PREPARATIVE CHROMATOGRAPHY COLUMN

Abstract: The invention is directed to a new and improved chromatographic column. The column comprises a housing having an inlet end, an outlet end, and an interior, a plurality of uniform fluid passageways within said housing interior extending axially between said inlet and outlet ends, said passageways being coated with a stationary phase material, and means for laterally interconnecting said passageways to permit fluid and/or diffusion communication between adjacent passageways along said passageways.

Description: This invention relates to chromatography and more particularly to a chromatographic column and a method of assembling a chromatographic column according to the preamble of claim 1 and 29 having particular utility in preparative gas chromatography. Previously, there have been essentially two formats of gas chromatographic columns. The more efficient format is that of an open tubular column with the walls coated with the stationary or fixed phase material. This format, sometimes referred to as a Golay or capillary column, is used for chemical analysis in which small samples are sufficient. When the output of a capillary column is not sufficient for the desired analysis or when larger outputs are required for further chemical processes as in preparative scale chromatography, the preferred format has been that of a tube packed with porous particles or granules impregnated or coated with the fixed phase material. This format, generally referred to as a packed column, has the advantage of relatively large throughput, but is slower and less efficient. Typically, with equal pressures being applied at the inlet of the columns, a separation requiring one minute with a capillary column will require several hours with a packed column. The poor efficiency of the packed column is explainable by certain nonuniformity characteristics of this format. Firstly, there is the circumstance that any one rivulet of gas snaking its way among the packing granules alternately encounters very narrow passages between three contacting granules which offer high resistance to flow and large passages which require relatively long times for the sample molecules to diffuse to and from the fixed phase which is coated on the walls of these larger passages. In contrast, the single passage of a capillary column is of uniform dimension and this single dimension determines both the resistance to flow and the diffusion time to and from the wall. Secondly, there is the circumstance that the various rivulets of gas which may have a column origin and which meet again further along the column may have required appreciably different times for their separate travels. These travel time differences cause an unwanted spread of the various separated components in space along the column and eventually in time at the column exit and consequently the components may merge into each other instead of being clearly separated. Thus, there are some undesirable attributes of lengthwise and crosswise nonuniformity of the column. From time to time there have been suggestions to provide a column of higher throughput and high time-wise efficiency by manifolding a number of like capillary working in parallel as a single column. However, this suggestion has not been successful. Firstly, such a column would be cost prohibitive, e.g., the cost of one hundred capillary columns would be prohibitive. Secondly, the task of trimming such a large number of columns so that they would have the same time of passage for all the components of a given sample would be practically hopeless. Accordingly, it is an object of the present invention to provide a chromatographic column having high efficiency and relatively large throughput suitable for preparative scale chromatography. Said object is achieved in accordance with the invention by a chromatographic column and a method of assembling a chromatographic column as stated in the characterising part of claim 1 and claim 29. Such a chromatographic column provides multiple uniform passageways with crosswise communication for attaining uniform frontal distribution of separated components. Those passageways have a high degree of lengthwise and crosswise uniformity. Furthermore such a chromatographic column can be economically manufactured and is very efficient in operation. Especially the new and improved technique for forming a chromatographic column in accordance with the invention is economical and efficient. Within said chromatographic column a plurality of uniform fluid passageways are provided extending actually within the housing between its inlet and outlet ends. The passageways are coated with a stationary phase material and lateral openings disposed longitudinally along the passageways laterally interconnect adjacent passageways to permit fluid communication and/or molecular diffusion therebetween. Brief Description of the Drawings Figure 1 is a partly broken away perspective view of a chromatographic column according to the present invention. Figure 1A illustrates an end view of a fiber of a layer with the stationary phase material coated thereon. Figure 2 is a cross-sectional view of an alternate fiber element. Figure 3 is a cross-sectional view of another alternate fiber element. Figure 4 is a schematic diagram of a gas chromatography system including the column of the present invention. Referring to Figure 1, the chromatography column of the present invention is designated by the numeral 10 and generally comprises an elongated column housing 11, an elongated central core element 12, a configuration of fibers, generally designated by the numeral 14, disposed about the core element 12 so as to form a plurality of fluid passageways through the housing 11, and a coating 13 of stationary phase material on the passageways. The core element 12 is a cylindrical fiber extending coaxially within the cylindrical housing 10 between the inlet end 16 and outlet end 17 of the housing. The fiber configuration 14 comprises a plurality of annular, concentric, wound fiber layers 18, 20, 22, 24 extending between the core fiber 12 and the inner wall 26 of the cylindrical housing 11. The innermost fiber layer 18 is formed by a plurality of uniformly spaced cylindrical fibers 28 helically wound about the core fiber 12. The spaces 30 between the fibers 28 form uniform parallel fluid passageways being bound on the inner side by the core element 12 and on the opposing outer side by the adjacent fiber layer 20. The fiber layer 20 is similarly formed by a plurality of uniformly spaced cylindrical fibers 32 helically wound about the innermost layer 18 in reverse hand relative to the fibers 28 of layer 18. The spaces 34 between adjacent fibers 32 form parallel uniform passageways bound on the inner side by the next innermost adjoining layer 18 and bound on the outer side by the next outermost adjoining layer 22. In the illustrated embodiment, the helically wound fibers 28 of the innermost layer 18 are right hand wound so that the passageways 30 follow identical right hand helical paths about the core fiber 12 between the inlet end 16 and the outlet end 17 of the housing 11. Conversely, the passageways 34 formed by the left hand helically wound fibers 32 follow a left hand helical path about the inner layer 18 between the inlet and outlet ends of the housing 11. Consequently, the left hand oriented passageways 34 cross over the right hand oriented passageways 30 so that common uniform lateral openings are formed between the passageways 30, 34 where the passageways 34 adjoin the passageways 30 to thereby fluidly interconnect the overlapping fluid passageways at a plurality of locations longitudinally along the passageways. Similarly, the fibers 38 of layer 22 are uniformly spaced and helically wound in right hand orientation about the layer 20. The spaces 40 between the fibers 38 form uniform fluid passageways being bound on one side by the next inwardly adjacent fiber layer 20 and being bound on the opposite side by the next outwardly adjacent fiber layer 24. The passageways 40 follow a right hand oriented helical path about the layer 20 and therefore crossover the left hand helical passageways 34 of layer 20. Common uniform lateral openings 42 are formed between the passageways 40, 34 where the passageways 40 adjoin the passageways 34 to thereby fluidly interconnect the overlapping passageways longitudinally along the passageways between the inlet and outlet ends of the housing. The outermost fiber layer 24 is similarly formed by a plurality of uniformly spaced cylindrical fibers 44 helically wound in left hand orientation about the fiber layer 22. The spaces 46 between the fibers 44 form passageways bounded on the outer side by the inner wall 26 of housing 10 and on the inner side by the fiber layer 22. The housing 11 is in close fitting disposition about the annular layer 24. The left hand helical passageways 46 of layer 24 cross over the right hand helical passageways 40 of layer 22 so that common uniform lateral openings 48 are formed between the passageways 46, 40 where the passageways 46 adjoin the passageways 40 to thereby fluidly and/or diffusively interconnect the overlapping fluid passageways at a plurality of locations longitudinally along the passageways. Overall, the uniform lateral openings disposed longitudinally along the column 10 provide for cross-communication or cross-diffusion of carrier gas and sample for equilibrium between the passageways for the entire column. The fibers 28, 32, 38, 44 are of equal diametrical size being typically 0,020 cm (0.008 inch) diameter titanium wire. The core fiber 12 has a diametrical size typically 5 times the size of the other fibers, being thus approximately 0,1 cm (0.04 inch) diameter titanium wire. Alternately, a core element of another dimension may be used, such as a fiber similar to those used in the fiber layers. In the typical configuration shown, the innermost layer 18 has 9 fibers and each radially outwardly successive fiber layer increases by three fibers, i.e., fiber layer 20 has 12 fibers, fiber layer 22 has 15 fibers, and fiber layer 24 has 18 fibers. As can be appreciated, the number of uniform passageways formed by each fiber layer is equal to the number of fibers in the respective layer. The fibers 32, 38 of the intermediate layers 20, 22 are equi-spaced by approximately their diametrical size, i.e., 0,02 cm (0.008 inches). The climbing angles of the helically wound fibers of the intermediate layers 20, 22 are equal being approximately 20°. Since the fluid velocity through the passageways 46 of the outermost layer 24 is slowed by the influence of the adjacent inner wall 26 of housing 11, the climbing angle of this outermost layer is steeper so that the distance between the adjacent fibers 44 is greater than the diameter of the fibers; also, the path lengths along this outer layer will also be shorter than the neighboring inner layer, all for the purpose of attaining uniform frontal distribution of the sample elements. A similar compensation