Devices, systems, and methods for spectroscopy having low volume and long adjustable pathlength

Abstract

A device (200) for measuring light absorbance of a sample (208) includes a light guiding hollow fiber (202) having proximal and distal ends (202a, 202b) and an axial bore (202c), and a solid optical fiber (204) having proximal and distal ends (204a, 204b), where the solid optical fiber (204) is axially movable within the axial bore (202c) of the light guiding hollow fiber (202). A light source (102) is operably coupled to the solid optical fiber probe (204). A sample holder (206) has a bottom surface, and the distal end (202b) of the light guiding hollow fiber (202) is engaged with the bottom surface. An optical detector (210) is aligned with the distal end (202b) of the light guiding hollow fiber (202) for receiving light therefrom. A method of using the device.

Description

Attorney Docket No.: 1580.00206WO INTERNATIONAL PATENT APPLICATION FOR DEVICES, SYSTEMS, AND METHODS FOR SPECTROSCOPY HAVING LOW VOLUME AND LONG ADJUSTABLE PATHLENGTH INVENTORS: CESAR D. RAMOS I-TSUNG SHIH CRAIG HARRISON PREPARED BY: KDW FIRM PLLC 2601 WESTON PARKWAY SUITE 103 CARY, NC 27513 (609) 270-4983DEVICES, SYSTEMS, AND METHODS FOR SPECTROSCOPY HAVING LOW VOLUME AND LONG ADJUSTABLE PATHLENGTH Cross-Reference to Related Applications

[0001] This application claims priority to pending U.S. Provisional Patent Application Serial Number 63 / 656,812, filed June 6, 2024, the entirety of which is incorporated by reference herein. Field of the Disclosure

[0002] The present disclosure relates to spectroscopy with light emitting components including, e.g., UV and / or visible wavelength light, for various applications, including, e.g., chromatography, and more particularly, for a sampling device that facilitates spectroscopic measurements with a variable pathlength and methods for such a device. Discussion of Related Art

[0003] Absorption spectroscopy is used to measure composition and / or properties of a material in any phase, gas, liquid, solid. For example, the optical absorption spectra of liquid substances may be measured to determine concentration or other properties of a species of interest, within a liquid medium. An absorption spectrum may provide the distribution of light attenuation (due to absorbance) as a function of light wavelength. In a known spectrophotometer the sample substance to be studied is placed in a transparent container, so that electromagnetic radiation (light) of a known wavelength, λ, (i.e. ultraviolet, infrared, visible, etc.) and intensity, I, may be measured after passing through the transparent container, using a suitable detector.

[0004] Known ultraviolet (UV) / visible spectrophotometers utilize containers such as standard cuvettes which containers may have a standard pathlength through which the incident light is conducted within the liquid containing the substance to be measured. For a sample consisting of a single homogeneous substance having a concentration c, the light transmitted through the sample will follow a relationship know as Beer's Law: A=εCL where A is the absorbance (also known as the optical density (OD) of the sample at wavelength λ where OD=the −log of the ratio of transmitted light to the incident light), ε is the absorptivity or extinction coefficient (normally is a constant at a specific wavelength), C is the concentration of the sample, and L is the pathlength of light through the sample. Thus, in principle, information regarding concentration of the homogenous substance may be determined based upon recorded light intensity of a signal passing through the sample container. However, under some circumstances, the determination of concentration in such apparatus may be difficult. Often a compound of interest in solution is highly concentrated. For example, certain biological samples, such as monoclonal antibodies, proteins, DNA or RNA are often isolated in concentrations that fall outside the linear range of the spectrophotometer when absorbance is measured. Therefore, dilution of the sample is often required to measure an absorbance value that falls within the linear range of the instrument. As will be appreciated, it is useful to obtaining samples without knowledge of the possible concentration and to measure the absorption of these samples without dilution. One resulting feature common to these known ultraviolet (UV) / visible spectrophotometers is that the pathlength L be known with great accuracy so that an accurate concentration measurement can be made.

