WO2012055432A1 - Cellule à guide d'ondes présentant une ouverture numérique améliorée - Google Patents

Cellule à guide d'ondes présentant une ouverture numérique améliorée Download PDF

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Publication number
WO2012055432A1
WO2012055432A1 PCT/EP2010/066205 EP2010066205W WO2012055432A1 WO 2012055432 A1 WO2012055432 A1 WO 2012055432A1 EP 2010066205 W EP2010066205 W EP 2010066205W WO 2012055432 A1 WO2012055432 A1 WO 2012055432A1
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Prior art keywords
optical fiber
light
numerical aperture
cell
waveguide
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PCT/EP2010/066205
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English (en)
Inventor
Bernd Nawracala
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Agilent Technologies, Inc.
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Priority to PCT/EP2010/066205 priority Critical patent/WO2012055432A1/fr
Publication of WO2012055432A1 publication Critical patent/WO2012055432A1/fr

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    • 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
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/05—Flow-through cuvettes
    • 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
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/0303—Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment
    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
    • 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
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N2021/0346—Capillary cells; Microcells
    • 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
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/05—Flow-through cuvettes
    • G01N2021/052—Tubular type; cavity type; multireflective
    • 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
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/645—Specially adapted constructive features of fluorimeters
    • G01N2021/6482—Sample cells, cuvettes
    • 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
    • G01N2030/746—Optical detectors detecting along the line of flow, e.g. axial
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/032—Optical fibres with cladding with or without a coating with non solid core or cladding
    • G02B2006/0325—Fluid core or cladding

Definitions

  • the present invention relates to a waveguide cell, to a photometric apparatus, and to a separation system.
  • the present invention further relates to a method of determining an optical property of a liquid in a waveguide cell.
  • US Patent 4,392,712 describes a light distributor comprising a plurality of optical fibers each having a tapered portion.
  • International Patent application WO 94/04892 describes spectroscopic systems for the analysis of small and very small quantities of substances.
  • US Patent 6,281 ,975 discloses a capillary flow cell with bulbous ends.
  • US Patent 6,542,231 relates to a fiber-coupled liquid sample analyzer with liquid flow cell.
  • International Patent application WO 2009/043968 describes an active optical fiber and a method for fabricating an active optical fiber.
  • International Patent application WO 2009/143217 discloses light-guiding flow cells and analytical devices using the same. DISCLOSURE
  • a waveguide cell comprises a capillary tubing enclosing a cell volume of the waveguide cell, the capillary tubing having a first end and a second end opposite to the first end, a fluid inlet located at the first end of the capillary tubing, a fluid outlet located at the second end of the capillary tubing, a first optical fiber located at the first end of the capillary tubing, the first optical fiber being configured for coupling light into the cell volume of the waveguide cell, the first optical fiber being implemented as a first tapered optical fiber, and a second optical fiber located at the second end of the capillary tubing, the second optical fiber being configured for uncoupling light from the cell volume of the waveguide cell, the second optical fiber being implemented as a second tapered optical fiber.
  • the first optical fiber and the second optical fiber are implemented as tapered optical fibers.
  • tapered optical fibers are capable of transforming numerical aperture.
  • a tapered optical fiber is capable of transforming a standard numerical aperture of light launched into an input side of the optical fiber into an augmented numerical aperture of light obtained at the fiber's tapered end.
  • the capillary tubing of the waveguide cell can accept large numerical apertures which are considerably higher than the numerical apertures provided by conventional optical fibers.
  • the use of tapered optical fibers has several advantages. Because of the small cell volume, the chromatographic resolution of the waveguide cell is quite good. The light throughput is higher than before, and therefore, even for waveguide cells with small cell volumes, a good signal- to-noise ratio is obtained . Furthermore, by selecting a capillary tubing having a minimum length, it is possible to realize a waveguide cell with good sensitivity.
  • the capillary tubing is capable of accepting a light cone with a numerical aperture of at least 0.4.
  • the first tapered optical fiber has a numerical aperture of at least 0.4.
