WO1993003493A1 - Interfacing liquid chromatograph and fourier transform - Google Patents
Interfacing liquid chromatograph and fourier transform Download PDFInfo
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- WO1993003493A1 WO1993003493A1 PCT/US1992/006341 US9206341W WO9303493A1 WO 1993003493 A1 WO1993003493 A1 WO 1993003493A1 US 9206341 W US9206341 W US 9206341W WO 9303493 A1 WO9303493 A1 WO 9303493A1
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- Prior art keywords
- receiving surface
- particles
- cryogenic
- stream
- solvent
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/84—Preparation of the fraction to be distributed
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N2021/3595—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using FTIR
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/74—Optical detectors
- G01N2030/743—FTIR
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/84—Preparation of the fraction to be distributed
- G01N2030/8411—Intermediate storage of effluent, including condensation on surface
- G01N2030/8417—Intermediate storage of effluent, including condensation on surface the store moving as a whole, e.g. moving wire
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/84—Preparation of the fraction to be distributed
- G01N2030/8423—Preparation of the fraction to be distributed using permeable separator tubes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/84—Preparation of the fraction to be distributed
- G01N2030/8447—Nebulising, aerosol formation or ionisation
- G01N2030/8464—Uncharged atoms or aerosols
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/84—Preparation of the fraction to be distributed
- G01N2030/8447—Nebulising, aerosol formation or ionisation
- G01N2030/8476—Nebulising, aerosol formation or ionisation by thermal means
Definitions
- This invention relates to an apparatus and method for interfacing a liquid chromatograph with a fourier transform infrared spectrometer which is applicable to continuous flow use in, e.g., both normal phase and reverse phase separations, and, more particularly, to an improved apparatus and method for removing solvent from continuous flow liquid chromatograph eluent and collecting the sample particles thereby generated for reliable and accurate infrared spectroscopy.
- MS mass spectrometer
- FTIR Fouriertransform infrared
- Browner and coworkers developed a monodisperse aerosol generator interface for combining LC and FTIR spectrometry, known as the MAGIC interface. With this interface, mobile phase elimination was to be accomplished at room temperature, wherein effluent from an HPLC enters the interface through a 25 micrometer diameter orifice to form a liquid jet. The jet is dispersed by a Helium (He) stream to create a fine aerosol which is directed from a desolvation chamber into first and second momentum separators.
- He Helium
- evaporated solvent and Helium are removed by vacuum pumps, and the nonvolatile analyte continues into the second momentum separator where any residual volatile material is to be removed.
- the nonvolatile analyte is then deposited on a KBr (potassium bromide) window which is removed and placed in a beam condenser for IR analysis. Because the solvent is eliminated priorto deposition on the substrate, the isolated analyte can be deposited on a variety of substrates for various IR detection methods.
- M.L Vestal, et al. described similar apparatuses and methods for coupling LC and solid phase detectors, including the use of thermospray vaporizers which vaporize most of the solvent priorto introduction to a desolvation chamber.
- the device set forth in the '958 patent further contemplates passing the vaporized solvent and added carrier gas through one or more sol ent removal chambers, which can remove solvent by condensation or diffusion through a membrane to a counterf lowing gas stream.
- This device may further include a momentum separatorto concentrate particles relative to the remaining solvent vapor and carrier gas, and teaches the direction of a particle beam for impactwith a cryogenically cooled deposition surface.
- a moving belt is provided for receiving the particle beam, and a temperature transducer is positioned adjacent the belt to maintain the belt at a temperature where no significant amount of the particle sample will be vaporized, yetwarm enough that residual liquid solvent is vaporized efficiently in a stream of counterf I owing gas which passes over the belt.
- the Vestec Universal Interface incorporates many of the features described in the Vestal patents mentioned above, and is available inthe industry from Vestec Corporation of Houston, Texas. An apparatus for combining LC technology with mass spectrometry is described in
- the Dorn, et al. device includes a nebulizer which volatilizes the LC eluate to form an aerosol which passes through a desolvation chamber.
- the nebulizer introduces an inert gas which helps vaporize the solvent and carries the aerosol to a momentum separator which accelerates the particles to sonic velocities.
- the momentum separator includes three vacuum pumping stages, wherein the first two stages are defined by conical skimmer nozzles, and the third chamber includes a long inlet tube which provides the vacuum pumping restriction. The resulting particle beam is provided to the MS ion source for analysis.
