Elemental analyser and elemental analysis method

Abstract

The invention relates to an analyser (1) having a ballast chamber (7) and an aliquot chamber (10) and to a corresponding analysis method. According to the invention, the aliquot chamber (10) has an adjustable aliquot volume for receiving a variable aliquot from the ballast chamber (7). In another variant, a movable piston is arranged in the ballast chamber (7) and separates said ballast chamber into two partial chambers.

Description

[0001] ELEMENTAL ANALYSIS INSTRUMENT AND ELEMENTAL ANALYSIS METHOD

[0002] One aspect of the invention relates to an analytical instrument according to the preamble of claim 1 and an analytical method for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample according to the preamble of claim 8.

[0003] In elemental analysis, combustion analysis is a common method for determining the concentration of specific elements in a sample. In this process, solid or liquid samples are first completely oxidized in a furnace. The resulting gaseous reaction products are then analyzed for their elemental content using appropriate methods.

[0004] The total quantity of combustion products is often comparatively large, making a complete analysis relatively complex in terms of equipment and time. However, since different fractions of the sample can exhibit different reaction rates over time, examining only a fraction of the combustion gases will lead to erroneous results if such a subsample is taken directly from the gas stream originating from the combustion reaction.

[0005] A well-known approach to addressing the aforementioned problem involves first collecting the gaseous reaction products and gathering them in their entirety in a ballast volume. After homogenizing the gaseous fractions in the ballast volume, an aliquot, i.e., a comparatively smaller volume of gas with a composition representative of the sample, is extracted. Subsequent analysis of the aliquot provides direct information about the relative elemental composition of the sample. To determine the absolute content of the elements in question, the results can be scaled according to the known ratio of the extracted aliquot to the total amount of reaction products collected.

[0006] However, an evaluation of the aforementioned type can only be performed if the aliquot is supplied to the analysis with a well-defined volume. For this reason, the flow of further combustion products from the ballast volume to the point of analysis must be prevented. Therefore, after its removal from the ballast volume and its separation from it, the aliquot is purged with a purge gas, in particular an inert gas, and transported to the actual analysis, with a noble gas such as helium being used as the purge gas.

[0007] In the conventional design of such analytical instruments, the aliquot volume is formed either by the volume of corresponding gas lines that can be separated from the ballast volume, and optionally by a separate aliquot chamber of also known volume. A suitable valve arrangement allows the relevant section of the piping system to be supplied with purge gas after it has been isolated.

[0008] The setup described above has the advantage that it is relatively simple and inexpensive to implement and is therefore the common approach for carrying out the elementary analysis in question.

[0009] A disadvantage of the known procedure, however, is that a considerable amount of purge gas is generally required to ensure that the reaction products of the aliquot are completely flushed out of the aliquot volume and passed on to the analysis. Depending on the geometry of the lines or chambers used, turbulence can be promoted. In this case, signals may still be measured even after a comparatively long purge time following the detection of the main part of the aliquot. If the purge of the aliquot volume is stopped too early in such a case, the relevant signals would be suppressed in the overall analysis. Particularly in the case of a relatively small aliquot volume compared to the total amount of reaction products, the aforementioned problem can lead to significant errors in determining the total content of certain elements in the sample.To prevent the analysis from becoming worthless in this way, it is common practice to allow purge gas to run for a comparatively long time and flow through the aliquot volume.

[0010] However, this results in significant disadvantages, firstly with regard to the throughput rate of such analyses. Secondly, the use of high-purity helium in large quantities represents a considerable cost factor. Against this background, the object of the present invention is to overcome the disadvantages of the prior art and to provide a means of performing elemental analyses of the aforementioned type more quickly and cost-effectively, while minimizing any impairment of the reliability of the measurement results.

[0011] To solve the aforementioned problem, an analytical instrument is proposed which is particularly suitable for determining the nitrogen, carbon, hydrogen, and / or sulfur content in a sample. The sample in question can be completely combusted in a combustion unit, for example, a furnace. The gaseous combustion products can then be collected in a ballast chamber or ballast volume chamber, after which a corresponding aliquot can be extracted by transferring a portion of the collected combustion products from the ballast chamber into an aliquot chamber. According to the invention, the aliquot chamber provides an adjustable aliquot volume, so that the amount of combustion products taken from the ballast chamber can ultimately be variably adjusted.This allows for the use of a larger or smaller aliquot volume depending on the application situation, without having to change the analyzer or undertake complex modifications.

[0012] Furthermore, extensive investigations have shown that such a variable system design not only allows for the selection of the aliquot volume, but also enables the modification of the flow conditions within the aliquot chamber caused by the volume change. For example, by setting a reduced aliquot volume, depending on the basic shape of the aliquot chamber or the relevant section of the gas pipeline system, the occurrence of turbulence during the aliquot purge can be significantly reduced compared to utilizing the maximum possible volume.

[0013] A particularly advantageous embodiment has proven to be one in which the aliquot chamber has an at least substantially cylindrical shape. It is further preferred that a separate aliquot chamber is provided, which supplies the majority of the aliquot volume, so that any portions contained in the associated gas transport lines of the system are small or, ideally, negligible. A specially provided chamber, especially one with a cylindrical shape, offers significant advantages with regard to the possibility of completely flushing the aliquot from the aliquot volume. This is especially true compared to known systems in which the aliquot volume is primarily formed by the volume of the lines from the ballast volume to the location of the actual analysis. In such systems, the occurrence of angles in the piping system that are unfavorable for flushing is almost unavoidable.Furthermore, a dedicated chamber, especially with a cylindrical base shape, allows for the concentrated collection of the extracted aliquot, which ultimately promotes the advantageous homogenization of the aliquot with respect to the fractions it contains.

[0014] To adjust the aliquot volume, the aliquot chamber preferably has an adjustment device. This device can be, for example, a piston or a comparable displacement element that limits or reduces the aliquot volume in the aliquot chamber in a defined manner. The adjustment device is designed in such a way that defined volume values ​​can be set reliably and reproducibly. A piston movably arranged within the aliquot chamber is particularly suitable for this purpose.

[0015] In a preferred embodiment, the adjusting device is motor-driven, in particular by electric motor, pneumatic, hydraulic, and / or magnetic or magnetomechanical means. Especially in connection with hot reaction products in combustion analysis, there are often corresponding hazards associated with manual operations on or in the corresponding analytical instrument. By designing the adjusting device in the aforementioned manner, manual adjustment of the aliquot volume can therefore be largely, and preferably completely, eliminated.

[0016] A particularly advantageous embodiment of the analytical device according to the invention has proven to be one in which the adjusting device is not only provided for setting a specific aliquot volume, but also at least assists in the discharge of the aliquot from the aliquot chamber, preferably wherein the discharge of the aliquot from the aliquot chamber is effected at least substantially by means of the adjusting device. If the adjusting device is moved in such a way that the volume of the aliquot chamber filled with the aliquot is significantly reduced, with a corresponding outlet valve being open, the aliquot is actively discharged to a corresponding extent. Consequently, a correspondingly smaller amount of purge gas is required. Preferably, the use of a separate purge gas can be completely dispensed with. Alternatively or additionally, the aforementioned embodiment of the adjusting device can...The aliquot chamber can be designed so that the rinsing of the aliquot and its transport for further analysis can be carried out, at least substantially, and in particular completely, using an oxygen stream already employed for combustion. The resulting cost advantages are obvious.

[0017] Even in an embodiment of the analytical instrument according to the invention, in which the adjustment device actively assists the removal of the aliquot from the aliquot chamber, but purging by means of a corresponding purge gas flow still takes place, advantages arise with regard to the flow conditions. Due to the dynamic change in the geometry of the aliquot chamber during the movement of the adjustment device, various configurations are typically traversed, which either promote or hinder the local occurrence of turbulence and / or laminar flow. This effectively prevents the formation of undesirable dead zones inside the aliquot chamber, from which the reaction products of the sample located there are not, or only with difficulty, purged.

[0018] A suitable control device is preferably provided to actuate the adjusting device in a defined and reproducible manner. This can, in particular, be an electronic control unit. The movement of the adjusting device can be precisely controlled by the control device via appropriate control means. It is understood that the appropriate control means are selected according to the design of the adjusting device. Thus, the adjusting device can be actuated, in particular, by a motor, especially an electric motor, pneumatic, and / or hydraulic system. The analytical device or adjusting device according to the invention is preferably also remotely controllable and / or automatable with regard to the execution of analyses by means of a control device.

