Analysis device

Abstract

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 receiving of combustion products in two sub-chambers (52, 53) separated from each other by the piston (54).

Description

[0001] The invention relates to an analysis device according to the preamble of claim 1.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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 capabilities and more complex operation, which in turn necessitates higher qualifications for the operating personnel.

[0009] 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.

[0010] 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.

[0011] 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 of 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.

[0012] The piston is specifically designed for the 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 inner 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 the two samples that could distort the measurement results.

[0013] 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 sub-chamber 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 passed consecutively through a common piping system and a single common inlet and outlet valve, the probability of mixing with any contaminants potentially present in the lines or in the area of ​​the valves is reduced.Remaining traces of combustion gases from the previous sample. This further increases the reliability of the analysis.

[0014] 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 enabled, 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.

[0015] Thermal losses can be prevented by thermally insulating the ballast chamber from the environment. Such insulation also allows for faster temperature control of the entire apparatus and a largely constant temperature during operation. The combustion products collected in the ballast volume or in the individual sub-chambers of the ballast chamber are thus not cooled upon entering the ballast chamber, which could lead to undesirable changes in the thermodynamic properties of the gas and / or the fractions it contains.

[0016] 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, for example, the point at which combustion is complete. Delay times and / or the coordinated switching of the various valves can thus be precisely set.

[0017] 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.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 compressed 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.

[0024] 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.

[0025] It shows: Fig. 1 a schematic representation of an analysis device according to the invention, Fig. 2 a perspective schematic representation of part of an analysis device according to the invention, Fig. 3 a schematic cross-sectional representation of the in Fig. 2 of the part shown, Fig. 4 another schematic cross-sectional representation of the in Fig. 2 of the part shown, Fig. 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, Fig. 6A - 6C each represent a schematic representation of a preferred embodiment of the analytical device according to the invention in various operating states, Fig. 7 a perspective schematic representation of a preferred embodiment of a ballast chamber of the analytical device according to the invention and Fig. 8 a schematic cross-sectional view of the ballast chamber of Fig. 7.

[0026] 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.

[0027] In Fig. Figure 1 is an analytical instrument 1 of the type according to the invention, with its basic components shown schematically. 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.

[0028] Sample P is burned for further analysis, that is, oxidized, in particular completely burned.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The reaction products are then collected in a ballast volume provided by a ballast chamber 7 and, in particular, collected in their entirety.

[0033] The ballast chamber 7 can have a corresponding inlet valve 8 for controlling the incoming gas flow.

[0034] 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.

[0035] 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.

[0036] The aliquot chamber 10 can be separated from the ballast chamber 7 with respect to the gas flow by means of appropriate valves.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] After analysis in the analysis unit 13, the gaseous components leave the analysis unit 1 through a gas outlet 14.

[0042] In a preferred embodiment of the analytical device 1 according to the invention, a special embodiment of the valve arrangement 12 is used, as exemplified in Fig. Figure 2 is shown in perspective. The valve arrangement 12 serves for the selective introduction, discharge, and / or diversion 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 removed from the ballast volume. On the other hand, the valve arrangement 12 regulates the gas flow from the ballast chamber 7 to the ballast chamber 10. Fig. 2 The valve arrangement 12 shown controls the purge gas flow for rinsing the aliquot volume or aliquot chamber 10 and for transporting the aliquot to the analysis device 13.

[0043] 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 certain partial volume is directed into the aliquot chamber 10 and from there together with the purge gas to the analysis device 13, is in the following also uniformly referred to as "analyte gas".

[0044] The in Fig. The valve arrangement shown in Figure 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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 shown in the cross-sectional view according to Fig. As can be seen in Figure 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 in a gas-tight manner by means of seals 28.

[0049] 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.

[0050] 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.

[0051] The valve pistons 25 can thus be moved into different positions within 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.

[0052] 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.

[0053] The valve arrangement 12 also has stop devices 31, preferably with a stop device 31 assigned to each valve channel 26.

[0054] By means of the stop devices 31, a mechanical stop 32 can be provided, which prevents further movement of the valve piston 25 in the direction of 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 in the direction of 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] In the present example, the aliquot chamber 10 is arranged directly adjacent to the valve arrangement 12, as shown in Fig. Figure 4 shows a cross-sectional view. The aliquot chamber 10 here has an at least substantially cylindrical shape, wherein its length is in particular greater than its diameter, preferably a multiple of the diameter.

