29, wherein at least one of the elements H, O, C, S, P and N is contained in said starting substance, is present in the gaseous reaction product for said isotopic or elemental analysis, and is the chemical element for which the isotopic or chemical analysis is conducted.

31. The process according to claim 29, wherein said continuous separation of said gaseous reaction product from said liquid residual substance is carried out at a membrane, said membrane being gas-permeable and liquid-impermeable, and wherein said gaseous reaction product is entrained and removed by a carrier gas stream on a gas side of said membrane.

32. The process according to claim 29, wherein at least one constituent of said reagent substance equilibrates with at least one of the chemical elements of said liquid starting substance.

33. The process according to claim 29, wherein at least one of said liquid starting substance, said gaseous reagent substance, said reaction product, and said residual substance is heated.

34. The process according to claim 29, wherein the steps a), through d) are carried out at a temperature at which at least some of the water is a liquid.

35. The process according to claim 29, wherein step d) is carried out at a temperature at which water is a liquid.

36. The process according to claim 29, wherein in steps c) or d) liquid water is present.

37. The process according to claim 29, wherein said starting substance is present in gaseous and liquid state during step c).

38. The process according to claim 29, wherein after step d) residual water is removed from the gaseous reaction product.

39. The process according to claim 38, wherein the water removal is done through a gas impermeable but water, including steam, permeable membrane.