Abstract:
A heated rotary valve for use in connection with a sample to be separated in a column for heating the sample to temperature within the valve. The heated rotary valve permits introduction of compounds, having a wide boiling range, into a gas chromatograph with improved precision of area and retention time. The valve includes a stator, an elongate body, a rotor seal, a drive shaft, and an internal element for generating heat. The rotor seal may be laterally captured by a ring to prevent movement or creep due to heat absorption during operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND 
     1. Field 
     The present disclosure pertains to valves and systems for use in chromatography. More particularly, the present disclosure pertains to a heated rotary valve for use in connection with a sample to be separated in a column for heating the sample to temperature within the ports of the valve. The heated rotary valve permits introduction of a wide boiling range compounds into a gas chromatograph with improved precision of area and retention time. 
     2. Description of the Related Art 
     Gas chromatography (GC) is generally performed on a sample using a column positioned within and heated by an oven or other heating device, wherein the sample is heated before introduction to the column. The separated sample is then introduced to a detector for identification of compounds. Chromotagraphy ovens may be operated at elevated temperatures in the range of 40′ C to 400′ C. Because the column is typically a coil of thin tube, such as of metal or fused silica, with an internal polymer coating, the column rapidly reaches the ambient temperature within the oven or applied by an external heating element, which permits movement of the sample through the column. Problematically, the sample needs to be heated to the elevated temperature of the column. This is sometimes accomplished using a heated injection port where the sample size is sufficiently small, such that the injection can be accomplished using a syringe which peirces a septum—a thick, rubber disk. Heated injection ports are sufficiently hot that the sample boils and is carried into the column as a gas by helium or another carrier. 
     Historically, liquid injection for gas chromatography has included liquid injection by a syringe, whether split on column, but which, while simple, suffered from issues of septum lifetime and an automation system more complex that associated with a valve. The historic alternative was injection by valve, whether a one zone system such as standard liquid sample valves) or two zone injection systems, in which a sampe is moved from a cool zone, such as a sample supply, to a hot zone, such as the column. While more easily controlled and repeatable, these valve systems suffered the difficulty of ensuring the sample was at the temperature of the hot zone when reached. 
     Additionally, because of the large internal volumes of the valves known in the art, not only was heating unfeasible, but recycling of samples through columns repeatedly for high separation was largely only theoretical as those valves, typically using releatively large fitting adapters ( 1/16 inch or 1/32 inch, for example) introduced peak broadening in each switch, as those fittings were incompatible with small bore columns. Alternatives have included use of Dean&#39;s switching and other pressure differential methods using external solenoid valves to control the carrier gas direction. None have been highly effective for column switching. 
     It would be desirable to incorporate a sample which may be introduced according to a mechanically controlled system and which would be at temperature for processing through the chromatography system, but otherwise would not transfer heat or suffer from heat soak. 
     Additionally, in chromatography systems, it is typical that the sample may be flowed through a valve during times when no analysis is desired or ongoing. Providing a valve at an elevated temperature during those off-analyzing periods in contact with a flowing sample could be detrimental to the sample, as it could result is repeated vaporization of the sample prior to analysis. 
     It would therefore be desirable to provide a valve for communication with a sample source, where the valve would permit sample to flow to the column while simultaneously heating the sample to temperature for during the analysis period, but which would otherwise not introduce heat into the surrounding system or to the sample. 
     It would therefore be desirable to provide a valve having an internal volume of only a few nanoliters which could be used for column switching at an elevated temperature without undesirable cooling or unnecessary additional heating equipment. 
     SUMMARY 
     The present disclosure therefore meets the above needs and overcomes one or more deficiencies in the prior art by providing a heated rotary valve for use in connection with one or more heated columns so that a sample, heated to, or maintained at, temperature in the valve may then be separated in a column heated to the same temperature. 
     The present disclosure provides a heated rotary valve which includes a stator, an elongate body, a rotor seal, a drive shaft and an element for generating heat. The stator has a stator first surface and a stator second surface, where the stator first surface has a plurality of stator connectors while the stator second surface includes a flat plate. The stator has a plurality of stator ports, each extending from a connector to the flat plate of the stator second surface. 
     The elongate body has an internal bore from a body first end to a body second end in which a drive shaft is positioned so as to free rotate. The stator is affixed at its second surface to the body at the body first end, so as to form an integral unit in which the rotor seal may be rotated. The rotor seal is a polymeric disk that makes a high pressure seal against the stator and therefore has a rotor seal first surface which is positioned adjacent the stator second surface. The rotor seal has at least one channel in its first surface to connect two stator ports when desired. The drive shaft, which extends beyond the second end of the body, is affixed to the rotor seal so that an actuator may switch the valve to connect particular parts when desired. The element for generating heat is affixed to the body in or at the body first end proximate the rotor seal&#39;s first surface and the stator&#39;s second surface, or in the stator head so that heat is transmitted to stator ports by the body, and/or the stator, which are composed of a material to transmit heat from said element for generating heat to said stator ports. 
     In an alternative embodiment, the valve is part of a rotary valve system which further incorporates a controller which is adapted to receive a start instruction and to activate the element for generating heat upon receipt of that start instruction. 
     In a further embodiment, the rotary valve system may be incorporated into a chromatography system wherein the controller is further adapted to receive an oven temperature from a temperature sensor in the oven so that the valve may be heated by the element for generating heat to the oven temperature, together with a chromatography column, a sample supply, an oven, and a temperature sensor. In the chromotography system, the valve is in communication with the chromatography column at a column inlet and with a sample supply at a supply outlet. The column, the sample supply and the temperature sensor are positioned within the oven, while the valve is positioned through the oven wall, so that the rear of the oven-side body section contact the oven wall while the oven-external body section is positioned external the oven. 
     Additional aspects, advantages, and embodiments of the disclosure will become apparent to those skilled in the art from the following description of the various embodiments and related drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the described features, advantages, and objects of the disclosure, as well as others which will become apparent are attained and can be understood in detail; more particular description of the disclosure briefly summarized above may be had by referring to the embodiments thereof that are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate only typical preferred embodiments of the disclosure and are therefore not to be considered limiting of its scope as the disclosure may admit to other equally effective embodiments. 
       In the drawings: 
         FIG. 1  is an illustration of one embodiment of the valve of the present disclosure as assembled. 
         FIG. 2  is an illustration of a cross-sectional view of the embodiment  FIG. 1  along line B-B of the valve of the present disclosure as assembled. 
         FIG. 3  is an illustration of an isometric view of the embodiment of the valve of the present disclosure. 
         FIG. 4  is an illustration of the outer surface of the stator of the valve of the present disclosure. 
         FIG. 5  is an illustration of the face of the rotor seal of the valve of the present disclosure. 
         FIG. 6  is an exploded view of an alternative embodiment of the present disclosure. 
         FIG. 7  is an illustration of a further embodiment of the present disclosure illustrating a heated rotary valve system and a chromatography system in an oven. 
         FIG. 8  is an illustration of a further embodiment of the present disclosure illustrating a heated rotary valve system and a heated column system. 
         FIG. 9  is an illustration of two column recycling using the valve of the present disclosure. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-7 , a heated rotary valve  100  is provided for use in connection with a sample to be separated in a column  704 , heated by an oven  712  or other heating systems, for heating the sample within the ports of the valve to the temperature of the column during periods of analysis, but not otherwise heating the sample. The valve  100  may be placed so that the first surface  104  and stator connectors  108  of the stator  102  are exposed in a chromatography oven  712  in communication with a sample source  708 , so that a sample to be introduced to the column  704  is heated within the valve  100  body first end  100  to the temperature of the associated chromatography column  704 , but which otherwise does not introduce excess heat into the surroundings of the valve  100 . Referring to  FIG. 8 , the heated rotary valve  100  may be positioned adjacent a column  804  which is heated by direct or indirect heat transfer, such as by a heating element bound to the column  804 . The valve  100  includes a stator  102 , an elongate body  112 , a rotor seal  230 , a drive shaft  134 , all of which may be composed of stainless steel, and a element for generating heat  236 , internal or external to the body  112  of the valve  100 . 
     Referring to  FIG. 7 , the stator  102  is made integral to the elongate body  112  and provides the point of connection for the valve  100  to the sample supply  708  and the column  704 . Referring to  FIGS. 1-6 , the stator  102  has a stator first surface  104  and a stator second surface  106 . The stator first surface  104  has a plurality of stator connectors  108  which provide the point of communication with the sample supply  708  and the column  704 . The stator second surface  106  includes a flat plate  502  which provides a portion of the flow path for the sample in operation of the valve  100 . The stator  102  has a plurality of stator ports  210 , each extending from a connector  108  to the flat plate  502  of the stator second surface  106 . Preferably each stator port  210  is constructed for use with 360 micrometer fittings, which reduces the volume of sample in the stator  102 , and therefore further increases the heat transfer rate from the stator  102 . 
     Referring to  FIGS. 1-7 , the elongate body  112  has sections intended to permit heat transfer to the stator, but not to the second end  118  wherein the drive shaft  134  is connected to an actuator  718 , which permits control of the valve  100  and control over the flowpaths used. Referring to  FIGS. 2 and 6 , the body  112  has an internal bore  214  which extends from the body first end  116  to the body second end  118 . The drive shaft  134  is positioned within the internal bore  214  of the elongate body  112  so as to freely rotate when activated by the actuator  718 . Heating is desirable only in the body first end  116 . 
     Referring to  FIGS. 1-6 , the stator  102  is therefore affixed at the stator second surface  106  to the body  112  at the body first end  116 . As it is desirable that the stator  102  heat rapidly, while it is desirable the body  112  not retain any conducted heat, the body  112  is sized to be smaller in diameter than the stator  102  such that heat will not readily be conducted toward the body second end  118  and any conducted heat will be readily shed. The elongate body  112  may therefore have a body diameter  140  which is less than seventy-five percent (75%) of the stator diameter  504  of the stator  102 . 
     Referring to  FIGS. 2 and 6 , the rotor seal  230  completes the flow path through the valve  100  depending on its position. The rotor seal  230  has a rotor seal first surface  232 , which when the valve  100  is assembled, is adjacent the stator second surface  106 . The rotor seal  230  has at least one channel  606  on or in the rotor seal first surface  232  which provides, when positioned, the connection of two of the stator ports  210 . Referring to  FIG. 7 , the rotor seal  230  may be positioned to permit flow of a sample from the sample supply  708  through the valve  100  and to the column  704 , or may be positioned to preclude such flow, may be positioned to cause the sample to enter a loop, or may be positioned for other desired flowpaths. Referring to  FIG. 6 , the rotor seal  230  is maintained in contact with the stator second surface  106  by driving the drive shaft  134  forward, such as by use of a spring  608  and end cap  610  in conjunction with the body  112 . 
     As the heat into the valve  100  from the element for generating heat  236  may also be conducted to the rotor seal  230 , a rotor ring  634  may be provided about the rotor seal  230  to contain the rotor seal  230  and prevent movement, such as creep, during heating. This is particularly true for seals provided of polymeric material, which may become more pliable, and more likely to move, when heated. 
     Referring to  FIGS. 2 and 6 , the drive shaft  134  is affixed to, or may be formed integral with the rotor seal  230 . Referring to  FIGS. 1-7 , the drive shaft  134  extends from the rotor seal  230  to beyond the body second end  118  so that an actuator  718  may be affixed thereto which may control the position of the rotor seal  230  and therefore the flowpath through the valve  100 . 
     Referring to  FIGS. 2 and 6 , the valve  100  includes an element for generating heat  236  which may be affixed, internally or externally, to the body  112  at the body first end  116  proximate the rotor seal first surface  232  and the stator second surface  206  or may be affixed, internally or externally, to the stator  102 . Referring to  FIG. 6 , the element for generating heat  236  may be positioned in an external groove  602  about a body first end side surface  604 . The element for generating heat  236  may be any of several heating elements known in the art, whether chemically or electrical, but whose temperature is controllable externally. Thus, in one embodiment, the element for generating heat  236  is an electrically-driven heating element with leads  250 ,  252  for connection to provide electrical energy to the element for generating heat  236 , which becomes hotter due to application of electricity and which may be temperature controlled, such as by measurement of power, current, voltage and/or resistance, or which may include a thermocouple, thermistor, resistance temperature detector (RTD), or other temperature detecting device. The element for generating heat  236  may be connected to a power supply for provision of electrical energy, which may be incorporated into a controller or which may be external to the controller. 
     The small sizes of the components associated with chromatography ensure low mass and therefore high heat transfer rates. Maintaining the size only as necessary to permit operation minimizes mass. In particular, the stator connectors  108  and associated stator ports  210  and the rotor seal channels  606  are sized for 360 micrometer fittings. The resulting low mass may be heated directly, even by an air bath oven. As a result, the internal volume of the valve  100  is also ultra low, which speeds the heat transfer to the sample while the sample passes through the stator  102 . As a result, the valve  100  may have a high maximum operating temperature, such as around 400 degrees Celcius and, because the small rotary distances, may provide fast switching between positions, such as around 125, or 250, milliseconds. Moreover, the low mass of the valve  100  provides for heating at 200 degress Celcius per minute and also provides for rapid cooling. As result, there is minimum sample vaporization during injection and low carry over. Additionally, this may provide for a sample size of a few nanoliters, up to 40 nanoliters, and beyond. 
     The relative small size and mass, and associated rapid heating and switching, of the valve  100  provide an improved choice for liquid injection in gas chromatography. The ease of operation of the valve  100  eliminates the issue associated with syringe injection while providing an improve valve injection. 
     When activated, such as a by a start signal in connection with sample introduction to a column  704 ,  804 , the element for generating heat  236  provides heat to the valve  100 , whether the stator  102 , the drive shaft  134 , or the body  112 , which is composed of a material to transmit heat from the element for generating heat  236 , to the stator ports  210 , such as metal, such as stainless steel. Thus, the element for generating heat  236  is used to indirectly heat the stator ports  210 , though other components are directly heated to provide the heat transfer to the stator ports  210 , and therefore to the sample flowing through the stator port  210 , which are sufficient small to ensure rapid heat transfer to the sample. In operation, the element for generating heat  236  is activated when needed to heat a sample, which quickly vaporizes the sample at the temperature of the column  704 . When not needed, particularly when no analysis is on-going, the element for generating heat  236  is deactivated and the valve  100  begins to cool, to the ambient temperature of the oven  712  in the case of the body first end  116 . 
     Referring to  FIGS. 1-3 , to reduce the heat soak through the body  112 , the body  112  may include a plurality of lateral vents  138  radially through the body  112  from the internal bore  214  distant the stator  102 . 
     Referring to  FIG. 7 , the valve  100  may be integrated into a heated rotary valve system together with a controller  702 . The controller  702  may adapted to receive a start instruction, such as when analysis using the column  704  is to be permited, to simultaneously activate the element for generating heat  236  and to cause the valve actuator  718  to position the valve  100  to permit the flow to the column  704 . 
     Referring to  FIG. 7 , the heated valve system may be coupled with an improved controller  702 , a chromatography column  704 , which may be connected to a detector, a sample supply  708 , and oven  712 , and a temperature sensor  716  to provide a chromotagraphy system. In the chromotagraphy system, the controller  702  may further be adapted to receive an oven temperature from a temperature sensor  716  in the oven  712 . The chromography column  704 , also positioned in the oven  712 , such as by suspension lines  720 , is attached for communication with the valve  100  at a column inlet  706  while the sample supply  708 , which may also be in the oven  712 , is attached for communication with the valve  100  at a supply outlet  710 . The valve  100  may be positioned through the oven wall  714 , so that only the stator first surface  104  and stator connectors  108  are exposed to the interior  722  of the oven  712 , while the body second end  118  and the end of the driveshaft  134  are sufficient external the oven wall  714  to permit connection with the valve actuator  718 . 
     Referring to  FIG. 8 , the heated valve  100  may be coupled with an improved controller  802 , a chromatography column  804 , which may be connected to a detector, and a sample supply  808  to provide an alternative chromotagraphy system. In the alternative chromotagraphy system, the controller  802  may further be adapted to control the temperature of a column  804  which may be heated by direct contact, or indirect contact, with a heating element. The chromography column  804  is attached for communication with the valve  100  at a column inlet  806  while the sample supply  808  is attached for communication with the valve  100  at a supply outlet  810 . Thus, the valve  100  and column  804  may be adapted for a portable chromatography system. 
     The construction of the valve  100  permits rapid column switching which may be useful in complex separations or in two-dimensional gas chromatography separations. 
     Moreover, the valve  100  permits two column recycling, such as illustrated in  FIG. 9  to achieve improved separation of compounds in a gas chromatography system. The ultra low internal volume and the rapid heating of the stator ports  210  to permit cycling of sample constituents, from a sample supply  908 , back and forth through a first column  902  and a second column  904  multiple times, producing extremely high plate numbers and resulting in improbable separations, not possible with microfluidics or Dean&#39;s switching. Additionally, any peak broadening may be reduced, and peak capacity increased, by using negative temperature programming on the downstream column  904  connected to the detector  906 . 
     Additionally, with its low mass, ultra-low internal volume, fast switching and high temperature limit, the valve  100  may be utilized as a comprehensive two-dimensional gas chromatography (GCxGC) modulator. As can be appreciated, the valve  100  provides better performance than a diaphragm valve, has faster switching time and longer secondary duration time that a microfluidic device, and allows use of a lower secondary flow rate and use of a microbore secondary column. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof.