US 3808125 A
Description (OCR text may contain errors)
April 30, R. J Go OD CHROMATO'GRAPHIC APPARATUS 2 Sheets-Sheet 1 .Filed Aug. 25, 1972 F/GZ FIG. 4
A ril 30, 1974 R .,.OOD 3,808,125
CHROMATOGRAPHIC APPARATUS Filed Aug. 25, 1972 I 2 Sheets-Sheet 2 HEXANE HEPTANE PENTANE TIME n-HEPTANE n-HEXANE N n-PENTANE fi-QCTANE FIG. 5
United States Patent 3,808,125 CHROMATOGRAPHIC APPARATUS Robert J. Good, Grand Island, N.Y., assignor to Phillips Petroleum Company Filed Aug. 25, 1972, Ser. No. 283,776 Int. Cl. B0111 15/08 US. Cl. 210-31 C 13 Claims ABSTRACT OF THE DISCLOSURE A chromatographic column for the separation of components of a mixture comprising a hollow member; a means for introducing a mixture into and withdrawing components from said member; means for detecting components issuing from said member; said column :being provided with a partitioning agent comprising a polymeric material bonded to an interior surface of said member either directly or through an intermediate film or coupling agent. A partition agent-forming polymerizing monomer is deposited within the interior of the hollow member and fl ice has been coated with a thin film of partitioning liquid 'for which the liquid or gaseous constituents of the sample have anaffinity.
The separation columns generallyused in chromatw graphic analysis have been either a packed column or a capillary column, depending upon the particular sample being analyzed and the amount thereof. As the name suggests, packed columns contain packed into the column discrete particles which can function as a stationary phase per se by virtue of absorbing surfaces thereof or'as a support for a stationary phase comprising a thin film of partitioning liquid. Capillary columns are generally of a polymerized in situ. Comonomers may be employed, and
chain-stopping agents, an alkyl halide, can be used to regulate the chain length.
This invention relates to chromatographic analyzers. More particularly, the invention relates to novel separating columns used in chromatographic analyzers and to a method of preparing such columns. 7
Chromatographic analyzers are a widely used tool for the measurement and control of chemical processes. As a process control device, chromatographic columns are usually divided into two distinct units-an analyzer unit located quite near the process stream and a programmer unit that can be located where needed. The analyzer must obtain its own sample, analyze it, and process the detector information into some useful quantity. Depending on the intended use, this quantity is then delivered to either recorder, controller, or computer means..The instrument must continue to repeat the same cycle, sometimes as often as once each minute, for many uninterrupted months with the high degree of reliability.
Briefly, analysis of a sample by the chromatographic technique involves injecting a smallsample into an appropriate fluid carrier stream. The fluid carrier stream conveys the sample through a separation column which contains a material for which each of the respective components of the sample mixture has its own unique affinity or retention time. The difference in the afiinity or retention time of the respective components causes the individual components of the sample to stay within the column for different lengths of time before emerging. The aflinity of most liquid and gaseous compounds for various materials is well known and the order of emergence of the individual components of a sample mixture can be easily determined. As each component emerges from the column, it is passed through a detector device which measures a particular property of the respective component against a reference property of the carrier fluid. The output of the detector is representative of the amount of the particular component in the sample. A recording of the input of the detector for a particular sample generally results in "a multipeaked curve, wherein each peak may represent one component of the sample, and from which the quantity or percentage of each of the components can be ascertained by known procedures. a
The material causing the separation within thecolumn of the respective liquid or gaseous components of the sample is commonly called the stationary phase of the column. Separation is effected either because the stationary phase has absorbing surfaces or because the; surface smaller diameter than packed columns and are not packed with a particulate separation material. Rather, such columns have the inner surface thereof coated with a separating liquid phase, with the column wall functioning as the support for the separation or partitioning agent.
Generally, in both types of columns, the bonding forces between the partitioning agent and the support column, whether it be the column wall or discrete particles, has been due to physical adsorption. This physical bonding is relatively weak and can be overcome by thermal fluctuations in the system or by displacement by another chemical species. Further, because the effects of the bonding forcesare not easily controlled, a uniform and optimum thickness of the film is diflicult to obtain. If too much of the partitioning agent is used, the result may be an uneven film which adversely afiects column etliciency, or film in which the slow diffusion of the species that are to be separated causes a loss of separating speed and inefficiency. If too little partitioning agent is used, the result maybe that column capacity and efliciency are too low for effective separations. Most serious, the partitioning agent may migrate and the separating behavior of the column will then be unstable. i 'Itis' an'object of this invention to provide novel chromatographic columns. It is another object of this invention to provide chromatographic columns wherein the partitioning agent comprises a discrete polymeric film.'-It is another object of this invention to provide anovel ,apparatus' for making chromatographic separations. A still further object of this invention is to provide a me'thod for making capillary and packed chromatographic columns. These and other objects, aspects an'd 'advantages will be apparent from the disclosure and the accompanying drawings.
