Abstract:
Solid phase extraction (SPE) disks may be manufactured by providing a suspension comprising glass microfibers and a suspension comprising one or more sorbents and forming a disk by combining the suspensions or by layering the suspensions. This may be followed by a drying procedure to create the finished disk. A disk mold including a collar and plug may be used to establish the size and shape of the disk. Examples of various constructions and processes for forming the disks are provided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional application Ser. No. 61/151,362, filed Feb. 10, 2009, which is incorporated by reference herein to the extent it is consistent. 
     
    
     FIELD 
       [0002]    This invention relates generally to sample testing products and techniques, and more particularly to improved solid phase extraction (SPE) filtration disks and methods for their manufacture. 
       BACKGROUND 
       [0003]    In the art which can be broadly described as separation science, means are provided for isolating, separating, and analyzing mixtures of solutions by selective adsorption on materials such as polymeric materials (e.g. polydivinylbenzene (PDVB) and polymer gel), alumina, silica, and bonded silica. The process is based on differences in the distribution ratios of the components of mixtures between a mutually immiscible mobile and a fixed stationary phase. 
         [0004]    Solid phase extraction (SPE) is a laboratory technique for analyzing liquid and mixed liquid/solid samples. The basic objective of such apparatus is to filter the solid portion of the sample and to selectively adsorb compounds from the liquid portion onto a sorbent. The analytes of interest can be subsequently extracted with the solvent and eluted from the sorbent with a minimal amount of an appropriate solvent. 
         [0005]    Typical SPE disk apparatus may dispose a sorbent-impregnated SPE disk between an upper funnel and a lower base. A sample may be poured into the funnel, and a vacuum source applied to the base to draw the sample through the disk. The process may be continued until all of the sample to be filtered has passed through the disk. 
         [0006]    The analytes bound by the sorbents and trapped in solids filtered out by the disk may be collected by elution. The vacuum may be disconnected and a small amount of extraction solvent applied. The procedure may include a soak period, where analytes bound by the sorbents within the disk desorb and partition into the extraction solvent. After soaking, vacuum may be reapplied, and the solvent collected. 
       SUMMARY 
       [0007]    A solid phase extraction (SPE) filtration disk comprises a cake, having glass microfibers and one or more sorbents, with a fiber mesh, which provides support and an outer covering on at least one side of the cake. In an exemplary embodiment, a layer of glass microfibers may be provided on one or more sides of the cake to increase the integrity of the disk, with the layer of glass microfibers in layered and/or in adjacent disposition with the cake. The sorbent may include polymeric materials, such as polystyrene-divinylbenzene (PS-DVB), and/or bonded silica materials including, but not limited to, carbon-18 bound silica, carbon-8 bound silica, tertiary amine bound silica and combinations thereof. Additional sorbent materials are also disclosed herein. 
         [0008]    In an exemplary embodiment, a solid phase extraction filtration disk is provided which comprises an inner member located within an outer member. The inner member is in the form of a circular cake comprising a sorbent mixed with glass microfibers, with the cake having a first circular side, a cylindrical side and a second circular side. The outer member comprises a first circular portion covering the first circular side of the cake, a cylindrical ring portion covering the cylindrical side of the cake, and a second circular portion covering the second circular side of the cake. The outer member first circular portion comprises a microfiber mesh, while the outer member cylindrical ring portion and second circular portion comprise a layer of glass microfibers molded over the cylindrical side of the cake. The microfiber mesh may be a particulate filter media. The microfiber mesh may comprise a glass microfiber mesh, and the glass microfiber mesh may be a binderless borosilicate glass microfiber. 
         [0009]    The outer member first circular portion may be joined directly with the first circular side of the cake. 
         [0010]    The outer member cylindrical ring portion and outer member second circular portion may each comprise glass microfibers having a diameter in a range of 0.2-10 microns. The outer member cylindrical ring portion and outer member second circular portion may be of a same composition, which may be from a liquid suspension. The outer member cylindrical ring portion and the outer member second circular portion may comprise glass microfibers having a diameter in a range of 0.2-10 microns. 