[0059] 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.

[0060] 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.

[0061] 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 is one in which the adjusting device 34 can be moved by motor, pneumatic, hydraulic and / or magnetomechanical means.

[0062] To move the adjusting device 34 inside the aliquot chamber 10, a manipulator 35 is provided. This manipulator can, in particular, be designed as a rod which is connected internally to the adjusting device 34, especially the piston, and whose opposite end protrudes 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 thread pitch, 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] According to the invention, a combined embodiment 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.

[0067] If the removal of the aliquot from the aliquot chamber 10 is supported or substantially effected by the adjusting device 34, the amount of purge gas usually 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] In a preferred embodiment of the invention, the use of the aliquot proceeds at least essentially in the following manner.

[0073] In the Fig. Figures 5A to 5F schematically represent different configurations or setting situations of the valve arrangement 12 with respect to the flow paths of the respective incoming and outgoing gaseous components.

[0074] In the Fig. In the initial position or neutral configuration of the valve arrangement 12 shown in Figure 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.

[0075] To adjust the in Fig. In the bypass configuration shown in Figure 5A, the valve pistons 25 are positioned in the valve channels 26 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.

[0076] To fill the aliquot volume in the aliquot chamber 10, the valve arrangement 12 is now switched, in particular by moving the valve pistons 25, so that the Fig. Adjust the flow conditions shown in Figure 5B. With regard to the purge gas path, a bypass situation still 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.

[0077] On the side of the analyte gas stream, the view is as follows: Fig. However, the switching position of the valve arrangement 12 shown in Figure 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 according to the switching position shown between the aliquot inlet 24 and the analyte gas outlet 16.

[0078] Will the aliquot chamber 10 be used as in Fig. As shown in Figure 5B, when the analyte gases flow through the system from ballast chamber 7, there is generally an overpressure in gas line 6 and in aliquot chamber 10, which is determined at least substantially by the conditions in ballast chamber 7. To equalize the atmosphere in the aliquot chamber with the ambient pressure, the valve assembly 12 is therefore opened after a certain period of flow. Fig. The switching position shown in Figure 5C is brought into the position described above. 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 proceeds as shown in Figure 5C. Fig. In the position shown in Figure 5C, the analyte gas flows first 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 assembly 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 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 relieved 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.

[0079] Monitoring of the prevailing pressure and / or temperature can be carried out using the control device 36 and several sensors 37 located before, in, and / or after the aliquot chamber 10 (in each case in the direction of flow). This allows, for example, the determination of the overpressure in the gas lines 6 or in the aliquot chamber 10 caused by the ballast volume. 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 using an I 2 Transfer via the C interface to the control unit 36 ​​and / or the control unit.

[0080] 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 closed on the outlet side. For this purpose, the valve assembly 12 is returned to the bypass position, as shown in Fig. As shown in Figure 5D, both the analyte gas path and the purge gas path now completely bypass 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 located upstream of the aliquot chamber 10, so that the aliquot chamber 10 is completely 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.

[0081] 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 moved to a switching 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 moving the valve assembly 12 into the Fig. The configuration shown in Figure 5E is activated. Here, the inlet side of the valve arrangement 12 is adjusted by appropriately aligning the valve pistons 25 in the valve channels 26 so 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.

[0082] Once the appropriate pressure has been established in the aliquot chamber 10 after a short time, the valve assembly 12 can be inserted into the Fig. The switching position shown in Figure 5F is then transferred, 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 arrangement 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.

[0083] 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 procedure described above. Fig. Phases 5E and / or 5F are shown. 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 purge 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 method effectively prevents measurement errors caused by this.

[0084] In the Fig. Figures 6A to 6C schematically depict a part of the analytical instrument 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] Downstream of ballast chamber 7 in the direction of flow, the in Fig. The setup shown in Figures 6A to 6C includes an outlet-side switching valve 59, which is connected via a first outlet line 60 and a second outlet line 61 to the ballast chamber 7 and the respective outlet valves 57 and 58 assigned to the sub-chambers 52 and 53, respectively. 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.