is likewise required for the innermost layer 18 because of the influence of the adjoining core fiber 12, i.e., a steeper climbing angle. In the illustrated embodiment, the climbing angles of the fibers 28 and 44 are 10°. Although only two intermediate fiber layers 20, 22 have been shown in the illustrated embodiment, it is understood that any suitable plurality of such intermediate layers may be utilized depending upon the output desired with the fibers of each successive fiber layer being helically wound in reverse hand relative to the next adjacent layer and with the intermediate layers having equal climbing angles. The cylindrical housing 11 closely envelopes the outermost fiber layer and withstands the input pressure of the conventional chromatographic process. A suitable housing can be formed of TEFLON and heat shrunk by conventional methods to frictionally retain the fibers in the wound fiber configuration. The passageways 30, 34, 40, 46 formed by the respective fibers 28, 32, 38, 44 are coated with a conventional stationary phase material such as CARBOWAX. For purposes of explanation, only a portion of the fibers 44 of layer 24 are illustrated with the coating 13 thereon. Such coating is accomplished by coating the fibers prior to assembly or, alternately, after assembly. Titanium wire is the preferred material for the fiber elements although other metal wires such as aluminum provide acceptable results. Alternately, the fibers may be made of glass or glass-like substances such as fused silica. Alternate fiber forms may be utilized for the wound fiber layers. A square fiber 50, such as shown in cross-section in Figure 2, may be utilized as well as a fiber 52 being quadrilateral in cross-section with a pair of opposed incurvated sides as shown in Figure 3. The intended advantage of the quadrilateral configuration is to avoid narrow corners that would constitute a stream holdup. In operation, the column 10 of the present invention is utilized in a conventional system which is schematically illustrated in Figure 4 and need not be described in great detail. As shown in Figure 4, the inlet end 16 of the column is connected to the sample introduction system 54. A source of carrier gas 56 is interconnected to the sample introduction system 54 by a flow control regulator 58. A conventional detector 60 is connected to the outlet end 17 of the column 10. The method of forming or assembling the column of the present invention includes maintaining the core element in a linear disposition and helically winding a plurality of wire elements about the core element in uniform predetermined spaced disposition at a predetermined climbing angle as previously explained. A second layer is formed by helically winding a plurality of fiber elements in opposite hand about the first layer in predetermined spaced disposition and at a predetermined climbing angle as previously explained. Successive fiber layers are similarly formed each being wound in reverse hand relative to the previous adjacent layer. When the desired number of layers have been appropriately wound, the column housing is mounted about the fiber configuration. The housing is formed of TEFLON and heat shrunk by conventional methods to frictionally retain the fiber configuration. The passageways formed by the fiber layers are coated with a stationary phase material by coating the fiber elements defining the passageways. The fiber elements are coated prior to winding or, alternately, after winding. As can be seen, a chromatographic column is provided which achieves a high degree of lengthwise and crosswise uniformity as well as crosswise diffusion for attaining uniform frontal distribution of all components of a sample. The column has high efficiency and relatively large throughput suitable for preparative scale chromatography and is economical to manufacture and efficient in operation.

Claims: A chromatographic column (10) comprising an elongated column housing (11) having first and second end portions (16, 17), characterized by an elongated central core element (12) within said housing (11) extending between said first and second end portions (16, 17), a configuration of fiber layers (18, 20, 22, 24) disposed about said central element (12) forming a plurality of fluid passageways (30, 34, 40, 46) extending between said first and second end portions, said configuration comprising, an innermost layer (18) having a plurality of fibers (28) helically wound about said central element (12) with the fibers being in predetermined spaced disposition for forming a fluid passageway (30) between adjacent fibers extending between said first and second end portions, and a plurality of outwardly successive layers (20, 22, 24) of fibers disposed about said innermost layer (18) with an outermost layer (24) being disposed adjacent said housing (11), each said successive layer having a plurality of fibers helically wound in reverse hand relative to the next adjacent layer and in predetermined spaced disposition for forming a fluid passageway between adjacent fibers extending between said first and second end portions with a plurality of lateral openings fluidly interconnecting overlapping fluid passageways longitudinally along said passageways, and a coating (13) of stationary phase material on said passageways. The device of Claim 1 wherein said fibers forming said plurality of fluid passageways are coated with a stationary phase material. The device of Claim 1 wherein said wound fibers of said successive layers have equal climbing angles. The device of Claim 1 wherein said wound fibers (44) of said outermost layer (24) have a first predetermined climbing angle and said wound fibers (32, 38) of said successive layers (20, 22) between said innermost and outermost layers (12, 24) have a second predetermined climbing angle, said first climbing angle being steeper than said second climbing angle. The device of Claim 4 wherein said wound fibers (28) of said innermost layer (18) have a third predetermined climbing angle being steeper than said second climbing angle. The device of Claim 1 wherein said wound fibers (28) of said innermost layer (18) have a first predetermined climbing angle and said wound fibers of said successive layers (20, 22) between said innermost and outermost layers (18, 24) have a second predetermined climbing angle, said first climbing angle being steeper than said second climbing angle. The device of Claim 1 wherein said wound fibers of said successive layers are equi-spaced. The device of Claim 1 wherein said fibers of each said successive layer are equi-spaced a predetermined amount and said fibers are of equal diametrical size, said diametrical size being said predetermined amount. The device of Claim 1 wherein said wound fibers (44) of said outermost layer (24) are spaced a first predetermined distance and said wound fibers of said successive layers (22, 20) between said innermost and outermost layers (24, 18) are spaced a second predetermined distance, said first distance being greater than said second distance. The device of Claim 9 wherein said wound fibers of said innermost layer (18) are spaced a third predetermined distance being greater than said second distance. The device of Claim 9 wherein said wound fibers of said outermost layer (24) have a first predetermined climbing angle and said wound fibers of said successive layers (20, 22) between said innermost and outermost layers (18, 24) have a second predetermined climbing angle, said first climbing angle being greater than said second climbing angle. The device of Claim 11 wherein said wound fibers of said innermost layer (18) have a third predetermined climbing angle being greater than said second climbing angle. The device of Claim 12 wherein said wound fibers of said innermost layer (18) are spaced a third predetermined distance being greater than said second distance. The device of Claim 1 wherein said wound fibers of said innermost layer (18) are spaced a first predetermined distance and said wound fibers of said successive layers (20, 22) between said innermost and outermost layers (18, 24) are spaced a second predetermined distance, said first distance being greater than said second distance. The device of Claim 1 wherein said innermost layer (18) has a first predetermined number of wound fibers (28) and the next outwardly adjacent layer (20) of fibers (32) has a second predetermined number of wound fibers, said second number of fibers being greater than said first number. The device of Claim 15 wherein each outwardly successive adjacent layer of fibers has a predetermined number of fibers greater than the next inwardly adjacent layer of fibers. The device of Claim 16 wherein the number of fibers of outwardly successive adjacent layers of fibers increases in multiples of three. The device of Claim 1 wherein said central element (12) comprises a fiber. The device of Claim 18 wherein the diametrical size of said central element (12) is greater than said diametrical size of said fibers (28, 32, 38, 44) forming said configuration of fiber layers (18, 20, 22, 24). The device of Claim 1 wherein said fibers have a circular cross section. The device of Claim 1 wherein said fibers have a rectangular cross section. The device of Claim 1 wherein said fibers in cross section are quadralateral with a pair of opposed incurvated sides. The device of Claim 1 wherein said fibers are glass. The device of Claim 1 wherein said fibers are metal. The device of Claim 1 wherein said fibers are titanium. The device of Claim 1 wherein said fibers are aluminum. The device of Claim 1 wherein said housing (11) is an imperforate envelope in close-fitting disposition to the outermost layer (24). The device of Claim 1 wherein said housing (11) is an elongated cylindrical tube. A method of assembling a chromatography column, characterized by providing a cylindrical core element, winding an innermost layer of uniformly spaced fibers helically about the core element, winding a plurality of concentric annular layers of uniformly spaced fibers about the innermost layer so that the fibers of each layer are helically wound about the next inwardly adjacent layer in reverse hand orientation relative to the next inwardly adjacent layer, enveloping the outermost layer of fibers in a column housing, and coating the fibers with stationary phase material. The method of Claim 29 wherein the fibers are coated with a stationary phase material after the step of winding a plurality of concentric annular layers. The method of Claim 29 wherein the fibers are coated with a stationary phase material prior to winding the fibers into said layers. The method of Claim 29 wherein the windings of fibers form a fiber configuration and the step of enveloping the outermost layer of fibers comprises mounting the fiber configuration in a close-fitting housing to frictionally retain the fiber configuration.

Inventors: GOLAY, MARCEL
Applicants: THE PERKIN-ELMER CORPORATION
Application year: 1988
Main classification: B01D15
IPC codes: B01D15, G01N30