         [0011]    The outer member cylindrical ring portion may be of a first composition, and the outer member second circular portion may be of a second composition. The first composition may have a greater density than the second composition. The first composition may be from a first liquid suspension, and the second composition may be from a second liquid suspension. 
         [0012]    The outer member cylindrical ring portion and outer member second circular portion may be molded in situ to the cylindrical side of the cake and the second circular side of the cake, respectively. 
         [0013]    The sorbent may comprises at least one of a polymeric material or a bonded silica material. 
         [0014]    In method form, solid phase extraction (SPE) disks may be manufactured by providing a suspension comprising glass microfibers and a suspension comprising one or more sorbents, mixing the suspensions, introducing the mixture of suspensions to a molding apparatus and thereafter evacuating the liquid phase of the suspensions from the molding apparatus, particularly with the aid of a vacuum. This may be followed by applying a suspension comprising glass microfibers over the cake and evacuating the liquid phase, particularly with the aid of a vacuum. This may be followed by a drying procedure to create the finished disk. A molding apparatus including a mold base, a collar and plug may be used to establish the size and shape of the cake, as well as the disk. A fiber mesh, such as a glass fiber mesh, may be used as a foundation for the sorbent/fiber cake. Examples of various constructions and processes for forming the disks are provided. 
         [0015]    In one exemplary embodiment, a method of providing a solid phase extraction filtration disk comprises providing a molding apparatus having a cavity, placing a microfiber mesh in the cavity of the molding apparatus, introducing a mixture of sorbent and glass microfibers to the cavity over the microfiber mesh, molding the sorbent and glass microfibers to form a cake having an exposed cylindrical side and an exposed circular side, and forming a layer of glass microfibers over the exposed cylindrical side of the cake and exposed circular side of the cake, and molding a layer of glass microfibers over the exposed cylindrical side of the cake and exposed circular side of the cake. 
         [0016]    Molding the layer of glass microfibers over the exposed cylindrical side of the cake and exposed circular side of the cake may be performed by applying a liquid suspension comprising glass microfibers over the exposed cylindrical side of the cake and exposed circular side of the cake and evaluating the liquid. 
         [0017]    Molding the layer of glass microfibers over the exposed cylindrical side of the cake and exposed circular side of the cake may be performed by applying a first liquid suspension comprising glass microfibers over the exposed cylindrical side of the cake and then applying a second liquid suspension comprising glass microfibers over the exposed circular side of the cake and evaluating the liquid. 
         [0018]    The molding apparatus may include a porous member; and the step of placing a microfiber mesh in the cavity of the molding apparatus may further comprise placing the microfiber mesh in the cavity of the molding apparatus over the porous member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The objects, features and advantages of the present invention will be apparent in the following detailed description thereof when read in conjunction with the appended drawings wherein the same reference numerals denote the same or similar parts throughout the several views. 
           [0020]      FIG. 1  is a perspective view of an exemplary SPE disk in accordance with the present invention; 
           [0021]      FIG. 2  is a cross-sectional view of the SPE disk of  FIG. 1 ; 
           [0022]      FIG. 3  is another exemplary cross-sectional view of an SPE disk; 
           [0023]      FIG. 4  is another exemplary cross-sectional view of an SPE disk; and 
           [0024]      FIG. 5  is an exploded view of the molding apparatus used in the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Referring to the drawings,  FIG. 1  is a perspective view of a solid phase extraction (SPE) filtration disk  10  according to the present disclosure. Generally, these disks  10  may be about 47 mm (millimeters) in diameter and in a range of and any increments between about 2-25 mm in thickness, although they may have other dimensions, e.g. diameters in a range of and any increments between 5-100 mm in diameter, and thickness in a range of and any increments between 1-50 mm in thickness. 
         [0026]    The disk  10  may comprise an arrangement of various combinations of an inner member, particularly in the form of a circular cake  14 , which may particularly comprise a mixture of sorbent and glass microfibers, in layered and/or in adjacent disposition with an outer member which particularly provides a covering for cake  14 , which may particularly comprise glass microfibers.  FIG. 2  is a cross-sectional view of the filtration disk  10  illustrating an exemplary configuration comprising a sorbent and glass microfiber cake  14  in which the sorbent and glass microfiber are dispersed as a mixture throughout the cake  14 . Cake  14  is supported on and located in layered disposition within and between adjacent outer member portions  12  and  16 , respectively, which together surround and encapsulate cake  14 . 