  • the second tapered optical fiber has a numerical aperture of at least 0.4.
  • the waveguide cell is configured to guide light by total internal reflection.
  • the capillary tubing is an air-clad capillary.
  • the capillary tubing is an air-clad capillary that can accept light with a numerical aperture of 0.4 or more.
  • the capillary tubing is an air-clad capillary, with light being reflected at an outer glass-air boundary of the capillary tubing.
  • the cell volume is less than 1 0 microliter. According to a preferred embodiment, the cell volume is less than 4 microliter.
  • an inner diameter of the capillary tubing is below 700 ⁇ .
  • the length of the capillary tubing is in a range between 8 mm and 60 mm. According to a preferred embodiment, the length of the capillary tubing is in a range between 8 mm and 12 mm.
  • the fluid inlet is configured for supplying a flow of liquid to the cell volume of the waveguide cell.
  • the fluid outlet is configured for withdrawing a flow of liquid from the cell volume of the waveguide cell.
  • the first tapered optical fiber is configured for transforming a numerical aperture of light.
  • the first tapered optical fiber is configured for receiving light at a regular numerical aperture and for transforming said light into light having an augmented numerical aperture.
  • the first tapered optical fiber is configured for transforming a regular numerical aperture of light launched into the first tapered optical fiber at a first end into an increased numerical aperture of light at a tapered end of the first tapered optical fiber.
  • the second tapered optical fiber is configured for transforming a numerical aperture of light.
  • the second tapered optical fiber is configured for receiving light at an augmented numerical aperture at its tapered end and for transforming said light into light having a regular numerical aperture.
  • the second tapered optical fiber is configured for transforming an augmented numerical aperture of light received at its tapered end into a regular numerical aperture.
  • the second optical fiber is configured for receiving light having an augmented numerical aperture at its tapered end and for transforming said augmented numerical aperture into a regular numerical aperture.
  • the enhanced numerical aperture of the first tapered optical fiber causes an increase of light throughput of the waveguide cell.
  • the enhanced numerical aperture of the first tapered optical fiber causes an increase of light throughput of the waveguide cell and a corresponding increase of photo current.
  • the enhanced numerical aperture of the first tapered optical fiber causes a reduction of noise of a detected signal.
  • the enhanced numerical aperture of the first tapered optical fiber causes an improvement of a signal-to-noise ratio of a detected signal.
  • the enhanced numerical aperture of light provided by the first tapered optical fiber causes an increase of light throughput and a corresponding increase of photo current, which in turn leads to an improved signal-to-noise ratio.
  • the enhanced numerical aperture of light received by the second tapered optical fiber corresponds to an increase of light throughput.
  • the enhanced numerical aperture of light received by the second tapered optical fiber corresponds to an increase of light throughput and a corresponding increase of photo current.
  • the enhanced numerical aperture of light received by the second tapered optical fiber corresponds to a reduction of noise of a detected signal.
  • the enhanced numerical aperture of light received by the second tapered optical fiber corresponds to an improvement of signal-to-noise ratio of a detected signal.
  • the enhanced numerical aperture of light received by the second tapered optical fiber corresponds to an increase of light throughput and a corresponding increase of photo current, which in turn leads to an improved signal-to-noise ratio.
  • the waveguide cell is used in at least one of these application areas: absorbance spectroscopy, Raman spectroscopy, fluorescence spectroscopy, high performance liquid chromatography, capillary electrophoresis.
  • a photometric apparatus is configured for determining an optical property of a liquid, the photometric apparatus comprising a light source; a liquid core waveguide cell according to any of the preceding claims; and a spectroscopic detection unit.
  • a fluid separation system is configured for separating compounds of a sample fluid in a mobile phase, the fluid separation system comprising: a mobile phase drive, preferably a pumping system, configured to drive the mobile phase through the fluid separation system; a separation unit, preferably a chromatographic column, configured for separating compounds of the sample fluid in the mobile phase; and a photometric apparatus according to the preceding claim, the photometric apparatus being configured to detect separated compounds of the sample fluid.
  • Embodiments of the present invention might be embodied based on most conventionally available HPLC systems, such as the Agilent 1290 Series Infinity system, Agilent 1200 Series Rapid Resolution LC system, or the Agilent 1 100 HPLC series (all provided by the applicant Agilent Technologies - see www.agilent.com - which shall be incorporated herein by reference).
  • HPLC system comprises a pumping apparatus having a piston for reciprocation in a pump working chamber to compress liquid in the pump working chamber to a high pressure at which compressibility of the liquid becomes noticeable.
  • One embodiment of an HPLC system comprises two pumping apparatuses coupled either in a serial or parallel manner.
  • serial manner as disclosed in EP 309598 A1
  • an outlet of the first pumping apparatus is coupled to an inlet of the second pumping apparatus
  • an outlet of the second pumping apparatus provides an outlet of the pump.
  • parallel manner an inlet of the first pumping apparatus is coupled to an inlet of the second pumping apparatus, and an outlet of the first pumping apparatus is coupled to an outlet of the second pumping apparatus, thus providing an outlet of the pump.
  • a liquid outlet of the first pumping apparatus is phase shifted, preferably essentially 180 degrees, with respect to a liquid outlet of the second pumping apparatus, so that only one pumping apparatus is supplying into the system while the other is intaking liquid (e.g. from the supply), thus allowing to provide a continuous flow at the output.
  • both pumping apparatuses might be operated in parallel (i.e. concurrently), at least during certain transitional phases e.g. to provide a smooth(er) transition of the pumping cycles between the pumping apparatuses.
  • the phase shifting might be varied in order to compensate pulsation in the flow of liquid as resulting from the compressibility of the liquid. It is also known to use three piston pumps having about 120 degrees phase shift.
  • the separating device preferably comprises a chromatographic column providing the stationary phase.
  • the column might be a glass or steel tube (e.g. with a diameter from 50 ⁇ to 5 mm and a length of 1 cm to 1 m) or a microfluidic column (as disclosed e.g. in EP 1577012 A1 or the Agilent 1200 Series HPLC-Chip/MS System p ro v i d e d b y t h e a p p l i c a n t A g i l e n t T e c h n l o g i e s , s e e e .
  • a slurry can be prepared with a powder of the stationary phase and then poured and pressed into the column.
  • the individual components are retained by the stationary phase differently and separate from each other while they are propagating at different speeds through the column with the eluent. At the end of the column they elute one at a time. During the entire chromatography process the eluent might be also collected in a series of fractions.
  • the stationary phase or adsorbent in column chromatography usually is a solid material.
  • the most common stationary phase for column chromatography is silica gel, followed by alumina.
  • Cellulose powder has often been used in the past. Also possible are ion exchange chromatography, reversed-phase chromatography (RP), affinity chromatography or expanded bed adsorption (EBA).
  • RP reversed-phase chromatography
  • EBA expanded bed adsorption
  • the stationary phases are usually finely ground powders or gels and/or are microporous for an increased surface, though in EBA a fluidized bed is used.
  • the mobile phase can be either a pure solvent or a mixture of different solvents. It can be chosen e.g. to minimize the retention of the compounds of interest and/or the amount of mobile phase to run the chromatography. The mobile phase can also been chosen so that the different compounds can be separated effectively.
  • the mobile phase might comprise an organic solvent like e.g. methanol or acetonitrile, often diluted with water. For gradient operation water and organic is delivered in separate bottles, from which the gradient pump delivers a programmed blend to the system.
  • Other commonly used solvents may be isopropanol, THF, hexane, ethanol and/or any combination thereof or any combination of these with aforementioned solvents.
  • the sample fluid might comprise any type of process liquid, natural sample like juice, body fluids like plasma or it may be the result of a reaction like from a fermentation broth.
  • the fluid is preferably a liquid but may also be or comprise a gas and/or a supercritical fluid (as e.g. used in supercritical fluid chromatography - SFC - as disclosed e.g. in US 4,982,597 A).
  • the pressure in the mobile phase might range from 2-200 MPa (20 to 2000 bar), in particular 10-150 MPa (100 to 1500 bar), and more particular 50-120 MPa (500 to 1200 bar).
  • the HPLC system might further comprise a sampling unit for introducing the sample fluid into the mobile phase stream, a detector for detecting separated compounds of the sample flu id, a fractionating unit for outputting separated compounds of the sample fluid, or any combination thereof. Further details of HPLC system are disclosed with respect to the aforementioned Agilent HPLC series, provided by the applicant Agilent Technologies, under www.agilent.com which shall be in cooperated herein by reference.
  • a method of determining an optical property of a liquid in a waveguide cell comprising a capillary tubing that encompasses a cell volume, the method comprising coupling light into the cell volume of the waveguide cell via a first tapered optical fiber at a first end of the capillary tubing, and uncoupling the light, after the light has traversed the cell volume, from the cell volume of the waveguide cell via a second tapered optical fiber at a second end of the capillary tubing, the second end being opposite to the first end.
  • Embodiments of the invention can be partly or entirely embodied or supported by one or more suitable software programs, which can be stored on or otherwise provided by any kind of data carrier, and which might be executed in or by any suitable data processing unit.
  • Software programs or routines can be preferably applied in or by the control unit.
  • Fig. 1 shows a setup of a liquid core waveguide cell
  • Fig. 2 shows the properties of a waveguide cell in dependence on the proportions of the respective waveguide cell
  • FIG. 3 shows a waveguide cell with conventional optical fibers
  • Fig. 4 indicates a numerical aperture of a waveguide cell filled with solvent as a function of the refractive index n ext outside of the waveguide cell;
  • Fig. 5 shows a tapered optical fiber;
  • Fig. 6 shows a waveguide cell equipped with two tapered optical fibers, the waveguide cell having a cell volume of 4 ⁇ ;
  • Fig. 7 shows a waveguide cell with two tapered optical fibers, the waveguide cell having a cell volume of 1 ⁇ ;
  • Fig. 8 depicts accessible concentration limit of detection (CLOD) as a function of cell volume for two different waveguide cells; and
  • Fig. 9 shows a CLOD (concentration limit of detection) enhancement factor as a function of cell volume.
  • F ig . 1 shows a l iq u id core waveg u ide cel l configu red for determining an optical property of a solution.
  • the waveguide cell 1 comprises a capillary tubing 2 that contains the liquid.
  • the capillary tubing 2 may e.g. be made of glass or fused silica.
  • a first fitting 3 is fixed to a first end of the capillary tubing 2, and a second fitting 4 is fixed to a second end of the capillary tubing 2, which is opposite of the first end.
  • the first fitting 3 comprises an inlet 5 configured for supplying a liquid to the waveguide cell 1 , as indicated by arrow 6. Via the inlet 5, the waveguide cell 1 may be filled with a liquid that is to be analyzed.
  • the second fitting 4 comprises an outlet 7 configured for withdrawing liquid from the waveguide cell 1 , as indicated by arrow 8.
  • the waveguide cell 1 further comprises a first optical fiber 9 that is mounted to the first fitting 3.
  • the first optical fiber 9 is configured for emitting a light cone 10. The light emitted by the first optical fiber 9 traverses the liquid contained in the capillary tubing 2, with the light being totally reflected multiple times when traversing the liquid.
  • the waveguide cell 1 further comprises a second optical fiber 12 configured for receiving light after the light has passed through the liquid in the capillary tubing 2.
  • the second optical fiber 12 is configured to guide the received light to a detection unit.
  • a waveguide cell of the kind shown in Fig. 1 may e.g. be used in diverse spectroscopic applications, for example in absorbance spectroscopy, in Raman spectroscopy and in fluorescence spectroscopy.
  • a waveguide cell of the kind shown in Fig. 1 may also be applied in high performance liquid chromatography (HPLC) or in capillary electrophoresis (CE), in particular for detecting and analyzing various different components of a liquid sample.
  • HPLC high performance liquid chromatography
  • CE capillary electrophoresis
  • Figs. 2A, 2B and 2C illustrate various different design considerations for designing a liquid core waveguide cell.
  • a waveguide cell 18 is shown, with the waveguide cell 18 comprising a first optical fiber 19, a capillary tubing 20 and a second optical fiber 21 .
  • the dimensions of the capillary tubing are chosen such that the length L-i of the capillary tubing 20 is quite small, whereas the inner diameter ID-, is comparatively large. Due to the large inner diameter IDi of the capillary tubing 20, light throughput is quite large, because light throughput is proportional to
  • the length L-i of the capillary tubing 20 is quite small. Therefore, the cell volume of the waveguide cell is quite small as well, which is advantageous in view of the waveguide cell's resolution: A comparatively small cell volume corresponds to a high resolution when analyzing a flow of liquid. As a rule of thumb, the cell volume should not exceed 1/10 of the sample volume.
  • the length L-i of the waveguide cell determines the waveguide cell's sensitivity.
  • the absorbance A can be expressed in terms of the waveguide cell's sensitivity S and the concentration c of a light-absorbing moiety as follows:
  • Fig. 2B another waveguide cell 22 is shown.
  • the waveguide cell 22 comprises a first optical fiber 23, a capillary tubing 24 and a second optical fiber 25.
  • both the l ight throughput and the sensitivity of the waveguide cell 22 are satisfactory.
  • both the inner diameter ID 2 and the length L 2 of the waveguide cell 22 are rather large, and therefore, the cell volume is quite large as well. This implies that the resolution of the waveguide cell 22 is quite low. In terms of resolution, the waveguide cell 22 shown in Fig. 2B does not yield satisfactory results.
  • a waveguide cell with reduced inner diameter is shown in Fig . 2C.
  • the waveguide cell 26 comprises a first optical fiber 27, a capillary tubing 28 and a second optical fiber 29.
  • the length L 3 of the capillary tubing 28 is quite large, whereas the inner diameter ID 3 of the capillary tubing 28 is relatively small . Due to the small inner diameter ID 3 , the cell volume of the waveguide cell 26 is small, and accordingly, the resolution of the waveguide cell 26 is quite good.
  • Fig . 3 shows the light path in a waveguide cell 30.
  • the waveguide cell 30 comprises a first optical fiber 31 , a capillary tubing 32 and a second optical fiber 33.
  • the first optical fiber 31 is configured for emitting a light cone 34.
  • the second optical fiber 33 is configured for receiving the light after it has passed through the liquid contained in the capillary tubing 32.
  • the waveguide cell 30 may e.g . have a cell volume of 10 ⁇ I . In order to achieve a good sensitivity, the length of the waveguide cell 30 may be chosen as 10 mm.
  • the angle Ch corresponds to half of the aperture angle of the light cone 34.
  • the numerical aperture NAi is determined by the properties of the first optical fiber 31 .
  • the numerical aperture lies in the range between 0.21 and 0.25.
  • the numerical aperture NAi of the light cone 34 lies in the range between 0.21 and 0.25.
  • V of the aqueous solution may be approximately 1 .33.
  • the refractive index n tub of the capillary tubing 32 is 1 .5
  • the refractive index n tub is 1 .45.
  • ⁇ is the angle of incidence
  • ⁇ 2 is the angle of refraction
  • the refracted light ray hits the outer surface of the capillary tubing 32, and there, the light ray is totally reflected, because the angle ⁇ 2 is larger than the angle of total reflection. Hence, the light rays in the light cone 34 are totally reflected at the outer surface of the capillary tubing 32 and remain within the cell volume of the waveguide cell 30.
  • the numerical aperture NA-i of the light cone 34 is mainly determined by the properties of the first optical fiber 31 .
  • the capillary tubing 32 can accept a light cone 36 having a numerical aperture that is much larger than the numerical aperture NAi of the light cone 34 provided by the first optical fiber 31 .
  • the capillary tubing 32 can accept incident light having a numerical aperture that is much larger than a typical numerical aperture of a typical optical fiber.
  • the capillary tubing 32 can accept incident light having a numerical aperture of 0.4 or even more.
  • n SO iv being the refractive index of the liquid in the tubing
  • n ext denoting the refractive index at the exterior of the tubing
  • 5i min denoting the angle of incidence relative to the capillary tubing 32.
  • the maximum angle ai max is known, and hence, the upper limit of the numerical aperture NA max that can be accepted by the capillary tubing 32 can be written as:
  • the upper limit of the acceptable numerical aperture NA max (n S oiv, n ex[ ) is shown as a function of the refractive index n ext , which is the refractive index at the exterior of the capillary tubing 32.
  • V which is the refractive index of the liquid in the capillary tubing 32, is equal to 1 .33, which corresponds to an aqueous solution.
  • the ideal waveguide cell requires fibers of large A-NA 2 product together with small cross-sectional area at cell input allowing for a small cell diameter.
  • a high NA tapered optical fiber is well suited for this purpose.
  • Fig. 5 shows a tapered optical fiber 50 comprising a core 51 surrounded by a cladding 52.
  • the diameter d in of the core 51 may e.g. be 400 ⁇ , and the clad/core ratio may e.g. be 1 .1 .
  • a tapered tip 53 is formed, the tapered tip 53 having a reduced diameter d ou t ⁇
  • the tapered tip 53 is formed by at least partly heating the optical fiber, pulling the ends of the optical fiber apart and cutting the optical fiber at the thinned portion.
  • the core 51 may e.g. consist of fused silica, whereas the cladding 52 may be made of fluorine doped fused silica.
  • the numerical aperture NA 0Ut n S0
  • V ⁇ sin(a) at the output side is rather large.
  • the numerical aperture of light provided by the tapered optical fiber 50 is much larger than the numerical aperture of a regular optical fiber.
  • the waveguide cell 5 may be used both for supplying light to the waveguide cell and for receiving light from the waveguide cell.
  • the waveguide cell's capability of accepting light with a large numerical aperture is taken advantage of.
  • light throughput of the waveguide cell is considerably increased, and the signal-to-noise ratio is improved.
  • Fig. 6 shows a waveguide cell 60 according to a first embodiment of the present invention .
  • the waveguide cell 60 comprises a capillary tubing 61 , a first tapered optical fiber 62 configured for supplying light to the waveguide cell 60, and a second tapered optical fiber 63 configured for receiving light that has been transmitted through the waveguide cell 60.
  • the length of the capillary tubing 61 is chosen to be 10 mm, which is the same length as in Fig. 3. However, compared to the waveguide cell shown in Fig. 3, the cell volume has been reduced considerably. While the cell volume of the waveguide cell 30 shown in Fig. 3 amounts to 10 ⁇ , the cell volume of the waveguide cell 60 shown in Fig . 6 is equal to 4 ⁇ .
  • the cross- sectional area A 2 at the tapered tip of the first tapered optical fiber 62 is considerably smaller than the corresponding cross-sectional area of the optical fiber 31 shown in Fig. 3.
  • the first tapered optical fiber 62 supplies a light cone 64 to the waveguide cell 60, with a 2 denoting half of the angle of aperture of the light cone 64. Due to the tapered end of the first tapered optical fiber 62, the angle a 2 is considerably larger than the corresponding angle Ch indicated in Fig. 3.
  • the numerical aperture NA 2 n S0
  • V sin(a 2 ) is much larger than the numerical aperture NA-, of light supplied to the waveguide cell 30.
  • light throughput depends both on the cross-sectional area A 2 and on the numerical aperture NA 2 of the light cone 64.
  • the light throughput T 2 is proportional to:
  • T 2 oc A 2 NA 2 2 with A 2 denoting the cross-sectional area at the tapered end of the first tapered optical fiber 62 and with NA 2 denoting the numerical aperture of the light cone 64.
  • the cross- sectional area A 2 is considerably smaller than the corresponding cross-sectional area A-, shown i n F ig. 3. Nevertheless, the increased numerical aperture NA 2 overcompensates the reduction of A 2 , and because of the large numerical aperture NA 2 of the light cone 64, an acceptable light throughput T 2 is achieved.
  • tapered optical fibers 62, 63 an acceptable light throughput can be obtained even in cases where the cell volume is rather small. Because of the small cell volume, the resolution of the waveguide cell 60 is quite good.
  • the light throughput T 2 is quite good as well. Furthermore, a length of 10 mm is sufficiently large to accomplish a good sensitivity of the waveguide cell 60. In summary, due to the use of tapered optical fibers 62, 63, a waveguide cell 60 with large light throughput, small cell volume and high sensitivity is obtained.
  • Fig. 7 shows a waveguide cell 70 according to a second embodiment.
  • the waveguide cell 70 comprises a capillary tubing 71 , a first tapered optical fiber 72 configured for supplying light to the waveguide cell 70, and a second tapered optical fiber 73 configured for receiving light that has traversed the waveguide cell 70.
  • the length of the capillary tubing 71 is equal to 10 mm, which is equal to the respective lengths of the waveguide cells shown in Fig. 3 and Fig. 6.
  • the cell volume of the waveguide cell 70 has been further reduced.
  • the cell volume of the waveguide cell 70 is about 1 ⁇ .
  • the light throughput T 3 is proportional to: T 3 oc A 3 NA 3 2 , with A 3 denoting the cross-sectional area at the tapered end of the first tapered optical fiber 72 and with NA 3 denoting the numerical aperture of the light cone 74.
  • the cross-sectional area A 3 is considerably smaller than before, the numerical aperture NA 3 has been further increased, and hence, an acceptable light throughput is obtained even for the very narrow capillary tubing 71 .
  • tapered optical fibers waveguide cells with very small cell volumes of for example 1 ⁇ can be realized, which are characterized by an excellent chromatographic resolution. Due to the large numerical aperture NA 3 , the light throughput is still acceptable, and the signal-to-noise ratio is quite good .
  • the length of the capillary tubing 71 is equal to 1 0 mm.
  • the sensitivity of the waveguide cell 70 is as good as in the embodiments shown in Fig. 3 and Fig. 6.
  • Fig. 8 shows an accessible concentration limit of detection (CLOD) as a function of cell volume (in ⁇ ) both for the case of a waveguide cell equipped with conventional optical fibers and for the case of a waveguide cell equipped with tapered optical fibers.
  • Curve 80 corresponds to a waveguide cell with conventional optical fibers having a rather low numerical aperture of e.g. 0.22. As the cell volume gets smaller, the concentration limit of detection (CLOD) increases strongly.
  • Curve 81 corresponds to a waveguide cell with tapered optical fibers having a numerical aperture of 0.66.
  • CLOD concentration limit of detection
  • the concentration limit of detection rises as the cell volume becomes smaller.
  • the curve 71 is considerably below the curve 80, and hence, it can be concluded that by employing tapered optical fibers, a more sensitive waveguide cell is obtained, which can be used for detecting small concentrations of a certain species.
  • a waveguide cell with tapered optical fibers is superior to a waveguide cell with conventional optical fibers.
  • a CLOD enhancement factor is shown as a function of cell volume, with the CLOD enhancement factor indicating the ratio of the concentration limit of detection (CLOD) of a waveguide cell with tapered optical fibers and a waveguide cell with conventional optical fibers. It can be seen that for a cell volume of 10 ⁇ , the enhancement factor is equal to 1 . As cell volume gets smaller, the enhancement factor rises up to 3, and for cell volumes in the range between 0.01 and 1 ⁇ , the enhancement factor is equal to 3.

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Abstract

La présente invention concerne une cellule à guide d'ondes (60). Ladite cellule à guide d'ondes (60) comprend un tube capillaire (61) délimitant le volume de ladite cellule à guide d'onde (60), ledit tube capillaire (61) comportant une première extrémité et une seconde extrémité opposée à la première, un orifice d'admission de fluide situé au niveau de la première extrémité du tube capillaire, un orifice d'évacuation de fluide situé au niveau de la seconde extrémité du tube capillaire, une première fibre optique (62) située au niveau de la première extrémité du tube capillaire, ladite première fibre optique étant conçue pour assurer le couplage de la lumière à l'entrée dans le volume de la cellule à guide d'ondes et se présentant sous la forme d'une première fibre optique conique. Une seconde fibre optique (63) est située au niveau de la seconde extrémité du tube capillaire ; elle est conçue pour assurer le découplage de la lumière à la sortie du volume de la cellule à guide d'ondes, ladite seconde fibre optique se présentant sous la forme d'une seconde fibre optique conique.
PCT/EP2010/066205 2010-10-27 2010-10-27 Cellule à guide d'ondes présentant une ouverture numérique améliorée WO2012055432A1 (fr)

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Cited By (8)

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CN103630638A (zh) * 2012-08-21 2014-03-12 株式会社岛津制作所 流通室
WO2014058897A1 (fr) * 2012-10-12 2014-04-17 Perkinelmer Health Sciences, Inc. Ensemble cuve à circulation pour analyseur d'échantillons de liquide
US8958072B2 (en) 2012-07-31 2015-02-17 Buerkert Werke Gmbh Microphotometer
WO2017189783A1 (fr) * 2016-04-26 2017-11-02 Cytek Biosciences, Inc. Cytomètre en flux multicouleur compact
US20180299367A1 (en) * 2016-04-26 2018-10-18 Cytek Biosciences, Inc. Compact multi-color flow cytometer having compact detection module
US10788411B2 (en) 2016-04-21 2020-09-29 Cytek Biosciences, Inc. Flow cytometry with dual laser beams
US11169076B2 (en) 2016-07-25 2021-11-09 Cytek Biosciences, Inc. Compact detection module for flow cytometers
WO2024112726A1 (fr) * 2022-11-21 2024-05-30 Fei Company Cuve à circulation avec guide d'ondes à partie centrale creuse

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8958072B2 (en) 2012-07-31 2015-02-17 Buerkert Werke Gmbh Microphotometer
CN103630638A (zh) * 2012-08-21 2014-03-12 株式会社岛津制作所 流通室
WO2014058897A1 (fr) * 2012-10-12 2014-04-17 Perkinelmer Health Sciences, Inc. Ensemble cuve à circulation pour analyseur d'échantillons de liquide
US8797528B2 (en) 2012-10-12 2014-08-05 Perkinelmer Health Sciences, Inc. Flow cell assembly for liquid sample analyzer
US8947654B2 (en) 2012-10-12 2015-02-03 Perkinelmer Health Sciences, Inc. Flow cell assembly for liquid sample analyzer
US9025142B1 (en) 2012-10-12 2015-05-05 Perkinelmer Health Sciences, Inc. Flow cell assembly for liquid sample analyzer
US10788411B2 (en) 2016-04-21 2020-09-29 Cytek Biosciences, Inc. Flow cytometry with dual laser beams
US20180299367A1 (en) * 2016-04-26 2018-10-18 Cytek Biosciences, Inc. Compact multi-color flow cytometer having compact detection module
US10739245B2 (en) 2016-04-26 2020-08-11 Cytek Biosciences, Inc. Compact multi-color flow cytometer
WO2017189783A1 (fr) * 2016-04-26 2017-11-02 Cytek Biosciences, Inc. Cytomètre en flux multicouleur compact
US11333597B2 (en) * 2016-04-26 2022-05-17 Cytek Biosciences, Inc. Compact multi-color flow cytometer having compact detection module
US11169076B2 (en) 2016-07-25 2021-11-09 Cytek Biosciences, Inc. Compact detection module for flow cytometers
WO2024112726A1 (fr) * 2022-11-21 2024-05-30 Fei Company Cuve à circulation avec guide d'ondes à partie centrale creuse

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