[0019] The control unit preferably has one or more memory locations for storing and / or recalling predefined positions of the adjustment device. The control unit is therefore designed to be programmable, allowing preset positions and / or movement sequences of the adjustment device to be pre-programmed. This significantly simplifies the operation of the analytical instrument according to the invention in practice. Particularly advantageous flow conditions during the rinsing of the aliquot chamber were observed when the aliquot chamber is designed to introduce the aliquot in an axial direction. In particular, when the rinsing gas is introduced into the aliquot chamber through the same inlet by means of a suitable valve arrangement, the chamber can be rinsed in a particularly efficient manner, at least substantially, and in particular completely.It is understood that an introduction direction of the aliquot parallel to a pronounced longitudinal axis of the aliquot chamber can be combined, in particular, with a cylindrical basic shape of the chamber. However, according to the invention, other geometries of the aliquot chamber are also suitable to achieve the advantages of introducing the aliquot in the axial direction. Compared to systems known from the prior art, in which an aliquot chamber is filled with the aliquot only in the radial direction and / or no aliquot chamber with a defined longitudinal axis is formed, the aforementioned embodiment of the invention allows for a particularly reliable analysis of the aliquot due to the improved homogenization and the largely complete flushing of the aliquot into and out of the aliquot chamber.

[0020] A corresponding analytical method for determining the nitrogen, carbon, hydrogen, and / or sulfur content of a sample also possesses inventive significance. For this purpose, the sample is, if necessary after appropriate sample preparation or pretreatment, in particular completely combusted. The oxide compounds formed are then transferred to a separate ballast volume and initially collected there. After a suitable time, the combustion gases in the ballast volume become at least largely homogenized. After combustion of the sample, the ballast volume preferably contains the majority, and in particular all, of the original sample material as oxide compounds and / or as products of secondary reactions following combustion.

[0021] After reaching the aforementioned state, a certain portion of the collected combustion products, i.e., an aliquot, is transferred from the ballast volume to a separately provided aliquot volume, thus separating the aliquot volume from the ballast volume. Particularly after extensive homogenization of the contained fractions has also occurred in the aliquot volume, the aliquot can be forwarded for analysis using a suitable analytical method. For this purpose, the aliquot is purged by introducing a suitable purge gas, for example, an inert gas, especially a noble gas, preferably helium, into the aliquot volume via a suitable valve arrangement, thereby transporting the reaction products originating from the combustion of the sample through a corresponding gas piping system.

[0022] According to the invention, the analytical method discussed here provides that the aliquot volume for taking a variable aliquot of the collected combustion products is adjusted. The size of the aliquot volume is specifically adapted to the application situation, i.e., for example, to the nature or size of the sample to be analyzed, and is set accordingly.

[0023] The aliquot volume can be adjusted using an adjustment device. Specifically, a piston is inserted into the aliquot chamber, or a piston already located in the aliquot chamber is moved so that the desired volume is achieved.

[0024] The adjusting device, in particular the piston, can be moved manually to the appropriate position. Preferably, however, this is done by means of a motor, pneumatic, and / or hydraulic force. In a particularly preferred embodiment of the analysis method, the adjusting device is further controlled by a control unit. Here, for example, stored values ​​for specific positions of the adjusting device can be retrieved, which are ultimately translated by the control unit into a corresponding positioning of the adjusting device, i.e., into the provision of a specific aliquot volume. Preferably, a user selects a specific position of the adjusting device or a specific aliquot volume via a suitable operating device and / or enters corresponding values ​​individually, whereupon the system is configured by the control unit for the desired sequence of the analysis method.It may also be possible to save specific positions of the setting device or specific aliquot volumes.

[0025] In a preferred embodiment of the inventive method, the discharge of the aliquot from the aliquot volume or chamber can also be achieved completely or partially by moving the adjusting device in such a way as to reduce the volume in the aliquot chamber. The gaseous reaction products forming the aliquot are thus actively expelled from the aliquot chamber and introduced into the downstream piping system. This process step can also be controlled by a corresponding control device and, in particular, can be fully or partially automated. Furthermore, the control device can be used to return the adjusting device to its initial position. This can be the position before the discharge of the aliquot.Alternatively, a different position of the adjustment device can be controlled to provide a new, individually adapted aliquot volume for the subsequent analysis of another sample.

[0026] Within the framework of the inventive method, or in preparation for its execution for the analysis of a series of samples, the control device can preferably be programmed. The programming includes, in particular, specific positions of the adjustment device or various aliquot volumes, which can be individually adapted to the properties of the samples to be examined. In this way, several samples can be examined in rapid succession, preferably automatically, with minimal effort.

[0027] Alternatively or additionally to removing the aliquot from the aliquot volume or aliquot chamber using the adjustment device, the aliquot volume can also be purged with a purge gas as part of the inventive method. In a preferred embodiment, particularly, but not exclusively, in combination with the assisted removal using the adjustment device, the use of an inert gas, for example in the form of costly helium, can be largely avoided, and the purge is carried out at least substantially, and in particular exclusively, with oxygen. Since oxygen is generally provided anyway for the oxidation of the sample and therefore does not represent a contamination, the existing oxygen reservoir can also be used according to the method for purging the aliquot chamber or for transporting the aliquot to the actual analysis.The analysis of the sample can thus be considerably simplified, especially since no instrumental steps are necessary to connect different gases to the piping system of a corresponding analyzer and to ensure the maintenance and sufficient supply of the different gases.

[0028] Another aspect of the invention relates to an analytical instrument according to the preamble of claim 13 and an analytical method for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample according to the preamble of claim 20.

[0029] A method frequently used in elemental analysis is combustion analysis, in which a solid or liquid sample of unknown composition is first completely oxidized in a furnace. This process primarily produces gaseous reaction products, which can be analyzed for their elemental content using appropriate methods.

[0030] However, a direct analysis of the combustion products is generally not practical, as the oxidation of the various components of the sample can occur on different timescales, leading to fractionation of the reaction products. To determine the composition of the sample completely and with sufficient accuracy, a comparatively long, time-resolved measurement of the reaction products or combustion gases passed through a suitable analytical instrument would be necessary. Such a time-resolved analysis is significantly more complex than a momentary measurement of a specific composition. Furthermore, this approach would be correspondingly time-consuming and is also subject to various sources of error, for example, if the temporal resolution is too coarse to capture fluctuations in the element concentrations of the flowing combustion gases.

[0031] One approach to addressing the aforementioned problem typically involves first collecting all gaseous combustion products of the sample in a ballast volume. Within this ballast volume, diffusion processes lead to a high degree of homogenization of the combustion gases, rendering spatial fractionation negligible, and each portion of the ballast volume ultimately represents the elemental composition of the original sample. It is then possible, in particular, to extract a smaller portion, a so-called aliquot, from such a ballast volume and subject it to analysis. A complete analysis of all combustion products, i.e., the entire sample, is therefore unnecessary.

[0032] Typically, the homogenization of the sample gases within the ballast volume requires a certain amount of time, during which thermodynamic processes also occur. The medium flowing into the ballast volume shortly after combustion usually has a correspondingly high temperature. In contrast, the chamber that provides the ballast volume to hold the combustion gases typically has a temperature not significantly above the ambient temperature, i.e., room temperature. Consequently, the medium cools down as it flows in, and the ballast chamber, often formed by a glass body, is heated accordingly.

[0033] To drain the sample medium, a piston is often used inside the ballast chamber or ballast volume chamber, which is moved by compressed air on the side facing away from the medium. The compressed air introduced to move the piston is also usually at room temperature or even below. This, in turn, cools the chamber material. Depending on the duration of the sample medium draining from the ballast volume, further heat is extracted from it.

[0034] In this context, it is important to note that thermodynamic quantities are related to each other, for example, via the ideal gas law pV = nRT. Thus, different values ​​for the temperature and / or pressure of a gas volume result in correspondingly different values ​​for the amount of substance contained in a given volume. A problem arising from the processes described above is that uncontrollably fluctuating temperatures lead to non-reproducible amounts of substance in the gas volume being analyzed. This results in a significant source of error, particularly for quantitative analyses.