         [0027]    More particularly, a lower circular side  11  of cake  14  is covered by and located on an underlying outer member circular portion  16 , which provides a foundation to support the use of cake  14  and disk  10 . As further shown in  FIG. 2 , the remaining cylindrical side  13  of cake  14  and upper circular side  15  of cake  14  are covered and surrounded by overlying outer member cylindrical ring portion  12 A and outer member circular portion  12 B, respectively, of outer member  12 . The outer member portions  12  and  16  may provide integrity to the sorbent/glass microfiber cake  14  so that it may be handled and used for the filtration purposes. 
         [0028]    With respect to materials for cake  14 , exemplary sorbent materials include polymeric materials, such as polydivinylbenzene (PDVB) and polystyrene-divinylbenzene (PS-DVB), and/or bonded silica materials including, but not limited to, carbon-18 bound silica, carbon-8 bound silica, tertiary amine bound silica and combinations thereof. Other sorbent materials may include molecularly imprinted polymer (MIP), sulfonated resins for strong cation exchangers, carboxylated moieties for weak cation exchangers (resin based), quaternary amines bound to either silica or resin for strong anion exchangers, and covalently bonded ligands for chelation or molecular recognition media (silica or resin based). The sorbent for cake  14  may have a weight percentage in a range of and any increments between 10-90 percent of the cake  14 , and more particularly have a weight percentage in a range of and any increments between 25-75 percent of the cake  14 , and even more particularly have a weight percentage in a range of and any increments between 40-60 percent of the cake  14 , 
         [0029]    Exemplary glass microfibers for cake  14  may include product number 704BBC from Evanite Fiber Corp. Evanite 704BBC is an extremely pure glass wool. The glass microfibers are not surface treated, so they contain no additives that can absorb moisture or cause the microfibers to adhere to themselves. The glass microfibers disperse easily in water and other liquids with minimum energy (e.g. stay suspended in a water alcohol solution). The glass microfibers may have a length in a range of and any increments between 1 μm (microns or micrometers) to 3 mm, and more particularly have a length in a range of and any increments between 50 μm to 2 mm, and even more particularly have a length in a range of and any increments between 100 μm to 1 mm. The glass microfibers may have a diameter in a range of and any increments between 0.2-10 μm, and more particularly have a diameter in a range of and any increments between 0.3-8.5 μm. Even more particularly, the glass microfibers may have a diameter in a range of and any increments between 0.4-0.6 μm, such as 0.5 μm. The glass microfibers for cake  14  may also possess the ability to keep the sorbent suspended in a liquid slurry solution prior to being introduced to a mold as described in greater detail below. The glass microfiber for cake  14  may have a weight percentage in a range of and any increments between 10-90 percent of the cake  14 , and more particularly have a weight percentage in a range of and any increments between 25-75 percent of the cake  14 , and even more particularly have a weight percentage in a range of and any increments between 40-60 percent of the cake  14 . 
         [0030]    For the materials of outer member portion  12 , outer member portion  12  also may particularly comprise the glass microfibers used for cake  14 , and particularly product number 704BBC from Evanite Fiber Corp with the material characteristics as described above. 
         [0031]    For the materials for outer member portion  16 , outer member portion  16  may particularly comprise a fiber mesh, and more particularly a nonwoven (random) matrix glass fiber mesh comprising microfibers which may be provided in the form of a thin, planar configuration (e.g. flat circular sheet). Exemplary glass microfibers for outer member portion  16  include grade A-E glass microfiber mesh from I.W. Tremont, which comprises binderless, 100% borosilicate glass microfiber. Such may particularly provide a particulate depth filter for disk  10  and as such may be referred to as a porous fibrous filter media or paper which functions by trapping particulate within the random matrix of fibers found within the thickness of the media. Grade A-E may be considered to have a fine porosity and fast flow rate, with a 1.0 μm size particle retention and a DOP efficiency of 99.98%. The efficiency rating of the filter is characteristic of the complex pore structure that develops as the fibers over-lap. Additional properties for grade A-E, as well as other possible grades within the scope of the invention, are as follows: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                   
                 Particle 
                 Filtration 
                   
                 Basis 
               
               
                   
                   
                 Retention 
                 Speed 
                 Thickness 
                 Weight 
               
               
                   
                 Grade 
                 (μm) 
                 (sec.) 
                 (mm) 
                 (g/m 2 ) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 A 
                 1.6 
                 12 
                 0.30 
                 55 
               
               
                   
                 B 
                 1.0 
                 30 
                 0.65 
                 140 
               
               
                   
                 C 
                 1.2 
                 25 
                 0.28 
                 50 
               
               
                   
                 D 
                 2.7 
                 5 
                 0.60 
                 120 
               
               
                   
                 E 
                 1.3 
                 12 
                 0.35 
                 70 
               
               
                   
                 A-E 
                 1.0 
                 15 
                 0.33 
                 60 
               
               
                   
                   
               
             
          
         
       
     
         [0032]    While outer member portion  16  may be particularly provided in the form of a fiber mesh, the sorbent/glass microfiber cake  14  and glass microfiber outer member portion  12  may be particularly provided by compositions formed from suspensions of glass microfibers and of sorbents in vehicles, such as deionized water and alcohol, casting or otherwise introducing a quantity of such in a molding apparatus (e.g. disk mold) and evacuating or otherwise removing the liquid portion, particularly with the aid of a vacuum. This will be described in greater detail in the examples that follow. The filter  10  so formed may then be dried in an oven. 
         [0033]      FIG. 5  is an exploded view of exemplary molding apparatus used to manufacture the solid phase extraction (SPE) disk  10  according to the present disclosure. A mold base  20  may be provided to act as a forming mold including a cylindrical cavity  32 , an evacuation port  30  and aspiration grooves  28 . Mold base  20  may further include a porous member  22 , such as a circular metal screen, may be first placed in the cavity  32  of mold base  20  (as illustrated by reference numeral  1 ), over the aspiration grooves  28  to provide a foundation to support the manufacturing the cake  14 , and inhibit the disk  10  from deforming into the aspiration grooves  28  during the manufacture thereof. Outer member portion  16 , which may particularly comprise a circular fiber mesh of glass microfibers, and which is preformed relative to cake  14  (i.e. prior to the formation of cake  14 ), may then be placed in the cavity  32  of mold base  20  over the porous member  22 . Unlike porous base  22 , outer member portion  16  becomes a permanent part of disk  10  upon the manufacture of disk  10 . Conversely, porous base  22  is reused for the manufacturing of additional disks  10  and as such is separated from the disk  10  after the disk  10  is removed from cavity  32  of mold base  20 . 
         [0034]    A cylindrical collar  24  having an outer diameter approximating the inner diameter of the mold base  20  may then be used to establish the outer cylindrical dimensions (e.g. diameter) of the cake  14  by placing the collar  24  inside the cavity  32  of mold base  20  (as illustrated by reference numeral  2 ). 
         [0035]    To form cake  14 , a liquid suspension comprising glass microfibers and sorbent may then be poured or otherwise introduced into the cavity  32  of mold base  20  (within the confines of collar  24 ) and applied onto outer member portion  16 , and any liquid from the suspension evacuated through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto in which case the aspiration grooves  28  form part of a vacuum chamber. In this manner, the cake  14  is molded in situ relative to outer member portion  16  to join outer member portion  16  directly at the lower circular side  11  of cake  14  and adhere the outer member portion  16  and the cake  14  together. 
         [0036]    Subsequent to the formation of cake  14 , the collar  24  may be removed from cavity  32  of mold base  20 . Collar  24  may be particularly removed while vacuum is still applied to cake  14  to inhibit cake  14  from being removed from mold base  20  with collar  24 . Thereafter, a composition in the form of a liquid suspension comprising glass microfibers may be poured into the cavity  32  of mold base  20  and above and around the cake  14 , and any liquid from the suspension evacuated through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto. In this manner, a cylindrical ring portion  12 A and upper circular portion  12 B of outer member portion  12  are molded over and in situ around cake  14  to join outer member portion  12  with the cylindrical side  13  and upper circular side  15  of cake  14 , respectively, and adhere the outer member portion  12  and cake  14  directly together. Additionally, cylindrical ring portion  12 A of outer member portion  12  is molded over and in situ to a perimeter ring of outer member portion  16  to join cylindrical ring portion  12 A of outer member portion  12  with outer member portion  16  and adhere the cylindrical ring portion  12 A of outer member portion  12  and outer member portion  16  directly together. Cylindrical ring portion  12 A, in addition to increasing the structural integrity of disk  10 , also inhibits the sorbent material of the cake  14  from fragmenting and being lost from the perimeter of disk  10 . 
         [0037]    After evacuation to remove substantially all of the liquids, a disk  10  may be formed, as shown in  FIG. 2  with circular side  11  of sorbent/glass microfiber cake  14  covered by underlying outer member portion  16 , and cylindrical side  13  and circular side  15  of cake  14  covered by cylindrical ring portion  12 A and upper circular portion  12 B, respectively, of outer member portion  12 . 
         [0038]    In another embodiment, a plug  26 , as shown in  FIG. 5 , may be placed on to the upper circular side  15  of cake  14  (as illustrated by reference numeral  3 ) and a different composition provided by a different liquid suspension comprising glass microfibers (other than the suspension for outer member portion  12 B), as shown at  12 A, may be poured or otherwise applied around the cylindrical periphery side  13  of the cake  14  and the liquid thereafter removed from the suspension through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto, to form cylindrical ring portion  12 A of outer member portion  12  of the SPE disk  10 ′ shown in  FIG. 3 . The plug  26  may then be removed and a composition provided by another liquid suspension comprising glass microfibers may be applied over circular surface  15  of cake  14  and cylindrical ring portion  12 A of outer member portion  12 , with the liquid thereafter removed from the suspension through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto, to form upper circular portion  12 B of outer member  12 . Thus, in this embodiment cylindrical ring portion  12 A and upper circular portion  12 B of outer member  12  are formed of different compositions from different liquid suspensions, whereas in the prior embodiment both were formed from the same composition. With the present embodiment, the percentage of glass microfibers and density in cylindrical ring portion  12 A may be increased as compared to upper circular portion  12 B to provide greater integrity to disk  10 . 
         [0039]    In yet another embodiment,  FIG. 4  illustrates in cross-section a disk  10 ″ formed with a cake  14  of sorbent and glass microfibers surrounded by outer member portion  12  and  16 A, which may particularly be provided from a liquid suspension comprising glass microfibers formed (molded) on both circular sides  11  and  13  of the cake  14  rather than just one side  13  as shown in the prior embodiments. 
         [0040]    As described in Example E, the glass microfiber layers of circular outer member portion  16 A may be formed by first pouring or otherwise introducing into the cavity  32  of mold base  20  a liquid suspension comprising glass microfibers applied onto outer member portion  16  and evacuating the liquid phase through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto. In this manner, outer member portion  16 A is formed in situ on circular outer member portion  16  to join and adhere the outer member portion  16  and  16 A together. Thus, in this embodiment, the outer member portion  16 ,  16 A beneath subsequently formed cake  14  will comprise two layers. This may be followed by inserting the collar  24  in the cavity  32  of mold base  20  to form a cylindrical periphery for the cake  14 . 
