SOLVENT DELIVERY WITH A REDUCED VOLUME SINGLE STROKE PUMPING ARRANGEMENT PROVIDING CONTINUOUS SOLVENT FLOW

Abstract

The exemplary embodiments control solvent pumps so that system flow is constant. One or more controllers may control the flow rate produced by the pumps over time. The one or more controllers control a first pump so that, as the first pump is refilling, a second pump maintains a sufficient flow rate to compensate for the lost flow due to the refilling event. In some exemplary embodiments, the one or more controllers control the timing of the refilling event for the first event such that the refilling event overlaps with the equilibrating of the chromatography column with solvent(s) from the second pump. Similarly, the one or more controllers control the timing of the refilling event for the second pump such that the refilling event overlaps with the equilibrating of the chromatography column.

Claims

1. A solvent delivery system for a chromatography system having a chromatography column from which analytes of interest elute, comprising: a first pump with a single plunger for pumping a first component of a solvent gradient over a first fluid path to the mixing tee, the first pump having a repeating operational cycle with a delivery phase and a refilling phase; a second pump with a single plunger for pumping a second component of the solvent gradient over a second fluid path to the mixing tee, the second pump having a repeating operational cycle with a delivery phase and a refilling phase; a first proportioning valve connected to an input of the first pump for providing proportions of multiple solvents for the first component of the solvent gradient to the first pump; a second proportioning valve connected to an input of the second pump for providing proportions of multiple solvents for the second component of the solvent gradient to the second pump; and one or more processors configured to control the first pump and the second pump so that: as the first pump is in the refilling phase, the second pump is in the delivery phase, and as the second pump is in the refilling phase, the first pump is in the delivery phase; and wherein the refilling phases of the first pump and the second pump do not occur during the eluting of the analytes of interest from the chromatography column.

2. The solvent delivery system of claim 1, further comprising multiple solvent reservoirs connected to the first proportioning valve or the second proportioning valve.

3. The solvent delivery system of claim 1, wherein the first pump and the second pump are single stroke pumps.

4. The solvent delivery system of claim 1, wherein the one or more processors are part of a controller for both the first pump and the second pump.

5. The solvent delivery system of claim 1, wherein the one or more processors comprise multiple processors and wherein the multiple processors include a first processor that is part of a controller of the first pump and a second processor that is part of another controller for the second pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 depicts a conventional single stroke valve for a solvent delivery system of a chromatography system.

[0018] FIG. 2 depicts a conventional pump arrangement using two plungers to provide continuous flow in a solvent delivery system.

[0019] FIG. 3 depicts a conventional two pump arrangement where each pump includes two plungers to provide continuous flow in a solvent delivery system.

[0020] FIG. 4 depicts an example of the noise in a chromatogram resulting from an arrangement like FIG. 3 due to refilling events.

[0021] FIG. 5 depicts an illustrative chromatography system for exemplary embodiments.

[0022] FIG. 6 depicts illustrative components of a solvent delivery system for exemplary embodiments.

[0023] FIG. 7 depicts a storage suitable for controller(s) of pump in exemplary embodiments.

[0024] FIG. 8 depicts an illustrative arrangement for two single stroke pumps for an exemplary embodiment.

[0025] FIG. 9 depicts a diagram of varying flow rates of pumps in an exemplary embodiment.

[0026] FIG. 10 depicts a flow chart of steps that may be performed to control the pumps with the controller(s) in exemplary embodiments.

[0027] FIG. 11 depicts an alternative arrangement of pumps where gradient proportioning valves are used.

DETAILED DESCRIPTION

[0028] The exemplary embodiments may provide a solvent delivery system that avoids the pitfalls discussed above of flow perturbations and pressure pulses that may produce noise and band broadening with conventional solvent delivery systems. In addition, the exemplary embodiments may only need a single plunger per solvent. Thus, for a system delivering two solvents, only two pumps with single plungers are needed. The exemplary embodiments may use single stroke pumps with a single plunger. These pumps are less expensive than the conventional arrangement of FIG. 3. Moreover, these pumps may be smaller than the conventional arrangement of FIG. 3.

[0029] The exemplary embodiments control pumps so that system flow is without interruptions. This eliminates the refilling events that cause flow perturbations and pressure pulses. The pumps of the exemplary embodiments may be controlled by one or more controllers. The one or more controllers control the flow rate produced by the pumps over time. As will be explained in more detail below, the one or more controllers control a first pump so that as the first pump is refilling, a second pump maintains a sufficient flow rate to compensate for the lost flow rate due to the refilling event.

[0030] The exemplary embodiments may use the pumps to deliver a solvent system. The solvent system is a combination of solvents, modifiers, and additives comprising the mobile phase. Isocratic solvent systems are comprised of one or more components which stay constant in relative proportion while the analytes of interest are eluted from the column. The composition may be altered after the analytes of interest elute to wash the column. If a wash step is performed, an equilibration period must be performed before the next injection to ensure consistent retention times.

