Methods and devices for open-bed atmospheric collection for supercritical fluid chromatography

Abstract

A supercritical fluid chromatography system comprises a first pump for pumping a first flow stream comprising a compressible fluid and a second pump for pumping a second flow stream comprising a modifier fluid. The second pump is in parallel with the first pump. A column is located in a combined flow stream. The column is located downstream of the first and second pumps. The combined flow stream comprises the first flow stream, the second flow stream, and a sample. A detector is located downstream of the column. A gas-liquid separator is located downstream of the detector. The gas-liquid separator is configured to vent a majority of the compressible fluid while maintaining a majority of the sample, thus preventing aerosolization of the flow stream and minimizing sample loss as well as cross contamination. An open bed collector is located after the gas-liquid separator.

Claims

1. A supercritical fluid chromatography system comprising: a first pump for pumping a first flow stream comprising a compressible fluid; a second pump for pumping a second flow stream comprising a modifier fluid, the second pump in parallel with the first pump; a column located in a combined flow stream, the column located downstream of the first and second pumps, the combined flow stream comprising the first flow stream, the second flow stream, and a sample; a detector located downstream of the column; a gas-liquid separator located downstream of the detector, the gas-liquid separator configured to receive and separate the combined flow stream into a compressible fluid flow and a remaining flow, the gas-liquid separator further configured to vent a majority of the compressible fluid while maintaining a majority of the sample to avoid sample loss and cross-contamination resulting in the remaining flow; a collector arm located downstream of the gas-liquid separator positioned to receive the remaining flow; a collector arm adapter coupled to the collector arm, the collector arm adapter configured to reduce aerosols when the remaining flow is at atmospheric conditions; and an open bed XY type collector located downstream of the collector arm adapter and positioned such that the remaining flow is directed to pass through the collector arm and into the open bed XY type collector.

2. The supercritical fluid chromatography system of claim 1, further comprising an adjustable container rack coupled to the open bed XY type collector.

3. The supercritical fluid chromatography system of claim 1 wherein the gas-liquid separator is made from stainless steel, polymer, or glass.

4. The supercritical fluid chromatography system of claim 1 further comprising a back pressure regulator located upstream of the gas-liquid separator.

5. The supercritical fluid chromatography system of claim 1 wherein the compressible fluid is carbon dioxide (CO.sub.2).

6. The supercritical fluid chromatography system of claim 1, wherein the collector arm adapter comprises an inlet, an outlet, and an enclosure portion, the inlet positioned to receive the remaining flow and conduct the remaining flow to the outlet, the outlet positioned to release the remaining flow into a space around the outlet, and the enclosure portion positioned to confine the space around the outlet.

7. The supercritical chromatography system of claim 6, wherein the enclosure portion is sufficiently large that substantially all aerosols resulting from the release of the remaining flow into the space around the outlet are collected by the enclosure portion.

8. The supercritical fluid chromatography system of claim 6 wherein the enclosure portion is concentric with and wider than the outlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other features and advantages provided by the present disclosure may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the technology.

(2) FIG. 1 is a diagram of an SFC system with an open-bed XY type collector, according to an illustrative embodiment of the technology.

(3) FIG. 2 shows the installations of Waters Fraction Collector III (“WFCIII”), an XY type collector installed with both a collector arm adapter and a rack adapter for SFC instrumentation, according to an illustrative embodiment of the technology.

(4) FIG. 3A shows the collector arm adapter design on a WFCIII, according to an illustrative embodiment of the technology.

(5) FIG. 3B shows a schematic representation of the collector arm adapter, according to an illustrative embodiment of the technology.

(6) FIG. 4 shows one embodiment of a rack adapter design on WFCIII that is compatible with SFC instrumentation, according to an illustrative embodiment of the technology.

(7) FIG. 5 is a top view of a rack adapter design on WFCIII that is compatible with SFC instrumentation, according to an illustrative embodiment of the technology.

(8) FIG. 6 is a diagram of an embodiment of the gas-liquid separator used in the technology.

(9) FIG. 7 shows diagrams of an embodiment of a dripper of the gas-liquid separator used in the technology.

(10) FIG. 8 shows another embodiment of the gas-liquid separator used in the technology.

(11) FIG. 9 shows a schematic embodiment of the open bed atmospheric collection system.

DETAILED DESCRIPTION

(12) In order to prevent sample loss and cross-contamination when collecting fractions for SFC, the technology takes advantage of a gas-liquid separator (GLS) installed into a flow stream after a BPR, of which the purpose is to vent the majority of gaseous carbon dioxide (CO.sub.2), or any supercritical fluids used in the process, while maintaining the incompressible modifying liquid in which the sample is dissolved. Although CO.sub.2 may be one common supercritical fluid used for SFC, other suitable supercritical fluids may be nitrous oxide (N.sub.2O), sulfur hexafluoride (SF.sub.6), or chlorofluorocarbons (CFCs) such as Freon. One of ordinary skill in the art can vary the dimensions, geometry and the operational settings of the GLS to optimize the GLS so that it is suitable for flow rates ranging from approximately a few mil/min to hundreds of ml/min.

(13) The GLS, described in International publication number WO 2010/056313, hereby incorporated by reference in its entirety, comprises a chamber in which a specially tapered tube with an increasing internal diameter is inserted. The end of the tapered tube is angled such that as the gas-liquid mixture flows out of the tapered tube and into the larger chamber, flow is directed to impact an inner wall of the chamber at an angle tangential to the impact wall of the separator.

(14) Because the gas-liquid flow is not straight down upon exiting the tapered tube, coalescence of the modifying liquid and sample begins inside the GLS. The impact point and angle of impact serve to direct the liquid stream into a downward spiral towards a liquid exit point. Simultaneously, compressible fluids such as CO.sub.2 are vented upon exiting the tapered tube. Because the modifying liquid and sample coalesce in a controlled manner inside the GLS as the compressible fluid is vented, the modifying liquid and sample are able to drain towards the bottom of the GLS.

(15) In embodiments, after passing through the GLS, the modifying liquid has been separated from the compressible fluid such as CO.sub.2 and therefore is no longer in danger of being aerosolized. The modifying liquid now behaves just as any other mobile phase fluid common to other types of chromatography such as HPLC, MPLC, LPLC or Flash chromatography. Therefore, it can be collected using a standard open bed XY type fraction collector known to one of skill in the art without fear of sample loss or cross contamination.

(16) Some embodiments of the technology further comprise a collector arm adapter (see e.g., FIG. 3A) that can be attached to an XY type collector arm that can be downstream of the GLS. The function of this collector arm adapter is to curb and/or diminish the aerosols generated once the fluid flow is subject to atmospheric conditions, for example, the location where the fluid flow leaves the collector tip of the robot arm. For example, the collector arm adapter is appropriate in the event that trace residual amounts of CO.sub.2 (e.g. 0.001%-1%, 0.01%-0.1%) remain in the flow stream after passing through the GLS. The collector arm adapter includes a cover that surrounds a tip which disperses the sample to the collector rack. The collector arm adapter creates an enclosure to trap any remaining aerosols that may be generated as a result of trace residual CO.sub.2 left in the incompressible fluid after the combined stream has passed through the GLS. By coupling the GLS to the collector arm adapter, the aerosols can be well confined within a very limited range around the fluid flow stream between the space where the stream leaves the collector and the container underneath the collector, at a significantly reduced scale. In some embodiments, the aerosols are completely diminished and are not observable in this design.

(17) The process can include an adjustable container rack that can be coupled to the GLS and collector arm adapter. Corresponding dimensions and openings of receiving ports of the container rack, in addition to the adjustable height of the rack, can accommodate a wide range of fluid flow characteristics to ensure high collection efficiency of fraction flow.

(18) The technology can also include optimum processes for hardware development for characteristic SFC instrumentation. The processes can include designs of GLS and collector arm adapters based on actual SFC flow characteristics to optimize the capability for maximum control of gas venting and aerosol diminishing. The GLS can be made of stainless steel, a polymer, glass or other types of compatible materials for the process. The geometry and dimensions of the GLS can be commensurate with the actual flow capacity to ensure proper ventilation flow while preserving most fluid flow drained down to the collector. The collector arm adapter (see, e.g., FIGS. 3A and 3B) can include various dimensions and geometries for optimized aerosol confinement and diminished capability based on flow rate and compositions. The rack adapter (see, e.g., FIGS. 4 and 5) can include designs for adjustable height and for accommodation and connection to various types of containers from, for example, tubes, bottles, and vessels, to carboys, to ensure maximum collection efficiency, encapsulation of liquid flow and minimum aerosol generation.

(19) The present technology can also include optimum processes for method development. The processes can include optimization of method parameters such as pressure settings on GLS, which can range from about a few psi to 50-60 bar, combined with specific adapted geometry and dimensions for the best performance for gas-liquid separation and venting. The process can also include adjustment of the collector arm adapter in terms of its dimensions and spatial arrangement on the robot arm for best efficiency of aerosols control.

(20) The present technology also includes various integrations of applications for the methods and devices for fraction collection purposes. Such development with an XY type collector includes, but is not limited to, routine fraction collections from high performance SFC, secondary collection in addition to conventional fraction collection in SFC, fraction collection for high flow, high speed supercritical fluid flash chromatography, and any other type of pressurized liquid processes where there is potential risk of aerosol generation during the collections.

(21) One such embodiment of the above mentioned technology is depicted in FIG. 1, which shows a mass-directed preparative SFC100 (MD-SFC100) system 100. The components of the system are interconnected via a suitable tubing 101 that is capable of withstanding the intense pressures and temperatures necessary to reach supercritical conditions without corrosion or other safety concerns. In one embodiment, the system comprises a CO.sub.2 supply 105, followed by a flow meter 106 to control the flow of CO.sub.2 through the system. There is also a separate reservoir 111 which contains the modifier solvent, e.g. methanol. In some embodiments, there are pumps for both CO.sub.2 and modifier solvents 110, 115, respectively. In some embodiments, there is a Waters 2767 sample manager 120 (including a sample injection 116 and an open bed collector 160). There are also in-line heaters 125, a separation column 126 surrounded by a column oven 127. In some embodiments, there is a tunable splitter 128 that directs a portion of the flow to a mass spectrometry detector 135 and a remaining portion of the flow to a UV/PDA detector 130. In some embodiments, there is an automated BPR 131 located downstream of the UV/PDA detector. There is a make-up pump 132 located downstream of the BPR, and a heat exchanger 133. In some embodiments, the GLS 140 is used to remove the compressible fluid (e.g. 100% removal, 99.98% removal, 99.8% removal, 99% removal) from the combined flow stream and vent it without aerosolization and corresponding sample loss and cross contamination. After a junction point 141 a portion of the stream is directed to a waste receptacle 150 while the remaining flow is directed to a fraction collector 160 shown here as a Waters 2767 fraction collector and a Waters Fraction Collector (WFCIII) 155. In this configuration the Waters Fraction Collector (WFCIII), an XY type fraction collector, is integrated as the secondary collector. WFCIII is plumbed along side with Waters 2767 fraction collector 160, and is controlled by Waters Masslynx software that controls the whole chromatography system 100. In one embodiment, the Waters 2767 fraction collector 160 is the primary fraction collector and is responsible for collecting the majority of fractions. In one embodiment, the WFCIII can optionally be used as a secondary fraction collector 155. The purpose of the optional secondary collector 155 is to collect any fractions that may be missed by the primary collector 160. For example, glitches in software or other unforeseen circumstances may prevent the primary collector from collecting all fractions, thus the secondary collector may be present to collect any uncollected fractions. Thus in some embodiments it is possible to use only one fraction collector (e.g. Waters 2767 fraction collector 160) whereas in some embodiments it is possible to use multiple fraction collectors.

(22) In other embodiments, not shown, the system 100 can be used in combination with other fluids for performing SFC. That is, other compressible fluids which can be processed to form a supercritical phase for chromatography can be used in place of CO.sub.2. For example, in one embodiment, nitrous oxide (N.sub.2O) may be used. Alternatively, in one embodiment, other compressible fluids such as sulfur hexafluoride (SF.sub.6) or chlorofluorocarbons (CFCs) such as Freon may be used.

(23) FIG. 2 shows the installation of WFCIII, (e.g. part number 155 in FIG. 1) an XY type collector installed with both collector arm adapter 230 (for example, the collector arm adapter 305 of FIG. 3A) and rack adapter 220 (for example, the rack adapter 405 in FIGS. 4 and 505 in FIG. 5) for SFC instrumentation. In this embodiment, the collectors work to collect fractions of compounds of interest based on criteria set by instrument methods from UV, Mass Spectrometer and/or Evaporative Light Scattering Detector (“ELSD”) and other signals. The WFCIII collector can be fully integrated and controlled by operating software that controls the entire chromatography system. The WFCIII works with the Waters 2767 collector in either a complementary way to ensure higher collection efficiency, or the Waters 2767 collector acts as a standalone collector. WFCIII can be trigged by line of injection, peak-based signals from Mass Spec., UV, ELSD or any kind of detectors from the system, and different kinds of algorithm combinations with these signals, or it can collect fractions by time windows, peak-triggered time slicing mode, or any other manual mode controllable by preset methodologies. The configuration in this embodiment can ensure a high collection efficiency and can reduce the risk of potential sample loss from random malfunction. The configuration can also enrich versatile collection features to further extend the applicability, robustness, economy and flexibility of SFC instrumentation for more chromatography applications, such as, but not limited to, high throughput analysis and purifications, chiral analysis, flash chromatography for pharmaceutical, natural product, food analysis, environmental monitoring, petroleum analysis, and/or alternative energy development.