- LC/FT1R interfaces have provided only limited success i ⁇ roviding interpretable IR spectra from normal-phase and reverse-phase separations, due to inadequate solvent elimination and/or limited applicability to IR analysis.
- an apparatus for interfacing a liquid chromatograph (LC) with a spectrometer such as a Fourier transform infrared spectrometer the LC having an eluant, the eluant containing a solvent and a component of interest.
- the apparatus includes five basic parts. The first is a means for generating a stream of droplets of the eluant, such as a nebulizer.
- the second is a means for removing most of the sol vent from the stream of droplets of the eluant to thereby generate a stream of particles, the particles containing the component of interest and any residual solvent, such as a membrane solvent separator/momentum separator combination.
- the third is a cryogenic receiving surface, such as a gold drum.
- the forth is a means for focusing the stream of particles onto the cryogenic receiving surface so that the particles adhere to the cryogenic receiving surface, such as a one and two-tenths millimeter inside diameter stainless steel tube positioned with a gap between the distal end of the tube and the cryogenic receiving surface of one-quarter millimeter.
- the fifth is a means for controlling the temperature of the cryogenic receiving surface, such as a helium refrigerator.
- the cryogenic receiving surface is maintained at a temperature effective to cause the particles to adhere to the cryogenic receiving surface to form a region of adhered particles, such as a temperature of between seventy and one hundred and five degrees Kelvin, the cryogenic receiving surface being maintained in a partial vacuum. Then, the cryogenic receiving surface is warmed, e.g., to between one hundred and five and two hundred degrees Kelvin, to volatalize essentially all of any remaining solventfrom the region of adhered particles priorto spectroscopic analysis of the region of adhered particles.
- FIG. 1 is a schematic illustration of an apparatus for interfacing a liquid chromatograph with a fourier transform infrared spectrometer made in accordance with the present invention
- Fig. 2 is an enlarged schematic view of a preferred embodiment of a momentum separator of an interfacing apparatus made in accordance with the present invention
- Fig. 3 is a phase sensitive IR reconstructed chromatogram of an infrared analysis of DOWCOTM 441 butyl ester and XRD-433 1-methyl heptyl ester sample mixture where the collection disk was not warmed priorto cooling and IR analysis, wherein relative concentration is plotted on the left axis against retention time (in minutes) on the horizontal axis;
- Fig.4 is a single beam spectrum plot of one of the peaks of the chromatogram of Fig. 3 associated with DOWCOTM 441 butyl ester, wherein emissivity is plotted on the vertical axis against wavenumber along the lower horizontal axis, and wavelength (in microns) along the upper horizontal axis;
- Fig. 5 is a phase sensitive IR reconstructed chromatogram of an infrared analysis of DOWCOTM butyl ester and XRD-433 1-methyl heptyl ester sample mixture where the collec ⁇ tion disk was warmed after chromatography priorto cooling and IR analysis, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 6 is a phase sensitive I R reconstructed chromatogram of various concentrations of XRD-433 1-methyl heptyl ester, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 7 is an ultraviolet (UV) chromatogram of DOWCOTM 441 butyl ester and XRD- 433 1-methyl heptyl ester which was injected onto a C ⁇ chromatographic column, wherein relative absorbance is plotted on the vertical axis against time on the horizontal axis;
- Fig.8 is a phase sensitive IR reconstructed chromatogram of the separated mixture of Fig.7, wherein relative concentration is plotted on the left axis against retention time (in minutes) on the horizontal axis;
- Fig.8a illustrates an infrared spectrum obtained from chromatography of the DOWCOTM 441 Butyl Ester component of the mixture separated and illustrated in Fig.8, wherein relative absorbance is plotted on the vertical axis against wavenumber along the lower horizontal axis.and wavelength (in microns) along the upper horizontal axis;
- Fig.8b illustrates an infrared spectrum obtained from chromatography of the XRD-433 1-methyl Heptyl Ester component of the mixture separated and illustrated in Fig. 8, wherein relative absorbance is plotted on the vertical axis against wavenumber along the lower horizontal axis,and wavelength (in microns) along the upper horizontal axis;
- Fig.9 is a phase sensitive IR reconstructed chromatogram of a mixture of compounds frequently used as polymer additives, utilizing a capillary inlet tube having an inside diameter of 1.2 mm, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 10 is a phase sensitive IR reconstructed chromatogram of the polymer additives mixture plotted in Fig.9, but utilizing a capillary inlet tube having a tip inside diameter of 0.5 mm, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 11 is a phase sensitive I R reconstructed chromatogram of selected compounds injected into the chromatograph and processed in accordance with the present invention using THF as the solvent, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 12 is a UV chromatogram of the separation of a mixture of polystyrene molecular weight standards, wherein relative absorbance is plotted on the vertical axis against time (minutes) on the horizontal axis;
- Fig. 13 is a phase sensitive IR reconstructed chromatogram of a mixture of polystyrene molecular weight standards, wherein relative concentration is plotted on the vertical axis against retention time (in minutes) on the horizontal axis;
- Fig. 13a illustrates an infrared spectrum obtained from chromatography of the
- Fig. 13 illustrates an infrared spectrum obtained from chromatography of the
- Fig. 14 illustrates the infrared spectrum obtained from chromatography of a 1200 molecular weight styrene/ acrylonitrile copolymer wherein relative absorbance is plotted on the vertical axis against wavenumber along the lower horizontal axis, and wavelength (in microns) along the upper horizontal axis.