[0035] One approach to addressing the aforementioned problem could be to measure the temperature and pressure of the gas and the surrounding environment of the ballast volume, and to derive appropriate correction factors from these measurements. However, such measurements require specialized sensors and are therefore comparatively expensive. Furthermore, the measured values ​​themselves may be subject to certain errors. Performing a correction calculation in this manner also requires additional time and appropriate analytical equipment. This results in correspondingly higher demands on the analytical instrument's equipment and more sophisticated operation, which in turn necessitates higher qualifications for the operating personnel.

[0036] Another option is to use a heater to maintain a constant temperature in the area of ​​the analyzer containing the ballast volume. Besides the increased design complexity of this approach, it also results in additional costs due to the required heating power. Furthermore, to keep the temperature of the ballast volume or chamber truly constant, a control system linked to the heating unit is necessary. This also represents additional effort in terms of design and maintenance, significantly increasing the overall costs for such an analyzer and its operation.

[0037] Against the background of the situation described above, the object of the present invention is to overcome the disadvantages of the prior art and to provide a means of effectively and cost-efficiently reducing temperature fluctuations occurring in the ballast volume of an analytical instrument. A further object is ultimately to increase the reliability of elemental analyses using a ballast volume.

[0038] To solve the aforementioned problem, an analytical instrument, particularly for elemental analysis, preferably for determining the nitrogen, carbon, hydrogen, and / or sulfur content in a sample, is proposed according to the invention. This instrument comprises a combustion unit for burning the sample, a ballast chamber for collecting gaseous combustion products, and a movable piston arranged within the ballast chamber. By designing the ballast chamber with two separate sub-chambers, which are separated from each other by the piston, selective collection of combustion products into the ballast chamber is possible. The gaseous combustion products generated during the combustion of the sample in a furnace can thus be selectively introduced into one of the sub-chambers of the ballast chamber on either side of the piston.This significantly increases the throughput rate when analyzing multiple samples consecutively. Furthermore, by supplying the ballast chamber exclusively or almost exclusively with hot combustion products, a largely constant temperature within the ballast chamber is ensured. In particular, compared to the known approach of first filling the ballast volume with hot combustion products and then purging them with a comparatively cold purge gas, the solution according to the invention greatly reduces or eliminates the thermal influence of the ballast volume on the analysis. This significantly improves the quality of the analyses in terms of accuracy, reproducibility, and comparability.

[0039] The piston is specifically designed for fluid-tight separation of the sub-chambers. For this purpose, the piston can be equipped with a suitable seal that is in contact with the inside wall of the ballast chamber. Combustion products from the samples under investigation, located in the ballast volume or in the sub-chambers, are thus reliably separated from one another. This prevents any mixing of two samples that could distort the measurement results.

[0040] Preferably, each of the sub-chambers is assigned an inlet valve through which the combustion products from the combustion unit, i.e., for example, a furnace, can be introduced into the respective sub-chambers in a controlled manner. Similarly, each of the sub-chambers is preferably alternatively or additionally assigned an outlet valve, which allows the controlled discharge of the combustion products from the ballast volume, particularly after homogenization. Separate inlet and outlet valves for the sub-chambers, and correspondingly separate routing of the supply lines (at least partially), further support the separation of two successive samples. If two samples are not introduced consecutively through a common piping system and a single common inlet valve, the following applies:By directing the sample through the outlet valve, the probability of mixing with any residual combustion gases from the previous sample that may remain in the lines or around the valves is reduced. This further increases the reliability of the analysis.

[0041] A suitable switching valve allows the combustion products of different samples to be selectively directed to or redirected to one of the sub-chambers. By incorporating a separate switching valve, precise and, in particular, time-accurate control is achieved, determining which combustion products are directed to the ballast chamber or to one of the sub-chambers, when, and via which route. The switching action of the valve can be timed to coincide with the point at which the combustion of the sample is complete. Thermal losses can be minimized by thermally insulating the ballast chamber from the environment. Such insulation also allows for faster temperature control of the entire apparatus and a high degree of temperature stability during operation. The ballast volume...The combustion products collected in the sub-chambers of the ballast chamber are therefore not cooled down upon entering the ballast chamber, which could lead to undesirable changes in the thermodynamic properties of the gas and / or the fractions it contains.

[0042] In a preferred embodiment, the analyzer includes a control unit for selectively directing the combustion products to each of the sub-chambers. Particularly through automatic control, the timing of switching the supply of combustion products to one of the sub-chambers can be precisely aligned with the point at which combustion is complete. Delay times and / or the coordinated switching of the various valves can thus be precisely set.

[0043] In addition to simplified operation by a user, a control unit can preferably also enable automated operation of the analyzer. Automated processes thus allow for the analysis of a large number of samples in a very short time. Furthermore, the routing or diversion of combustion products and / or the switching operations of one or more valves can also be made dependent on parameters other than time, for example, environmental and / or operating parameters, particularly those acquired by appropriate sensors. These can include, for example, one or more values ​​for temperature, pressure, and / or flow rate.

[0044] Particularly in conjunction with a control device, but also generally independently of one, the ballast chamber, especially one or both sub-chambers, can be equipped with at least one sensor for determining temperature, gas flow, and / or piston position. The measured values ​​are to be understood as relating specifically to the interior of the ballast chamber or the interior of one or both sub-chambers. Particularly in conjunction with a control device, the achievement of specific parameter values ​​can be monitored by appropriate sensors. If predetermined conditions are reached, which represent a criterion, for example, for switching a changeover valve and / or opening or closing an inlet or outlet valve, the operating state can be adjusted accordingly, depending on a measured value from the sensor(s).

[0045] Furthermore, an analytical method possesses inventive significance by which the nitrogen, carbon, hydrogen, and / or sulfur content of a sample can be determined. In this method, the sample is completely combusted, and the gaseous combustion products are collected in a ballast chamber. According to the invention, in multiple analyses, the combustion products of successive samples are collected alternately in one of two sub-chambers of the ballast chamber. As described above, this allows for a particularly efficient elemental analysis of a large number of samples in a very short time. With a sufficiently high throughput rate, this results in an almost continuous sequence of combustion and analysis of samples, with the collection of the combustion products in the ballast chamber occurring without a separate rinsing step and, moreover, at a nearly constant temperature.Due to the constant temperature of the ballast chamber - in contrast to a constant temperature change caused by the alternating inflow of hot combustion products and comparatively cold, especially room-temperature, purge gas - the achievable analytical quality is significantly increased compared to known approaches of the aforementioned type.

[0046] Alternatively or additionally, a heating device can be provided which allows pre-heating of the ballast chamber, in particular one or both sub-chambers. Such a heating device can be assigned to the ballast chamber as a separate module, but can also be at least partially integrated into it. The invention also provides for the use of multiple heating devices, in particular one heating device for each sub-chamber. In particular, the heating device heats the environment of the ballast chamber to a defined temperature in order to reduce the temperature gradient between the combustion products in the ballast chamber and the environment, and thus counteract thermal losses.

[0047] Within the scope of the present invention, the use of a heating device is preferably only provided as a supplementary measure. In a particularly preferred embodiment, the analysis device according to the invention, or the execution of a corresponding analysis procedure, is carried out over the successive analysis of several samples with at least substantially a constant temperature of the ballast chamber, particularly without the support of a heating device for heating the ballast chamber itself, but primarily, preferably exclusively, by the alternating flow of the hot combustion products of successive samples, which heat the ballast chamber or a wall of the ballast chamber from the inside.

[0048] The analysis of the hydrogen content can be carried out in particular before the combustion products are introduced into the ballast volume, while the analysis of the proportion of other elements such as nitrogen, carbon and / or sulfur is preferably carried out after the homogenization of the medium in the ballast volume.

[0049] In a preferred embodiment of the method according to the invention, the inflow of combustion products from a sample into a sub-chamber of the ballast chamber moves a piston in the ballast chamber such that combustion products contained in the other sub-chamber, i.e., located beyond the piston, are discharged from the ballast chamber. This eliminates the need for the additional use of compressed air or pressurized gases to move the piston and discharge the combustion products from the ballast chamber, as well as the need for additional purge gases to flush out the combustion products contained in the ballast chamber. This results in a significant increase in efficiency, both in terms of time and cost.