(24) The collector arm adapter 305 of FIG. 3A is an optional feature. In the event that not all of the CO.sub.2 or compressible fluid is vented and some small portion remains, the adapter arm 305 can prevent sample loss/cross contamination by confining the space around the exit tip.

(25) FIG. 3B shows a schematic of the internal geometry of the collector arm adapter pictured in 3A, i.e. adapter 305. Fluid enters through the inlet 355, and flows through outlet 360. Any aerosolization resulting from this transition is collected by the enclosure portion 365. In one embodiment, the inlet portion 355 is 8 mm in length. In one embodiment, the outlet portion 360 is 6 mm in length. In one embodiment, the enclosure element 365 is 14 mm in length.

(26) While the collector arm adapter 305 is an optional element, which can enhance performance, the GLS is a required component. The GLS vents a significant portion (e.g. 100%, 99%) of the CO.sub.2 from the combined flow stream.

(27) The gas-liquid separator used in the system of FIG. 1, e.g. GLS 140, is shown in more detail in FIG. 6. The separator comprises an inlet flow port 650, a gas vent 655, a top cap 660, an outer vessel 670, a bottom cap 680, a liquid outflow port 685, and a drain port 690. A specially tapered tube with an increasing internal diameter, called the dripper 665, is inserted into the separator. The mouth of the dripper 667 (through which the flow exits the dripper into the separator, the outlet) is wider than the diameter of the dripper where the flow enters the dripper 666 (inlet). The dimensions of the dripper are optimized for the system's flow rates, which assist in consolidating aerosol into a unified liquid stream. In general, the ratio of the diameter of the outlet to the diameter of the inlet is between 2-100 to one. For flow rates up to about 100 gm/minute, the ratio of the diameter of the outlet to the diameter of the inlet is between about 2-4 to one, preferably about three to one. The ratio can be adjusted to accommodate flow rates of up to 1000 gm/minute.

(28) The dripper shown in FIG. 7, e.g. the dripper 665 of FIG. 6, has an angle, relative to the separator's downward pointing vertical axis, between 10 and 80 degrees. In other words, the exit of the dripper is neither straight down nor straight sideways, but rather in-between. This angle is in a vertical orientation, and is not the tangential angle.

(29) Another embodiment of the GLS is shown in FIG. 8. Flow is directed into the GLS via the inlet port 805. As the fluid travels through the dripper 810, it exits through the mouth of the dripper 815. The incompressible fluid collects on the inner wall 820 and falls under the action of gravity towards the collecting basin 825 and finally flows through the outlet 830. Meanwhile, the compressible fluid escapes through the gas vent 835.

(30) The GLS can be located anywhere downstream of the BPR and, most effectively, upstream of the fraction collectors. In one embodiment shown in FIG. 1, the GLS is located after the heat exchanger. In another embodiment, a plurality of gas-liquid separators may be located after the junction point 141.

(31) FIG. 9 shows a schematic embodiment of the open bed atmospheric collection system. It shows the collector arm adapter working in combination with the rack adapter to deliver the sample to the container. Fluid flows in through the GLS 905 (i.e. the GLS 140 in FIG. 1). After a portion of the sample is collected by the primary fraction collector 910, i.e. the Waters 2767 fraction collector 160 from FIG. 1, a portion of the sample passes through the collector arm adapter 920, i.e. part 305 shown in FIG. 3A. Any remaining traces of aerosols are collected by the rack adapter 930, i.e. part 220 in FIG. 2, part 405 in FIG. 4, and part 505 in FIG. 5. The fractions then pass into the container 940.

(32) The technology described above can adapt to XY type fraction collectors with no Z-movement (e.g., movement in a vertical direction) arm for preparative SFC use. The technology can modify existing XY type fraction collectors with no Z-movement so that the collector meets the requirements of both technical and safety usage in SFC systems. Safety concerns can arise when aerosols are generated outside of the SFC system. Additionally, by reducing the presence of aerosols, the technology significantly reduces sample loss and cross contamination when collecting fractions.

(33) This technology significantly improves and expands the scope of SFC technology for use in a variety of settings, including the chemical industry and academic research laboratories. By eliminating technical concerns such as cross contamination, sample loss, and unsafe venting of compressed fluids, the technology makes SFC a more robust and reliable process. Additionally, the technology makes SFC a more convenient process because it allows the use of standard, open bed atmospheric XY type fraction collectors already in use with other types of chromatography and familiar to one of ordinary skill in the art.

(34) The technology can be used in any process where there is a danger of unwanted aerosols being generated. The flow conditions of the system can be optimized to diminish aerosols generated from depressurization of pressurized fluids to ensure collection efficiency and safety operation under atmospheric conditions.

(35) Although various aspects of the disclosed apparatus and method have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications.