CN1815218A - Ultraviolet-ray visible absorbing/fluorescent dual-purpose flow cell - Google Patents

Abstract

The ultraviolet-visible absorption/fluorescence dual-purpose flow cell relates to a component used for a liquid chromatograph, in particular to an ultraviolet-visible absorption/fluorescence dual-purpose flow cell for a portable liquid chromatograph detector. Provides an integrated UV-visible absorption/fluorescence dual-purpose flow cell, which is equipped with a cell body, a photoconductive quartz capillary, a polyether ether ketone liner, a self-focusing lens, a sealing gasket, a gasket, an optical fiber, and a liquid flow line . The light-guiding quartz capillary is installed in the polyetheretherketone liner and filled in the lumen of the cell body; the self-focusing lens is arranged in the direction of the light entrance, and is sealed and fixed with the cell body with a sealing gasket; the gasket is located between the self-focusing lens and the polyetherether ether Between the ketone liners, the notch of the gasket is aligned with the direction of the flow path, and its function is to fill the excess space formed between the two; the inlet and outlet fibers and the inlet and outlet pipes are respectively fixed on the cell body by joints and ferrules Form a sealed flow path.

Description

UV-vis absorption/fluorescence dual-purpose flow cell

technical field

The invention relates to a component for a liquid chromatograph, in particular to an optical fiber type ultraviolet-visible absorption/fluorescence dual-purpose flow cell for a portable liquid chromatograph detector.

Background technique

UV-Vis absorption detectors and fluorescence detectors are the two most common detectors found on liquid chromatography instruments. Flow cells are important components in both UV-Vis absorption and fluorescence detectors. After the light from the light source in the HPLC UV-Vis absorption detector passes through a certain length of the sample solution in the flow cell, part of the light energy is absorbed by the sample molecules, and the measured light intensity can be converted to obtain the absorbance data. A schematic diagram of a common Z-type UV-Vis absorption flow cell is shown in Figure 1. In the HPLC fluorescence detector, the light from the light source irradiates the sample solution in the fluorescence cell, part of the light energy is absorbed by the sample molecules, and the sample molecules are excited to emit fluorescent light, which forms a certain angle (usually The direction of the right angle) detects the intensity of the emitted fluorescence. A common fluorescent flow cell structure is shown in Figure 2.

For the detector itself, the longer the optical path of the flow cell, the higher the sensitivity; for the HPLC detector, the smaller the cell volume, the smaller the dead volume of the detector, and the smaller the impact on the separation effect of the column. This constitutes a pair of contradictions. Extending the length of the flow cell to improve sensitivity will increase the volume of the cell, increase the extra-column effect and reduce the chromatographic separation effect; reduce the channel cross section of the flow cell to reduce the volume of the cell and affect the design of the optical path, etc. bring about problems.

Portable instrument systems have strict restrictions on the size, weight, power consumption and other parameters of each component. Usually, the UV-visible absorption detectors and fluorescence detectors used in chromatographic instruments are relatively large in size and complex in structure. Absorption flow cells and fluorescence flow cells cannot be used universally, and two detectors must be equipped to realize UV-visible absorption detection and fluorescence detection respectively. At present, there is no dual-purpose flow cell and corresponding dual-purpose detector integrating the functions of ultraviolet-visible absorption detection and fluorescence detection. Due to the limitations of the above factors, it is difficult to apply the common liquid chromatography UV-visible absorption detector and fluorescence detector in the portable chromatography system.

Contents of the invention

The invention uses a micro-capillary monolithic column for the portable liquid chromatography instrument, and the injection volume is very small, which requires the detector to have a small volume and high detection sensitivity. In addition, portable liquid chromatography instruments require detection systems with small volume, light weight, and low power consumption. For this reason, the present invention provides an integrated ultraviolet-visible absorption/fluorescence dual-purpose micro-flow cell, which is used in conjunction with a micro-LED light source, a micro-grating spectrometer, and supporting optical fiber components to perform ultraviolet-visible-absorption and fluorescence in the same flow cell. Two fluorescence detection methods realize the combination of ultraviolet-visible absorption detector and fluorescence detector.

The invention is provided with a pool body, a photoconductive quartz capillary, a polyether ether ketone (PEEK) liner, a self-focusing lens, a sealing gasket, a spacer, an optical fiber and a liquid flow pipeline. The light-guiding quartz capillary is installed in the polyetheretherketone liner and filled in the lumen of the cell body; the self-focusing lens is arranged in the direction of the light entrance, and is sealed and fixed with the cell body with a sealing gasket; the gasket is located between the self-focusing lens and the polyetherether ether Between the ketone liners, the notch of the gasket is aligned with the direction of the flow path, and its function is to fill the excess space formed between the two; the inlet and outlet fibers and the inlet and outlet pipes are respectively fixed on the cell body by joints and ferrules Form a sealed flow path.

The wall of the light-guiding quartz capillary is a three-layer concentric tubular structure, the outer layer is polyimide coating, and the inner layer is doped quartz layer and pure quartz inner wall layer, and the interface between doped quartz layer and pure quartz inner wall layer is a fully reflective interface.

Because the present invention selects the photoconductive quartz capillary tube as the inner wall of the optical path part of the flow cell, its tube wall is a three-layer concentric tubular structure, and the outer layer is a polyimide coating, which plays a supporting and protective role; inwards are doped quartz layer and In the inner wall of pure quartz, the interface between the two layers of quartz forms a total reflection interface. When the incident angle of light from the inside of the tube to the tube wall is greater than a certain critical angle, total reflection will occur. Using a light-guiding quartz capillary with a small inner diameter as the inner wall of the flow cell can have a longer optical path length while maintaining a small cell volume.

In the present invention, in order to solve the difficult problem of optical path connection caused by the small inner diameter of the optical quartz capillary, an optical fiber is used to connect the optical path of the flow cell, and the optical coupling between the optical fiber and the optical capillary uses a self-focusing lens as a light concentrating device. Self-focusing lens, also known as gradient variable refractive index lens, refers to a cylindrical optical lens whose refractive index distribution is gradually changed along the radial direction. Through the self-focusing lens, the light with a certain divergence angle emitted by the optical fiber is converged into the light-guiding quartz capillary. Since the inner wall of the light-guiding quartz capillary can completely reflect and transmit the light along the tube, it will not be absorbed and lost by the tube wall, and can be used in a small optical path section. maintain a high optical density.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a commonly used Z-type ultraviolet-visible absorption flow cell.

Fig. 2 is a schematic structural diagram of an existing commonly used fluorescent flow cell.

Fig. 3 is a schematic diagram of the structural composition of an embodiment of the present invention. In Fig. 3, the name marks of each part: cell body 31; photoconductive quartz capillary 32; PEEK liner 33; C-shaped gasket 34; self-focusing lens 35; sealing gasket 36; gasket 37; Optical path exit optical fiber and connector 39 ; flow path inlet pipeline and connector 310 ; flow path inlet pipeline and connector 311 .

Fig. 4 is a schematic diagram of the ultraviolet-visible detection mode of the present invention.

Fig. 5 is a schematic diagram of the fluorescence detection mode of the present invention.

Fig. 6 is a structural diagram of a photoconductive quartz capillary according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of the light-gathering principle of the self-focusing lens of the embodiment of the present invention.

Fig. 8 is a schematic diagram of the structure of the cell body according to the embodiment of the present invention.

Fig. 9 is a component diagram of the entrance end of the optical path of the flow cell according to the embodiment of the present invention. In Fig. 9, the names of each part are marked: PEEK liner 33; optical quartz capillary 32; C-shaped gasket 34; self-focusing lens 35;

Fig. 10 is a detailed assembly diagram of parts at the entrance end of the optical path of the flow cell according to the embodiment of the present invention. In Fig. 10, the name marks of each part: cell body 31; PEEK liner 33; photoconductive quartz capillary 32; C-shaped gasket 34; self-focusing lens 35; Optical fiber sleeve 41; tapered ferrule 42; finger tight connector 43.

Detailed ways

The structural composition, working mode and principle of the present invention will be further described below in conjunction with the accompanying drawings.

The main components and assembly positions of the flow cell are shown in Figure 3. The present invention is provided with a cell body 31, a photoconductive quartz capillary 32, a polyetheretherketone (PEEK) liner 33, a C-shaped gasket 34, a self-focusing lens 35, a sealing Gaskets 36 and 37, optical fibers 38 and 39, liquid flow pipelines 310 and 311 and other components. The light-guiding quartz capillary 32 is installed in the PEEK liner 33 and filled in the lumen of the cell body 31; the self-focusing lens 35 is arranged in the light entrance direction, and is sealed and fixed with the cell body 31 by sealing gaskets 36 and 37; the C-shaped gasket The sheet 34 is located between the self-focusing lens 35 and the PEEK liner 33, and the gap of the C-shaped spacer 34 is aligned with the direction of the flow path, and its function is to fill up the redundant space formed between the two; the entrance optical fiber 38 and the exit optical fiber 39 And the liquid inlet and outlet pipes 310, 311 are respectively fixed on the cell body by joints and ferrules to form a sealed flow path.

The working principles of the two working modes of UV-Vis absorption and fluorescence detection are shown in Figures 4 and 5. In the ultraviolet-visible absorption detection mode, the light emitted from the light source is introduced into the flow cell by one branch of the bifurcated optical fiber, and after being absorbed by the sample solution, it is introduced into the micro-grating spectrometer by the single-strand optical fiber at the outlet to measure its absorbance; in the fluorescence detection mode Next, the light emitted from the light source is introduced into the flow cell by one branch of the bifurcated optical fiber, and irradiates and excites the fluorescent active substance in the sample. The other strand of the optical fiber enters the micro-grating spectrometer to measure its light intensity, and obtain the fluorescence intensity after deducting the stray light background.

Referring to Figure 6, the wall of the light-guiding quartz capillary is a three-layer concentric tubular structure, the outer layer is a polyimide coating, and the inner layer is a doped quartz layer and a pure quartz inner wall layer, and the doped quartz layer and a pure quartz inner wall layer The interface between them is a total reflection interface.

Referring to Fig. 7, in the present invention, in order to solve the difficult problem of optical path connection caused by the small inner diameter of the light-guiding quartz capillary, an optical fiber is used to connect the optical path of the flow cell, and the optical path coupling between the optical fiber and the light-guiding capillary uses a self-focusing lens as Concentrating devices. Through the self-focusing lens, the light with a certain divergence angle emitted by the optical fiber is converged into the light-guiding quartz capillary. Since the inner wall of the light-guiding quartz capillary can completely reflect and transmit the light along the tube, it will not be absorbed and lost by the tube wall, and can be used in a small optical path section. maintain a high optical density.

Referring to Fig. 8, the pool body is integrally processed from polyimide material, and the dimensions of length, width and height are 47.2mm×22.4mm×20mm. There is a through hole with an inner diameter of 1.6mm along the central axis of the pool body. The inner diameters of both ends of the hole are thickened and processed with inner threads for matching with optical fiber connectors. There is a channel with an inner diameter of 1.6mm on each side of the pool body, which communicates with the central channel to form a Z-shaped flow path. The outer ends of these two channels are also processed with internal threads for connecting liquid flow lines. connector. There are two through holes drilled at the opposite corners of the top of the cell body, which are used to pass through the bolts when fixing the flow cell. These two bolt holes are not connected with the channel inside the pool body.

Referring to Figure 9, the components at the entrance of the optical path of the flow cell are introduced as follows: PEEK liner 33 has an inner diameter of 0.38 mm, an outer diameter of 1.58 mm, and a length of 20 mm; an optical quartz capillary 32 has an inner diameter of 0.25 mm, an outer diameter of 0.375 mm, and a length of 20 mm; C-shaped The spacer 34 is made of polytetrafluoroethylene, and there is a gap of 0.6mm wide; the self-focusing lens 35 is made of special optical glass, with a diameter of 1.8mm and a length of 5.8mm; the sealing gasket 36 is made of rubber The spacer 37 is made of polytetrafluoroethylene, the optical fiber and the joint 38 at the entrance of the optical path include an optical fiber liner, a tapered ferrule and a finger-tight joint, and the specific structure will be described separately.

Referring to FIG. 10 , the installation positions of the components at the entrance of the optical path of the flow cell are introduced as follows: the PEEK liner 33 is filled in the central channel of the cell body 31 ; the photoconductive quartz capillary 32 is filled in the PEEK liner 33 . The C-shaped gasket 34 is located between the PEEK liner 33 and the self-focusing lens 35, and is clamped and fixed by the two. ; Flow path outlet pipeline 310 is inserted into the cell body and one end of the outlet is just aligned with the PEEK liner outlet; two sealing gaskets 36 are set on the cylinder of the self-focusing lens; two gaskets 37 are set on the self-focusing lens On the cylinder of the focusing lens; the fiber optic sleeve 41 is screwed into the threaded hole at one end of the central channel of the pool body by the thread on the hand-tight joint 43, and the tapered ferrule 42 presses the self-focusing lens and gasket inwardly, and the gasket presses and seals The deformation of the ring seals the self-focusing lens from the cell body.

The outlet end of the optical path of the flow cell is similar to the inlet end, but there is no self-focusing lens, sealing ring, and gasket installed, and it is sealed with the cell body by the tapered ferrule and finger-tight joint on the optical fiber connector. The flow pipes entering and exiting the flow cell are connected and sealed with the cell body by tapered ferrules and finger-tight fittings.

The optical path length of this flow cell is 20mm, which is larger than most of the flow cells currently common. The volume of the pool is about 1 μL, which can meet the requirements of capillary microcolumn chromatography.

Claims (2)

1, the dual-purpose flow cell of ultraviolet-visible absorption/fluorescence is characterized in that being provided with pond body, photoconduction quartz capillary, polyether-ether-ketone liner tube, GRIN Lens, packing washer, pad, optical fiber and liquid flow path pipeline; The photoconduction quartz capillary is installed in the polyether-ether-ketone liner tube and is seated in the tube chamber of pond body; GRIN Lens is arranged on the light entrance direction, with the pond body with packing washer sealing and fixing; Pad between GRIN Lens and polyether-ether-ketone liner tube, the notch alignment path direction of pad, inlet optical fiber and outlet optical fiber and liquid in-out pipe are fixed on by joint and cutting ferrule respectively and constitute the sealing stream on the body of pond.

2, the dual-purpose flow cell of ultraviolet-visible absorption/fluorescence as claimed in claim 1, the tube wall that it is characterized in that the photoconduction quartz capillary is three layers of concentric tubular structure, skin is a polyimide coating, inwardly be doping quartz layer and pure quartz wall layer successively, the interface between doping quartz layer and the pure quartz wall layer is the total reflection interface.

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