         [0041]    Next, a liquid suspension comprising a sorbent and glass microfibers may be applied inside the collar  24  and any liquid evacuated through aspiration grooves  28  and the port  30 , particularly by applying a vacuum thereto, to form cake  14 . In this manner, the cake  14  is formed in situ relative to outer member portion  16 A beneath it to directly join the outer member portion  16 A at the lower circular side  11  of cake  14  and adhere the outer member portion  16 A and the cake  14  together. 
         [0042]    Thereafter, collar  24  may be particularly removed while vacuum is still applied to cake  14  to inhibit cake  14  from being removed from mold base  20  with collar  24 . After removing the collar  24  from cavity  32  of mold base  20 , a layer of glass microfibers for cylindrical ring portion  12 A and upper circular portion  12 B of outer member portion  12  may be formed by applying additional liquid suspension comprising glass microfibers above and around cake  14  and evacuating the liquid phase from cavity  32  of mold base  20 , particularly by applying a vacuum thereto. 
         [0043]    Alternatively, the plug  26  may be placed on the upper circular side  15  of cake  14  after the collar  24  has been removed and a second liquid suspension comprising glass microfibers, which may have a different length and/or diameter than the glass microfibers for used for outer member portion  16 A, to form outer member cylindrical ring portion  12 A around the cylindrical periphery side  13  around the cake  14 . Subsequently, an additional layer of glass microfibers for upper circular portion  12 B of outer member portion  12  may be formed over the cake  14 , which may comprise the same composition used for outer member portion  16 A The edges of the layers of glass microfibers are indicated by the dashed lines  18 . 
       Example A 
       [0044]    In a first example, liquid suspension comprising glass microfibers (S 1 ) may be provided by adding about 11,356 mL (milliliter) of deionized water to a 19,000 mL container, followed by 51 grams of glass microfibers, such as 704BBC from Evanite Fiber Corp., and about 10 mL of concentrated HCl. These ingredients may be mixed using a Cuisinart and a Stir-Pak mixer for about 5 minutes on high speed to provide a relatively uniform dispersion and, in certain embodiments, to provide a microfiber length which may be less than the length of the microfibers prior to mixing. 
         [0045]    A liquid suspension comprising sorbent (S 2 ) may be provided by adding 400 mL of isopropanol to a 1,000 mL beaker followed by 16 grams of a polymeric sorbent such as C18 polydivinylbenzene from Jordi Polymeric (p/n 40512MS) and stirring the mixture with a spatula until the sorbent is relatively uniformly dispersed. Next, the 416 mL of S 2  may be combined with 3,500 mL of Si and mixed thoroughly to form a glass/sorbent dispersion (S 3 ). 
         [0046]    Outer member portion  16  in the form of a 50 cm A-E glass microfiber mesh may be placed in a cavity  32  of mold base  20  (see  FIG. 5 ) and a collar  24  inserted to establish the area of the sorbent cake  14  to be formed. Type A-E glass microfiber mesh  16  has a 50 cm diameter and a thickness of 0.3 mm, and may comprise binderless borosilicate glass microfiber with a 1.0 μm (micron) particle size retention, such as from I.W. Tremont. 
         [0047]    Twenty-five (25) mL of suspension S 3  may then be poured into in the cavity  32  of mold base  20  (within the confines of collar  24 ), overlying porous member  22 , and the cavity  32  and a vacuum applied via outlet  30  until the liquid portion is substantially removed and a cake  14  is formed on the glass microfiber mesh  16 . Note that the mold base  20  may include aspiration channels  28  to aid in evacuation of the liquid portion of the suspension and better ensure an even distribution or layer of glass microfibers and sorbent forms over fiber mesh  16 . The collar  24  may then be then removed. Collar  24  may be particularly removed while vacuum is still applied to cake  14  to inhibit cake  14  from being removed from mold base  20  with collar  24 . With the vacuum on, the cavity  32  of mold base  20  may next be filled with suspension S 1  (about 100 mL) and a glass layer outer member  12  comprising cylindrical ring portion  12 A and upper circular portion  12 B drawn down onto and around the cake  14  of sorbent/glass. The resultant disk  10  may then be dried in an oven for about 12 hours at about 60° C. This disk construction is illustrated in  FIG. 2 . 
