Method for pressure equalization of concurrently operated columns

Abstract

The invention relates to a method for pressure equalization of concurrently operated columns. The invention relates to a method for operating a chromatography system. The method includes the system assuming a first configuration in which a first pump is fluidly connected to a first separation column and a second pump is fluidly connected to a second separation column. Further, the method includes, when in the first configuration, providing fluid to the first separation column by the first pump and providing fluid to the second separation column by the second pump; determining a second pump target pressure; determining a first pump target pressure based on the second pump target pressure; and setting the first pump to provide fluid at the first pump target pressure. Further, the method includes switching the system to a second configuration in which the first pump is fluidly connected to the second separation column while the first pump provides fluid at the first pump target pressure. In addition, the invention relates to a corresponding chromatography system and a computer program product.

Description

Technical Field

[0001] The present invention relates generally to the operation of chromatography systems and to pressure equalization in chromatography applications, in particular to pressure equalization of simultaneously operating separation columns in chromatography applications such as liquid chromatography (LC) applications. Background Art

[0002] In chromatographic applications, the number of samples that can be analyzed may generally be limited by the capacity and number of corresponding chromatographic systems. Therefore, it may generally be desirable to increase the efficiency of the analysis in order to improve the use of the available chromatographic systems. Therefore, in the field of chromatography such as liquid chromatography (LC), particularly in the field of high performance liquid chromatography (HPLC) and ultra high performance liquid chromatography (UHPLC), there is a need to increase the throughput of sample analysis in order to reduce the time to result and the associated costs.

[0003] An established way to increase the throughput of a chromatography system is to employ a specially tailored workflow, such as a tandem LC workflow, in which time-shifted parallel analysis is possible by using 2 or more columns in the respective chromatography system. In other words, higher throughput can be achieved by employing a workflow (such as tandem LC) that allows certain steps of sample analysis to be performed in parallel. Thus, multiple separation columns can be employed in a single HPLC system (e.g., instrument).

[0004] However, the workflow utilizing multiple separation columns may need to switch between multiple separation columns to analyze usually.That is, separation column can for example be prepared and loaded with sample, and is subsequently switched to the analysis flow path, and another separation column is switched out of the analysis flow path simultaneously.That is, in whole workflow, separation column can be switched to be connected with the fluid of corresponding pump, for example because some pumps can be designated for some tasks (for example, a pump can be dedicated to provide gradient, and column condition and sample loading can be performed by another pump). The described switching between separation column can be carried out by means of column valve usually. The switching between separation column may cause adverse effects, because the pressure at different posts may not always match. This may damage analysis result and cause the shortening of column life.In other words, in the HPLC application relating to multiple separation columns (such as series LC), when for example switching between separation columns by corresponding column valve, the lack of pressure alignment between separation column may cause the pressure at the inlet of described separation column to change suddenly (for example, pressure drop or more generally pressure jump).

[0005] Such pressure differences, and resulting pressure variations, may have a variety of causes, which may include differences in column backpressure due to different column types, manufacturing tolerances and / or column aging (e.g., aggregation of particles or changes in the column bed), different flow conditions (such as flow rate, solvent composition and / or column temperature), and / or differences in fluid flow paths. Some of these causes may be unavoidable even in an otherwise symmetrical setup.

[0006] Thus, employing such a workflow may carry the risk of compromised quality of the analysis and / or shortened column life, which would reduce or even negate the benefits of higher throughput. In other words, it may generally be advantageous that the quality of the analysis at least not be significantly compromised in such a workflow scenario. Summary of the invention

[0007] In view of the above, it is an object of the present invention to overcome or at least alleviate the disadvantages and deficiencies of the prior art. More specifically, it is an object of the present invention to reduce and ideally prevent pressure changes when switching between columns.

[0008] The present invention achieves these objects.

[0009] In a first embodiment, the present invention relates to a method for operating a chromatography system, the method comprising: the system adopts a first configuration, in which a first pump is fluidically connected to a first separation column and a second pump is fluidically connected to a second separation column. In addition, the method comprises: in the first configuration, the first pump provides fluid to the first separation column and the second pump provides fluid to the second separation column; determining a second pump target pressure (P target,eq ); Based on the second pump target pressure (P target,eq ) to determine the first pump target pressure (P target,grad ); and setting the first pump to a first pump target pressure (P target,grad ) provides fluid. The method also includes: the system switches to a second configuration, in which the first pump is fluidly connected to the second separation column, and the first pump is at a first pump target pressure (P target,grad ) provides fluid.

[0010] That is, the present invention relates to a method in which the chromatography system adopts a first configuration in which the first pump is connected to the first separation column and the second column is connected to the second separation column. In addition, the method comprises: determining the second pump target pressure and determining the first pump target pressure to which the first pump is set based on the second pump target pressure, all of which are when the system is in the first configuration. Subsequently, the system switches to the second configuration in which the first pump provides fluid to the second configuration column at the first pump target pressure. This can advantageously allow the second pump target pressure to be preferably determined so that pressure fluctuations at the second separation column (and preferably the first separation column) can be avoided when the system switches to the second configuration.

[0011] The second pump target pressure can be determined based on the expected flow rate. This expected flow rate can be a gradient flow rate, that is, a flow rate for running a gradient to perform sample analysis. The method can also include that in a second configuration, the first pump provides fluid to the second separation column at an expected flow rate. In other words, the first pump that provides fluid to the second separation column at the first pump target pressure can correspond to the first pump that provides fluid at an expected flow rate. This can be achieved by determining the second pump target pressure based on the expected flow rate and then determining the first pump target pressure based on the second pump target pressure. For example, the second pump target pressure can be determined so that in a first configuration, when there is a second pump target pressure at the second pump, the second pump supplies fluid through the second separation column at an expected flow rate.

[0012] Determining the second pump target pressure can include calculating the target pressure. In addition, calculating the target pressure can include determining the second pump back pressure of the fluid path between the second separation column and the outlet of the second pump and the inlet of the second separation column. In other words, the back pressure caused by the second separation column and the fluid path between the second pump and the second separation column can be determined. Determining the second pump back pressure can be based on the pressure at the second pump and the flow rate of the fluid delivered to the second separation column at this pressure. For example, the second pump back pressure can be determined, for example, by measuring the pressure and flow rate at which the fluid is delivered to the second separation column by the second pump. Then, the second pump back pressure can be given by the ratio of pressure and flow. Calculating the target pressure can be based on the second pump back pressure and the desired flow rate. Usually, the target pressure can be calculated as the product of the second pump back pressure and the desired flow rate. The second pump target pressure can be determined to correspond to the target pressure.

[0013] The method may also include that the second pump is set to provide fluid with the second pump target pressure in the first configuration. Therefore, the method may include that the second pump provides fluid to the second separation column with the second pump target pressure in the first configuration. The second pump is set to provide fluid with the second pump target pressure in the first configuration and may include operating the second pump in a flow controlled mode and setting the flow rate to the desired flow rate. Alternatively, the second pump is set to provide fluid with the second pump target pressure in the first configuration and may include operating the second pump in a pressure controlled mode and setting it to the target pressure. In this case, the method may include operating the second pump in a flow controlled mode once the target pressure has been reached, wherein the second pump is set to provide the desired flow rate. That is to say, the second pump may initially operate in a pressure controlled mode, with the purpose of providing fluid with the target pressure, and once the target pressure has been reached, the pump may be changed to provide fluid with the desired flow rate. This may advantageously be faster than only operating the second pump in a flow controlled mode and waiting until the desired flow rate has been reached.

