Ovens for analytical systems, titration systems and titration methods

Abstract

The present invention relates to an oven (1, 1') for an analytical system, in particular for a titration system, in particular for a Karl Fischer titration system. The oven (1, 1') comprises a housing, a blocking system (2a, 2a', 2b, 2b', 2c, 2c') and an insert (3, 3') for a sample container. The blocking system (2a, 2a', 2b, 2b', 2c, 2c') is arranged at least partially around the insert (3, 3'). At least one heating element is arranged between the blocking system (2a, 2a', 2b, 2b', 2c, 2c') and the insert (3, 3') and at least partially surrounds the insert (3, 3'). The present invention also relates to a titration system and a titration method having such an oven (1, 1').

Description

[Technical field]

[0001] The present invention relates to an oven for an analytical system, in particular for a titration system, a titration system comprising such an oven and a titration method. [Background technology]

[0002] The use of ovens is known in the prior art, particularly in connection with titration systems, and in particular with Karl Fischer titration. Ovens allow thermal sample preparation of samples that cannot be titrated directly. This may be the case, for example, when the sample is poorly soluble, when water can only be released at high temperatures, or when the sample reacts with the Karl Fischer (KF) reagent. In the oven method, the sample is heated and the released water is transported to the titration cell using a dry carrier gas. Since only water comes into contact with the KF reagent, contamination of the electrodes and the titration cell is avoided and carryover and memory effects that may distort the results are eliminated.

[0003] The common ovens currently available on the market have the disadvantage that the waiting time to reach the set temperature is relatively long. The solid metal block heated by the heating cartridge reacts very slowly to temperature changes due to its thermal mass. In addition, it takes a lot of energy to heat the ovens currently used. Also, the ovens lack compactness.

[0004] EP 3441757 A1 describes an oven arrangement for a Karl Fischer titration system. The oven arrangement has a ventilation system for cooling the housing. A blocking system prevents heat loss during the heating phase. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to overcome the drawbacks of the prior art. In particular, it is an object of the present invention to provide an oven for an analytical system which allows for fast and effective sample heating with low energy consumption. It is also an object of the present invention to provide a compact oven. Furthermore, it is an object of the present invention to provide a titration system and a titration method comprising such an oven. [Means for solving the problem]

[0006] The problem is solved by the independent claims. Particular embodiments can be found in the dependent claims.

[0007] A first aspect of the invention relates to an oven for an analytical system, in particular for a titration system, more particularly for a Karl Fischer titration system. The oven comprises a housing, a blocking system and an insert for a sample vessel. The blocking system is arranged at least partially around the insert. At least one heating element is arranged between the blocking system and the insert and at least partially surrounds the insert.

[0008] Preferably, the at least one heating element is clamped to the insert by internal tension. A cutout in the wall of the insert in which the at least one heating element is or can be positioned is also conceivable.

[0009] Such an oven is characterized by the fact that at least one heating element can be particularly close to the sample, thus allowing a particularly fast and effective heating of the sample, which also makes it possible to reduce the energy required compared to known ovens.

[0010] The housing can be formed by the insulation system or can further surround the insulation system in the form of an outer shell. The insulation system can comprise two side half shells and a basic insulation. However, it is also possible to design the side insulation in one piece. The insulation material preferably has a thermal conductivity of less than 0.5 W / (m*K). The insulation system is therefore preferably a thermal insulation system. For example, the insulation material can be made of the insulation material WDS Ultra (for example, from Morgan Advanced Materials PLC), which is a mineral microporous insulation material made of inorganic silicate substances. The insulation material can also be coated with aluminum, for example with an aluminum adhesive tape. Pyrogels are also possible.

[0011] The at least one heating element may be a tubular cartridge. The tubular cartridge may have a thermocouple. Optionally, the thermocouple may be a separate temperature sensor or a temperature sensor integrated into the tubular cartridge.

[0012] The tubular cartridge can be arranged in a spiral around the insert. Preferably, in the case of a spiral tubular cartridge, only one tubular cartridge is used. The tubular cartridge can be wrapped around the insert for sample containers with a volume of 6 mL and 8 mL with 7-8 turns.

[0013] Tubular cartridges have the advantage that they are available as standard items and are easy to handle. Tubular cartridges are available in various designs and custom made tubular cartridges can be easily realized. The helical configuration allows optimal heating of the insert and placing it as close as possible to the sample.

[0014] However, it is also possible to position several heating cartridges vertically around the insert and supply them through a common connection. Heating mats or Mikanite surface heating elements can also be used. The heating elements used should be, among other things, capable of generating the temperatures required for sample preparation and / or analysis. For example, heating mats are not well suited for high temperatures around 300 °C.

[0015] The insert preferably has an inner diameter of 16 mm to 31 mm, particularly preferably 22 mm to 24 mm. Typically, an insert for a 6 mL sample vessel may have an inner diameter of 22.45 mm. An insert for an 8 mL sample vessel may have an inner diameter of, for example, 23.25 mm.