[0093] 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, or alternatively or additionally dependent on certain environmental and / or process parameters.

[0094] The control unit is preferably designed for at least partially automatic control of the valve positions. Furthermore, the control unit can also be connected to and / or integrated into a higher-level control system of the analyzer 1.

[0095] 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.

[0096] 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, 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.

[0097] In the Fig. In the configuration shown in Figure 6A, the bypass valves 38 and 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.

[0098] To fill the ballast volume in ballast chamber 7, the structure is now built in the Fig. The state shown in Figure 6B is achieved. For this purpose, the bypass valves 38 and 40 are switched so that incoming combustion products are directed along the flow path through the ballast volume. As shown in Figure 6B. Fig. As can be seen in Figure 6B, the ballast chamber 7 in the example shown here is in a state in which the piston 54 is fully positioned at one of its end positions. Therefore, one of the subchambers 52, 53 formed by the separation by means of the piston 54, in this case the first subchamber 52, is maximized in volume and fills almost the entire internal volume of the ballast chamber 7. The volume of the second subchamber 53 is correspondingly almost completely minimized in this state.

[0099] 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.

[0100] 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 usually 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 inflow of the medium into the first subchamber 52 in this case moves the piston 54, which will be discussed further below in connection with Fig. Section 6C will be discussed in more detail. In principle, the achievement of the respective end position by the piston 54 and / or the detection of a stop in the piston movement can also be used as a criterion for the completion of the filling of the respective sub-chamber 52, 53, either as an alternative or in addition to other parameters.

[0101] 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 total 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 along the further flow path and fed to an analysis unit 13 of the analyzer 1.

[0102] The output-side diverter valve 59 is located in the Fig. The condition shown in Figure 6B during and after filling the first sub-chamber 52 is adjusted such that its first inlet 62 is closed, or the transfer 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 retain 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 the outlet-side switching valve 59.

[0103] In particular, after the homogenization of the gas fractions in the first subchamber 52, the combustion products collected there can be rinsed out, for example, to at least partially transfer them to an aliquot chamber 10 or subsequently subject them to the actual elemental analysis. For this purpose, the system is used, especially in the sections described below. Fig. The state shown in Figure 6C is brought into operation. The inlet-side changeover 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 changeover valve 59 is preferably switched accordingly, such that the second outlet line 61 at the second inlet 63 of the changeover valve 59 is closed, thus blocking further transport of the combustion products beyond the outlet-side changeover valve 59.

[0104] The inflow of the medium increases the pressure in the second sub-chamber 53 and consequently exerts a force on the piston 54, which moves it towards the first sub-chamber 52, in particular until the piston 54, as in Fig. 6C schematically shows that it has reached its opposite end position. The fluid-tight or gas-tight separation of the sub-chambers 52, 53 is maintained by sealing the piston 54 against a wall 65 of the ballast chamber 7.

[0105] For sealing purposes, the piston 54 preferably has a sealing element 66 for contact with the wall 65, which is shown in the highly schematic representation of the Fig. 6A to 6C are not shown in detail. 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 Fig. 7 and Fig. Figure 8 shows the sealing element 66. The sealing element 66 can be an O-ring, a sealing lip, or the like. The sealing element 65 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.

[0106] 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.

[0107] 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 is controlled by the above-described, in Fig. In the switching position shown in 6C, the medium arriving at the first input 62 is directed to its output 46. The medium is then transported further via the gas line 6 connected there and, for example, at least partially supplied to an aliquot chamber 10.

[0108] For the analysis of the subsequent sample P, the processes described above are carried out with the subchambers 52, 53 and their associated equipment, such as supply lines 50, 51, valves 55-58, and outlet lines 60, 61, assigned in reverse order. The system is examined in particular with regard to the position of the switching valves 47, 59 in the Fig. The state shown in Figure 6B is brought into the sequential 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 then be transported further for use, in particular for taking an aliquot and / or for analysis.

[0109] The Fig. 7 and Fig. Figure 8 each shows an exemplary embodiment of the ballast chamber 7 of the analysis device 1 according to the invention, each schematically in perspective view ( Fig. 7) and in cross-sectional view from the side direction ( Fig. 8) In particular, a preferred embodiment of the piston 54 with a sealing element 66 on the edge can be seen, with which a mutual sealing of the sub-chambers 52, 53 on the wall 65 of the ballast chamber 7 is achieved.

[0110] 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.

[0111] While the wall 65 typically limits the ballast chamber 7 in a radial direction, as in the Fig. 7 and Fig.In the case shown in Figure 8, a limitation in the axial direction, i.e., in particular on the upper and / or lower side, is achieved by cover plates 67. The wall 65 preferably seals gas-tight against the cover plates 67. A cover plate 67 may have and / or carry further devices, in particular valves 55-58, connections or the like.

[0112] Further aspects of the present invention, which can be implemented independently but can also be combined with the aspects, features and properties explained above, are in particular: 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 by 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. Analysis device according to aspect 1, characterized in that the aliquot chamber 10 has a basic shape that is at least substantially cylindrical. 3. Analyzer according to aspect 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 aspect 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 aspect 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 aspects 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 aspects, 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 sample P; capture and collection of gaseous combustion products in a ballast volume; Diverting an aliquot of the collected combustion products from the ballast volume into an aliquot volume; Diverting the aliquot from the aliquot volume to an analysis facility 13; analysis of the aliquot, characterized by that the aliquot volume is set to allow for the removal of a variable aliquot of the combustion products. 9. Analysis method according to aspect 8, characterized in that the aliquot volume is adjusted by means of an adjusting device 34, preferably by means of a piston. 10. Analysis method according to aspect 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 aspect 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. Analytical method according to one of the preceding aspects, characterized in that the aliquot volume is rinsed with oxygen at least substantially, in particular exclusively, when the aliquot is removed.

[0113] Individual features and aspects of the present invention can be implemented independently of one another, but also in any combination. Reference symbol list: 1 analyzer 2 crucibles 3 Sample lock 4 Burner tube 5 Oven 6 Gas pipeline 7 Ballast chamber 8 Inlet valve 9 Exhaust valve 10 aliquot chamber 11 Purge gas connection 12 Valve arrangement 13 Analysis Unit 14 Gas outlet 15 Analyte gas inlet 16 Analyte gas outlet 17 Purge gas inlet 18 Purge gas outlet 19 First transfer exit 20 First transfer entry 21 Second transfer exit 22 Second transfer entry 23 Aliquot outlet 24 Aliquot admission 25 valve pistons 26 valve channels 27 piston bodies 28 Seal 29 connecting rods 30 control connections 31 Stop device 32 stops 33 Stop bar 34 Adjustment device 35 Manipulator 36 Control device 37 Sensor 38 Inlet-side bypass valve 39 Bypass line 40 Outlet-side bypass valve Entrance 41 42 Bypass output 43 Ballast outlet 44 Bypass input 45 Ballast inlet 46 Exit 47 Inlet-side changeover valve 48 First Exit 49 Second Exit 50 First supply line 51 Second supply line 52 First Chamber 53 Second Chamber 54 pistons 55 First inlet valve 56 Second inlet valve 57 First exhaust valve 58 Second exhaust valve 59 Output-side switching valve 60 First exit line 61 Second output line 62 First Entrance 63 Second Entrance 64 Sensor 65 wall 66 Sealing element 67 Cover plate P sample

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 a movable piston (54) arranged in the ballast chamber (7), characterized by , 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). [2] Analyzer according to claim 1, characterized by , that the piston (54) is designed for fluid-tight, in particular gas-tight, separation of the sub-chambers (52, 53). [3] Analyzer according to claim 1 or 2, characterized by , that each of the sub-chambers (52, 53) is assigned an inlet valve (55, 56) and / or an outlet valve (57, 58). [4] Analyzer according to any one of the preceding claims, characterized by, 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). [5] Analyzer according to any one of the preceding claims, characterized by , that the ballast chamber (7) has thermal insulation from the environment. [6] Analyzer according to any one of the preceding claims, characterized by , 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). [7] Analyzer according to any one of the preceding claims, characterized by, that the ballast chamber (7), in particular one or both sub-chambers (52, 53), is assigned at least one sensor (64) for determining a temperature, a gas flow and / or a position of the piston (54), each preferably within the ballast chamber (7), in particular within one or both sub-chambers (52, 53).

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