[0014] The step of setting the first pump to provide fluid at the first pump target pressure can be performed after the step of setting the second pump to provide fluid at the second pump target pressure. Determining the second pump target pressure can include measuring the pressure existing at the second pump when providing the desired flow rate, wherein the second pump target pressure is determined to correspond to the measured pressure. Measuring the pressure existing at the second pump when providing the desired flow rate can be advantageously more accurate than simply calculating the pressure. That is, although the second pump target pressure can be simply derived from the calculated target pressure, it may be advantageous to use the target pressure to set the second pump to the desired flow rate, which can be faster using the pressure-controlled operation of the second pump, and then measuring the actual pressure existing at the second pump when supplying fluid to the second separation column at the desired flow rate, because this can lead to more accurate results.

[0015] Determining the first pump target pressure can also be based on the fluid resistance of the fluid connection downstream of the second pump, which is independent of whether the system is in the first configuration or the second configuration. In other words, determining the first pump target pressure can also be based on the fluid resistance of the fluid connection unique to the second pump. This can advantageously allow consideration of the difference in fluid resistance between the fluid connection of the second pump with the second separation column in the first configuration and the fluid connection of the first pump with the second separation column in the second configuration.

[0016] In some embodiments, the first pump target pressure can be determined as the difference between the second pump target pressure and the back pressure of the fluid connection downstream of the second pump, regardless of whether the system is in the first configuration or the second configuration. It should be understood that this may only be an approximation because the fluid resistance of the fluid connection specific to the first pump is not taken into account, however, its contribution is generally negligible. Alternatively, the fluid resistance of the fluid connection specific to the first pump can be increased accordingly. More generally, determining the first pump target pressure can also be based on the fluid resistance of the fluid connection downstream of the first pump, regardless of whether the system is in the first configuration or the second configuration.

[0017] In some embodiments, determining the first pump target pressure can also be based on the difference in fluid resistance between the fluid connection of the second pump and the second separation column in the first configuration and the fluid connection of the first pump and the second separation column in the second configuration. This can substantially correspond to taking into account the fluid resistance of the fluid connection of both the first pump and the second pump.

[0018] The first pump target pressure can be determined such that when the first pump target pressure is present at the first pump while the second separation column is provided with fluid, the pressure at the inlet of the second separation column is substantially equal to the pressure at the inlet of the second separation column when the same fluid is supplied with the second pump target pressure by the second pump. Therefore, when switching from the first configuration to the second configuration or vice versa, pressure jumps can be advantageously avoided.

[0019] The term is generally used to include deviations due to measuring tolerances of the corresponding pressure sensor and manufacturing tolerances of system components (such as fluid conduits, pumps, separation columns, sensors and valves), which can, for example, lead to slight deviations in pressure and / or fluid composition.

[0020] When a first pump target pressure exists at the first pump while providing fluid to the second separation column, the pressure at the inlet of the second separation column can be substantially equal to the pressure at the inlet of the second separation column when the same fluid is supplied by the second pump at the second pump target pressure.

[0021] The second pump target pressure can be determined for the desired fluid composition. The desired fluid composition can preferably correspond to the gradient starting composition, that is, the solvent composition for starting the gradient. The second pump back pressure can be determined for the desired fluid composition. The fluid delivered when determining the back pressure can include the desired fluid composition. When switching to the second configuration from the first configuration, the first pump and the second pump can both supply the fluid with the desired fluid composition. This can advantageously enable to directly start running the gradient when switching to the second configuration from the first configuration, without any significant pressure jump.

[0022] The method may further include, immediately before the system switches from the first configuration to the second configuration, the first pump supplying the fluid at a first pump target pressure and the second pump supplying the fluid at a second pump target pressure.

[0023] The method may also include operating the first pump in a flow-controlled mode when the system switches from the first configuration to the second configuration.

[0024] Immediately before the system switches from the first configuration to the second configuration, the second pump may provide fluid at a desired flow rate.

[0025] The method may further include providing the first pump with a fluid having a desired fluid composition to the first separation column when the first pump is set to provide the fluid at a first pump target pressure.

[0026] The method may also include that in a first configuration, the first pump provides a gradient to the first separation column. Additionally or alternatively, the method may also include that in a second configuration, the first pump provides a gradient to the second separation column. In this case, it is desired that the fluid composition may correspond to the starting solvent composition of the gradient.

[0027] The method may also include that in the first configuration, the second pump provides a washing fluid to the second separator column. Additionally or alternatively, the method may also include that in the first configuration, the second pump provides a balancing fluid to the second separator column. When both the washing fluid and the balancing fluid are provided, the balancing fluid may be provided after the washing fluid. The balancing fluid may include a desired fluid composition.

[0028] The method may also include injecting the sample into the flow path between the second pump and the second separation column in the first configuration. Additionally, the method may include providing a loading fluid to the second separation column in the first configuration with the second pump. The loading fluid may include a desired fluid composition. The loading fluid may be provided after the balancing fluid. The fluid delivered when determining the second pump back pressure may be the loading fluid.

[0029] When the system is switched from the first configuration to the second configuration, the relative pressure change at the inlet of the second separation column can be less than 10%, preferably less than 5%, more preferably less than 1%. Additionally or alternatively, when the system is switched from the first configuration to the second configuration, the relative flow rate change at the inlet of the second separation column is less than 10%, preferably less than 5%, more preferably less than 1%.

[0030] The desired flow rate may be in the range of 0 to 100 μL / min. The first pump target pressure is in the range of 50 bar to 1500 bar. The second pump target pressure is in the range of 50 bar to 1500 bar.

[0031] In a second configuration, a second pump may be fluidly connected to the first separation column, with the second pump providing fluid at a second pump target pressure.

[0032] In another embodiment, the present invention relates to a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to perform the method as described above.

[0033] In yet another embodiment, the present invention relates to a chromatography system comprising a first pump, a second pump, a first separation column and a second separation column, wherein the system is configured to take a first configuration in which the first pump is fluidically connected to the first separation column and the second pump is fluidically connected to the second separation column. In addition, the system is configured to take a second configuration in which the first pump is fluidically connected to the second separation column, and wherein the system further comprises a controller configured to perform the method as described above.

[0034] The system may further include a column distribution valve fluidly connected to the first pump, the second pump, the first separation column, and the second separation column and configured to enable switching of the system between the first configuration and the second configuration.

[0035] The system may also include an automatic sample injector configured to pick up and inject the sample. The automatic sample injector may be fluidically connected to the first pump. If present, the automatic sample injector may be fluidically connected to the column distribution valve, wherein the automatic sample injector is located downstream of the first separation column and upstream of the column distribution valve.

[0036] The first pump may be a gradient pump configured to provide a solvent gradient to a fluidically connected separation column. The second pump may be a balancing pump configured to provide a fluid for washing, balancing and / or loading a fluidically connected separation column.

[0037] The system can be a liquid chromatography system. In addition, the system can be a high performance liquid chromatography system. In some embodiments, the system can be an ultra high performance liquid chromatography system.

[0038] The system can be configured for tandem chromatography. That is, the system can be configured to perform a tandem workflow, where throughput and detector utilization can be increased by switching between columns and running column equilibration on one column in parallel with sample separation on another column.

[0039] The first pump may be configured to provide a pressure of at least up to 50 bar, preferably at least up to 100 bar, more preferably at least up to 500 bar, such as up to 1500 bar.

[0040] In a second configuration, the second pump may be fluidly connected to the first separation column.

[0041] The chromatography system as previously described may be a chromatography system according to that described above.

[0042] The following is a description of the method embodiments. These embodiments are abbreviated as the letter "M" followed by a number. Whenever "method embodiments" are mentioned herein, these embodiments are intended.

[0043] M1. A method for operating a chromatography system, the method comprising

[0044] The system adopts a first configuration, in which

[0045] a first pump fluidly connected to the first separation column;

[0046] a second pump fluidly connected to the second separation column;

[0047] In the first configuration:

[0048] The first pump provides fluid to the first separation column;

[0049] The second pump provides fluid to the second separation column;

[0050] Determine the second pump target pressure (P target,eq );

[0051] Based on the second pump target pressure (P target,eq ) to determine the first pump target pressure (P target,grad );as well as

[0052] The first pump is set to operate at the first pump target pressure (P target,grad ) providing a fluid;

[0053] The method further comprises

[0054] The system switches to a second configuration in which the first pump is fluidly connected to the second separation column while the first pump is operated at the first pump target pressure (P target,grad ) provides fluid.

[0055] M2. The method according to the previous embodiment, wherein the second pump target pressure is determined based on a desired flow rate.

[0056] M3. The method according to the previous method implementation, wherein the method further includes

[0057] In the second configuration, the first pump provides fluid to the second separation column at the desired flow rate.

[0058] M4. A method according to any one of the foregoing two method embodiments, wherein the second pump target pressure is determined so that in the first configuration, when the second pump target pressure exists at the second pump, the second pump supplies fluid through the second separation column at a desired flow rate.

[0059] M5. A method according to any of the preceding method embodiments, wherein determining the second pump target pressure comprises calculating a target pressure.

[0060] M6. A method according to the preceding method embodiment, wherein calculating the target pressure comprises determining a second pump back pressure originating from the second separation column and a fluid path between an outlet of the second pump and an inlet of the second separation column.

[0061] M7. A method according to the preceding method embodiment, wherein determining the second pump back pressure is based on a pressure at the second pump and a flow rate of the fluid delivered to the second separation column at that pressure.

[0062] M8. A method according to any one of the preceding two method embodiments and having the features of M2, wherein calculating the target pressure is based on the second pump back pressure and the desired flow rate.

[0063] M9. A method according to any one of the preceding three method embodiments and having the features of M2, wherein the target pressure is calculated as the product of the second pump back pressure and the desired flow rate.

[0064] M10. A method according to any one of the foregoing five method embodiments, wherein the second pump target pressure is determined to correspond to the target pressure.

[0065] M11. A method according to any of the preceding method embodiments, wherein the method further comprises, in the first configuration, configuring the second pump to provide fluid at the second pump target pressure.

[0066] M12. A method according to the previous method embodiment and having the features of M2, wherein in the first configuration setting the second pump to provide fluid at the second pump target pressure includes operating the second pump in a flow-controlled mode and setting the flow rate to the desired flow rate.

[0067] M13. A method according to the penultimate method embodiment and having the features of M5, wherein in the first configuration setting the second pump to provide fluid at the second pump target pressure includes operating the second pump in a pressure controlled mode and setting it to the target pressure.

[0068] M14. A method according to the preceding method embodiment and having the features of M2, wherein the method comprises operating the second pump in a flow-controlled mode once the target pressure has been reached, wherein the second pump is configured to provide the desired flow rate.

[0069] M15. A method according to any one of the aforementioned four method embodiments, wherein the step of setting the first pump to provide fluid at the first pump target pressure is performed after the step of setting the second pump to provide fluid at the second pump target pressure.

[0070] M16. A method according to any of the foregoing method embodiments and having the characteristics of M2, wherein determining the second pump target pressure includes measuring the pressure existing at the second pump when providing the desired flow rate, wherein the second pump target pressure is determined to correspond to the measured pressure.

[0071] M17. A method according to any of the preceding method embodiments, wherein determining the first pump target pressure is also based on a fluid resistance of a fluid connection downstream of the second pump independent of whether the system is in the first configuration or the second configuration.

[0072] M18. A method according to any of the preceding method embodiments, wherein the first pump target pressure is determined as the difference between the second pump target pressure and a back pressure originating from the fluid connection downstream of the second pump regardless of whether the system is in the first configuration or the second configuration.

[0073] M19. A method according to any one of the aforementioned method embodiments, wherein determining the first pump target pressure is also based on the difference in fluid resistance between the fluid connection between the second pump and the second separation column in the first configuration and the fluid connection between the first pump and the second separation column in the second configuration.

[0074] M20. A method according to any of the preceding method embodiments, wherein determining the first pump target pressure is also based on a fluid resistance of a fluid connection downstream of the first pump independent of whether the system is in the first configuration or the second configuration.

[0075] M21. A method according to any one of the aforementioned method embodiments, wherein the first pump target pressure is determined so that when the first pump target pressure exists at the first pump while supplying fluid to the second separation column, the pressure at the inlet of the second separation column is substantially equal to the pressure at the inlet of the second separation column when the same fluid is supplied by the second pump at the second pump target pressure.

[0076] The term is generally used to include deviations due to measuring tolerances of the corresponding pressure sensor and manufacturing tolerances of system components (such as fluid conduits, pumps, separation columns, sensors and valves), which can, for example, lead to slight deviations in pressure and / or fluid composition.

[0077] M22. A method according to any one of the aforementioned method embodiments, wherein, when the first pump target pressure exists at the first pump while supplying fluid to the second separation column, the pressure at the inlet of the second separation column is substantially equal to the pressure at the inlet of the second separation column when the same fluid is supplied by the second pump at the second pump target pressure.

[0078] M23. A method according to any of the foregoing method embodiments, wherein the second pump target pressure is determined based on a desired fluid composition.

[0079] M24. A method according to the preceding method embodiment and having the features of M5, wherein the second pump back pressure is determined for the desired fluid composition.

[0080] M25. A method according to any one of the preceding two method embodiments and having the features of M7, wherein the fluid delivered when determining the back pressure comprises the desired fluid composition.

[0081] M26. A method according to any of the preceding method embodiments, wherein, when switching from the first configuration to the second configuration, both the first pump and the second pump supply fluid having the desired fluid composition.

[0082] M27. A method according to any one of the aforementioned method embodiments, wherein the method further includes: immediately before the system switches from the first configuration to the second configuration, the first pump supplies fluid at the first pump target pressure and the second pump supplies fluid at the second pump target pressure.

[0083] M28. A method according to any of the preceding method embodiments, wherein the method further comprises operating the first pump in a flow-controlled mode when the system switches from the first configuration to the second configuration.

[0084] M29. A method according to any of the preceding method embodiments and having the features of M2, wherein, immediately before the system switches from the first configuration to the second configuration, the second pump provides fluid at the desired flow rate.

[0085] M30. A method according to any one of the aforementioned method embodiments and having the characteristics of M23, wherein the method further comprises: when the first pump is set to provide fluid at the first pump target pressure, the first pump provides fluid having the desired fluid composition to the first separation column.

[0086] M31. A method according to any of the preceding method embodiments, wherein the method further comprises, in the first configuration, the first pump providing a gradient to the first separation column.

[0087] M32. A method according to any of the preceding method embodiments, wherein the method further comprises, in the second configuration, the first pump providing a gradient to the second separation column.

[0088] M33. A method according to any one of the preceding two method embodiments and having the features of M23, wherein the desired fluid composition corresponds to the starting solvent composition of the gradient.

[0089] M34. A method according to any of the preceding method embodiments, wherein the method further comprises, in the first configuration, the second pump providing a washing fluid to the second separation column.

[0090] M35. A method according to any of the preceding method embodiments, wherein the method further comprises, in the first configuration, the second pump providing a balancing fluid to the second separation column.

[0091] M36. A method according to the preceding method embodiment and having the features of the penultimate embodiment, wherein the balancing fluid is provided after the washing fluid.

[0092] M37. A method according to any one of the foregoing two method embodiments and having the characteristics of M23, wherein the balancing fluid comprises the desired fluid composition.

[0093] M38. A method according to any of the preceding method embodiments, wherein the method further comprises injecting a sample into a flow path between the second pump and the second separation column in the first configuration.

[0094] M39. A method according to the previous method embodiment, wherein the method also includes the second pump providing a loading fluid to the second separation column in the first configuration.

[0095] M40. A method according to the preceding method embodiment and having the features of M23, wherein the loading fluid comprises the desired fluid composition.

[0096] M41. A method according to any one of the 2 preceding method embodiments and having the features of M35, wherein the loading fluid is provided after the balancing fluid.

[0097] M42. A method according to any one of the 3 preceding method embodiments and having the features of M6, wherein the fluid delivered when determining the second pump back pressure is the load fluid.

[0098] M43. A method according to any of the aforementioned method embodiments, wherein, when the system switches from the first configuration to the second configuration, the relative pressure change at the inlet of the second separation column is less than 10%, preferably less than 5%, and more preferably less than 1%.

[0099] M44. A method according to any one of the aforementioned method embodiments, wherein, when the system switches from the first configuration to the second configuration, the relative flow rate at the inlet of the second separation column changes by less than 10%, preferably less than 5%, and more preferably less than 1%.

[0100] M45. A method according to any of the preceding method embodiments and having the features of M2, wherein the desired flow rate is in the range of 0 to 100 μL / min.

[0101] M46. A method according to any of the preceding method embodiments, wherein the first pump target pressure is in the range of 50 bar to 1500 bar.

[0102] M47. A method according to any of the foregoing method embodiments, wherein the second pump target pressure is in the range of 50 bar to 1500 bar.

[0103] M48. A method according to any of the preceding method embodiments, wherein, in the second configuration, the second pump is fluidly connected to the first separation column, and the second pump provides fluid at the second pump target pressure.

[0104] In the following, reference will be made to computer program product embodiments. These embodiments are abbreviated as the letter "P" followed by a number. Whenever "program embodiments" are mentioned herein, these embodiments are intended.

[0105] P1. A computer program product, comprising instructions, which, when the program is executed by a computer, cause the computer to perform a method according to any one of the aforementioned method implementations.

[0106] The following description is made in conjunction with the chromatographic system embodiments. These embodiments are abbreviated as the letter "S" followed by a number. Whenever "system embodiments" are mentioned herein, these embodiments are intended.

[0107] S1. A chromatography system, the chromatography system comprising

[0108] First pump;

[0109] Second pump;

[0110] a first separation column;

[0111] a second separation column;

[0112] The system is configured to adopt a first configuration, in which

[0113] The first pump is fluidly connected to the first separation column; and

[0114] the second pump being fluidly connected to the second separation column;

[0115] wherein the system is configured to assume a second configuration in which the first pump is fluidly connected to the second separation column; and

[0116] The system further comprises a controller, wherein the controller is configured to execute the method according to any one of the aforementioned method implementations.

[0117] S2. A system according to the previous system embodiment, wherein the system also includes a column distribution valve, which is fluidly connected to the first pump, the second pump, the first separation column and the second separation column and is configured to enable the system to be switched between the first configuration and the second configuration.

[0118] S3. A system according to any of the preceding system embodiments, wherein the system further comprises an autosampler configured to pick up and inject a sample.

[0119] S4. A system according to the previous system embodiment, wherein the autosampler is fluidly connected to the first pump.

[0120] S5. A system according to the previous system embodiment and having the features of S2, wherein the autosampler is also fluidly connected to the column distribution valve, wherein the autosampler is located downstream of the first separation column and upstream of the column distribution valve.

[0121] S6. A system according to any of the preceding system embodiments, wherein the first pump is a gradient pump configured to provide a solvent gradient to a fluidly connected separation column.

[0122] S7. A system according to any of the preceding system embodiments, wherein the second pump is a balancing pump configured to provide fluid for washing, balancing and / or loading a fluidically connected separation column.

[0123] S8. A system according to any of the preceding system embodiments, wherein the system is a liquid chromatography system.

[0124] S9. A system according to any of the preceding system embodiments, wherein the system is a high performance liquid chromatography system.

[0125] S10. A system according to any one of the preceding system embodiments, wherein the system is an ultra-high performance liquid chromatography system.

[0126] S11. A system according to any of the preceding system embodiments, wherein the system is configured for tandem chromatography.

[0127] That is, the system can be configured to perform a tandem workflow, where throughput and detector utilization can be increased by switching between columns and running column equilibration on one column in parallel with sample separation on another column.

[0128] S12. A system according to any of the preceding system embodiments, wherein the first pump is configured to provide a pressure of at least up to 50 bar, preferably at least up to 100 bar, more preferably at least up to 500 bar, such as up to 1500 bar.

[0129] S13. A system according to any of the preceding system embodiments, wherein, in the second configuration, the second pump is fluidly connected to the first separation column.

[0130] M49. A method according to any one of the aforementioned method embodiments, wherein the chromatography system is a chromatography system according to any one of the aforementioned system embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0131] Embodiments of the present invention will now be described with reference to the accompanying drawings, which should only be used to illustrate and not limit the present invention.

[0132] Figure 1 An exemplary tandem chromatography system is depicted;

[0133] Figure 2 An exemplary tandem workflow is depicted;

[0134] Figure 3 Schematic diagram depicting the pump signal during a sample run;

[0135] Figure 4 A method according to the invention is described; and

[0136] Figure 5 An exemplary total ion current chromatogram showing the effect of pressure changes on analytical results is depicted.

[0137] It should be noted that not all figures carry all reference numerals. On the contrary, in some figures, some reference numerals have been omitted for brevity and simplicity of illustration. Embodiments of the present invention will now be described with reference to the attached drawings. DETAILED DESCRIPTION

[0138] Now refer to Figure 1 , which depicts an exemplary chromatographic system configured in series. Very generally, such a system may include two pumps 1, 12 (which may be referred to as the first pump 1 and the second pump 12), an automatic sample injector 3 including an injection valve 10, a column compartment 2 including a distribution valve 13 (also referred to as a column switching valve 13) and two separation columns 5, 8 (which may be referred to as the first separation column 8 and the second separation column 5), and corresponding fluid connections 4, 6, 7, 9, 11. Separation columns 5, 8 may be fluidically connected to at least one detector 15, wherein in the case of a single detector, typically only one of the separation columns 5, 8 may be simultaneously connected to the detector 15, for example, by adopting a corresponding valve that selectively connects one of the separation columns to the detector. In this case, the other separation column may, for example, be fluidically connected to waste. In some embodiments, each separation column 5, 8 may be fluidically connected to a separate detector 15, wherein, for example, when washing the column, the separation pump may be again alternatively fluidically connected to waste.

[0139] The pumps 1, 12 can generally be configured to supply fluids, in particular solvents, at a desired flow rate and / or pressure. For LC and in particular (U)HPLC applications, these pumps can be high pressure pumps capable of providing fluids at a pressure of at least 50 bar, preferably at least 100 bar, more preferably at least 500 bar, such as at least 1000 bar, for example up to 1500 bar.

[0140] The first pump 1 can be configured to provide a solvent gradient to the selected separation column 5, 8 for sample analysis. Therefore, the first pump 1 can also be called a gradient pump 1. The second pump 12 can be configured to provide a fluid for column balancing and a fluid for washing and / or loading the corresponding column 5, 8. Therefore, the second pump 12 can be called a balancing pump 12.

[0141] The automatic sampler 3 can generally be configured to pick up a sample and can generally include a sampling device (also referred to as a metering device), such as an automatic syringe and a sample pickup device, which can generally be a needle that is fluidically connected to the sampling device. In addition, the automatic sampler 3 can include a seat configured to receive the sample pickup device, and a sample storage portion, such as a sample ring. This can allow the automatic sampler 3 to pick up a sample by placing the sample pickup device in a sample vial and sucking the sample from the sample vial into the sample storage portion by means of the sampling device. Typically, the sample storage, the sampling device, the sample pickup device and the seat are fluidically connected to the injection valve 10, which can particularly allow the sample storage portion to be switched to the fluid path between the balancing pump 12 and the column compartment 2.

[0142] The column compartment 2 may be configured to accommodate a plurality of separation columns 5, 8. In some embodiments, the column compartment 2 may also be configured to provide temperature control for the plurality of separation columns, ie, the column compartment 2 may be configured to provide a specified temperature to the plurality of columns individually or to all the columns together.

[0143] The separation columns 5, 8 may be identical or different and are typically configured to separate the sample by chromatographic separation. That is, the separation columns 5, 8 may include a solid phase, such as an adsorbent, which may interact with components of a mobile phase (particularly components of the sample) passing through the separation column, thereby separating different compounds of the mobile phase, due to different interactions of different compounds of the mobile phase with the adsorbent, resulting in characteristic retention times that can be measured in a subsequent detector 15.

[0144] The column distribution valve 13 may be a distribution valve configured to switch the fluid connection between the pumps 1, 12 and the separation columns 5, 8. In the depicted analysis setup, the column distribution valve 13 may always fluidly connect the gradient pump 1 to one separation column (e.g., the first separation column 8 as depicted) and fluidly connect the autosampler 3 (and thus typically the balancing pump 12) to the other separation column (in the depicted configuration, the second separation column 5).

[0145] The fluid connections 4 , 6 , 7 , 9 , 11 may generally be fluid conduits such as capillaries, which may be connected to system components, for example, via corresponding fittings.

[0146] At least one detector 15 can generally be configured to provide time-resolved measurements of the components reaching the detector 15, thereby allowing the corresponding retention times to be determined. Such a detector 15 can be, for example, a mass spectrometer (MS) (e.g., an inductively coupled plasma mass spectrometer (ICP-MS)), a fluorescence detector, a charged aerosol detector (CAD), a refractive index detector, an absorption detector, etc.

[0147] Thus, the chromatography system can generally be configured to assume at least a first configuration in which the first pump 1 is fluidly connected to the first separation column 8 and a second pump is fluidly connected to the second separation column 5 (in the first configuration and the second configuration). Figure 1 ), in this second configuration, the first pump 1 is fluidically connected to the second separation column 5. Switching between these configurations can be achieved by means of a column distribution valve 13. Preferably, in the second configuration, the second pump 12 can be fluidically connected to the first separation column 8.

[0148] Reference Figure 2 , discusses the use of chromatographic systems (such as those described above with reference to Figure 1 ) of the chromatography system described above. The workflow can be broken down into several subroutines, which are depicted as separate items or building blocks related to certain tasks during the workflow. The lateral extension of the corresponding items along the horizontal axis can indicate the duration of the corresponding subroutine, and the position of the items relative to the horizontal axis can further indicate the timing of the corresponding subroutine. That is, the horizontal axis can generally indicate time. The vertical position of the items can indicate their association with components of the chromatography system. That is, the tandem workflow advantageously allows certain subroutines to be performed simultaneously by different system components. It should be understood that Figure 2 The schematic diagram in FIG. 1 is simplified, and details such as, for example, switching of certain valves (eg, column distribution valve 13 and / or injection valve 10 ) are not included in the illustration.

[0149] As indicated, the leftmost point on the horizontal axis corresponds to the time of column switching, i.e., switching of the column distribution valve 13 results in a change in the configuration of which pump 1, 12 provides fluid flow to which separation column 5, 8. For example, the chromatography system may now take the following actions: Figure 1 The first configuration is depicted in FIG.

[0150] Therefore, the balancing pump 12 can be fluidically connected to the second separation column 5, and the gradient pump 1 can be fluidically connected to the first separation column 8. The balancing pump 12 can wash (wash) and then balance (balance) the second separation column 5, and the automatic sampler 3 can simultaneously initialize (initialize), wash the sample loop (loop wash), optionally wait (wait) and pick up the sample (sample pick up). Waiting can be used to align sample pick up and balance so that both are basically ended at the same time, so that the sample is then injected, for example, by switching the sample loop to the flow path between the balancing pump 12 and the separation column 5. This term is basically used to include deviations caused by manufacturing tolerances and measurement uncertainties. Then, the balancing pump 12 can supply fluid to load the sample onto the second separation column 5 (load).

[0151] In parallel, the gradient pump 1 can supply a corresponding gradient to the first separation column 8 (Gradient), and the detector 15 can detect the composition of the corresponding effluent and acquire associated data (Data Acquisition). The measurements and data acquisition of the detector 15 can be offset by a gradient delay volume (GDV) relative to the gradient supplied by the gradient pump 1. That is, the starting point (horizontal position) of the data acquisition subroutine can be delayed relative to the starting point of the gradient subroutine to take into account the GDV, i.e., the volume between the mixing of the mobile phase and the inlet of the separation column 8.

[0152] Both the balancing pump 12 and the gradient pump 1 can perform an alignment subroutine that can be used to align the operation of the two pumps before the next column switch, which will change the configuration of the chromatography system so that the balancing pump 12 is now fluidly connected to the first separation column 8 that was previously connected to the gradient pump 1, and vice versa. This allows the loaded sample to be analyzed with the gradient provided by the gradient pump 1, while the autosampler 3 and the balancing pump 12 can adjust and load the first separation column 8 with the next sample. According to the present invention, the alignment subroutine can be used additionally or alternatively to align the pressures before switching between columns.

[0153] When utilizing this series connection to be set to measure the chromatogram that provides corresponding retention time for the different components of mobile phase (particularly sample), if the pressure at the separator column does not match, some problems may occur.Under ideal conditions (that is, pump and fluid path are both identical) and constant flow conditions (that is, all operations are carried out under gradient flow rate without any flow change), and when symmetrical column configuration (that is, post has identical back pressure), the retention time in the chromatogram of two separator columns will not have differences.Yet, even if the back pressure difference between the separator column that may also exist under identical flow conditions (constant, identical solvent composition) will have caused the pressure difference between two posts 5,8.That is to say, different pressures will be present at the inlet of corresponding separator column 5,8.This back pressure difference may often occur in typical (U) HPLC application, and it is derived from aging post, for example, by the aggregation of particle, the variation of post filling and / or from sample.

[0154] When gradient pump 1 is switched from one column to another column, this pressure difference may effectively cause a sudden change of pressure (e.g., pressure drop or more generally pressure jump). Pressure change may be positive or negative. In either case, and depending on the size of the pressure change, the flow rate and solvent composition during the early stage of the gradient may be negatively affected. In particular, the pressure change may interfere with the flow control of the pump, which may result in incorrect solvent composition and / or total flow rate. Additionally, the pressure change may result in a flow error of the total flow rate, which is derived from the flow contribution of the compression (negative pressure change) or relaxation (positive pressure change) of the liquid. Therefore, the corresponding flow error may be proportional to the pressure change. More precisely, the flow error may depend on the back pressure of the fluid path produced by the compressibility of the solvent in the conduit, the relaxation or compression, and the size of the pressure change affected by the pressure change. Therefore, the quality of the analysis result (i.e., chromatogram) may be impaired due to washing out and therefore missing (early elution) compounds.

[0155] Likewise, when switching the column valve 13, i.e. when changing which pump is fluidically connected to which separation column, this pressure change occurs. Therefore, each column may experience a pressure change, wherein the magnitude of the pressure change depends on the relative pressure difference between the columns. Typically, the pressure change may occur due to at least one of the following reasons or a combination: a difference in column back pressure and the fluid resistance therefor, a difference in flow conditions and / or a difference in the fluid flow path of the column.

[0156] The difference in column back pressure between separation columns can be, for example, due to different types of columns, for example, including different sizes, and / or including different stationary phases (i.e., adsorbents), additionally or alternatively, the difference in back pressure may be caused by manufacturing tolerances during the manufacturing process of the column and / or due to the aging of the column. Aging can, for example, include the aggregation of particles in the column or the change of the column bed, such as the loss of the stationary phase and / or the change of the stationary phase (e.g., by rearranging the stationary phase). The change of the stationary phase may mainly appear in the case of a packed column (i.e., a column filled with beads), while the monolithic column will, for example, not be affected by the change of the stationary phase. However, for any type of column, the life span may be impaired by the mechanical stress caused by the pressure jump. Here, the term column bed refers to the components of the packed column, such as beads, and the term stationary phase can generally refer to any solid substance of the column to which the compounds in the solution can bind or interact respectively. Therefore, the column bed can be only related to the packed column, while the stationary phase also includes the material of the monolithic column.

[0157] The difference of flow conditions can for example comprise different flow velocities, different solvent compositions and / or different column temperatures.That is, usually this may be due to operating the separation column under different conditions (particularly flow conditions), which may affect the fluid flow through the corresponding separation column.

[0158] Differences between the fluid flow paths of the columns may, for example, include different lengths of fluid conduits between the respective pumps and the columns, different diameters of the fluid conduits, etc. Such differences may be necessitated, for example, by architectural constraints on the arrangement of components within the system.

[0159] Therefore, when switching between separation columns, in particular at the separation column that is subsequently subjected to the gradient (that is to say the column that is connected to the gradient pump during the switching), it may be at least desirable, if not necessary, to reduce and ideally prevent corresponding pressure changes. The present invention therefore aims to provide a method that enables such pressure changes to be reduced and potentially even prevented by carefully aligning the pumps and in particular their pressures and / or flow rates before switching between separation columns.

[0160] Thus, the method includes pressure alignment between multiple pumps. Figure 2 , Figure 3 Depicted in Figure 2 During the workflow depicted in FIG. 1 , the pressure, solvent composition and flow rate of pump 12 and gradient pump 1 are balanced. It should be noted that Figure 3 A) to Figure 3 F) includes a different scale on the y-axis and is only illustrative. Figure 3 A) to Figure 3 That is, for example, the flow of E3 cannot be easily compared with the relative changes in pressure, solvent composition, and flow rate in each of F). Figure 3 F) because the y-axis may include different scales.

[0161] As described above, the balancing pump 12 can perform subroutines related to column washing, column balancing, and loading the sample into the separation column (also referred to as the analytical column). To increase throughput, these subroutines (also referred to as steps) can be performed at a relative gradient flow rate f grad That is, the equilibrium flow rate f eq Can be higher than the gradient flow rate f eq >f grad (See Figure 3 C)).

[0162] The pressure during this phase can therefore be significantly higher (up to several hundred bar) than the pressure P during the initial phase of the gradient. start (See Figure 3 In other words, the pressure during the wash, equilibration and loading subroutines may be higher than the gradient pressure at the beginning of the gradient (also referred to as the gradient starting pressure P start ). This pressure difference is one of the causes of pressure changes when switching between separation columns. It is therefore an object of the present invention to reduce, preferably minimize or even avoid any such pressure differences.

[0163] In order to prepare the separation columns 5, 8 for the subsequent gradient subroutine, the pressure of the separation columns 5, 8 can be adjusted to match the gradient starting conditions, in particular the gradient starting pressure P of the respective column. start That is, for the two separation columns, the gradient starting pressure P start may be different. This can be done in the Pressure Alignment subroutine eq occurs during the gradient flow rate f grad That is, the balancing pump 12 can be operated in a flow-controlled mode and is set to provide a desired gradient flow rate f grad However, especially in the case of long separation columns with small particles and small diameter (e.g. fluidic resistance (back pressure) > 200 bar per 1 μL / min flow), such adjustments may consume a considerable amount of time until the corresponding target pressure P is reached due to the considerable fluidic resistance of such columns. target,eq .P target,eq represents the pressure at the column under steady flow conditions at the gradient start conditions, ie, the solvent composition and flow rate (and column temperature) at the start of the gradient.

[0164] By switching the balancing pump 12 to a pressure-controlled mode for regulation, a significantly faster pressure regulation can be achieved. To this end, P is first determined. target,eq It can be determined by determining the fluid resistance (back pressure) of the column, R eq To obtain, because P target,eq =R eq *f grad , where R eq =P eq / f eq It should be noted that only when determining R eq The solvent composition at the time of the gradient is the same as the starting solvent composition %B start In (almost) the same situation, P target,eq Once P is reached, target,eq , the pump can again switch to flow-controlled mode to deliver a gradient flow rate f grad and gradient starting solvent composition %B start (See Figure 3 ).

[0165] In pressure alignment (stage alignment eq -See also Figure 3), the sample can still be loaded onto the separation column. Therefore, the flow rate delivered during this stage contributes to the volume for loading the sample onto the separation column. Balancing pump 12 continues to deliver the gradient starting conditions until column dispensing valve 13 switches. Therefore, the separation column fluidically connected to balancing pump 12 is advantageously adjusted to the desired parameters for starting the gradient run. After switching, balancing pump 12 will begin to adjust another column that has previously been subjected to the gradient. For this reason, it can be operated in a flow-controlled or pressure-controlled mode.

[0166] At the same time, gradient pump 1 can continue to deliver the gradient. Once this phase is complete, it can start aligning its pressure to prepare for the gradient starting conditions for the next separation column, which is currently subject to the flow of balancing pump 12. This step occurs after aligning eq The phase alignment that starts after the start grad (See Figure 3 D) to Figure 3 At the same time, the fluid conduit 4 between the pump outlet of the gradient pump 1 and the column distribution valve 13 can be flushed (see Figure 1 ) to ensure it contains the correct solvent composition %B start For pressure alignment, the pump can preferably be operated in a pressure-controlled mode (ie, an operating mode in which a constant pressure is maintained). To this end, the column pressure P of the equilibrium column can be determined. target,grad It should be noted that the balancing pump has reached its target pressure P at this point in time. target,eq .P target,grad It can be obtained by reading the pressure sensor of the balancing pump 12 and additionally considering the fluid resistance between the pump outlet of the balancing pump 12 and the column distribution valve 13. That is, the gradient pump can be set to the column pressure P of the balancing column target,grad The target pressure P of the balancing pump can be target,eq , which target pressure is corrected for the contribution of the back pressure originating from the fluid resistance of the fluid connection between the outlet of the second pump and the column distribution valve. Thus, the pressures of the two columns can be (almost) the same, and the just-equilibrated column is adjusted so that its pressure level represents the gradient starting condition under which it will operate after the column valve is switched. However, it should be understood that the pressure level of the column distributed by the gradient pump at P target,grad The flow rate provided align Usually can be different from the balance pump with P target,eq Provided gradient flow f grad . Alignment at the completion stage grad Afterwards, the pump can continue to deliver the gradient for the next sample run. To do this, it is switched again to flow-controlled mode.

[0167] exist Figure 3 In the example depicted in F), f grad Higher than f alignThis corresponds to a configuration in which the column currently subjected to the flow of the gradient pump has a lower flow resistance than the column subjected to the flow of the balancing pump. This difference serves the purpose of having (almost) the same pressure at both columns before switching the column valves. If the backpressure difference is reversed (or if the columns are switched), then f align Of course it will be higher than f grad .

[0168] That is, the pressure of the gradient pump 1 can be set so that it matches the pressure required to provide a gradient flow rate to the column currently fluidly connected to the balancing pump 12. By further setting the balancing pump 12 to provide a gradient flow rate, pressure changes that may occur when switching between columns can be reduced, preferably minimized, or even completely avoided.

[0169] In other words, the present invention provides a method which allows to align the pressure between two separation columns before switching the gradient pump from one separation column to the other, thereby at least reducing, if not preventing, pressure variations which could impair the analysis results.

[0170] Reference Figure 4 Further discussion of the method according to the present invention. Very generally, the present method provides operating a chromatography system, the chromatography system comprising a first pump 1, a second pump 12, a first separation column 8 and a second separation column 5. The system can be configured to selectively provide a fluid connection between the pump and the separation column. For example, the system can be as described in reference Figure 1 The system in question.

[0171] In the first step 210, the system can take a first configuration, in which the first pump 1 is fluidically connected to the first separation column 8 and the second pump 12 is fluidically connected to the second separation column 5, for example, by means of a column distribution valve 13. When this configuration is taken, the method also includes the first pump 1 and the second pump 12 each providing fluid to the corresponding separation columns 5, 8 (step 220). In particular, the first pump can provide fluid to the first separation column 8, and the second pump 12 can provide fluid to the second separation column 5.

[0172] In addition, the method includes determining the second pump target pressure while still in the first configuration (step 230). That is, the target pressure of the second pump 12 (or the balancing pump 12) may be determined, such as P in the above example. target,eq The pressure can usually be selected so as to provide a desired flow rate to the second separation column 5. The desired flow rate may be a gradient flow rate desired for subsequent analysis of a sample previously loaded into the second separation column 5, such as f in the above example. grad For example, the second pump 12 may be operated in a flow controlled mode and set to provide a desired flow rate.

[0173] Alternatively, the second pump 12 can be operated in a pressure-controlled mode. In particular, the second pump 12 can be switched to a pressure-controlled mode. Then, the target pressure can be calculated based on the fluid resistance of the fluid connection between the second separation column and the inlet of the second pump 12 and the second separation column 5 or the corresponding back pressure (felt at the outlet of the second pump, so it can also be called the second pump back pressure). The second pump back pressure can be determined as the ratio of the current pressure and flow rate existing at the second pump 12 before changing the pressure and / or flow rate of the second pump during determining the second pump target pressure. The current pressure and flow rate can, for example, correspond to the flow rate and pressure during sample loading or preferably at the end of sample loading. Then, the calculated target pressure of the second pump can be given by the product of the second pump back pressure and the desired flow rate, such as P in the above example. target,eq =R eq *f grad , where R eq =P eq / f eq Thus, the second pump may be arranged to provide the calculated target pressure and, once the target pressure has been reached, switch back to flow controlled mode to provide the desired flow rate f grad Operating the second pump in a pressure controlled mode to set the second pump to provide a desired flow rate may advantageously be faster than operating the pump only in a flow controlled mode.

[0174] Once the desired flow rate has been established, either by directly setting the desired flow rate or by first estimating the target pressure, the second pump target pressure may be determined by measuring the pressure at the second pump 12, in particular the pressure at the outlet of the second pump 12. Alternatively, the second pump target pressure may be determined as a calculated target pressure, however, the measured second pump target pressure may advantageously be more accurate than the calculated target pressure.

[0175] Subsequently, the first pump target pressure can be determined based on the second pump target pressure (step 240). Typically, there may be a difference in fluid resistance between the fluid connection of the second pump 12 with the second separation column 5 in the first configuration and the fluid connection of the first pump 1 with the second separation column 5 in the second configuration. For example, the fluid connection between the second pump 12 and the second separation column 5 may (at least in part) include an autosampler, which may apply some fluid resistance and therefore contribute to the second pump back pressure. Therefore, when it is intended to avoid a pressure change at the second separation column when switching from the first configuration to the second configuration, this contribution should be deducted from the second pump target pressure.

[0176] Therefore, determining the first pump target pressure can also be based on the difference in fluid resistance (and therefore corresponding back pressure) between the second pump and the second separation column in the first configuration and between the first pump and the second separation column in the second configuration. It should be understood that generally fluid resistance always results in an associated back pressure, and therefore any back pressure is derived from fluid resistance.

[0177] However, since the fluidic resistance of the first pump 1 specific fluid connection is usually negligible (as it may be only a short fluid conduit), its contribution may be neglected for simplicity. A pump specific fluid connection means that the fluidic connection to the respective pump is independent of the configuration adopted by the system. For example, referring to Figure 1 , the fluid connection specific to the second pump 1 is the fluid conduit 4. Therefore, determining the pump target pressure may alternatively also be based on the fluid resistance of the fluid connection specific to the second pump 12. That is, the fluid resistance of the fluid connection downstream of the second pump 12 is independent of whether the system is in the first configuration or the second configuration. Figure 1 In the exemplary system of FIG. 1 , this would be the fluid connection between the second pump 12 and the column distribution valve 13, since it is connected to the second pump 12, regardless of the configuration adopted by the column distribution valve 13, and therefore regardless of whether the system adopts the first configuration or the second configuration. Therefore, the characteristic fluid connection of the second pump 12 would include the fluid conduits 9, 11 and the injection valve 10 of the autosampler 3.

[0178] Thus, the first pump target pressure can be determined as the difference between the second pump target pressure and the back pressure of the fluid resistance of the fluid connection specific to the second pump. In other words, the first pump target pressure can be determined as the difference between the second pump target pressure and the back pressure of the fluid connection downstream of the second pump regardless of whether the system is in the first configuration or the second configuration.

[0179] Once determined, the first pump 1 can be set to provide fluid at a first pump target pressure (step 250), preferably with a desired fluid composition for sample analysis. In particular, the desired fluid composition may correspond to a desired solvent composition for the start of a gradient provided by the first pump 1, such as % B for the above example. start . In addition, the second pump 12 can continue to supply fluid at a second pump target pressure. Preferably, the fluid provided by the second pump 12 also has a desired target composition. Therefore, the two pumps can supply fluid at very similar pressures, wherein the pressure is selected so that when the configuration adopted by the switching system, the first pump 1 in the second configuration provides fluid to the second separation column 5 at a desired flow rate, and further so that there is no significant pressure change at the inlet of the second separation column 5 when switching from the first configuration to the second configuration. The term "no specific pressure change" means that the relative pressure change at the inlet of the second separation column is less than 10%, preferably less than 5%, and more preferably less than 1%.

[0180] It should be understood that the second pump target pressure is preferably determined for the desired fluid composition. That is, when determining the second pump target pressure, especially when determining the second pump back pressure, the second pump 12 may have provided the desired fluid composition.

[0181] Similarly, when determining the second pump target pressure, the second separation column 5 can preferably be operated at a desired temperature. In addition, when setting the first pump 1 to the first pump target pressure, the first separation column 8 can preferably be operated at a desired temperature. The desired temperature can be a temperature required for a subsequent gradient run.

[0182] The advantage of aligning the pressure at the separation column before switching can be Figure 5 Seen in Figure 5 Two chromatograms are shown (panel A) and panel B). These chromatograms are total ion current chromatograms based on the corresponding MS analysis of the effluent in the tandem chromatography system. That is, for each retention time, all signals in the entire detected mass-to-charge ratio (m / z) range are added to provide the corresponding total ion current. Both chromatograms were recorded under similar conditions (except for the pressure adjustment according to the invention). Figure 5 A) depicts a chromatogram recorded using the present invention to align the pressure at the separation column before switching, while Figure 5 B) depicts the chromatogram recorded in the absence of such pressure alignment. In panel A), the first signal starts at about 2 minutes, while the initial signal in panel B) already exists at 0 minutes, thus showing a clear indication of the early eluting compound no longer fully captured by the chromatogram. In fact, most of the initial signal peaks of panel B) are not even recorded. In addition, compared with panel A), a small amount of signal after the initial signal peak in panel B) further proves the elution of the compound caused by the pressure jump. In other words, in the absence of pre-pressure alignment between the separation columns, the pressure change produced during the gradient pump is switched to the separation column to be analyzed causes the elution of the early eluting compound. This may lead to the loss of valuable information, therefore making the analysis result significantly less useful.

[0183] This clearly shows the advantage of the present invention, which allows taking into account any pressure difference between the two separation columns, for example also taking into account column aging, for which the actual influence on the back pressure is usually not precisely known. Thus, the present invention advantageously allows improving the quality of the analysis results, in particular due to improved precision of the measured retention times and extending the life of the separation columns, which may be damaged and / or experience increased wear due to the pressure changes that otherwise occur.

[0184] Whenever relative terms such as "about", "substantially" or "approximately" are used in this specification, such terms should also be interpreted as also including precise terms. That is, for example, "substantially straight" should be interpreted as also including "(exactly) straight".

[0185] Whenever a step is described above or otherwise in the appended claims, it should be noted that the order in which the steps are listed herein may be accidental. That is, unless otherwise stated or unless it is clear to the skilled person, the order in which the steps are described may be accidental. That is, when this document states that, for example, a method includes steps (A) and (B), this does not necessarily mean that step (A) is before step (B), but it is also possible that step (A) is (at least partially) performed simultaneously with step (B), or step (B) is before step (A). In addition, when step (X) is referred to as being before another step (Z), this does not mean that there is no step between step (X) and (Z). That is, step (X) before step (Z) covers the situation where step (X) is performed directly before step (Z), but also covers the situation where step (X) is performed before one or more steps (Y1) ... and then step (Z). When using terms such as "after" or "before", corresponding considerations also apply.

[0186] Although a preferred embodiment has been described above with reference to the accompanying drawings, skilled persons will appreciate that this embodiment is provided for illustration purposes only and should in no way be construed as limiting the scope of the present invention, which is defined by the claims.

Claims

1. A method for operating a chromatography system, the method comprising The system adopts a first configuration, in which A first pump (1) is fluidly connected to a first separation column (8); A second pump (12) is fluidly connected to the second separation column (5); In the first configuration: The first pump (1) provides fluid to the first separation column (8); The second pump (12) provides fluid to the second separation column (5); Determine the second pump target pressure (P target,eq ); Based on the second pump target pressure (P target,eq ) to determine the first pump target pressure (P target,grad ); as well as The first pump (1) is set to operate at the first pump target pressure (P target,grad ) providing a fluid; The method further comprises The system switches to a second configuration in which the first pump (1) is fluidly connected to the second separation column (5) while the first pump is pumped at the first pump target pressure (P target,grad ) provides fluid.

2. The method according to the preceding claim, wherein: The second pump target pressure is determined based on a desired flow rate.

3. The method according to the preceding claim, wherein: The second pump target pressure is determined such that in the first configuration, when the second pump target pressure is present at the second pump (12), the second pump (12) supplies fluid through the second separation column (5) at the desired flow rate.

4. The method according to any one of the preceding claims, wherein: Determining the second pump target pressure includes measuring a pressure present at the second pump (12) when providing the desired flow rate, wherein the second pump target pressure is determined to correspond to the measured pressure.

5. A method according to any one of the preceding claims, wherein: The method also includes configuring the second pump (12) to provide fluid at the second pump target pressure in the first configuration.

6. A method according to any one of the preceding claims, wherein: Determining the first pump target pressure is also based on a fluid resistance of a fluid connection downstream of the second pump (12) independent of whether the system is in the first configuration or the second configuration.

7. A method according to any one of the preceding claims, wherein: The first pump target pressure is determined so that when the first pump target pressure exists at the first pump (1) while supplying fluid to the second separation column (5), the pressure at the inlet of the second separation column (5) is substantially equal to the pressure at the inlet of the second separation column (5) when the same fluid is supplied at the second pump target pressure using the second pump (12).

8. A method according to any one of the preceding claims, wherein: When the system switches from the first configuration to the second configuration, the relative pressure at the inlet of the second separation column (5) changes by less than 10%, preferably less than 5%, more preferably less than 1%.

9. A chromatography system, comprising A first pump (1); A second pump (12); A first separation column (8); A second separation column (5); The system is configured to adopt a first configuration, in which The first pump (1) is fluidly connected to the first separation column (8); and The second pump (12) is fluidly connected to the second separation column (5); wherein the system is configured to assume a second configuration in which the first pump (1) is fluidly connected to the second separation column (5); and The system further comprises a controller configured to execute the method according to any one of claims 1 to 8.

10. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to any one of claims 1 to 8.

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