       Example B 
       [0048]    In a second example, the same procedure as in Example A may be used to form a disk  10 , except that a sorbent suspension (S 4 ) may be formed by stirring 400 mL of isopropanol, 11.2 grams of C18 polymeric sorbent from Jordi Polymeric (p/n 40512MS) and 80 grams of C18 bound silica sorbent such as octadecylsilyl from Alltech (p/n 211503) with a spatula. To this sorbent suspension (S 4 ), 3,500 mL of S 1  glass microfiber suspension may be added and stirred thoroughly to form sorbent/glass microfiber suspension S 5 . About 25 mL of S 5  may be poured into the cavity  32  of mold base  20  including glass microfiber mesh  16 , porous member  22  and collar  24  and evacuated to form a cake  14 , particularly be applying a vacuum thereto. After removing the collar  24  and with the vacuum on, the cavity  32  of mold base  20  may next be filled with suspension S 1  (about 100 mL) and a glass layer for outer member  12  comprising cylindrical ring portion  12 A and upper circular portion  12 B drawn down on to and around the cake  14  of sorbent/glass. The resultant disk  10  may then be dried in an oven for about 12 hours at about 60° C. 
       Example C 
       [0049]    In another example, to 11,356 mL of deionized water of deionized water, 51 grams of 704BBC glass microfibers and 10 mL of HCl (to bring the pH of the water to 2) may be added and mixed with a Magic Wand mixer on high speed for about 2 minutes. 
         [0050]    In certain instances, due to the volume of liquid, better mixing may be achieved by mixing a fractional portion of the foregoing quantities, and thereafter combining the fractional mixed portions to form the entire batch (e.g. 3 portions of ⅓ each). The suspension (S 6 ) may be allowed to stand for about 5 minutes, to allow the mixing device to cool, and then be mixed again for about 2 minutes to provide a relatively even dispersion. 
         [0051]    Next, a sorbent suspension (S 7 ) may be prepared by gently suspending 64 grams of polydivinylbenzene (PDVB) sorbent into 500 mL of methanol and stifling on a stir plate. After the suspension appears to be uniform, the total volume may be brought up to 800 mL. To about 3 liters of S 6 , 400 mL of S 7  may be gently added and folded in using a spatula. The total volume may then be brought up to 4.4 liters by adding more of S 6  and gently stirring with a spatula to form a DVB/microfiber suspension (S 8 ). 
         [0052]    One or more mold bases  20  may be provided. Type A-E glass microfiber mesh  16  may be added to each mold and wetted using deionized water. About 60 mL of suspension S 6  may be added to the disk mold and quickly evacuated with a vacuum at about −20 inches of Hg (mercury) to form a glass microfiber layer. 
         [0053]    Next, 50 mL of S 8  may be added on top of the S 6  glass microfiber layer and evacuated with a vacuum for approximately 1 minute. The disk may then be removed and dried in an oven for about 12-24 hours at 70° C. 
       Example D 
       [0054]    In another example, a suspension (S 1 ) may be provided by adding 11,356 mL of deionized water to a 19,000 mL container, followed by 51 grams of 704 BBC glass microfibers and 10 mL of concentrated HCl. These ingredients may be mixed using Cuisinart and Stir-Pak mixers for about 5 minutes on high speed. 
         [0055]    Next, a glass microfiber suspension (S 9 ) may be prepared by adding 11,356 mL of deionized water to a 19000 mL container, followed by 51 grams of 7804BBC glass microfibers and 10 mL of concentrated HCl. These ingredients may be mixed using a Cuisinart and a Stir-Pak mixer for about 6 minutes on high speed to provide a glass microfiber suspension S 9  having a shorter fiber length than S 1 . This suspension may be used around the cylindrical ring portion of the cake layer (see reference numeral  12 A in  FIG. 3 ) to increase the density thereof. 