[0016] The insert has the advantage that it is or can be optimally adapted to the sample vessel. This allows particularly efficient and rapid heating. The space between the insert and the sample vessel is minimized.

[0017] The oven may have an outer diameter of 60 to 62 mm, preferably 61 mm. As sample containers, vials, usually sealed with a septum, are typically used.

[0018] Regardless of the size of the vial, the outer diameter advantageously remains constant. Adjustments to different vial sizes can be made, for example, via the wall thickness of the barrier.

[0019] The oven may have an external height of 50 to 90 mm, preferably 51 to 88 mm, particularly preferably 55 to 56 mm, and an internal height of the insert in the range of 28 to 60 mm, preferably 33 mm.

[0020] The oven features a particularly compact design. Due to its small installation space, it can be installed almost anywhere and can, for example, be retrofitted into existing systems. It is also possible to use two ovens per analyzer.

[0021] The oven size relative to standard vial sizes can have, for example, the following oven dimensions:

[0022] [Table 1]

[0023] The insert may be made of a thermally conductive material, preferably having a thermal conductivity higher than 10 W / (m K).

[0024] The thermally conductive material can be, for example, brass, silver, aluminum (up to 250°C), stainless steel, carbon-filled PEEK or ceramic. Brass is particularly preferred. Stainless steel is of particular interest for its chemical resistance. This list is not exhaustive. In principle, all materials with suitable thermal conductivity are conceivable.

[0025] Materials with high thermal conductivity allow particularly efficient heating of the sample. The insert may have a temperature sensor. Preferably, the temperature sensor is attached or integrated into the wall of the insert. The wall of the insert may be very thin and may have a wall thickness of 1 mm to 3 mm, preferably 2 mm to 2.5 mm, most preferably 2.3 mm. The sensor therefore fits squarely into the wall, allowing the most accurate measurement possible, not distorted by excess wall thickness. However, as mentioned above, it is also possible for the temperature sensor to be an integral part of the tubular cartridge.

[0026] On the one hand, the thin wall thickness of the insert reduces the amount of material required and, on the other hand, allows the temperature within the insert to be determined quickly and accurately.

[0027] Advantageously, the oven may have a temperature protection switch, which may preferably be located under the insert. However, other positions of the switch are also conceivable. Due to the available space, positioning under the insert is preferred.

[0028] A temperature protection switch prevents the sample and / or the system from overheating, thus ensuring reliable long-term operation.

[0029] A further aspect of the invention relates to a titration system, in particular a Karl Fischer titration system, comprising at least one oven as described above.

[0030] However, the titration system is not limited to Karl Fischer, but can be any volumetric or coulometric titration system.

[0031] For fast sample throughput, it is also possible to equip the titration system with two ovens as described above.

[0032] Preferably, the titration system also has a sample exchanger and comprises at least one first transfer system for transferring samples from the sample rack to the at least one oven. The transfer system can be, for example, an automated lift system or a gripper arm or arms of a sample robot.

[0033] A sample changer allows handling several samples in one continuous run. Advantageously, the titration system may comprise at least a second transport system for transporting the sample from the oven to the titration cell.

[0034] For example, the at least second transfer system may comprise a double hollow needle with an inlet needle and an exhaust needle, a carrier gas flow, and a heated transfer tube. The sample is preferably located in a sample container, such as a vial sealed with a septum, in the oven.

[0035] Such a transfer system makes it possible to transfer only the gaseous components of the sample to the titration cell, preventing side reactions between other components of the sample and the titration reagent.

[0036] The system can be at least partially automated, and preferably fully automated.

[0037] At least partially automated systems are characterized by a continuous and therefore fast mode of operation, thus allowing samples to be analyzed more quickly, and also allowing for better control of the operating procedures, leading to improved reproducibility and precision.

[0038] A third aspect of the present invention relates to a titration method, preferably a Karl Fischer titration method, comprising the steps of: providing a titration system as described above, - providing a sample; - heating the sample in an oven as described above; -Titration of sample and Includes.

[0039] The water content of the sample is preferably determined using a titration method. In detail, the procedure can be carried out as follows: the sample or substance to be analyzed can be weighed into a vial, sealed and positioned in this way in an oven. The sample can be heated in the oven so that, for example, water can be released. A needle, preferably a double hollow needle, pierces the septum of the vial or container and a carrier gas stream, for example air or an inert gas, passes through the heated sample. The carrier gas carrying the expelled moisture flows through the exhaust needle and via a heated transfer tube into the titration cell. In the titration cell, the concentration of water can be determined by coulometric or volumetric titration.

[0040] This allows only water to enter the titration cell, thus avoiding side reactions between other substances contained in the sample and the titration reagent. It is understood that the method is not limited to the determination of water, but can in principle be carried out on any heatable sample.

[0041] The present invention will be described in more detail below using exemplary embodiments, which should not be understood as limiting. [Brief description of the drawings]

[0042] [Figure 1] FIG. 2 shows an oven according to the invention with side shields. [Diagram 2] FIG. 2 shows the oven according to the invention of FIG. 1 without the side shields. [Diagram 3] FIG. 2 shows an alternative embodiment of an oven according to the invention having two cable outlets. [Figure 4] FIG. 4 shows the oven according to the invention of FIG. 3 without the side shields. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] FIG. 1 shows a perspective view of an oven 1 according to the invention. The oven 1 comprises an isolation system consisting of two side half shells 2a and 2b and a bottom isolation body 2c. In this embodiment example, the isolation system forms the housing of the oven 1. The isolation body half shells 2a and 2b surround an insert 3. The insert 3 has an inspection port 5 for checking the temperature. The insert is surrounded by a tubular cartridge (not shown). The connection lines 4 of the tubular cartridge extend to the sides of the isolation bodies 2a and 2b. A connection line 6 for a temperature sensor and two connection lines 7 of a temperature protection switch extend from the basic isolation body 2c.

[0044] Figure 2 shows the oven 1 according to the invention of Figure 1, without a shut-off system. In addition to the insert 3 and the connecting lines 4, 6 and 7, the tubular cartridge 8 can also be seen here. The tubular cartridge 8 is wound spirally around the insert with 8 turns. The temperature protection switch 9 is located under the insert 3, and the temperature sensor 10 is located on the underside of the tubular cartridge 8.

[0045] FIG. 3 shows an alternative embodiment of an oven 1′ according to the invention. The oven 1′ has two cable outlets A and B. Both cable outlets A and B have connection lines 7′ and 7″ for a temperature protection switch (9′ in FIG. 4). A connection line 6′ for a temperature sensor is provided in cable outlet B. The other elements are essentially identical to those in FIG. 1.

[0046] FIG. 4 shows the oven 1' according to the invention of FIG. 3 without a cut-off body. The essential elements are identical to those of FIG. 2. The main difference between FIG. 4 and FIG. 2 is that the two connection lines 7' and 7" for the temperature protection sensors are physically separated from each other.

Claims

1. An oven (1, 1') for an analysis system, in particular for a titration system, in particular for a Karl Fischer titration system, comprising a housing, a shut-off system (2a, 2a', 2b, 2b', 2c, 2c'), and an insert (3, 3') for a sample container, wherein the shut-off system (2a, 2a', 2b, 2b', 2c, 2c') is at least partially arranged around the insert (3, 3'). In the oven (1, 1'), at least one heating element is arranged between the shut-off system (2a, 2a', 2b, 2b', 2c, 2c') and the insert (3, 3') and at least partially surrounds the insert (3, 3'). The oven (1, 1') is characterized by this.

2. The oven (1, 1') according to claim 1, wherein the at least one heating element is a tubular cartridge (8, 8').

3. The oven (1, 1') according to claim 2, wherein the tubular cartridge (8, 8') is arranged spirally around the insert (3, 3').

4. The oven (1, 1') according to claim 1, wherein the insert (3, 3') has an inner diameter of 16 mm to 31 mm, preferably 22 to 24 mm.

5. The oven (1, 1') according to claim 1, wherein the oven (1, 1') has an outer diameter of 60 to 62 mm, preferably 61 mm.

6. The oven (1, 1') according to claim 1, wherein the oven (1, 1') has an external height of 50 to 90 mm, preferably 51 to 88 mm, particularly preferably 55 to 56 mm, and an internal height of the insert (3, 3') in the range of 28 to 66 mm, preferably 33 mm.

7. The oven (1, 1') according to claim 1, wherein the insert (3, 3') is made of a thermally conductive material having a thermal conductivity preferably higher than 10 W / (m K).

8. The oven (1, 1') according to claim 1, wherein the insert (3, 3') has a wall thickness of 1 to 3 mm.

9. The oven (1, 1') according to claim 1, wherein the insert (3, 3') comprises a temperature sensor (10, 10'), preferably on the wall of the insert (3, 3').

10. The oven (1, 1') according to claim 1, wherein the oven (1, 1') has a temperature protection switch (9, 9'), which is preferably arranged under the insert (3, 3').

11. A titration system, in particular a Karl Fischer titration system, comprising at least one oven (1, 1') according to any one of claims 1 to 10.

12. The titration system according to claim 11, wherein the system further comprises a sample changer and at least a first transfer system for transferring a sample from a sample rack to the at least one oven (1, 1').

13. The titration system according to claim 11, wherein the system comprises at least a second transfer system for transferring a sample from the oven (1, 1') to a titration cell.

14. The titration system according to claim 11, wherein the system is at least partially automated, preferably fully automated.

15. A titration method, preferably a Karl Fischer titration method, comprising: - providing the titration system according to claim 11; - providing a sample; - heating the sample in the oven (1, 1') according to claim 1; and - titrating the sample.

16. The titration method according to claim 15, for quantifying the water content of a sample. ​

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