- FIG. 1 is a schematic illustration of an apparatus 40 for interfacing a liquid chromatograph (LC) device (e.g., 42) with a fourier transform infrared spectrometer (FTIR) device (e.g., 1 10).
- LC liquid chromatograph
- FTIR Fourier transform infrared spectrometer
- an LC effluent line 44 directly connects a standard chromatographic column of LC device 42 with interface apparatus 40, extending inwardly into desolvation chamber 50 in the form of a thermospray vaporizer 46.
- Thermospray vaporizers are well known in the industry, such as available from Vestec Corporation, Houston, Texas.
- a heating means 47 may preferably circumscribe a portion of effluent line 44 and/or comprise part of vaporizer 46 to facilitate vaporization of the solvent included in effluent 43 passing therethrough.
- the nebulized LC eluent 43 is entrained with an inert carrier gas, such as Helium (He), which is introduced via inlet 48 adjacent the upper portions of desolvation chamber 50.
- the entrained aerosol 49 i.e., a stream of droplets of the eluant, isthereby carried along desolvation chamber 50 and into carrier tube 52, and the flow rate of the incoming eluent 43 will preferably match the standard chromatographic column flow up to about 2 ml/minute or more.
- a generally U-shaped portion of carrier tube 52 enables collection of condensate from the vaporized solvent for removal via peristaltic pump 56 through vent 54, and deposition in waste collection device 57.
- Carriertube 52 directs aerosol 49 to membrane separator 60, which comprises a membrane 61 serially connected with carriertube 52.
- the membrane should be sufficiently permeable that the solvent vapor can diffuse freely across it, yet provide a sufficient barrier to flow of carrier gas such that any net flow of gas through the membrane is relatively small. In this way, sample particles to be analyzed will not pass through the membrane, and the membrane can effectively extract solvent vapor from aerosol 49.
- a fibrous porous form of PTFE available under the tradename "Zitex" has been found to be satisfactory for use as membrane 61.
- a gas diffusion cell 63 effectively surrounds membrane 61 to contain a counterflow gas stream provided by gas inlet 64 and outlet 66.
- this counterflow gas also be inert, and identical to the carrier gas uti I ized i n the system.
- the dry aerosol issuing from membrane separator 60 continues through a reduced diameter section 68 of carriertube 52 into momentum separator 70, situated downstream from membrane separator 60.
- Reduced section 68 can preferably comprise a TeflonTM tube having an inside diameter of approximately 6.25 mm.
- membrane 5 separator 60 can efficiently operate at substantially atmospheric pressure
- momentum separator 70 is provided with a pair of first and second pumping stations 72 and 80 respectively, each provided with a source of underpressure or vacuum.
- the dry aerosol from membrane separator 60 continues toward momentum separator 70 as a result of the momentum of the carrier gas being supplied via inlet 10 48, and as a result of being pulled by the underpressure present in interior 77 of first pumping stage 72.
- Such underpressure or vacuum is provided to first pumping stage 72 via vacuum fitting 79 which is connected to an appropriate pump (not shown).
- Interior 77 is defined by inlet nozzle 73 and conical skimmer device 75 having an opening 76 of predetermined diameter. Pressure within interior 77 may be set at an appropriate underpressure of 5 approximately 500 Torr.
- the de-gassed dry aerosol exiting first pumping stage 72 passes through opening 76 into second pumping stage 80 as a result of its momentum, and due to a relatively greater 0 underpressure within interior 85 of second stage 80.
- Conical skimmer 75 and a capillary inlet tube 83 having an inside diameter of approximately 1.2 mm effectively isolate second stage 80 from first pumping stage 72 and from the vacuum chamber 114 (and source) of FTIR device 110.
- Fitting 87 connects interior 85 to a second vacuum pump (not shown) which provides a relatively more significant underpressure (e.g., approximately .5 Torr) within second stage 80, 5 and enables removal of residual carrier gas and vaporized solvent passing within interior 85.
- aerosol 49 Upon removal of substantially all of the carrier gas and remaining vaporized solvent, aerosol 49 has been effectively transformed into a beam or stream of sample particles of the sample compound, i.e., of the component of interest.
- the particle beam Due to the momentum of the particle beam, and an even more severe 0 underpressure or vacuum within FTIRdevice 110, the particle beam continues its movement into capillary orifice 90, through tube 83, and out distal end 92 thereof.
- the particle beam is directed from capillary tube 83 and collimated, i.e, focused, onto a cryogenic collection disk or drum 112, i.e., onto a cryogenic receiving surface, within the interior or vacuum chamber 114 of the cryogenic chamber of FTIR device 110.
- the focusing results in a deposit of particles having a small area so that sensitivity of detection is maximized and so that chromatographic resolution is maintained.
- collection disk 112 be provided with a rotary stage 115to enable rotation for continuous collection and IR analysis. It has been found that interface apparatus 40 can enable a pressure of 5.4 x 10-5 Torr within chamber 114. Particles collected upon collection disk 112 can thereafter be analyzed by IR detector 128, with optical beam 122 being focused by mirrors 124 and 125 onto rotating collection disk 1 12, as illustrated. Further details of FTIR device 1 10 will be omitted herein, as commercial FTIR devices such as the Cryolect4800TM (manufactured by Mattson instruments, Inc. of Madison, Wl) are commonly available in the industry.
- Cryolect4800TM manufactured by Mattson instruments, Inc. of Madison, Wl
- heating capillary tube 83 can be provided to minimize condensation or other collection of particles along tube 83 and prior to deposition on the collection disk.
- a preferred manner of providing such heating means comprises coating the outside diameter of a glass capillary tube 83 with a uniform, at least partially conductive material (e.g., silver epoxy as available from Epoxy Technology, Inc., Billericq, Mass.), and passing current along the coating to apply a controlled amount of heat thereto.
- an 83 mm long tube 83 having an inside diameter of 1.2 mm coated with silver epoxy can be maintained at approximately 200°C through the use of 8 volts AC power controlled through two variacs (e.g., see 93 of Fig. 2) as seen in Fig. 2, a thermocouple 94 can be provided to control heater 93 to provide proper electrical powerthrough heating wires 88.
- a metal tube 83 is used, then heating of the tube 83 is less important, e.g., a one-sixteenth inch outside diameter, one and two-tenths millimeter inside diameter stainless steel tube 83.
- the inside diameter of the tube 83 is between about one-half and about two millimeters and more preferably it is between about one and one and one-half millimeter.
- the inside diameter of the tube 83 can be smaller than one-half millimeter, e.g., one-quarter millimeter or one-eighth millimeter.
- the inside diameter of the tube 83 can be larger than two millimeters, e.g., four millimeters or eight millimeters.
- the tube 83 is one means for focusing a stream of particles onto a cryogenic receiving surface, e.g., the disk 1 12.
- Another means for focusing a stream of particles onto a cryogenic receiving surface would be to replace the tube 83 with an aperture plate mounted just before the disk 112. In this case, it is preferable to reduce the spacing between the disk 112 and the skimmer 75. If the disk 1 12 were positioned adjacent the skimmer 75, then the skimmer 75 would serve as a means for focusing a stream of particles onto a cryogenic receiving surface. However, in this case, it would be more preferable to add an additional nozzle and pumping stage, like the nozzle 74, after the skimmer 75 and position the disk 112 very near the tip of the added nozzle.
- momentum separator 70 may preferably be connected to FTIR device 110 via a link housing 100 sealed within flange 103 via an o-ring 104, and connected at its opposite end to adapter 98 attached adjacent cryogenic chamber 1 10.
- Heated capillary tube 83 passes through link housing 100, and is supported therein by a spacer 105, and a pair of O-rings 104.
- O-rings 104 also serve to insulate tube 83 so that it can be heated electrically.
- Heating wires 88 and thermocouple connection wire 89 are appropriately connected to capillary tube 83 through housing 100 and seal 96.
- Cryogenic disk 112 is preferably provided with a rotary stage 115, and can be cooled via a source of liquid helium (not shown), such as through cooling line or cold finger 117.
- a source of liquid helium not shown
- the use of a helium refrigerator arrangementto facilitate achieving and maintaining cryogenictemperatures is well known in the industry, and will not be further described herein.
- other refrigeration means can be used such as liquid nitrogen.
- a control device 118 may be provided to control the temperature and rotary motion of collection disk 112. Rotation of disk 112 may be desired to allow deposition of particles thereon in a spiral-like pattern to enable continuous deposition and anaiysisfor extended periods of time.
- Capillary tube 83 serves to collimatethe particle beam so that the particles can be accurately targeted onto the cryogenic collection disk 112, either with or without a matrix gas such as argon.
- tube 83 is preferably heated (e.g., to a temperature of about 130-140°C) to help insure that sample particles do not condense or collect along the tube priorto deposition on disk 112.
- the gap between the tip of the tube 83, or other such means, and the disk 112 is important. This gap is preferably between about one-eighth and about one millimeter and more preferably it is between about one-quarter and about one-half millimeter. However, this gap can be smallerthan one-quarter millimeter, e.g., one-hundredth millimeter, one-fiftieth millimeter, one-twentyfifth millimeter or one-twelfth millimeter. On the other hand, this gap can be greater than one millimeter, e.g., two millimeters, four millimeters, eight millimeters or even more.
- Collection disk 112 is to be maintained in a preferred temperature range of between about 70K and about 105Kfor collection of particles. While this range is not critical, it has been found that collection at temperatures significantly below 70K may result in cracking or flaking of the material deposited on the disk, as a result perhaps of inelasticity at the lower temperatures. It may be important not to remove absolutely all of the solventfrom the stream of particles and the particles themselves prior to the particles impacting the cryogenic receiving surface- The residual solvent may be beneficial to "glue" the particles to the cryogenic receiving surface. However, it should be clearly understood that this is not known to be true at present. It is only hypothesized to help explain the invention and not to be limiting thereof.
- the temperature of the cryogenic receiving surface that is effective to cause the particles to adhere to the cryogenic receiving surface can be as low as two, four, eight, sixteen, thirty two, or sixty four degrees Kelvin or as high as one hundred fifty, two hundred, two hundred fifty or three hundred degrees Kelvin depending on the component of interest.
- the temperature of disk 1 12 is allowed to rise, e.g., to approximately 180K. It has been found that relative warming of the disk following collection of the particles is beneficial to optimizing IR test analysis results, and serves to remove trace residual amounts of solvent both from the disk and compounds collected on the disk. Following warming the disk, e.g., to approximately 180K, its temperature is then preferably cooled down to approximately 13K, so that the drum 1 12 contracts into better focus of the light beam 122, priorto undertaking the IR spectroanalysis. As will be seen in the examples below, resulting IR analysis following this serial warming and cooling procedure is essentially noise free, with the base line between analyzed components in the compound dropping to approximately zero. Temperature controller 1 18 can automatically implement the required temperature profile of collection disk 1 12, such as by computer supervision or the like.
- disk 1 12 can be cleaned by warming to room temperature, whereupon volatile particles will vaporize and can be extracted from chamber 110 via vacuum. Less volatile components may also require physical cleaning of the disk with solvent orthe like.
- a mixture of XRD-433 1-methyl heptyl ester (43 ng/ ⁇ l), and DOWCOTM 441 butyl ester (111 ng ⁇ l) was flow injected into the liquid chromatograph and the column eluent collected in accordance with the present procedure.
- a graph showing the phase sensitive IR reconstructed chromatogram of this mixture is shown in Fig.3, wherein immediately after the chromatography was complete, the collection disk was cooled to approximately 13K (without first warming it to 180K). The relatively ragged base line obtained in this reconstruction is believed to be the result of light scattering and excessive solvent obtained from the IR analysis.
- FIG. 6 A phase sensitive IR chromatogram for a series of flow injections of varying concentrations of XRD-433 1-methyl heptyl ester into the liquid chromatograph is illustrated in Fig. 6. While no generalized statement concerning the ultimate sensitivity of the present apparatus and method has been identified (since different compounds feature widely varying IR absorption characteristics), it is believed that beyond doubt, such sensitivity is superior to those obtainable utilizing previously known techniques for LGIR analysis.
- UV detection of separations was also undertaken utilizing the present apparatus and process.
- the UV chromatogram of the separation of DOWCOTM 441 butyl ester and XRD-433 1-methyl heptyl ester injected into a CQ chromatographic column is shown graphically in Fig. 7, where relative absorbance is plotted against time.
- the first peak is DOWCOTM 441, while the second, smaller peak is the XRD-433 compound.
- the phase sensitive IR reconstructed chromatogram of the XRD-433/DOWCOTM 441 mixture is shown in Fig. 8, where relative concentration of collected particles is plotted against retention time.
- a comparison of Figs. 7 and 8 shows that the base line separation of the two components was not clearly obtained under the chromatographic conditions.
- the phase sensitive IR reconstruction of Fig. 8 indicates that the degree of separation obtained in the UV portion of the experiment is not significantly degraded by either the LC interface, or by trapping the individual components on the cryogenic collection disk.
- Figs.8a and 8b illustrate infrared spectra of the individual components DOWCOTM 441 Butyl Ester and XRD-433 1-Methly Heptyl Ester, respectively. As can be seen in these figures, little or no spectral interferences are evident in either of these compounds. Effects of Capillary Diameter on Sensitivity
- the preferred capillary inner diameter is about 1.2 mm.
- a phase sensitive I R chromatogram obtained from a test mixture of compounds frequently used as polymer additives is shown in Fig.9, where relative concentration of collected particles is plotted against retention time.
- the peak furthest to the left represents the individual constituent Benzyl Butylphthalate, the second peak represents Naugard XL-1 , the third peakTinuvin 328, and small peak to the right Irganox 1076.
- These compounds are very common and well known in the industry, and are available from a variety of sources.
- Fig. 10 The phase sensitive IR chromatogram obtained using the 0.5 mm tipped tube with the identical mixture is shown in Fig. 10, where relative concentration of collected particles is again plotted against retention time.
- Fig. 10 A comparison of Fig. 10 with Fig.9 indicates that sensitivity was clearly lost when the smaller diameter capillary tube was used to interface the particle beam with the collection disk. Consequently, it is believed that reduction of the spot size and concentration of deposited solutes from the particle beam clearly reaches a point of diminishing returns below about 1.2 mm.
- the capillary tube 83 is made of glass or a glass like material, then it is preferably heated to minimize the possibility of condensation of sample particles from the particle beam along the tube priorto deposition on the collection disk 112.
- a series of flow injections of XRD-433 1-methyl heptyl ester was made using the 1.2 mm capillary tube diameter operating at ambient temperatures.
- the phase sensitive I R chromatogram documenting the analysis results of this example is shown in Fig. 5. Particularly, the first three concentration peaks in the nine to fourteen minute time retention period were obtained with the capillary tube being operated at ambienttemperature. The fourth (smaller) peak, however, was not the result of additional sample being injected into the system.
- this fourth, smaller peak resulted from activation of the heating means to heat capillary tube 83 to between about 135°C and 140°C.
- the heating of tube 83 caused particles which had condensed or otherwise collected along tube 83 to be released and carried to collection disk 112 for deposition. Consequently, to optimize accuracy and sensitivity of the apparatus, it is preferred to heat a glass capillary tube 83 as described above.
- Fig. 1 The phase sensitive IR reconstructed chromatogram of a mixture of selected compounds consisting of probucol and polystyrene of molecular weight 68,000 injected into the chromatograph using tetrahydrofuran (THF) as the mobile phase is shown in Fig. 1 1.
- the first three peaks (from the left) and the sixth peak each represent probucol, while the very low blips at about times 107 and 108 represent the polystyrene.
- FIG. 12 A U V chromatogram showing the results of separation of a mixture of polystyrene molecular weight standards is illustrated in Fig. 12. These polystyrene molecular weight standards are available in the industry, such as from Polymer Laboratories Inc., of Amherst, MA. Particularly, the peak shown near the ten minute retention time is molecular weight 1 ,950,000, that shown near the 12-minute interval is 1 15,000 molecular weight, that shown just beyond the 14-minute time period is 9,200 molecular weight, and 1,200 molecular weight shown at just beyond 16 minutes.
- the UV detector was set at 265 microns.
- the corresponding phase sensitive IR chromatogram for this experiment is shown in Fig. 13, wherein the first two concentration peaks from the left represent the 1 ,950,000 and 1 15,000 molecular weight constituents, respectively, the third peak at 46 minutes is 9,200 molecular weight, while the fourth peak at about 48 minutes is the 1 ,200 molecular weight constituent.
- the IR chromatogram clearly indicates that the separation of the four standards is maintained through the membrane separator and particle beam deposition process of the present invention, and it is also apparent that even the high molecular weight polystyrene sample is collected on the cryogenic collection disk.
- Figs. 13a and 13b illustrate infrared spectra of the 1,950,000 molecular weight and 1,200 molecular weight polystyrene components, and are representative of the mixture discussed above.
- Fig. 14 the IRspectrum obtained from chromatographing a 1200 molecular weight styrene/acrylonitrile copolymer is shown in Fig. 14, where relative absorbance is plotted along the vertical axis, wavenumber is plotted along the lower horizontal axis, and wavelength (in microns) is plotted along the upper horizontal axis.
- this plot clearly indicates the potential for utilizing the present apparatus and process for determining the composition of SAN copolymers based upon relative molecular weight.
- infrared analysis of systems separated by size exclusion chromatography will allow the determination of the composition of various polymer systems with respect to varying molecular weights, in addition to allowing the study and determination of composition of various fractions of polymer blends that have been separated by size exclusion chromatography.
- the present apparatus and process can also be readily interfaced with hydrodynamic chromatography and field flowfractionation chromatography, which will enable the accurate determination of composition of polymer species with respect to particle size.
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US73876991A | 1991-08-01 | 1991-08-01 | |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
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WO1996013159A1 (en) * | 1994-10-26 | 1996-05-09 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Cryo-preservation and low-temperature processing of biological objects |
US5798679A (en) * | 1995-06-07 | 1998-08-25 | Houston Advanced Research Center | Magnetic flux bending devices |
WO2015142906A1 (en) * | 2014-03-17 | 2015-09-24 | Prism Analytical Technologies, Inc. | Process and system for rapid sample analysis |
WO2020068280A1 (en) * | 2018-08-08 | 2020-04-02 | Brightspec, Inc. | Methods and apparatus for low-volatility sampling |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US4883958A (en) * | 1988-12-16 | 1989-11-28 | Vestec Corporation | Interface for coupling liquid chromatography to solid or gas phase detectors |
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1992
- 1992-07-30 WO PCT/US1992/006341 patent/WO1993003493A1/en active Application Filing
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US4883958A (en) * | 1988-12-16 | 1989-11-28 | Vestec Corporation | Interface for coupling liquid chromatography to solid or gas phase detectors |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1996013159A1 (en) * | 1994-10-26 | 1996-05-09 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Cryo-preservation and low-temperature processing of biological objects |
US5925511A (en) * | 1994-10-26 | 1999-07-20 | Fraunhofer Gesellschaft Zur Fordereung Der Angeweandten Forschung E.V. | Cryopreserving and cryogenically processing biological objects |
US5798679A (en) * | 1995-06-07 | 1998-08-25 | Houston Advanced Research Center | Magnetic flux bending devices |
WO2015142906A1 (en) * | 2014-03-17 | 2015-09-24 | Prism Analytical Technologies, Inc. | Process and system for rapid sample analysis |
US9606088B2 (en) | 2014-03-17 | 2017-03-28 | Prism Analytical Technologies, Inc. | Process and system for rapid sample analysis |
US10054486B2 (en) | 2014-03-17 | 2018-08-21 | MLS ACQ, Inc | Process and system for sample analysis |
US10551249B2 (en) | 2014-03-17 | 2020-02-04 | Mls Acq, Inc. | Process and system for sample analysis |
WO2020068280A1 (en) * | 2018-08-08 | 2020-04-02 | Brightspec, Inc. | Methods and apparatus for low-volatility sampling |
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