         [0056]    This may be followed by the preparation of a sorbent suspension (S 10 ) comprising 400 mL of methanol and 75 grams of Oasis polymeric sorbent (p/n WAT094287). The mixture may be stirred using a spatula and then combined with 3,500 mL of S 1  to form sorbent/glass microfiber suspension S 11 . 
         [0057]    A 50 cm A-E glass microfiber mesh  16  may be placed in the cavity  32  of mold base  20 , overlying porous member  22 , and the cavity  32  of mold base  20  filled to the rim (about 100 mL) with S 1 . The cavity  32  of mold base  20  may be evacuated, particularly with a vacuum, to draw the glass microfiber layer down (this forms  16 A) and the collar  24  inserted and the vacuum turned off. 
         [0058]    Fifty (50) mL of S 11  may be added to the disk mold and vacuum applied to form a cake  14 . The collar  24  may be removed and the vacuum turned off. 
         [0059]    Next, a plug  26  may be inserted into the cavity  32  of mold base  20  centering it over the cake  14 . The cylindrical ring space of cavity  32  between the plug  26  and mold base  20  may then be filled with S 9  and vacuum applied to draw the glass microfiber layer down. With the vacuum on, the plug  26  may be removed and cavity  32  of the mold base  20  filled with S 1  and vacuum applied until the glass microfiber layer is drawn down. The blunt end of the collar  24  may be applied to smooth out the disk edge. This may be followed by removing the disk  10  from the cavity  32  of mold base  20  and drying in an oven about 12 hours at 70° C. This construction is illustrated in  FIG. 4 . 
       Example E 
       [0060]    In another example, a suspension (S 1 ) may be provided by adding 11,356 mL of deionized water to a 19,000 mL container, followed by 51 grams of 704BBC and 10 mL of concentrated HCl. These ingredients may be mixed using Cuisinart and Stir-Pak mixers for about 5 minutes on high speed. 
         [0061]    This may be followed by the preparation of a sorbent suspension (S 12 ) comprising 800 mL of isopropanol and 160 grams of Oasis polymeric sorbent (p/n WAT094287). The mixture may be stirred using a spatula and then combined with 3,000 mL of S 1  to form suspension S 13 . 
         [0062]    A 50 cm A-E glass microfiber mesh  16  is placed in the cavity  32  of mold base  20 , overlying porous member  22 , and the cavity  32  of mold base  20  filled to the rim (about 100 mL) with S 1 . The mold base  20  may be evacuated to draw the glass microfiber layer down and the collar  24  inserted with the sharpened end down and the vacuum turned off. 
         [0063]    Next, 25 mL of S 13  may be added to the disk mold and evacuated to form a cake  14 . The collar  24  may be removed and a plug  26  may be added, centered over the cake  14 . The space, or cavity, between the plug  26  and the mold base  20  may next be filled with S 1  and vacuum applied until the glass microfiber layer has been drawn down. With the vacuum on, the plug  26  may be removed and the mold base  20  filled with S 1  and vacuum applied until the glass microfiber layer is drawn down. The blunt end of the collar  24  may be applied to smooth out the disk edge. This may be followed by removing the disk  10  from the mold base  20  and drying in an oven about 12 hours at 70° C. This construction is illustrated in  FIG. 4 . 
         [0064]    It should be understood that, while the present invention has been described in detail herein, the invention can be embodied otherwise without departing from the principles thereof, and such other embodiments are meant to come within the scope of the present invention. 
         [0065]    While a preferred embodiment of the present invention has been described, it should be understood that various changes, adaptations and modifications can be made therein without departing from the spirit of the invention and the scope of the appended claims. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. Furthermore, it should be understood that the appended claims do not necessarily comprise the broadest scope of the invention which the Applicant is entitled to claim, or the only manner(s) in which the invention may be claimed, or that all recited features are necessary. 
         [0066]    All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes to the extent they are consistent.