- elfectively' inhibits migration of the stationary phase and affords 'improved'separation of components by providing a continuous film, of partitioning agent oftcontrolled; .essentially'unifo 'm thickness.
, A particular feature of the present invention vision of a unique partitioning .agent. comprising apoly;
meric material which is at least-chemically bondedtQathc surfaces of the chromatographic column itself ;and also, to relatively inert support materials when such materials are used. The polymericmaterials canbe copolymerized among themselves. and with the column surfaces and .support ,materials in :an intimately intermixed order to provide a stable continuous film extending throughout; the column which is capable of attracting or having selective aflinitiesfor particular solid materials. y
Thus, according to this invention, there is provided in one embodiment a novel column having therein a partitioning agent formed from a low molecular weight compound having chemical groups or radicals which react with a selected support. In addition, one or more of the chemical groups are polymerizable functional groups, thereby permitting in situ polymerization of the partitioning agent. In another embodiment, the selected partitioning agent is at least chemically bonded to a selected coupling agent, which is in turn at least chemically bonded to a selected column support. In this embodiment, the elfective partitioning phase is a polymeric material formed in situ from a low molecular weight compound having two or more reactive groups or radicals'such that a chemical bond is formed to the coupling agent, without interference with the in situ polymerization. The partitioning agent may also be bound to the coupling agent by chain entanglement, the type of bonding which can normally be accomplished for polymers of unlike chemical composition only when one polymer is formed in situ from a solu tion of monomer in the other polymer. The coupling agent in this embodiment is selected which has at least one group or radical which will bond chemically to the selected support, and at least one group to which the partitioning phase will form a chemical bond; the coupling agent may also polymerize in situ, provided it does not lose the capability of chemically bonding to or chain entanglement with the partitioning phase. This invention is fully applicable to both liquid and gas chromatography.
The present invention provides chromatographic columns having several distinct advantages over prior art columns wherein the bonding between the partitioning agent and support is by physical means. For example, by controlling the extent of the in situ polymerization, the optimum eflective thickness of the partitioning agent film can be obtained. Also, because of increased strength afforded by the chemical bond, the stability of the column is greatly increased. Furthermore, since the bonding to the support is effected through chemical reaction, the probabilities of leaving exposed adsorption sites is reduced. In addition, migration of the stationary phase is inhibited.
The present invention provides a chromatographic column having a stable, uniform film of a polymeric stationary phase chemically bonded to the coumn and/or support material when used; as well as a method for preparing such columns by the in situ polymerization of the stationary phase. The polymeric stationary phase may be thermoplastic (i.e., a linear or branched polymer) or it may be crosslinked. If the latter, it shall be crossinked only to such an extent that the compounds that are to be separated have appreciable solubility in the polymer. The degree of crosslinking may be, in itself, a major contributor to the selectivity of absorption by the stationary phase.
The invention is particularly useful in capillary-type columns such as those disclosed in US. Pat. 2,920,478.
Such columns generally comprisea circular tube or hollow member of extended length having an internal diameter approaching capillary dimensions. The hollow member will generally have an internal diameter of from 0.001 to 0.003 inch and a length which can be on the order of 100 to 500 feet. The dimensions per se are not critical, although extreme lengths require that the column be coiled in order to fit into a temperature bath and the small diameter does require care in handling. In such capillary columns, the stationary phase can be directly bonded to the interior wall of the hollow member comprising the chromatographic separation column. Alternatively, the column can be first coated with a coupling agent which is capable of bonding chemically through valence bonds to the interior wall of the column. This finite film of coupling agent is overcoated with certain polymerizable monomers. The polymerizable monomer is polymerized in an t? a P y eric r ea? Wh te ms the p itio g agent and which is interlocked with the coupling agent by at least a chemical bond through valence bonds. The coupling agents, when used, can be monomeric or polymeric in nature.
Thus, the present invention provides chromatographic columns having, as the stationary phase or partitioning agent, a continuous discrete polymeric material of an essentially uniform finite thickness integrally bonded chemically through valence bonds to the interior wall or surface of the column and/ or other support material, when used. The invention further provides columns wherein the polymeric partitioning agent is bonded to the surfaces of the column or other support through a coupling material or agent, which itself may be either a monomeric or polymeric phase. 'In this latter embodiment, the coupling agent is directly bonded to the column wall or other support chemically through valence bonds and is bonded to the polymeric partitioning agent chemically through valence bonds, physically as by chain entanglement, or by a combination of physical and chemical bonding forces.
It is a feature of the present invention that the chromatographic column member per so be constructed of a rigid material having reactive groups on the surface exposed to the column interior, such as surface hydroxyl groups, and which is otherwise nonreactive with a polymeric partitioning agent and/or coupling agent. Suitable materials of construction for such columns which possess the requisite attributes include glass, quartz, steel and metals such as aluminum, iron, copper, tin, titanium, chromium, nickel and the like, whose surface contains hydrated metal oxide group which provide the requisite surface hydroxyl groups; the steel being presently preferred as a material of construction. For packed columns, any of the support materials commonly employed as support packing can be used in the practice of the invention, providing that such support materials have reactive groups on the surfaces thereof and are otherwise nonreactive with the polymeric partitioning agent and/ or coupling agent.
The polymeric materials applicable as partitioning agents in the practice of the invention can be broadly described as any addition or condensation polymer having terminal end groups capable of reacting with the surface hydroxyl groups of the column in their wall to effect a chemical bonding through valence forces through the polymeric stationary phase and the column wall; or which are capable of reacting with reactive groups of the coupling agent when used, to effect at least a chemical bonding through valence forces between the polymeric stationary phase and the coupling agent; it being understood that there is present in such cases at least some physical bonding as by chain entanglement of the individual polymeric segments. In certain cases, the bonding between the polymeric stationary phase and the coupling agent will be entirely physical, as by chain entanglement, i.e., in the case wherein the coupling agent is also a polymeric material which is not copolymerizable with the stationary phase or partitioning agent. In this instance, the solution comprising the monomeric partitioning agent and monomeric coupling agent is deposited upon the column wall; the coupling agent is polymerized in situ to leave the monomeric stationary phase dispersed throughout the polymeric coupling agent; the coupling agent is then coated with partitioning agent-forming polymerizable monomer; and the partitioning agent-forming polymerizable monomer is polymerized in situ, including the monomer dispersed throughout the polymeric coupling agent. Thus, since no reaction occurred between the monomer phases of the coupling agent and the partitioning agent, and no reaction occurred between the polymeric phase of the coupling agent and the polymeric phase of the stationary agent, the bonding between the polymeric phases is entirely physical in nature.
Polymeric materials which can be utilized as the part io s agent n the p ice at h P sent i vention ins elude homopolymers and copolymers of monomers having a structure:
wherein each R can be the same or diiferent and each is individually selected from the group consisting of hydro gen, halogen, furyl, pyridinyl, carbazoyl, aryl, alkyl, alkaryl, cycloalkyl, aryl, alkaryl, alkenyl, alkynyl, halogen-substituted aryl, halogen-substituted alkaryl, halogensubstituted alkenyl, halogen-substituted alkynyl, halogensubstituted alkyl, halogen-substituted aralkyl, halogen-substituted cycloal-kyl, alkoxy-substituted aryl, alkoxy-substituted alkaryl, alkoxy-substituted alkenyl, alkoxy-substituted alkynyl, alkoxy-substituted alkyl, alkoxy-substituted cycloalkyl, alkenylaryl, -COOR CONR CEN, -COR OR and R COO, wherein R is selected from the group consisting of hydrogen, alkyl, aryl, alkyl and aralkyl, the number of carbon atoms in each R, R or R being not more than 21. Some examples of monomers which can be polymerized alone or copolymerized together to form a polymeric partitioning agent in accordance with the invention include the olefins such as ethylene, propylene, l-butene, l-pentene, 4-methyl-1-pentene, l-pentene, 1- octene, l-decene, 3-phenylpropene-1, vinylcyclohexane, and the like; conjugated dienes such as butadiene (1,3- butadiene), 2,3-dimethyl-1,3-butadiene, isoprene, piperylene, 2-aryl-l,3-butadiene, 2-methoxy-1,2-butadiene, and the like; haloprenes such as chloroprene (2-chloro1,3- butadiene), bromoprene, 2-epoxy-l,3-butadiene, methylchloroprene (2-chloro 2 methyl-1,3-butadiene),and the like; aryl-substituted olefins such as styrene; various alkyl styrenes such as o-ethylstyrene, n-tetradecylstyrene, and the like; p-chlorostyrene, p-bromostyrene, m-methoxy-pisopropylstyrene, o-chloro-p-decylstyrene, 3-bromo-4 vi- 'nylbutene-1, p-methoxystyrene, alpha-methylstyrene, vi nylnaphthalene, 4-butoXy-5-vinylpentyne-l, and the like; acrylic and substituted acrylic acids and their esters, nitriles and their amides such as acrylic acid, methacrylic acid, methacrylate, ethacrylate, methyl-alpha-chloroacrylate, methylmetacrylate, ethylmethacrylate, butylmethacrylate, methylethacrylate, heptadecylmethacrylate, phenylacrylate, o tolylmethacrylate, benzylethacrylate, acrylonitrile, methacrylonitrile, methacrylamide, N,N-diphenylacrylamide, N,N-di-o-tolylacrylamide; methylisopropyl ketone, methylisopropanyl ketone, methylvinylether, l-naphthylvinyl ketone, methylvinylether, 2-anthrovinylether, vinyl alcohol, vinyl ether, vinyl chloride, vinyl idene chloride, vinyl furan, vinyl pyridine, vinyl carbazole, vinyl acetylene, and other unsaturated hydrocarbons, esters, alcohols, acids, ethers, etc., of the types described.
The present invention further provides processes for the manufacture of chromatographic separating columns comprising a hollow member having an interior wall, said interior wall having integrally bonded directly thereto, as by chemical means through valence bonds, a partitioning agent comprising a thermoplastic polymeric material or indirectly thereto through an intermediate monomeric or polymeric tfilm, wherein the said intermediate film is bonded to said interior wall as by chemical means through valence bonds and to said thermoplastic polymeric partitioning agent as by chemical means through valence bonds, physical interlocking, or a combination of physical and chemical means.
Broadly, the chromatographic columns of this invention are prepared by a process comprising coating the interior wall of the chromatographic column with a monomer solution and thereafter polymerizing said monomer solution in situ. In addition to forming a thermoplastic polymeric partitioning agent, the polymerization reaction effects bonding of the polymeric partitioning agent to said interior wall.
In FIG. 1, there is illustrated a first embodiment of the invention comprising a chromatographic column wherein the partitioning agent is directly bonded chemically to the interior wall of the column. In this embodiment, chromatographic column 10 comprises a hollow member 11 having an interior wall 12, a partitioning agent 13 bonded to the interior wall 12, and an axially extending opening 15 extending through the column 10. In practice, an inert carrier, such as gaseous helium or nitrogen, conveys a sample to be analyzed through the opening 15 and thereby provides a mobile phase for the chromatographic analysis. The partitioning agent 13 selectively absorbs or adsorbs the components of the samples, thereby acting as a stationary phase. Such a system can be described as the elution-partition technique. It is important that the internal wall 12 of hollow member 11 be covered with partitioning agent 13 and that the thickness thereof be as uniform as possible.
In FIG. 2, there is illustrated a second embodiment of the invention comprising a chromatographic column wherein the partitioning agent is indirectly bonded through an intermediate film or coupling agent to the interior wall of the column at least by chemical means. In this embodiment, the coupling agent 14 is chemically bonded to wall 12 of hollow member 11 and chemically, physically or by a combination of chemical and physical means to partitioning agent 13.
In FIG. 3, there is illustrated a third embodiment of the invention wherein the embodiment of FIG. 1 has been adapted for use in a packed column. In this embodiment, chromatographic column 20 comprises a hollow member 21 having an internal Wall 22, discrete particulate packing material 23 dispersed within the interior of hollow member 21, and partitioning agent 24. In this embodiment, partitioning agent 24 is directly bonded to both interior wall 22 of hollow member 21 and packing material 23 by chemical means. The packing material 23 provides, in combination with wall 22, support for the partitioning agent 24 and also provides contact area for the partitioning agent. In the packed columns, the carrier gas, in conveying the samples through the system, passes through the interstices of the porous medium provided by the packed column. Consequently, the loading, which refers to the amount of the stationary phase in this system, is critical. Too much partitioning algent collects in pools between the particles resulting in decreased etficiency in the column. On the other hand, if too little partitioning agent is used, the optimum capacity of the column is not obtained; and there may even be absorbing sites exposed which is detrimental to the column operation. The size of the particles will depend upon the pressure drop permissible in the system. For As-inch diameter columns, 100420 or -100 mesh particle size is preferred; for 4-inch diameter columns, 40-6O or 60-80 mesh particle size is preferred. The mesh numbers refer to standard ASTM screens.
In FIG. 4, there is illustrated a fourth embodiment of the invention wherein the embodiment of FIG. 2 has been adapted for use in a packed column in a manner akin to the embodiment of FIG. 3. In this case, partitioning agent 24 is directly bonded to packing material 23 by chemical means and to the intermediate film, i.e., coupling agent, 25 by physical means, chemical means, or a combination of such means, depending upon the nature of coupling agent 25. Coupling agent 25 is in turn directly bonded as by chemical means to the wall 22 of hollow member 21.
In FIGS. 5 and 6, there are illustrated other embodiment of the invention wherein the previously described embodiments have been adapted for use in packed columns. In the embodiment shown in FIG. 5, partitioning agent 24 is bonded to coupling agent 26 by chemical means physical means or a combination of such means, depending on the nature of the coupling agent and to wall 22 of hollow member 21 bychemical means. Coupling agent 26 is in turn directly bonded as by chemical means to packing material 23. In the embodiment shown in FIG. 6, the partitioning agent 24 is bonded to coupling agents 25 and 26 in the same manner as the bonding described in FIG. and coupling agents 25 and 26 are directly bonded as by chemical means to packing material 23 at wall 22 of hollow member 21, respectively.
FIG. 7 is a reproduction of a representative strip chart recording in which the partitioning agent was poly(vinyl stearate) bonded to the column wall through vinyl triethoxysilane coupling agent.
FIG. 8 is a reproduction of a representative strip chart recording in which the partitioning agent was a polymer made from dimethyl diethoxysilane grafted to the column wall with vinyl trimethoxysilane.
In a broad sense, the novel chromatographic columns of this invention are prepared by a process comprising depositing a partition agent-forming polymerizable monomer, either as a liquid, from solution or from the vapor state, within the interior of the column and thereafter polymerizing said monomer in situ, whereby the polymeric partitioning agent is anchored in place.
The novel chromatographic columns of this invention contemplate the chemical reaction of at least two materials. For example, in the first embodiment, i.e., FIG. 1, there is contemplated a chemical reaction between the partitioning agent 13 and the interior Wall 12 of column 10. In the embodiment of FIG. 2, there is contemplated a chemical reaction between wall 12 of column and the coupling agent 14. As noted earlier, under at least some conditions, there can be a chemical reaction between the coupling agent 14 and the partitioning agent 13. In the embodiments which illustrate packed columns, FIGS. 4-6, there is contemplated a chemical reaction between the particulate packing material 23 and the partitioning agent 24 and a chemical reaction between the partitioning agent 24 and the column wall 22, if no coupling agent is used. Thus, it is evident that the column wall material must be capable of chemical interaction with the partitioning agent or, if used, the coupling agent; and the particulate packing material, when used, must be capable of chemical interaction with the partitioning agent or, if used, the coupling agent. The coupling agents, when used, must not only be capable of chemical interaction between the column wall and particulate packing material but must also be capable of either or both chemical reaction and physical interlocking with the partitioning agent.
In view of the similarities between the capillary columns and the packed columns, the materials useful for one column are also useful for the other column. For example, a partitioning agent which can be used in a capillary column can also be used in a packed column; a coupling agent useful in a capillary column can be used in a packed column; and, in the case of a packed column, a coupling agent capable of reacting with the column Wall can also be used as the coupling agent between the particulate packing material and the partitioning agent providing that the reactive sites of the column wall and the packing material are chemically reactive with the coupling agent. In addition to the similarity between the materials useful for both the packed and capillary columns, the method for preparing the packed column is similar to that used for the capillary column embodiments.
The interior wall 12 or 22 of the chromatographic columns of this invention can comprise any material that is capable of entering into a chemical reaction with the partitioning agent or coupling agent, when used. Particularly preferred are such materials having exposed surface hydroxyl groups. Such materials include glass, steel, aluminum, chromium, tin, nickel, and the like, with steel being presently preferred. In a like manner, the particulate packing material of the packed columns comprises any material that is capable of entering into a chemical reaction with the partitioning agent or coupling agent, when used, through chemically reactive sites such as surface hydroxyl groups. Representative of suitable packing materials are diatomaceous earth, fire brick, silica, and the like. The intermediate film or coupling agent provides a means for chemical coupling or bonding the partitioning agent to the column wall or particulate packing material. Thus, the coupling agent must be a material which is capable of entering into a chemical reaction with the column wall or the particulate packing material, when used. In addition, the coupling agent must be capable of chemically interacting with the partitioning agent, or physically interlocking with the partitioning agents such as by chain entanglement, or a combination of chemically interacting with chain entanglement. Thus, coupling agents which are suitable for use in the practice of the invention must have a reactive group capable of chemically reacting with the reactive site provided by the column wall or the packing material, and, in order to chemically react with the partitioning agent, must have a polymerizable functional group, or a group upon which polymerization can be initiated, such as vinyl, vinylidene, amino, conjugated diene, and the like. The polymerizable functional group copolymerizes with the partitioning agent-forming monomer, or graft polymerization is initiated in the group, to form the initial bond between the coupling agent and the partitioning agent. Thus, in one embodiment, where the column wall contains surface hydroxyl groups, the formula representative of the coupling agent can be as follows:
wherein w, y and x are integers varying from 1 to 3 and where their sum equals 4; Z is halogen or a (R'-O) group, R being an alkyl, cycloalkyl or aryl hydrocarbon radical or combination thereof containing from 1 to 18 carbon atoms which may or may not contain substituent groups such as halogen, ester groups, etc.; R is a group which contains a polymerizable functional group such as vinyl, vinylidene, oxirane, amino, conjugated diene, and the like; and R is any inert group, such as an alkyl, cycloalkyl, aryl, aralkyl group, or such groups substituted with inert groups.
The partitioning agent can comprise any material that will chemically bond to the column wall according to the first embodiment of this invention or chemically bond to the particulate packing material according to the third embodiment of the invention. In addition, the partitionig agent must be capable of forming an integral chemical or physical bond or a combination of chemical and physical bonds, to the coupling agent according to the second embodiment of this invention or the embodiments of FIGS. 4-6.
By way of illustration, and not limitation, let it be assumed that the surface walls contain surface hydroxyl groups and a coupling agent is to be used according to the second embodiment of this invention. This illustration of the selected partitioning agent is to be polystyrene, a polymer having the general formula of:
The (Z) moiety, supra, which in this instance comprises CH CH O-, reacts with the surface hydroxyl of the wall and with adsorbed water molecules according to relationships such as the following:
E20 CHFCHSKOCaHQ! H I CH2=CHSKOC2HO2 1120 on1. on CH2=CHS1(OR')2 mo CHFCHS'KOR'): carton on" com. cm=onsuoml orn=ons1 orm or." orr=ont on.=os1-o-s1 0c2rn) 2 CH2=CH'. When the styrene monomer is introduced into the system, together with a polymerization catalyst such as a peroxide, the functional group CH -=CH- reacts therewith by reactions such as the following:
m can -oH-cm-oH-orn wherein R"'O- is a peroxy-free radical, and Y can be any of the silicone-containing groups listed in the previous set of equations, which at this point chemically bonded to the solvent R". It will be readily apparent that other free radical polymerization initiators can be used in lieu of peroxy-free radicals. The ultimate free radical equation is the start of a vinyl polymerization reaction yielding The conditions of reaction determines the value of n, which describes the degree of polymerization and thickness of the film of the partitioning agent.
10 Suitable combinations of coupling agents and partitioning agents include the following:
bisphenol A and epichlorohydrin, cured in situ with an aliphatic or aromatic amine, or amide, or a carboxylic acid anhydride.
Poly (ethylene oxide).
Poly(allyl glycidyl ether).
Epoxy-polymer, such as that formed irom bisphenol A and epichlorohydrin, cured in situ with an aliphatic or aromatic amine, or amide, or a carboxylic acid anhydride.
Poly (allyl glycidyl ether).
Epoxy polymer, such as that formed irom bisphenol A and epichlorohydrin, cured in situ with an aliphatic or aromatic amine, or amide, or a carhoxylic acid anhydride.
Dimethyldimethoxysilane. Diphenyldimethoxysilane. Di(cyanopropyl) dimethoxysilane.
If a monomer with functionality larger than 2, e.g., divinylbenzene, is used, it must be in a small proportion with a monomer having functionality 2, such as styrene, so that crosslinking will not occur to such an extent as to restrict solubility of compounds that are to be separated too severely.
Chromatographic columns are prepared by the processes of this invention by a process comprising coating the interior wall surface of the chromatographic column with a polymerizable partitioning agent-forming compound, said compound being characterized by reactive groups capable of chemically bonding to said column wall under conditions conducive to polymerization of said compound; polymerizing said polymerizable partitioning agentforming compound to a thermoplastic or lightly crosslinked polymeric state; and removing the excess partitioning agent. The steps of coating, polymerizing and removal of excess partitioning agent can be repeated as often as necessary to obtain the desired thickness of the partitioning agent.
Such processes comprise coating the interior wall surface of the chromatographic column with a coupling agent, said coupling agent being characterized by having reactive groups capable of chemically reacting with the column wall and a second set of reactive groups capable of entering into a polymerization reaction; removing the excess coupling agent, overcoating said coupling agent coating with a polymerizable partitioning agent-forming compound, said partitioning agent being characterized by reactive groups capable of interpolymerizing with said coupling agent; polymerizing in situ said polymerizable partitioning agent, together with said coupling agent; and removing the excess partitioning agent. The steps comprising coating the coupling agent coating with a polymerizable partitioning agent-forming compound, in situ polymerization and excess removal of excess partitioning agent can be repeated as often as necessary to obtain the desired thickness of partitioning agent.
In the formation of chromatographic columns containing a packing material such as diatomaceous earth, the above-described processes are modified as follows:
(1) The chromatographic column can be packed with the particulate packing material prior to the introduction of the polymerizable partitioning agent-forming compound into the interior volume of the capillary column.
(2) The partitioning agent can be deposited onto the packing material'and polymerized in situ prior to placing the packing medium within the interior of the column. In this case, a coupling agent and/or additional partitioning agent-forming material may then be introduced into the column interior in order to effect bonding and subsequent anchorage in place of the partitioning agent. Various other modifications will be readily apparent in view of this disclosure.
The initial coatingstep, i.e., the coating of the interior wall of the chromatographic column, can be performed by conventional methods such as are used for coating capillary columns which involves introducing a solution or vapor containing the polymerizable partitioning agentforming compound, the coupling agent, or an admixture of coupling agent and polymerizable partitioning agentforming compound, together with any necessary catalyst or polymerization initiators, into the column and forcing it -by air pressure or inert gas pressure therethrough.
The process steps directed to the removal of excess partitioning agent or coupling agent can be performed by measures such as flushing the column with a suitable solvent, by purging the system with an inert gas at room temperature or an elevated temperature, or such other methods as are readily avaliable to the art.
Those steps which involve polymerization or copolymerization can be performed at conditions known in the art. For example, if the coupling agent is characterized by a polymerizable vinyl group and the polymerizable partitioning agent-forming compound is a vinyl ester such as vinyl acetate, a free radical generating compound such as an organic peroxide, e.g., benzoyl peroxide, can be employed to initiate the polymerization in the presence of absence of an inert hydrocarbon diluent. Similarly, if the coupling agent characteristically contains an epoxy alkyl radical polymerizing unit and the polymerizable partitionin-g agent-forming compound is an oxirane, a catalyst such as a Lewis acid, e.g., boron trifiuoride or ferric chloride, or a Lewis base such as a tertiary amine, can be added to the oxirane and the treated column contacted with the mixture of oxirane and catalyst to effect grafting. Other suitable catalysts includue primary amines and acidic anhydrides. The polymerization step can be conducted in the presence or absence of an inert hydrocarbon diluent.
Known polymerization modifiers can be used to preventexcessive crosslinking of the grafted polymers. If it is desired to provide a light crosslinking and thereby improve dimensional stability, a small amount of difunctional monomer in admixture with monofunctional grafting monomers, e.g., divinylbenzene and styrene, can be used. The degree of polymerization can be controlled by the residence time in the presence of an initiator or catalyst at a given monomer concentration and temperature. The thickness of the film can be controlled by the number of successive repetitions of the process of coating with monomer and polymerization of monomer. If the polymerization process is employed, the thickening of the film may take place either by chain extension or by the formation of new chains which are entangled on the molecular scale with the chains in the first coat. It should be observed at this point that the present invention offers a convenient method for controlling or increasing the effective thickness of a polymer film in the column. Heretofore the thickness was controlled by the quantity of liquid, of constant molecular weight, transported into the column. Generally speaking, the ultimate purging step, i.e., removal of excess partitioning agent, will usually be accomplished by purging the column at an elevated temperature with an inert gas. The temperature at whichthe column, which had been prepared according to this invention, would then be employed and any separation process would be below the elevated temperature employed in the purging or conditioning step.
. 1-2 EXAMPLE I The interior surface of a 300-foot length of 0.001 inchpentane, acetone, and methanol. A coupling agent solution was prepared by mixing vinyl triethoxysilane, methanol, and water in the following volume percents: 15 percent, 75 percent, 10 percent, respectively. A slug (3-4 ml.) of the solution was forced through the column by pressurized helium to coat the interior surface of the column with the coupling agent soltuion. The column was then purged by flowing helium therethrough for about 2 hours. A partitioning agent solution was prepared by dissolving 5 grams of vinyl stearate and 0.06 gram of lauryl peroxide in 25 ml. of chloroform. A slug (3-4 ml.) of the partitioning agent solution was forced through the column by pressurized helium. The chloroform was evaporated by passing dry helium through the column at 60 C., leaving a film of vinyl stearate thereon. The vinyl monomer was polymerized in situ by passing dry helium through the column at C. for 16 hours. Following the polymerization step, the column was purged of un anchored materials by passing dry helium through the column for 24 hours at 250 C. The chromatographic column thus formed was found to be stable up to 210 C.
The column prepared according to the procedure set forth above was used to analyze a mixture of normal alkanes having from 5-7 carbon atoms. The chromatogram presented in FIG. 7 illustrates the effectiveness of the column in separating the mixture into the indicated components.
EXAMPLE II The interior surface of a ISO-foot length of 0.001 inch (I.D.) stainless steel tubing was washed successively with pentane, methanol, and chloroform. The column was then purged by passing water-saturated helium therethrough for 2 hours. The water-saturated helium hydrated the metal oxide surface forming surface hydroxyl groups. The following solution was prepared:
2.4 ml. of vinyl trimethoxysilane, 10 'ml. of dimethyl diethoxysilane (DMDES), and 12 ml. of methanol.
A slug (3-4 ml.) of the solution was forced through the column by pressurized dry helium coating the interior, wall thereof. The 'silane monomers coating thecolumn wall were polymerized by passing water-saturated helium through the column for 2 hours at room temperature, ca. 23 C.
The polymerization step was repeated by passing another slug composed of equal amounts of DMDES and methanol through the column followed by 2-hour treatment with water-saturated helium. This step was in accord with the principles already noted, that the thickness of the stationary phase (polymerized DMDES) can be increased by repeating the polymerization step.
The chromatographic column prepared by the above procedure was used to analyze a gas composed of n-octane, n-heptane, n-hexane, and n-pentane. As shown on the chromatograph presented in FIG. 8, the resolution of the mixture into its components was excellent.
Reasonable variations and 'rnodifications are possible within the scope of the disclosure, the drawingsand the appended claims.
1. A chromatographic column comprising a hollow member;
a partitioning agent within the inner volume of said member comprising a continuous film of a polymeric material integrally bonded to a coupling agent; and
a coupling agent, said coupling agent being disposed as an' essentially continuous discrete film between said partitioning agent and said hollow member, said coupling agent being integrally bonded at least chemically through valence bonds to the inner surface of said hollow member and bonded to said partitioning agent by a bonding means selected from the group consisting of chemically bonding through valence bonds, physical interlocking, or a combination of chemical and physical means.
2. A chromatographic column according to claim 1 wherein said coupling agent is vinyl triethoxysilane and said partitioning agent is poly(vinyl stearate).
3. A chromatographic column according to claim 1 wherein said coupling agent is vinyl triethoxysilane and said partitioning agent is poly(dimethyl diethoxysilane).
4. A chromatographic column according to claim 1 further comprising:
a particulate support material disposed within the inner volume of said hollow member;
wherein said partitioning agent is disposed within said inner volume of said hollow member as a continuous layer upon the exposed surface of said support material; and
wherein said partitioning agent is integrally bonded to the surface of said particulate support material at least chemically through valence bonds.
5. An apparatus for the separation of a fluid stream into component fractions comprising:
a hollow member;
a partitioning agent disposed within the inner volume of said hollow member, said partitioning agent comprising a continuous discrete film of a polymeric material, said polymeric material being integrally bonded to a coupling agent;
a coupling agent, said coupling agent being disposed as an essentially continuous discrete film between said partitioning agent and said hollow member, said coupling agent being integrally bonded at least chemically through valence bonds to the inner surface of said hollow member and to said partitioning agent by a bonding means selected from the group consisting of chemically bonding through valence bonds, physical interlocking or a combination of chemical and physical means;
means to introduce a fluid stream into said hollow member for separation of at least one component fraction;
means to drive said fluid stream in a generally axial direction through said hollow member; and
means to withdraw one or more component fractions from said hollow member.
6. An apparatus according to claim 5 further comprising:
a particulate support material disposed within the inner volume of said hollow member;
'wherein said partitioning agent is disposed within said inner volume of said hollow member as a continuous layer upon the exposed surface of said support material;
wherein said partitioning agent is integrally bonded to the surface of said particulate support material at least chemically through valence bonds; and
wherein said coupling agent is integrally bonded to the inner surface of said hollow member at least chemically through valence bonds and to said partitioning agent by at least one means selected fiom the group consisting of chemical bonding through valence bonds, physical interlocking or a combination of physical and chemical means.
7. An apparatus according to claim 6 wherein said coupling agent is vinyl triethoxysilane and said partitioning agent is poly(vinyl stearate).
8. An apparatus according to claim 6 wherein said coupling agent is vinyl triethoxysilane and said partitioning agent is poly(dimethyl diethoxysilane).
9. A process for preparing a chromatographic column comprising:
coating the interior surface of a hollow member with a coupling agent, said coupling agent being characterized by the presence of reactive groups capable of reacting with said interior surface and containing also polymerizable reactive sites; thereafter coating said coupling agent-coated interior surface with a polymerizable monomer to substantially uniform finite thickness, said polymerizable monomer being characterized by containing polymerizable groups; and polymerizing in situ said monomer to form an essentially continuous polymeric phase of substantially uniform finite thickness, said polymeric phase being integrally bonded to said coupling agent by at least one means selected from the group consisting of chemically bonding through valence bonds, physical interlocking or a combination of physical and chemical means. 10. A process according to claim 9 wherein said coupling agent is vinyl triethoxysilane and said polymeric phase is p'oly( vinyl stearate) 11. A process according to claim 9 comprising the steps of coating the interior surface of a hollow member with a mixture of a coupling agent and a partitioning agentforming. polymerization monomer, to a substantially uniform finite thickness,
said coupling agent being characterized by the presence of reactive groups capable of reacting with said interior surface, said coupling agent further being capable of self-polymerization and copolymerization with said partitioning agent-forming monomer; said partitioning agent-forming polymerizable monomer being capable of reacting chemically with said interior surface, said polymerizable monomer further being capable of self-polymerization and copolymerization with said coupling agent, polymerizing in situ said mixture of coupling agent and partitioning agent-forming polymerizable monomer to form an essentially continuous first thermoplastic polymeric phase of substantially uniform finite thickness, said first polymeric phase being integrally bonded at least chemically through valence bonds to said interior surface of said hollow member; coating said first polymeric phase with a partitioning agent-forming polymerizable monomer to a substantially uniform finite thickness; and
polymerizing in situ said polymerizable monomer to form an essentially continuous second thermoplastic polymeric phase of substantially uniform finite thickness, said second polymeric phase being bonded to said first polymeric phase by at least one means selected from the group consisting of chemical bonding through valence bonds, physical interlocking or a combination of physical and chemical means.
12. A process according to claim 11 wherein said coupling agent is vinyl triethoxysilane and said partitioning agent-forming polymerizable monomer is dimethyl diethoxysilane.
13. A process according to claim 9 wherein the resulting coupling agent-coated surface is washed with an inert diluent to remove excess coupling agent prior to the coating of said surface with said polymerizable monomer.
References Cited UNITED STATES PATENTS 3,514,925 6/1970 Bossart 55386 3,722,181 3/1973 Kirkland et a1 210-31 C 3,005,514 10/1961 Cole et a1. 55386 3,116,161 12/1963 Purnell 55386 X 2,920,478 1/ 1960 Golay 5567 X 3,663,263 5/1972 Bodre et a1 210-31 C JOHN ADEE, Primary Examiner U.S. Cl. X.R.