[0050] The present invention is explained in more detail below with reference to specific embodiments. All features described and / or illustrated in the drawings constitute independent, separate aspects of the invention, irrespective of their combination in the embodiments and / or the cross-references in the claims.

[0051] It shows:

[0052] Fig. 1 is a schematic representation of an analysis device according to the invention, Fig. 2 is a perspective schematic representation of a part of an analysis device according to the invention,

[0053] Fig. 3 is a schematic cross-sectional view of the structure shown in Fig. 2.

[0054] Part,

[0055] Fig. 4 shows another schematic cross-sectional view of the part shown in Fig. 2,

[0056] Figs. 5A - 5F schematic representations of an exemplary gas flow configuration of the analytical instrument according to the invention or during the execution of an analytical method according to the invention,

[0057] Figs. 6A - 6C are each schematic representations of a preferred embodiment of the analysis device according to the invention in various operating states.

[0058] Fig. 7 shows a perspective schematic representation of a preferred embodiment of a ballast chamber of the analytical instrument according to the invention and

[0059] Fig. 8 shows a schematic cross-sectional view of the ballast chamber of

[0060] Fig. 7.

[0061] In the figures, which are sometimes not to scale and only schematic, the same reference symbols are used for identical or similar parts, whereby corresponding or comparable properties and advantages can be achieved even if a repeated description is omitted.

[0062] Figure 1 schematically depicts an analytical instrument 1 of the type according to the invention with its basic components. The analytical instrument 1 serves to analyze a sample P with regard to its elemental composition, in particular with regard to the content of nitrogen, carbon, hydrogen and / or sulfur.

[0063] Sample P is burned for further analysis, that is, oxidized, in particular completely burned.

[0064] For combustion, the sample P is located in a crucible 2 and is introduced into a combustion tube 4 via a sample lock 3 in such a way that it is arranged in the area of ​​a furnace 5.

[0065] Heating the sample P in furnace 5 oxidizes the substances contained therein, producing primarily gaseous reaction products. To further support the oxidation of sample P, oxygen and / or another oxidizing or oxidation-promoting substance can also be introduced into the combustion tube 4.

[0066] The gaseous reaction products or combustion gases are transported from the combustion tube 4 after and / or during the combustion of sample P by means of a system of gas lines 6.

[0067] The reaction products are then collected in a ballast volume provided by a ballast chamber 7 and, in particular, collected in their entirety.

[0068] The ballast chamber 7 can have a corresponding inlet valve 8 for controlling the incoming gas flow.

[0069] After a given time, a largely homogeneous mixture of the reaction products formed during the combustion of sample P is present in ballast chamber 7. A portion of the reaction products can then be discharged from ballast chamber 7 via an outlet valve 9.

[0070] The volume of the portion of the reaction products discharged from ballast chamber 7, i.e. the aliquot, is set to a specific value and is defined in particular by the volume of an aliquot chamber 10 to which the aliquot is fed.

[0071] The aliquot chamber 10 can be separated from the ballast chamber 7 with respect to the gas flow by means of appropriate valves.

[0072] After the aliquot flows into the aliquot chamber 10, the contained substance fractions undergo extensive homogenization after a certain time. Following this homogenization, the aliquot is rinsed from the aliquot volume provided by the aliquot chamber 10 and transferred to further analysis. For this purpose, the analyzer 1 has a purge gas connection 11 through which a purge gas can be introduced.

[0073] The purge gas used is primarily an inert gas, preferably a noble gas, preferably helium and / or argon. Other purge gases can also be used alternatively or additionally. The selection is based in particular on the criteria of a known composition of the purge gas and the avoidance of undesirable reactions between the purge gas and the fractions contained in the aliquot.

[0074] By means of a switching valve 12, the aliquot chamber 10 can be supplied with the purge gas, whereupon the mixture of purge gas and aliquot is transported out of the aliquot chamber 10 by means of an outlet valve 9.

[0075] The aliquot is then transported via appropriate gas lines 6 to an analysis unit 13, where the elemental composition of the sample P is determined by a suitable analytical method. Within the scope of the present invention, the type of analytical method and / or the design of the analysis unit 13 are, in principle, freely selectable. The selection can be made, in particular, depending on the properties of the sample P and / or its expected composition.

[0076] After analysis in the analysis unit 13, the gaseous components leave the analysis unit 1 through a gas outlet 14.

[0077] In a preferred embodiment of the analytical instrument 1 according to the invention, a particular configuration of the valve arrangement 12 is used, as shown in perspective in Fig. 2. The valve arrangement 12 serves for the selective introduction, discharge, and / or redirection of gas flows. This includes, on the one hand, in particular, the gas flow from the ballast chamber 7 to the aliquot chamber 10, by means of which the aliquot, i.e., a specific portion of the gaseous reaction products collected in the ballast chamber 7, is extracted from the ballast volume. On the other hand, the valve arrangement 12 shown in Fig. 2 regulates the purge gas flow for purging the aliquot volume or the aliquot chamber 10 and for transporting the aliquot to the analytical unit 13.

[0078] The gas mixture containing the gaseous reaction products from the combustion of sample P, which is collected partly in the ballast chamber 7 and partly, with a specific partial volume, directed into the aliquot chamber 10 and from there, together with the purge gas, to the analysis device 13, is hereinafter referred to uniformly as "analyte gas". The valve arrangement shown in Fig. 2 has an analyte gas inlet 15 and an analyte gas outlet 16, as well as a purge gas inlet 17 and a purge gas outlet 18.

[0079] Furthermore, the valve arrangement 12 comprises a first transfer outlet 19 and a first transfer inlet 20, as well as a second transfer outlet 21 and a second transfer inlet 22. The first transfer outlet 19 and first transfer inlet 20, as well as the second transfer outlet 21 and second transfer inlet 22, are each fluidically connected to one another.

[0080] Depending on the setting of the valve arrangement 12, the transfer outlets 19, 21 and inlets 20, 22 serve to connect analyte gas inlet 15 and analyte gas outlet 16 or purge gas inlet 17 and purge gas outlet 18.

[0081] Furthermore, a connection can be established between the aliquot chamber 10 and, on the one hand, the analyte gas inlet 15 or the purge gas inlet 17 and / or, on the other hand, the analyte gas outlet 16 or the purge gas outlet 18 by means of a corresponding aliquot outlet 23 and an aliquot inlet 24.

[0082] The assignment of the various inlets and outlets, or the provision of a connection to the aliquot chamber 10, depends on the setting of the valve arrangement 12. As can be seen in the cross-sectional view according to Fig. 3, the valve arrangement 12 in the embodiment discussed here has two valve pistons 25, which are slidably mounted in valve channels 26. The valve pistons 25 have, in particular, a plurality, in this case three, piston bodies 27, which almost fill the valve channel 26 in the radial direction and separate the areas of the valve channel 26 located axially in front of and behind the piston body 27 from each other gas-tight by means of seals 28.

[0083] The piston bodies 27 are connected to each other by connecting rods 29 to form the entire valve piston 25 in such a way that, in particular, a synchronous movement of the piston bodies 27 of a valve piston 25 takes place in the axial direction.

[0084] The valve pistons 25 are pneumatically moved. For this purpose, the valve arrangement 12 has several, in particular four, control ports 30, by means of which the valve channel on the side of the outermost piston bodies 27 facing away from the valve piston 25 is pressurized, causing the movement of the valve piston 25 in the axial direction through the valve channel 26.

[0085] The valve pistons 25 can thus be moved into different positions in the valve channel 26, and therefore relative to the various inlets and outlets of the valve arrangement 12. The resulting relative position of the piston bodies 27 to the inlets and outlets is particularly important. Depending on the position of the valve piston 25 in the valve channel 26, one or more piston bodies 27 of the valve piston 25 can directly cover and, in particular, seal specific inlets and / or outlets. Alternatively or additionally, a piston body 27 can also be positioned between two inlets or outlets in such a way that they are fluid-tight, and in particular gas-tight, sealed off from each other.

[0086] In particular, the valve pistons 25 are movable into a position such that a fluidic connection is established between several, preferably exactly two, inlets or outlets, especially in the form of a specific pair of inlet and outlet, via the valve channel 26. In this way, a selective assignment of specific inlets to specific outlets is possible by means of a movement of the valve pistons 25.

[0087] The valve arrangement 12 also has stop devices 31, preferably with a stop device 31 assigned to each valve channel 26.

[0088] By means of the stop devices 31, a mechanical stop 32 can be provided, which prevents further movement of the valve piston 25 towards the stop 32. If the valve channel 26 on the side facing away from the stop device 31 is pressurized via the control port 30, the valve piston 25 moves towards the stop 32 and is stopped there. The stop device 31 is preferably designed for variable positioning of the stop 32, so that the end position of the valve piston 25 can be selected accordingly.

[0089] The positioning of the stop 32 can be achieved, in particular, by a pneumatically actuated displacement of the stop rod 33. Furthermore, alternatively or additionally, other adjustment options are possible according to the invention. For example, the stop rod 33 can be moved and locked mechanically, i.e., in particular manually and / or by motor, for instance by means of a threaded arrangement. Hydraulic and / or magnetomechanical adjustment of the stop rod 33 is also possible. It is understood that a combination solution in this context is also possible.

[0090] By appropriately adjusting the valve arrangement 12, gases introduced through the inlets 15, 17 can be introduced into an aliquot chamber 10. For this purpose, the valve arrangement 12 is adjusted in particular such that a fluidic connection is established between the analyte gas inlet 15 or the purge gas inlet 17 and the aliquot outlet 23.

[0091] In order to establish the aforementioned fluidic connection, the valve pistons 25 can be moved in the valve channel 26 by means of pressurization via the control ports 30, such that the respective inlet 15, 17 and the aliquot outlet 23 are each fluidically connected to the valve channel 26.

[0092] In the present example, the aliquot chamber 10 is arranged directly adjacent to the valve assembly 12, as shown in cross-section in Fig. 4. The aliquot chamber 10 here has an at least substantially cylindrical shape, its length being in particular greater than its diameter, preferably a multiple of the diameter.

[0093] The aliquot chamber 10 is designed such that its volume is variable or adjustable. The aliquot chamber 10 according to the invention is therefore suitable for holding a variable aliquot.

[0094] An adjusting device 34, in particular in the form of a piston, can serve to adjust the volume of the aliquot chamber 10 to a specific value. For this purpose, the adjusting device 34 or the piston is movably mounted in the aliquot chamber 10, preferably displaceable along its longitudinal axis.

[0095] The adjusting device 34 can be moved manually to a predetermined position to adjust the volume of the aliquot chamber 10. However, a preferred embodiment allows the adjusting device 34 to be moved by a motor, pneumatically, hydraulically, and / or magnetomechanically. To move the adjusting device 34 inside the aliquot chamber 10, a manipulator 35 is provided. This manipulator can be designed, in particular, as a rod connected internally to the adjusting device 34, especially the piston, and with its opposite end protruding from the aliquot chamber 10. Alternatively or additionally, the manipulator 35 can also have a thread, in particular as a threaded rod, micrometer screw, or the like.Depending on the pitch of the thread, a linear, axial movement of the manipulator 35 and thus of the adjusting device 34 can be achieved with a high degree of precision by rotating the manipulator 35 itself and / or a component connected to it.

[0096] The manipulator 35 can also be operatively connected to a drive unit via its end protruding from the aliquot chamber 10. In addition to a hydraulic, pneumatic and / or magnetic system, this can in particular be a stepper motor, which can effect rotation and / or linear movement of the manipulator 35 and the adjusting device 34 in fine increments.

[0097] In a preferred embodiment of the invention, the movement of the adjusting device 34 can not only serve to determine the aliquot volume, but also allows support for the discharge of the aliquot from the aliquot chamber 10.

[0098] The aliquot is preferably introduced axially into the aliquot chamber 10. For this purpose, the aliquot outlet 23 is arranged, in particular, at an axial end of the aliquot chamber 10. The aliquot outlet 23 can be arranged either in a central position with respect to the radial extent of the aliquot chamber 10 or offset from the central axis of the aliquot chamber 10. The same applies to the aliquot inlet 24 of the valve assembly 12, through which the aliquot can be transported from the aliquot chamber 10 back into the valve assembly 12 and by means of this to one of the further outlets.

[0099] According to the invention, a combined configuration with a combined access to the aliquot chamber 10 is also possible, which functions as both an aliquot outlet 23 and an aliquot inlet 24, depending on the operating situation. If the discharge of the aliquot from the aliquot chamber 10 is supported or substantially effected by the adjusting device 34, the amount of purge gas typically introduced to clean the aliquot chamber 10 can be reduced accordingly. This allows for a significant reduction in the high costs of noble gases such as helium, argon, or the like, which are typically used for purging.

[0100] In a preferred embodiment of the invention, the aliquot is almost completely discharged from the aliquot chamber 10 by means of the adjusting device 34, so that the introduction of a purge gas stream into the aliquot chamber 10 is minimal, if necessary, for the removal of residual analyte gas, and preferably can be dispensed with entirely. In this case, the use of expensive noble gases for purging can be largely avoided. To ensure the complete removal of residual analyte gas from the aliquot chamber 10, it may, for example, be sufficient to introduce a certain amount of oxygen into the aliquot chamber 10, which is introduced into the system anyway to support the combustion of the sample P and should be present at the point of use of the analytical instrument 1 according to the invention.

[0101] The adjusting device 34 can also be associated with a control unit (not shown in detail) by which the adjusting device 34 can be controlled in its position within the aliquot chamber 10. Preferably, different aliquot volumes can be set by means of the control unit, in particular by inputting and / or selecting them via a user interface, so that the control unit causes the adjusting device 34 to move to specific positions within the aliquot chamber 10, which correspond to the respective aliquot volumes. The control unit is preferably designed to store specific positions of the adjusting device 34 or of different aliquot volumes and to allow them to be retrieved by a user as needed. In particular, the control unit is thus suitable for remote control and / or automated operation of the system.

[0102] To measure and monitor the atmospheric conditions inside the aliquot chamber 10, a control device 36 is preferably assigned to it. In this way, various parameters, such as pressure, temperature, and / or the presence of a specific substance, can be determined, which can then be used to decide on the timing and / or method of the further analysis of sample P. Alternatively or additionally, the parameters recorded by the control device 36 can also be made available to the control unit, for example, to further automate the analysis process.

[0103] A sensor 37 is used in particular to record the various parameters, which is preferably arranged inside the aliquot chamber 10 and / or allows conclusions to be drawn about the prevailing conditions by being arranged close to the aliquot chamber 10.

[0104] In a preferred embodiment of the invention, the use of the aliquot proceeds at least essentially in the following manner.

[0105] Figures 5A to 5F schematically show various configurations or setting situations of the valve arrangement 12 with respect to the flow paths of the respective incoming and outgoing gaseous components.

[0106] In the initial position or neutral configuration of the valve arrangement 12 shown in Fig. 5A, a bypass situation exists. This is characterized by the fact that the analyte gases flowing in from the ballast chamber 7 enter through the analyte gas inlet 15 and flow out again through the analyte gas outlet 16. The same applies to any purge gas, which flows into the valve arrangement 12 through the purge gas inlet 17 and leaves it again through the purge gas outlet 18. Incoming analyte gases and / or purge gases would thus bypass the aliquot chamber 10.

[0107] To establish the bypass configuration shown in Fig. 5A, the valve pistons 25 in the valve channels 26 are positioned such that a fluidic connection is established between the analyte gas inlet 15 and the first transfer outlet 19, as well as between the purge gas inlet 17 and the second transfer outlet 21, via the valve channels 26. A corresponding setting is simultaneously present with respect to a fluidic connection between the first transfer inlet 20 and the analyte gas outlet 16, as well as between the second transfer inlet 22 and the purge gas outlet 18. For this purpose, the valve pistons 25 have each been moved to a central position in the valve channels 26.

[0108] To fill the aliquot volume in the aliquot chamber 10, the valve arrangement 12 is switched, in particular by moving the valve pistons 25, so that the flow conditions shown in Fig. 5B are established. With regard to the purge gas path, a bypass situation exists, characterized by a fluidic connection from the purge gas inlet 17 via the second transfer outlet 21, the second transfer inlet 22 directly connected to it, and the purge gas outlet 18.

[0109] On the analyte gas flow side, the switching position of the valve arrangement 12 shown in Fig. 5B provides that a fluidic connection is established between the analyte gas inlet 15 and the aliquot outlet 23 such that the analyte gas flowing into the analyte gas inlet 15 can flow from the ballast volume or ballast chamber 7 into the aliquot chamber 10. The switching position of the valve arrangement 12 further provides that the analyte gas flowing into or through the aliquot chamber 10 re-enters the valve arrangement 12 through the aliquot inlet 24 and continues to flow through the fluidic connection established by the switching position shown between the aliquot inlet 24 and the analyte gas outlet 16.

[0110] When the aliquot chamber 10 is permeated by the analyte gases from the ballast chamber 7, as shown in Fig. 5B, an overpressure generally prevails in the gas line 6 and in the aliquot chamber 10, which is determined at least substantially by the conditions in the ballast chamber 7. To equalize the atmosphere in the aliquot chamber with the ambient pressure, the valve assembly 12 is therefore moved to the switching position shown in Fig. 5C after a certain period of permeation. For this purpose, the inlet side of the valve assembly 12, with the analyte gas inlet 15 and the purge gas inlet 17, is returned to the bypass position described above. The purge gas path thus continues to bypass the aliquot chamber 10 completely. The analyte gas path also runs, according to the position shown in Fig. 5C, initially from the analyte gas inlet 15 via the first transfer outlet 19 to the first transfer inlet 20 connected to it.Due to the unchanged configuration of the outlet side of the valve arrangement 12 with the analyte gas outlet 16 and the purge gas outlet 18 compared to the previous position, a fluidic connection between the aliquot inlet 24 and the analyte gas outlet 16 is still maintained. The analyte gas path from the ballast chamber 7 thus terminates at the first transfer inlet 20, which preferably forms a gas-tight seal. Any overpressure in the aliquot chamber 10 can therefore be reduced via the analyte gas outlet 16, resulting in a pressure in the aliquot chamber 10 that is at least substantially equal to the ambient pressure. The prevailing pressure and / or temperature can be monitored by means of the control device 36 and / or several sensors 37 before, in, and / or after the aliquot chamber 10 (each in the direction of flow). This allows, for example, the overpressure in the gas lines 6 or 7 caused by the ballast volume to be monitored.in the aliquot chamber 10. Alternatively or additionally, it can be determined when the pressure inside the aliquot chamber 10 has sufficiently approached the ambient pressure. The measured data are preferably transmitted to the control unit 36 ​​and / or the control unit via a PC interface.

[0111] After the aliquot volume has been vented, i.e., after a pressure corresponding at least substantially to the ambient pressure has been established in the aliquot chamber 10, the aliquot chamber 10 is also sealed at the outlet. For this purpose, the valve assembly 12 is returned to the bypass position, as shown in Fig. 5D. Both the analyte gas path and the purge gas path now again run completely around the aliquot chamber 10. The aliquot inlet 24 of the valve assembly 12, which is connected downstream to the aliquot chamber 10, is sealed in this case, as is the aliquot outlet 23 of the valve assembly 12, which is located upstream of the aliquot chamber 10, so that the aliquot chamber 10 is completely sealed gas-tight from the environment or the system of gas lines 6 of the analyzer 1. Due to this isolation, the medium enclosed in the aliquot chamber 10 can distribute itself homogeneously.The aliquot volume equilibrated in this way therefore preferably contains no local concentrations of individual gas fractions and thus corresponds in particular to the relative overall composition of the ballast volume of all combustion gases collected in the ballast chamber 7.

[0112] After homogenization of the aliquot volume, it is purged from the aliquot chamber 10 and fed to the analysis device 13. For this purpose, the valve assembly 12 is switched to a position that allows a purge gas, for example helium, argon, and / or other inert gases, to be introduced into the aliquot chamber 10 and the analyte gases contained in the aliquot volume to be discharged from the aliquot chamber 10 together with the purge gas. To achieve this, the aliquot volume in the aliquot chamber 10 is first exposed to the system pressure of the secondary path, i.e., the purge gas path, and thus equalized. This is done, according to the flow direction, by first switching the valve assembly 12 to the configuration shown in Fig. 5E.Here, the inlet side of the valve assembly 12 is adjusted by appropriately aligning the valve pistons 25 in the valve channels 26 such that a fluidic connection is established between the purge gas inlet 17 and the aliquot outlet 23. The purge gas introduced via the purge gas inlet 17 can thus act on the aliquot volume and consequently lead to a corresponding pressure increase in the aliquot chamber 10. It is generally sufficient for this phase of the process to last only a very short time, in particular less than 1 second.

[0113] Once the appropriate pressure has been established in the aliquot chamber 10 after a short time, the valve assembly 12 can be switched to the position shown in Fig. 5F, in which the outlet side now also assumes a configuration in which a fluidic connection exists between the aliquot outlet 24 and the purge gas outlet 18. The analyte gases of the aliquot volume, pressurized as described above, as well as the purge gas flowing in via the purge gas inlet 17, thus flow from the aliquot chamber 10 into the valve assembly 12 via the aliquot inlet 24 and exit it via the purge gas outlet 18 towards the analysis device 13. Here, the actual analysis of the analyte gases of the aliquot volume, which corresponds in its composition to the combustion products collected in the ballast chamber 7, ultimately takes place.

[0114] The flushing of the aliquot volume from the aliquot chamber 10 is supported by the adjusting device 34 in the manner described above, particularly during the phases shown in Figures 5E and / or 5F. If a large portion of the aliquot volume is mechanically displaced by reducing the volume of the aliquot chamber 10 using the adjusting device 34, the possibility of a certain dead volume forming within the aliquot chamber 10 is simultaneously reduced. This dead volume would not be reached or would only be reached very slowly by the flushing gases. Otherwise, by appropriately creating areas with different flow conditions, i.e., areas with laminar flow and areas with turbulence, undesirable portions of the analyte gas from the aliquot volume could remain within the aliquot chamber 10. A corresponding preferred embodiment of the inventive design, or...The inventive method effectively prevents measurement errors caused by this. Figures 6A to 6C schematically depict a part of the inventive analyzer 1 according to a preferred embodiment. The section around the ballast chamber 7 is shown in particular to illustrate the supply and discharge of combustion products.

[0115] The combustion products from the furnace 5 (not shown in detail here) first reach an inlet-side bypass valve 38 via a gas line 6 in the exemplary setup described here. This valve allows the gaseous combustion products to be diverted past the ballast chamber 7 via a bypass line 39, thus enabling the ballast volume to be used without interruption. A further outlet-side bypass valve 40 is provided downstream in a similar manner.

[0116] For connecting the corresponding supply and discharge lines, the inlet-side bypass valve 38 comprises at least one inlet 41 and at least two separate outlets in the form of a bypass outlet 42 to the bypass line 39 and a ballast outlet 43, to which the supply lines to the ballast chamber 7 are connected. Correspondingly, the outlet-side bypass valve 40 has at least two inlets, in particular a bypass inlet 44 and a ballast inlet 45, as well as at least one outlet 46.

[0117] By switching the bypass valves 38 and 40, the combustion products can be selectively directed to or around the ballast chamber 7. This may be the case, for example, if, after introducing the combustion products into the ballast chamber 7, homogenization or equilibration within the ballast chamber 7 is to be awaited before the combustion products are flushed out of the ballast chamber 7.

[0118] Along the conduit leading to or through the ballast chamber 7, the combustion products pass through the bypass valve 38 to an inlet-side switching valve 47 with at least one inlet 41 and at least two outlets, which in particular comprise a first outlet 48 and a second outlet 49. The inlet-side switching valve 47 is connected to the ballast chamber 7 via a first supply line 50 and a second supply line 51.

[0119] The ballast chamber 7 has two subchambers in the form of a first subchamber 52 and a second subchamber 53, which are separated from each other by a piston 54. This piston prevents the combustion products from passing from the first subchamber 52 into the second subchamber 53. The piston 54 preferably separates the subchambers 52 and 53 from each other in a fluid-tight, and in particular gas-tight, manner.

[0120] The sub-chambers 52, 53 preferably each have at least one inlet valve (first inlet valve 55, second inlet valve 56) and at least one outlet valve (first outlet valve 57, second outlet valve 58), which serve to introduce or discharge the combustion products into or out of the respective assigned sub-chamber 52, 53.

[0121] Not shown in detail is an optional thermal insulation of the ballast chamber 7 or of one or both subchambers 52, 53, which reduces thermal losses to the environment that could negatively affect the reproducibility and comparability of the analysis results. The insulation comprises, in particular, a heat-insulating material with a comparatively low thermal conductivity. Alternatively or additionally, the insulation may also include a radiation-reflecting layer and / or one or more vacuum insulation panels.

[0122] Downstream of the ballast chamber 7 in the flow direction, the assembly shown in Figures 6A to 6C has an outlet-side switching valve 59, which in turn is connected to the ballast chamber 7 and to the respective outlet valves 57 and 58 associated with the sub-chambers 52 and 53 by a first outlet line 60 and a second outlet line 61. The outlet-side switching valve 59 serves to selectively switch between the combustion products discharged from the first sub-chamber 52 and the second sub-chamber 53. Depending on the configuration of the outlet-side switching valve 59, the corresponding combustion products enter the switching valve 59 through a first inlet 62 or a second inlet 63 and are conveyed from an outlet 46 of the switching valve 59 to the ballast inlet 44 of the outlet-side bypass valve 40.

[0123] Ballast chamber 7 is further equipped with a control device (not shown in detail) that can monitor and / or control the switching position of one or more of the bypass valves 38, 40, the switching valves 47, 59, the inlet valves 55, 56, and / or the outlet valves 57, 58. The control of the valves can be time-based, in particular, or alternatively or additionally dependent on certain environmental and / or process parameters. The control device is preferably designed for at least partially automatic control of the valve positions. Furthermore, the control device can also be connected to and / or integrated into a higher-level control system of the analyzer 1.

[0124] In order to be able to quantitatively record parameters, for example, relating to the environment and / or the interior of ballast chamber 7 or sub-chambers 52, 53, at least one corresponding sensor 64 is assigned to ballast chamber 7. In a preferred embodiment, at least one corresponding sensor 64 is also assigned to each of the sub-chambers 52, 53. The sensor(s) 64 can be arranged both outside and inside ballast chamber 7 or sub-chambers 52, 53 and can be configured for direct and / or indirect measurement.

[0125] Within the scope of the present invention, parameters detectable by a corresponding sensor 64 include, in particular, the temperature, pressure, flow rate, and / or flow velocity of gaseous substances or mixtures of substances, especially combustion products, which flow into, out of, and / or are located in the ballast chamber 7. Alternatively or additionally, state parameters of the analyzer 1, particularly with regard to the ballast chamber 7, such as the position, direction of movement, and / or speed of the piston 54, and / or the switching states of one or more valves, can also be detected by means of a corresponding sensor 64.

[0126] In the configuration shown in Fig. 6A, the bypass valves 38, 40 are each positioned such that a fluidic connection exists between the bypass line 39 and the incoming and outgoing gas lines 6. Combustion products from the burnt sample P coming from the furnace 5 are thus diverted past the ballast chamber 7.

[0127] To fill the ballast volume in ballast chamber 7, the assembly is now brought into the state shown in Fig. 6B. For this purpose, the bypass valves 38, 40 are switched so that incoming combustion products are directed along the flow path through the ballast volume. As can be seen in Fig. 6B, in the example shown here, ballast chamber 7 is in a state in which the piston 54 is fully positioned at one of its end positions. Therefore, one of the sub-chambers 52, 53 formed by the separation by means of the piston 54, in this case the first sub-chamber 52, is maximized in volume and fills almost the entire internal volume of ballast chamber 7. The volume of the second sub-chamber 53 is correspondingly almost completely minimized in this state.

[0128] The inlet-side switching valve 47 is in a position that allows the combustion products to flow through the first outlet 48, the first supply line 50, and the first inlet valve 55 into the first sub-chamber 52. Once a certain fill level is reached, for example, characterized by a specific pressure inside the first sub-chamber 52 or after a certain predefined time has elapsed, the flow is stopped, in particular by closing the first inlet valve 55. In this state, the medium contained in the first sub-chamber 52 preferably contains all the combustion products that resulted from the oxidation of sample P.

[0129] If this is not the first filling, i.e., the first in a series of successive analyses of different samples P, combustion products from the previous sample P are generally already present in the ballast chamber 7 or in the respective other subchamber 52, 53, which is located on the opposite side of the piston 54 from the subchamber 52, 53 to be filled next. In the present example, this would be the second subchamber 53. The flow of the medium into the first subchamber 52 in this case moves the piston 54, as will be discussed in more detail below in connection with Fig. 6C. Alternatively or additionally to other parameters, the piston 54 reaching its respective end position and / or the detection of a cessation of piston movement can also be used as criteria for the completion of the filling of the respective subchamber 52, 53.

[0130] In the subchamber 52, which is preferably sealed to the outside by closing the corresponding valves, the various fractions of the gas mixture homogenize after a certain time, so that each subset of the contained volume corresponds at least substantially to the overall composition of the combustion products and thus ultimately to the sample P. Therefore, a comparatively small subset can be taken as an aliquot or diverted further down the flow path and fed to an analysis unit 13 of the analyzer 1. In the state shown in Fig. 6B, the outlet-side switching valve 59 is set during and after filling the first subchamber 52 such that its first inlet 62 is closed, or the passage of the medium from the ballast volume through the switching valve 59 to its outlet 46 is blocked.Although closing the first outlet valve 57 is preferred to keep the combustion products in the first sub-chamber 52, the first outlet line 60 can alternatively or additionally be closed in the manner described above to prevent the combustion products from leaving through the outlet-side switching valve 59.

[0131] In particular, after the homogenization of the gas fractions in the first sub-chamber 52, the combustion products collected there can be flushed out, for example, to feed at least some of them to an aliquot chamber 10 or subsequently to the actual elemental analysis. For this purpose, the system is brought into the state shown in Fig. 6C. The inlet-side switching valve 47 is switched to supply the second supply line 51 with the media flow, so that the combustion products flow through the second inlet valve 56 into the second sub-chamber 53 of the ballast chamber 7. In parallel, the outlet-side switching valve 59 is preferably switched accordingly, so that the second outlet line 61 at the second inlet 63 of the switching valve 59 is closed, thus blocking further transport of the combustion products beyond the outlet-side switching valve 59.

[0132] The inflow of the medium increases the pressure in the second sub-chamber 53, consequently exerting a force on the piston 54, which moves it towards the first sub-chamber 52, in particular until the piston 54 reaches its opposite end position, as schematically shown in Fig. 6C. The fluid-tight and gas-tight separation of the sub-chambers 52 and 53 is maintained by the sealing of the piston 54 against a wall 65 of the ballast chamber 7.

[0133] For sealing, the piston 54 preferably has a sealing element 66 for bearing against the wall 65, which is not shown in detail in the highly schematic representation of Figures 6A to 6C. However, a corresponding sealing element 66 is shown in the perspective view and the cross-sectional view of an exemplary embodiment of the ballast chamber 7 according to Figures 7 and 8. The sealing element 66 can be an O-ring, a sealing lip, or the like. The sealing element 66 is made of, or has, an elastic material. Preferably, the material of the sealing element 66 is heat-resistant, so that even comparatively hot combustion products can be introduced into the ballast chamber 7 shortly after the oxidation of the sample P in the furnace 5 without impairing the sealing effect of the piston 54 or the sealing element 66.

[0134] The movement of the piston 54 reduces the volume of the first subchamber 52. The preferably homogenized combustion products inside the first subchamber 52 are consequently conveyed out of the ballast chamber 7 through the first outlet valve 57, which is open in this state. Due to the active mechanical expulsion of the combustion products, no additional purging or flushing of the first subchamber 52 with an inert gas or the like is necessary to completely remove the combustion products from the ballast chamber 7. The medium flowing into the second subchamber 53 in the form of the combustion products of the subsequent sample P thus preferably ensures the complete purging or expulsion of the combustion products of the preceding sample P. This is due to the fluid density of the first subchamber 53.Gas-tight separation of the sub-chambers 52, 53 by the piston 54 is possible, as mixing of the separate samples P is prevented and an unadulterated examination of the respective sample compositions is still possible.