[0005] To address these challenges, a technology based upon a variable pathlength spectrophotometer has been developed. This type of spectroscopy system may generallyemploy a known light source, such as a source based upon a UV / visible spectrophotometer. Light from the UV / visible spectrophotometer is then directed to a special probe in an analysis instrument that is arranged to dynamically change the pathlength L in a special sample chamber during an absorbance measurement. Thus, radiation that is generated from the UV / visible spectrophotometer source is detected after passing through the sample chamber, while the movement of the probe varies the pathlength L through multiple different positions. As such, a series of measurements are produced that generate a different value of A for each different value of L, in a manner that does not require knowledge of any particular pathlength L, in order to determine the concentration C.

[0006] Variable pathlength systems are often used in high concentration applications which employ short optical pathlengths and small sample volumes. For gene & cell therapy applications, however, the interested sample concentrations can be extremely low, and the availability of a desired sample volume can also be very limited. Due to the technical constraints of variable pathlength systems, such as light diversion angles and the sample coverage of light path, it can be a challenge to use variable pathlength systems in Low Volume and Long Pathlength (LVLP) applications such as gene & cell therapy application.

[0007] It would therefore be desirable to provide a variable pathlength system that can be used for low concentration measurements such as gene and cell therapy applications. Summary of the Disclosure

[0008] A device for measuring light absorbance of a sample includes a light guiding hollow fiber having proximal and distal ends and an axial bore, a solid optical fiber having proximal and distal ends, the solid optical fiber axially movable within the axial bore of thelight guiding hollow fiber, a light source operably coupled to the solid optical fiber probe, a sample holder having a light transmitting bottom surface, the distal end of the light guiding hollow fiber engaged with the bottom surface, and an optical detector aligned with the distal end of the light guiding hollow fiber for receiving light therefrom.

[0009] A method of determining a concentration of at least one material includes providing a light guiding hollow fiber having proximal and distal ends and an axial bore, providing a solid optical fiber within the axial bore of the light guiding hollow fiber, disposing respective distal ends of the light guiding hollow fiber and the solid optical fiber in a sample vessel containing a fluid sample, retracting the solid optical fiber within the light guiding hollow fiber to draw a portion of the fluid sample into the axial bore of the light guiding hollow fiber, directing a light signal through the solid optical fiber such that light is emitted from the distal end of the solid optical fiber and through the fluid disposed within the axial bore of the light guiding hollow fiber, measuring a transmitted intensity of the light after passing through the fluid sample, and determining a concentration of at least one material in the fluid sample based upon the measured transmitted intensity.

[0010] A device is disclosed for measuring light absorbance of a sample, comprising: a light guiding hollow fiber having proximal and distal ends and an axial bore, a solid optical fiber having proximal and distal ends, the solid optical fiber axially movable within the axial bore of the light guiding hollow fiber, a light source operably coupled to the solid optical fiber, a sample holder having a light transmitting bottom surface, and an optical detector aligned with the distal end of the light guiding hollow fiber for receiving light therefrom. In some embodiments the light guiding hollow fiber is positioned, in use, to define a gap between thedistal end of the light guiding hollow fiber and the light transmitting bottom surface of the sample holder. Brief Description of the Drawings

[0011] The accompanying drawings illustrate preferred embodiments of the disclosed method so far devised for the practical application of the principles thereof, and in which:

[0012] FIG.1 illustrates the general features of a known absorption spectroscopy apparatus.

[0013] FIG.2 illustrates a schematic view of the relationship between a vessel, probe, and fluid sample, of the apparatus of FIG.1.

[0014] FIG.3 illustrates a schematic view of a probe assemble according to embodiments of the present disclosure.

[0015] FIG.4 illustrates a schematic view of the probe arrangement of FIG.3 with the solid optical fiber retracted within the light guiding hollow fiber.

[0016] FIG.5 illustrates dimensional aspects of the probe arrangement of FIG.3.