[0031] The exemplary embodiments may provide a composition-programmed gradient elution solvent system. Such a solvent system includes more than one component and the relative proportion of the components is altered while the analytes of interest are being eluted from the chromatographic column. Most commonly, the composition of the mobile phase is altered from a weak solvent (i.e. a condition which promotes retention of the analyte) to a strong solvent (a condition which promotes elution of the analyte). Often, a wash step is performed with strong solvent. An equilibration step at initial composition is required prior to the next injection to promote consistent analyte retention times.

[0032] Each (gradient) chromatographic experiment is comprised of an inject stage, (occasionally an isocratic hold), a gradient stage, a wash stage and an equilibration stage. The gradient stage is when the two delivery rates by respective pumps change over time. The gradient stage changes the composition from predominately weak to predominately strong in composition. The gradient stage is often where data is recorded and is therefore the most important portion for maintaining low noise. The wash stage is when strong solvent (i.e. high organic in reversed-phase LC) flows through the chromatography column. The equilibration stage is when weak solvent (aqueous in RPLC) flows through the chromatography column.

[0033] We will generally speak of only two phases for each pump: a delivery phase when the pump is delivering solvent and a refilling phase when the pump is being refilled with a solvent or component of a solvent system.

[0034] In some exemplary embodiments, the one or more controllers control the timing of the refilling event for the first event such that the refilling event overlaps with the equilibrating of the chromatography column with solvent(s) from the second pump (i.e., part of the delivery phase for the second pump). Similarly, the one or more controllers control the timing of the refilling event for the second pump such that the refilling event overlaps with the equilibrating of the chromatography column with solvent(s) from the first pump (i.e., part of the delivery phase of the first pump). The approach enables the flow of solvents to be continuous through the cycles of the pumps and causes the flow anomalies to be outside of the gradient elution portion of an experiment. Since no transfer events are required during the gradient elution portion of the experiment, no pressure perturbations and compositional differences are incurred and the needs for mixing are dramatically reduced or eliminated. The reduction of mixing requirements results in reduced gradient delay volume, more accurate gradient shape, and reduced overall cost of the system. In the exemplary embodiment, the mixing element is a simple tee.

[0035] FIG. 5 depicts a block diagram of a chromatography system 500 suitable for exemplary embodiments. The chromatography system 500 includes a solvent delivery system 502 for delivering solvents to a chromatography column 506. The chromatography column 506 may be, for example, a liquid chromatography column, a supercritical fluid chromatography column or other type of chromatography column. A sample injector 504 may inject a sample solution into the flow of mobile phase (e.g., solvents) output by the solvent delivery system 502. The sample solution includes an analyte sample in solution. The mobile phase with the sample solution enters the chromatography column 506. The sample elutes from the chromatography column 506 and is detected by a detector 508.

[0036] FIG. 6 depicts a more detailed depiction of components of the solvent delivery system. The solvent delivery system 600 may include solvent reservoirs 602 for holding solvents that may be delivered by the solvent delivery system 600. The solvents in the solvent reservoirs 602 may be pumped out of the reservoirs by pumps 604. In the exemplary embodiments, these pumps 604 may include multiple single stroke pumps arranged as will be discussed below. The pumps 604 may be controlled by controller(s) 606. The controller(s) 606 may be for example, a single controller for all of the pumps 604 or a separate controller for each pump, where the controllers coordinate activity of the respective pumps. The controller(s) 606 may include processor(s) 608 for executing computer programming instructions. Each processor may be a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC) or a special purpose microcontroller. Each processor of the processor(s) 608 may include one or more cores.

[0037] The controller(s) 606 may include a storage 610. The storage 610 may include memory and/or storage components, such as Random Access Memory (RAM) components, Read Only Memory (ROM) components (including EPROM and EEPROM components), flash memory components, optical disk components, magnetic disk components, solid state memory components, removable memory media and/or other types of non-transitory computer-readable storage media. The storage 610 may hold data, files and/or programs. In some exemplary embodiments, as shown in FIG. 7, the storage 700 stores control program(s) 702 and Data 704. The control program(s) 702 include computer programming instructions that may be executed by the processor(s) 608 to control the pumps 604. It should be appreciated that the computer programming instructions for controlling the pumps 604 need not be a control program(s) 702 per se but rather may be realized in a module, an applet, a library, a method, a subroutine, a procedure, a function, an object or other form.

[0038] As shown in FIG. 6, the mobile phase is output by the pumps along fluid paths 612 created by fluid conduits, such as tubing and the like, to a mixing tee 614. The mixing tee 614 is a conjunction where the solvents from the respective pumps 604 mix. The resulting mobile phase is output 616 from the mixing tee into a fluidic path leading the chromatography column, such as shown in FIG. 5.

[0039] FIG. 8 shows an example of an arrangement for a solvent delivery system 800 for an exemplary embodiment. The solvent delivery system 800 includes a single stroke pump 802 and a single stroke pump 804. Single stroke pump 802 receives solvent B from a reservoir via an inlet 816. The solvent B is displaced by plunger 812 to outlet 818 on to a fluidic path 806 that leads to mixing tee 810. Single stroke pump 804 receives solvent A from a reservoir at inlet 820. Plunger 814 displaces solvent A through outlet 822 to fluidic path 808 that leads to the mixing tee. Solvent A and solvent B mix at the mixing tee and flow to the high-pressure system as described above. Not shown are inlet and outlet check valves to prevent backflow during delivery and refilling phases (like those depicted in FIG. 1).

[0040] The arrangement of FIG. 8 provides continuous flow by controlling the timing of the cycles of the pumps 802 and 804 to prevent interruption of system flow. The controller(s) 606 control the pumps 802 and 804 to realize such continuous flow.

[0041] FIG. 9 depicts a plot of the pump flow rates for two pumps, such as pump 802 and pump 804. Curve 902 represents the flow rate of pump 804 and curve 902 represents the flow rate of pump 802. Each of the pumps 802 and 804 has an operational cycle as described above that includes a delivery phase and a refilling phase. The operational cycle in repeatable during operation of the pumps 802 and 804. A time 0, the sample is introduced into the system and the gradient starts. The pumps start following a programmed gradient profile. As can be seen in the example diagram of FIG. 9, initially the pumps 802 and 804 are in the delivery phase (see 1 in FIG. 9). As can be seen, pump 804 is at a high flow rate and ramps down as indicated by the downward slope of curve 902. At the same time, pump 802 is a low rate and ramps up to a high flow rate as indicted by the upward slope of curve 904. The combined flow rate of the pumps is kept constant throughout the experiment. As this transition occurs, the percentage of Solvent A in the gradient decreases, and the percentage of solvent B in the gradient increases. Once delivery of the gradient is complete, pump 804 enters the refilling phase, and while pump 802 enters the delivery phase (see 2 in FIG. 9). In the refilling phase, solvent A refills pump 804. The flow rate of the pump 802 is high (see 904) and compensates for the absence of flow from pump 804 (see 902). The negative flow shown in FIG. 9 during the refilling phase indicates that solvent is being added to refill the pump chamber.

[0042] Next, it is time to equilibrate the chromatography column 506 with solvent A. Pump 802 enters the refilling phase (see the drop in curve 904), and at the same time pump 804 enters the delivery phase at a high flow rate (see curve 902 and see 3). The high flow rate of pump 802 compensates for the loss of flow from the pump 804 during the refilling phase and provides continuous flow. This approach substantially eliminates the flow perturbations and pressure waves experienced with refilling events in conventional systems during the important gradient region of the experiment when analytes of interest are eluting from the chromatography column for detection. Lastly, as a final part of the delivery phase cycles of pumps 802 and 804 they provide equilibration (see 4 in FIG. 9) to prepare for the next operational cycle instances.

[0043] Since no transfer events are required to maintain continuous flow and the individual pumping elements are refilling during wash and equilibration phases, there is no longer need for extremely fast pump movements. The exemplary embodiments therefore allow for gear reduction and enable smaller, lower torque motors. Further, since to transfer event is required, the pumping elements are not reversing direction during the gradient delivery portion of the experiment, but they are reversing during wash and equilibration steps. During the wash and equilibration stages, some pressure ripple is acceptable since it does not reduce the signal to noise ratio while analytes of interest are detected. Accordingly, there is increased tolerance for gear lash enabling less precise linear actuators and gear assemblies.

[0044] As was mentioned above, the controller(s) 606 control the flow rates to realize the timing synchronization of the pump that is illustrated in FIG. 9. FIG. 10 shows a flowchart 100 of illustrative steps that may be performed to realize this control. Initially, the controller(s) 606 are configured to regulate the flow rates in a manner consistent with a timing as defined in a chart like FIG. 9 or some other timing arrangement (1002). This may entail programming or configuring a single controller or multiple controllers, depending on whether one controller or multiple controllers are used. The pumps are the run under the control of the configured or programmed controller(s) 1004.

[0045] The arrangement of the solvent delivery system depicted in FIG. 8 has each pump 802 and 804 pumping a single solvent. In an alternative exemplary embodiment as depicted in FIG. 11, each pump 1102 and 1104 pumps multiple solvents as a component of the delivered solvent gradient that is output by mixing tee 1106. A gradient proportioning valve 1110 is provided to provide the first component of the solvent gradient to the inlet 1114 of pump 1102. The gradient proportioning valve 1100 is connected to reservoirs for solvents E, F, G and H and may create the first component from these solvents in varying proportions. The first component may include any combination of the solvents E, F, G and H ranging from a single solvent to all of the solvents. A gradient proportioning valve 1108 also is connected to solvent reservoirs for solvents A, B, C and D and may provide combinations of these solvents in varying proportions to the inlet 1112 of pump 1104 as the second component of the solvent gradient. The arrangement 1100 otherwise is configured and operates like the arrangement 800 of FIG. 8.

[0046] It should be appreciated that in some alternative embodiments, a gradient proportioning valve provides the input to only a single one of the pumps.

[0047] While the present invention has been described with reference to exemplary embodiments, various changes in form and detail may be made without departing from the intended scope as defined in the appended claims.