[0135] The discharged medium passes from the first sub-chamber 52 through the first outlet valve 57 and the first outlet line 60 to the first inlet 62 of the outlet-side switching valve 59, which, in the switching position described above and shown in Fig. 6C, directs the medium arriving at the first inlet 62 to its outlet 46. The medium is then transported further through the gas line 6 connected there and, for example, at least partially supplied to an aliquot chamber 10.

[0136] For the analysis of the subsequent sample P, the processes described above are carried out with a correspondingly reversed arrangement of the sub-chambers 52, 53 and their associated components such as inlet lines 50, 51, valves 55-58, and outlet lines 60, 61. The system is brought into the state shown in Fig. 6B, particularly with regard to the position of the switching valves 47, 59. During the successive analysis of a series of samples P, the steps described above are preferably carried out alternately, so that the combustion products of one sample P are each conveyed out of the ballast chamber 7 by the inflow of the combustion products of the following sample P, in order to be transported further for use, in particular for the diversion of an aliquot and / or for analysis.

[0137] Figures 7 and 8 each show an exemplary embodiment of the ballast chamber 7 of the analytical device 1 according to the invention, each schematically in perspective view (Fig. 7) and in cross-sectional view from the side (Fig. 8). In particular, a preferred embodiment of the piston 54 with a sealing element 66 at its edge can be seen, with which a mutual seal of the sub-chambers 52, 53 is achieved against the wall 65 of the ballast chamber 7.

[0138] In the preferred case presented here, the ballast chamber 7 has an at least substantially cylindrical shape. Due to the comparatively small external surface area relative to its volume, this offers advantages in terms of reducing thermal losses. According to the invention, other basic shapes for the ballast chamber 7, in particular prismatic shapes with triangular, rectangular, hexagonal, octagonal and / or generally polygonal bases, are also possible.

[0139] While the wall 65 typically delimits the ballast chamber 7 in the radial direction, as shown in Figures 7 and 8, it can also be delimited in the axial direction, i.e., particularly on the top and / or bottom, by cover plates 67. The wall 65 preferably forms a gas-tight seal against the cover plates 67. A cover plate 67 may have and / or carry further features, in particular valves 55-58, connections, or the like.

[0140] Reference symbol list:

[0141] Analytical instrument 36 Control unit Crucible 37 Sensor Sample lock 38 Inlet bypass valve Burn tube 39 Bypass line Furnace 40 Outlet bypass valve

[0142] Gas line 41 Inlet Ballast chamber 42 Bypass outlet Inlet valve 43 Ballast outlet Outlet valve 44 Bypass inlet

[0143] Aliquot chamber 45 Ballast inlet Purge gas connection 46 Outlet Valve assembly 47 Inlet-side changeover valve Analyzer 48 First outlet Gas outlet 49 Second outlet Analyte gas inlet 50 First supply line Analyte gas outlet 51 Second supply line Purge gas inlet 52 First sub-chamber Purge gas outlet 53 Second sub-chamber

[0144] First transfer outlet 54 Piston First transfer inlet 55 First inlet valve Second transfer outlet 56 Second inlet valve Second transfer inlet 57 First exhaust valve Aliquot outlet 58 Second exhaust valve Aliquot inlet 59 Output side changeover valve Valve piston 60 First output line Valve channels 61 Second output line Piston body 62 First inlet Seal 63 Second inlet

[0145] Connecting rods 64 Sensor control connections 65 Wall Stop device 66 Sealing element Stop 67 Cover plate Stop rod Adjustment device P Probe manipulator

Claims

Patent claims:

1. Analytical instrument (1), in particular for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample (P), comprising a combustion unit for combustion of the sample (P), a ballast chamber (7) for receiving gaseous combustion products and an aliquot chamber (10), wherein the aliquot chamber (10) is designed to receive an aliquot of the combustion products from the ballast chamber (7), characterized in that the aliquot chamber (10) has an adjustable aliquot volume for receiving a variable aliquot of the combustion products from the ballast chamber (7).

2. Analyzer according to claim 1, characterized in that the aliquot chamber (10) has a basic shape that is at least substantially cylindrical.

3. Analyzer according to claim 1 or 2, characterized in that the aliquot chamber (10) has an adjustment device (34), preferably a piston, for adjusting the aliquot volume.

4. Analyzer according to claim 3, characterized in that the adjusting device (34) is designed to be adjustable by motor, pneumatic, hydraulic and / or magnetic means.

5. Analyzer according to claim 3 or 4, characterized in that the adjusting device (34) is designed to discharge the aliquot or to assist the discharge of the aliquot from the aliquot chamber (10).

6. Analysis device according to one of claims 3 to 5, characterized in that a control device is assigned to the setting device (34), wherein the control device is designed to control the setting device (34) with respect to the intake of certain aliquot volumes assigned to positions.

7. Analyzer according to one of the preceding claims, characterized in that the aliquot chamber (10) is designed for introducing the aliquot in an axial direction.

8. Analytical method for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample (P), comprising the following steps: combustion, in particular complete combustion, of the sample (P); Capturing and collecting gaseous combustion products in a ballast volume; Diverting an aliquot of the collected combustion products from the ballast volume into an aliquot volume; Discharge of the aliquot from the aliquot volume to an analysis device (13); analysis of the aliquot, characterized in that the aliquot volume is adjusted to extract a variable aliquot of the combustion products.

9. Analysis method according to claim 8, characterized in that the aliquot volume is adjusted by means of an adjustment device (34), preferably by means of a piston.

10. Analysis method according to claim 9, characterized in that the adjusting device (34) is moved by motor, pneumatic, hydraulic and / or magnetic means to adjust the aliquot volume.

11. Analysis method according to claim 9 or 10, characterized in that the aliquot is at least partially diverted from the aliquot volume by means of the adjusting device (34).

12. Analysis method according to one of the preceding claims, characterized in that the aliquot volume is rinsed with oxygen at least substantially, in particular exclusively, when the aliquot is removed.

13. Analytical instrument (1), in particular for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample (P), comprising a combustion unit for combustion of the sample (P), a ballast chamber (7) for receiving gaseous combustion products and a movable piston (54) arranged in the ballast chamber (7), characterized in that the ballast chamber (7) is designed for the selective absorption of combustion products in two sub-chambers (52, 53) separated from each other by the piston (54).

14. Analytical instrument according to claim 13, characterized in that the piston (54) is designed for fluid-tight, in particular gas-tight, separation of the partial chambers (52, 53).

15. Analyzer according to claim 13 or 14, characterized in that each of the partial chambers (52, 53) is assigned an inlet valve (55, 56) and / or an outlet valve (57, 58).

16. Analyzer according to one of the preceding claims 13 to 15, characterized in that the analyzer (1) has at least one switching valve (47, 59) for selectively diverting the combustion products to each of the sub-chambers (52, 53).

17. Analytical instrument according to any one of the preceding claims 13 to 16, characterized in that the ballast chamber (7) has thermal insulation from the environment.

18. Analyzer according to one of the preceding claims 13 to 17, characterized in that the analyzer (1 ) has a control device for controlling the selective supply of the combustion products to each of the sub-chambers (52, 53).

19. Analysis device according to one of the preceding claims 13 to 18, characterized in that at least one sensor (64) for determining a temperature, a gas flow and / or a position of the piston (54), preferably within the ballast chamber (7), in particular within one or both sub-chambers (52, 53), is assigned to the ballast chamber (7), in particular within one or both sub-chambers (52, 53).

20. Analytical method for determining the content of nitrogen, carbon, hydrogen and / or sulfur in a sample (P), wherein the sample (P) is in particular completely combusted and wherein the gaseous combustion products are captured and collected in a ballast chamber (7), characterized in that in a plurality of analyses the combustion products are captured alternately in one of two sub-chambers (52, 53) of the ballast chamber (7).

21. Analysis method according to claim 20, characterized in that the temperature of the ballast chamber (7) is kept at least substantially constant over a plurality of successive analyses of different samples (P).

22. Analysis method according to claim 20 or 21, characterized in that by the inflow of combustion products of a sample (P) into a sub-chamber (52, 53) of the ballast chamber (7) a piston (54) in the ballast chamber (7) is moved in such a way that combustion products contained in the respective other sub-chamber (53, 52) are discharged from the ballast chamber (7).

Images