[0017] FIG.6 is a graph of results comparing concentration measurements obtained using the disclosed arrangement with minimal sample size to concentration measurements obtained using traditional variable pathlength technology and larger sample sizes.

[0018] FIGS.7A and 7B are isometric and cross-section views, respectively, of an embodiment for measuring concentration of a sample using the probe assembly of FIG.3.

[0019] FIGS.8A and 8B are isometric and cross-section views, respectively, of an embodiment for measuring concentration of a sample using the probe assembly of FIG.3.

[0020] FIGS.9A and 9B are isometric and cross-section views, respectively, of an embodiment for measuring concentration of a sample using the devices of FIGS.7A-8B coupled together.

[0021] FIGS.10A and 10B are isometric and cross-section views, respectively, an embodiment for measuring concentration of a sample using the arrangement of FIGS.9A and 9B.

[0022] FIGS.11A and 11B are first and second cross-section views, respectively, illustrating different modes of operation of the of the probe assembly of FIGS.10A and 10B.

[0023] FIG.12 is a cross-section view of a light path through a fluid sample contained within a light guiding hollow fiber according to the disclosure. Description of Embodiments

[0024] Separated samples (i.e., from chromatography) of lower concentration (e.g., compared to higher concentration samples, that may be comparatively dilute or diluted) may be difficult to measure by spectroscopy devices. For example, a dilute sample may require a largepathlength between a light emitting probe (e.g., a polished optical fiber, a fibrette, or the like) and a detector in order for separate molecules of the dilute sample to absorb the light emitted. The embodiments described herein include a variable pathlength spectrophotometer that may adapt to sample parameters (e.g., dilution, concentration, volume, or the like) to expand the dynamic range of spectroscopy such that samples of various concentrations can be measured without further dilution or further concentration of the sample or excess post-processing of data. These and other advantages of the disclosure are apparent from the description provided herein.

[0025] The absorption spectrum is the distribution of light attenuation (due to absorbance) as a function of light wavelength. For example, with use of a spectrophotometer, a sample substance to be studied may be positioned between a light source (e.g., emitted from a probe) and a detector. Electromagnetic radiation (e.g., light) of a known wavelength, λ, (e.g., ultraviolet, infrared, visible, etc.) and intensity I may be emitted from the probe. The detector opposite the probe and the sample may measure the intensity I of light received. The length that the light propagates through the sample is referred to as a pathlength. For a sample consisting of a single homogeneous substance (or a separate substance) with a concentration c, the light transmitted through the sample will follow a relationship know as Beer's Law: A=εc1 where λ is the absorbance (also known as the optical density (OD) of the sample at wavelength λ where OD=the −log of the ratio of transmitted light to the incident light), ε is the absorptivity or extinction coefficient (normally at constant at a given wavelength), c is the concentration of the sample, and 1 is the pathlength of light through the sample.

[0026] FIGS.1 and 2 depict an absorption spectroscopy apparatus, shown as system 100. The system 100 may include a light source 102, and a measurement instrument, shown as measurement module 104, coupled to the light source 102, and a detector 106, disposed next to the measurement module 104. The light source 102 may be configured as a light emitting diode (LED) assembly, including a plurality of LEDs that output radiation at a plurality of different wavelengths, respectively. Such an assembly of LEDs may be collocated in a common housing, or may be located separately from one another, according to different embodiments.

[0027] The light source 102 is arranged to output a probe signal 114 to a measurement module 104. In some embodiments, the probe signal 114 is provided as multi-monochromatic radiation. The measurement module 104 may include an optic probe 108 to direct the probe signal 114 through a fluid sample 112 contained in a vessel 110. The optic probe 108 may be movable between a plurality of probe positions, along a vertical direction as represented in the figure. As such, the optic probe 108 may change the distance that the probe signal 114 travels through the fluid sample 112. This distance is represented by a pathlength L, as shown.

[0028] The system 100 further includes an optical detector 106, disposed to detect an optical intensity of the probe signal 114 at the plurality of different wavelengths generated by the light source 102 after the composite probe signal 114 passes through the fluid sample 112.

[0029] In operation, the system 100 may be used to determine the concentration C of a material or substance that is contained in the fluid sample 112. In accordance with the principles of slope spectroscopy, the system 100 may determine C by measuring changes inabsorption of the composite probe signal 114 as a function of changes in the pathlength L shown in FIG.1.

[0030] As mentioned, traditional variable pathlength technology (as shown in FIGS.1 and 2) use a solution 112 positioned at the bottom of a vessel 110 and a fibrette 108 disposed in the solution to convey light from the light source 102, through the solution 112, and to a light detector located below the vessel 110. As will be understood, a relatively large volume of fluid is required to provide the longer pathlengths 1 needed to obtain accurate results in low- concentration liquid samples.

[0031] As shown schematically in FIG.3, the disclosed system 200 enables absorption spectroscopy system to achieve significantly greater pathlengths while using minimal sample volumes. The system includes a light guiding hollow fiber 202 having proximal and distal ends 202a, 202b, and axial bore 202c, a solid optical fiber 204 having proximal and distal ends 204a, 204b, sized to be received within the hollow core of the light guiding hollow fiber, and a sample vessel 206 for holding a quantity of the sample solution 208 under test. An optical detector 210 can be disposed beneath the sample vessel 206 to detect an optical intensity of light at a plurality of different wavelengths after the light passes through the fluid sample 208.

[0032] Through careful selection of light guiding hollow fiber and solid optical fiber sizes, the distal and 204b of the solid fiber 204 can be inserted into the axial bore 202c of the light guiding hollow fiber 202 until it reaches the distal end 202b of the light guiding hollow fiber. In non-limiting example embodiments, the outer diameter of the light guiding hollow fiber 202 can be about 850 microns + / - 20 microns, while the axial bore 202c of the light guiding hollow fiber may be about 700 microns + / - 10 microns. The outer diameter of the solidoptical fiber 204 may be about 500 microns + / - 10 microns. Thus, in some non-limiting example embodiments a radial gap of about 100 microns is formed between the solid optical fiber 204 and the light guiding hollow fiber 202.

[0033] Both fibers 202, 204 can then be inserted into the filled sample vessel 206 until the distal end of the solid fiber 204 is immersed in the sample 208 (see FIG.3). With the light guiding hollow fiber 202 held stationary, the solid fiber 204 can be retracted from the hollow fiber (i.e., by moving the distal end 204b of the solid fiber 204 toward the proximal 202a end of the hollow fiber 202). As the solid optical fiber 204 retracts, a vacuum is created within the axial bore 202c of the light guiding hollow fiber due to tight tolerances between the diameter of the axial bore 202c and the outer diameter of the solid optical fiber 204. This vacuum condition and the surface tension of the fluid sample (as shown in FIG.4) causes a portion of the fluid sample 208 to fill the portion of the axial bore 202c that previously housed the solid fiber 204 (see FIG.4).

[0034] In some embodiments the light guiding hollow fiber 202 and the solid optical fiber may be made from fused silica, although this is not critical, and any material property that makes the light guiding hollow fiber 202 suitable for light transmission / guiding may be used.

[0035] Light (e.g., received from a coupled light source 102 similar to or the same as that described in relation to FIG.1) can then be transmitted through the solid fiber 204 and can be emitted from the distal end of the solid fiber at its location inside the hollow fiber. The light will be continuously transmitted through the sample 208, guided by the light guiding hollow fiber 202. As will be appreciated, the light guiding hollow fiber 202 can be configured so that it does not transmit light, but rather reflects it along the inner surface of the fiber. By choosingcore and cladding materials with the proper index of refraction, all the light can be reflected within the walls of the light guiding fiber. Because the light is guided through the sample 208 by the light guiding hollow fiber 202, there is negligible loss through the light guiding hollow fiber, and thus all light loss or light absorption sensed by the optical detector 210 can be attributable to the sample 208 without affecting the result. In some embodiments a background correction can be performed in which a sample reading can be obtained using a buffer solution of known concentration. If the reading is within a predetermined margin then no background correction may re required. If the reading is outside the predetermined margin then a background correction factor can be applied. As will be appreciated, the portion of the hollow fiber that is filled with Law.

[0036] As will be understood, the light can be transmitted by the hollow light guide fiber 202 over a large distance. In some embodiments, the pathlength 1 can be increased substantially compared to prior devices and arrangements. In addition, the amount of sample 208 required fill the interior of the hollow light guide fiber 202 over such a large distance is relatively small, can be in the range of 10 microliters. Thus,pathlength technique to achieve a relatively long pathlength using a low sample volume. The presently disclosed arrangement exploits the capillary effect, in which retraction of the solid fiber 204 within the hollow light guide fiber 202 draws the sample 208 upward above the level of the sample in the sample holder 206. In some non-limiting example embodiments a vacuum source (or pumping source) may be used in addition to or alternatively to assist in drawing the sample 208 up into the hollow light guide fiber 202. Such a vacuum or pumping assist arrangement may be of usewhere capillary action is not sufficient to draw the sample 208 to achieve a very long pathlength.

[0037] In example embodiments, the minimum amount of volume needed to achieve a long pathlength using a hollow fiber is shown in FIG.5, where (a) represents the Internal diameter of the hollow fiber and (b) represents a height the light guiding hollow fiber as measured from a bottom surface of the sample vessel 206. The appropriate formula can be expressed as follows: ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^ ൌ ^గ∗^మସ∗ ^^^ (1)

[0038] In one non-limiting example embodiment, if a pathlength L of 50 millimeters (mm) is used with a sample vessel 206 having an internal diameter of 5 mm, the required volume of the sample 208 would be: ^^ ∗.71^^^^ଶ^^^^^^ @^^^^ ^^^^ ൌ ^ ଷ4∗ 50^^^^^ ൌ 19.8 ^^^^ ൌ ^^^^. ^^ µ^^

[0039] Various examples of pathlengths and fluid volumes calculated in accordance with the above formula are illustrated in Table 1 below:Pathlength volume mm µL 1 0.40 5 1.98 10 3.96 15 5.94 20 7.92 25 9.90 30 11.88 35 13.86 40 15.84 45 17.82 50 19.80 Table 1

[0040] FIG.6 illustrates data obtained using Repligen Corporation’s “Solo VPE” as the measuring instrument and a “Cary 60” as the light source. The disclosed method was used to measure three distinct low concentration samples with slopes values of 0.108, 0.054, and 0.024, respectively. The linearity of the three concentrations was determined using this methodand the results were satisfactory, with a value ^^ଶ ^ 0.999. The graph in FIG. 6 is an exampleof one of the low concentration measurements.

[0041] The data in Table 2 below indicate that the disclosed method yields comparable outcomes to the conventional variable path techniques. The study employed operational prototype components, but to evaluate substances with even lower concentrations, more accurate machined components are required. Additionally, since the present light source has a resolution of only .005 abs / mm, upgrading to a light source with superior resolution can be desirable to test lower concentrations effectively.Table 2

[0042] Referring now to FIGS.7A - 12 a probe assembly 300 according to embodiments of the disclosure will be described in greater detail. It will be appreciated that the arrangement of FIGS.7A-12 is an example, and other mechanisms can be used to move the solid optical fiber 204 with respect to the light guiding hollow fiber 202, including one or more robots.

[0043] FIGS.7A and 7B show a hollow fiber cap portion 212 coupled to the light guiding hollow fiber 202. The hollow fiber cap portion 212 serves to stabilize the light guiding hollow fiber 202, preventing it from moving along with the solid optical fiber 204 during operation. The hollow fiber cap portion 212 has a proximal end 212a having a chamfer 214 and a distal end 212b with a central recess 216. An axial bore 217 runs between the proximal and distal ends 212a, 212b and is sized to receive the light guiding hollow fiber 202 therein. As can be seen, the proximal end 202a of the light guiding hollow fiber 202 is disposed near the proximal end 212a of the hollow fiber cap portion 212 while the distal end 202b of the light guiding hollow fiber 202 extends a distance “D” beyond the distal end 212b of the hollow fiber cap portion 212.

[0044] FIGS.8A and 8B show a sample vessel 206 coupled to a sample vessel holder portion 218. The sample vessel holder portion 218 contains the sample vessel 206 and alsoserves as an engaging surface for the hollow fiber cap portion 212. The Sample vessel holder portion 218 includes a chamfered proximal portion 218a, and a distal portion 218b with a recess 220 for receiving the optical detector 210 (see FIGS.3 and 4). A central opening 218c runs between the proximal and distal portions 218a, 218b of the sample vessel holder portion 218, and is sized to receive the sample vessel 206 therein. A lower ledge 222 is formed within the central opening 218c adjacent the distal portion 218b of the sample vessel holder portion 218 and abuts a distal end 206b of the sample vessel 206. Thus arranged, the proximal end 206a of the sample vessel 206 extends above the proximal portion 218a of the sample vessel holder portion 218. In the illustrated embodiment the sample vessel 206 is generally cylindrical, with the proximal end 206a comprising a radially extending rim.

[0045] FIGS.9A and 9B show the hollow fiber cap portion 212 coupled to the sample vessel 206 and sample vessel holder portion 218. As can be seen, when a lower surface 212c of the hollow fiber cap portion 212 engages an upper surface 218d of the sample vessel holder portion 218, the proximal end 206a of the sample vessel 206 is received within the central recess 216 of the hollow fiber cap portion. Thus arranged, the sample vessel 206 is constrained between the hollow fiber cap portion and the sample vessel holder portion. In addition, when the hollow fiber cap portion 212 is coupled to the sample vessel holder portion 218 the distal end 202b of the light guiding hollow fiber 202 is in contact with the bottom surface 206c of the sample vessel 206.

[0046] FIGS.10A and 10B show the insertion of a solid optical fiber 204 into the axial bore 202c of the light guiding hollow fiber 202. The solid optical fiber 204 is inserted into theaxial bore 202c of the light guiding hollow fiber 202 with the assistance of the chamfer 214 on the hollow fiber cap portion 212.

[0047] FIGS.11A and 11B show the movement of sample solution 208 within the axial bore 202c of the light guiding hollow fiber 202. FIG.11A shows the assembly with the distal end 204b of the solid optical fiber 204 extended distally so that it corresponds to the distal end 202b of the light guiding hollow fiber 202 (i.e., both are engaged with the bottom surface 206c of the sample vessel 206). It will be appreciated that although the illustrated embodiment shows the distal end 202b of the light guiding hollow fiber 202 and the distal end 204b of the solid optical fiber being in contact / engaged with the bottom surface 206c of the sample vessel, that embodiments are contemplated in which a gap is present between the distal end 202b of the light guiding hollow fiber 202 and the bottom surface 206c of the sample vessel 206. In FIG.11B, the solid optical fiber 204 has been retracted within the light guiding hollow fiber 202 (i.e., in the direction of arrow “A”) so that the distal end 204b of the solid optical fiber is located a distance “RD” from the bottom surface 206c of the sample vessel 206. Since the light guiding hollow fiber 202 remains stationary, the sample solution 208 is drawn up within the axial bore 202c of the light guiding hollow fiber by the same amount as the solid optical fiber 204.

[0048] FIG.12 shows the path of light “L” as it travels from the distal end of the solid optical fiber 204 through the sample fluid 208 and is reflected off the inner surface 202d of the light guiding hollow fiber 202. As can be seen, the light “L” undergoes multiple reflections along the inner walls of the light guiding hollow fiber 202 before it ultimately arrives at the detector 210.

Claims

[0049] While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the spirit and scope of the invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.CLAIMS What is claimed is 1. A device for measuring light absorbance of a sample, comprising: a light guiding hollow fiber having proximal and distal ends and an axial bore; a solid optical fiber having proximal and distal ends, the solid optical fiber axially movable within the axial bore of the light guiding hollow fiber; a light source operably coupled to the solid optical fiber; a sample holder having a light transmitting bottom surface, the distal end of the light guiding hollow fiber engaged with the bottom surface; and an optical detector aligned with the distal end of the light guiding hollow fiber for receiving light therefrom.

2. The device of claim 1, further comprising a hollow fiber cap portion coupled to the light guiding hollow fiber.

3. The device of claim 2, further comprising a sample vessel holder portion for receiving the sample holder.

4. The device of claim 3, wherein the hollow fiber cap portion has a distal end comprising a recess configured to receive a proximal end of the sample holder when the hollow fiber cap portion is engaged with the sample vessel holder portion.

5. The device of claim 4, wherein the sample vessel holder portion has a ledge for engaging a distal end of the sample vessel.

6. The device of claim 3, wherein the hollow fiber cap portion and the sample vessel holder portion are sized so that when the hollow fiber cap portion and the sample vessel holder portion are coupled together the distal end of the light guiding hollow fiber contacts the bottom surface of the sample vessel.

7. The device of claim 1, wherein the light guiding hollow fiber has an outer diameter of about 850 microns + / - 20 microns and the diameter of the axial bore is about 700 microns + / - 10 microns.

8. The device of claim 4, wherein the solid optical fiber has an outer diameter of about 500 microns.

9. The device of claim 1, wherein a radial clearance between an outside diameter of the solid optical fiber and a diameter of the axial bore of the light guiding hollow fiber is about 100 microns.

10. The device of claim 1, wherein the light guiding hollow fiber and the solid optical fiber comprise fused silica.

11. The device of claim 1, further comprising a robot coupled to at least one of the light guiding hollow fiber and the solid optical fiber for moving the light guiding hollow fiber and the solid optical fiber with respect to each other.

12. A method of determining a concentration of at least one material, comprising: providing a light guiding hollow fiber having proximal and distal ends and an axial bore; providing a solid optical fiber within the axial bore of the light guiding hollow fiber; disposing respective distal ends of the light guiding hollow fiber and the solid optical fiber in a sample vessel containing a fluid sample; retracting the solid optical fiber within the light guiding hollow fiber to draw a portion of the fluid sample into the axial bore of the light guiding hollow fiber; directing a light signal through the solid optical fiber such that light is emitted from the distal end of the solid optical fiber and through the fluid disposed within the axial bore of the light guiding hollow fiber; measuring a transmitted intensity of the light after passing through the fluid sample, and determining a concentration of at least one material in the fluid sample based upon the measured transmitted intensity.

13. The method of claim 12, wherein the step of retracting the solid optical fiber within the light guiding hollow fiber comprises retracting the solid optical fiber by a predetermined amount.

14. The method of claim 12, wherein the step of directing the light signal comprises directing a source of ultraviolet light through the solid optical fiber.

15. The method of claim 12, wherein the step of directing the light signal comprises directing light at a plurality of different wavelengths through the solid optical fiber.

16. The method of claim 13, wherein the predetermined amount corresponds to a pathlength between 1 mm and 50 mm.

17. The method of claim 13, wherein the predetermined amount corresponds to a sample volume between 0.4 and 19.80 micro liters.

18. The method of claim 11, wherein the step of retracting the solid optical fiber within the light guiding hollow fiber is performed using a robot coupled to at least one of the solid optical fiber and the light guiding hollow fiber.

19. A device for measuring light absorbance of a sample, comprising: a light guiding hollow fiber having proximal and distal ends and an axial bore;

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