CZ309152B6 - Equipment for narrowing the spectral half-width and selecting the exact wavelength - Google Patents

Abstract

The invention is a device for narrowing the spectral half-width and selecting the exact wavelength in a chromatography detector with LEDs, where behind the LEDs (3) behind the slits (2) there is a concave mirror (1), in front of which is a holographic grating (9) and focusing slit (4) behind which is a beam splitter (5) for reflecting the beam to the reference diode (8) and via a cuvette (6) to the measuring diode (7).

Description

Equipment for narrowing the spectral half-width and selecting the exact wavelength

Field of technology

The technical solution concerns the construction of an optical solution for the narrowing of the spectral half-width and the selection of the exact wavelength of a detector for chromatography with LED diodes.

State of the art

Recently, chromatographic detectors with LEDs have been used as a source of monochromatic light. The disadvantage of LEDs is that they have a large tolerance of the emitted spectrum, usually +/- 5 nm and a very wide spectral half-width, usually 12 to 20 nm, and in addition, at the base of the spectrum, the emitted spectrum is usually 20 to 40 nm wide. These properties of LEDs limit the use of such detectors in applications where accurate wavelength and a greater range of measurement linearity is required.

The essence of the technical solution

The above drawbacks are largely eliminated by the spectral half-width narrowing and precision wavelength selection device of the LED chromatography detector of the present invention. Its essence is that behind the LEDs there is a concave mirror behind the slits, in front of which there is a holographic grating and a focusing slit, behind which there is a beam splitter for reflecting the beam into the reference diode and through the cuvette into the measuring diode.

The device uses a holographic grating with a precise location of the slits, thus obtaining a spectrum with a precise wavelength with a tolerance of less than +/- 1 nm and a precise half-width controllable width of the slit in the range from 2 nm.

The proposed solution uses a diffraction grating, where the LEDs are located in the first order places of the spread spectrum. The direction of the rays of light here is inverted than that used for Diode Array Detectors. By combining the widths of the slits located in front of the LEDs and at the output of the monochromator, the spectral half-width of the light entering the detector cuvette can be influenced. At the same time, the exact position of the LEDs and slots allows you to select the exact wavelength from a wide range of LEDs. The device thus makes it possible to modify the spectrum of LEDs by selecting only a certain wavelength from this spectrum by means of a holographic grating and by limiting the spectral half-width by means of suitably selected slits. The production of such a detector is a bit more complicated than the existing constructions and additionally contains some optical and mechanical components, but it is balanced by the achievement of excellent parameters. This solution allows the use of these detectors in the most demanding analytical applications at much lower acquisition and operating costs.

In addition, this solution is less expensive to manufacture, and its small size allows for easy placement in higher units. The undeniable advantage is the low consumption of the detector and the long life of the LED diodes compared to conventional light sources such as a deuterium lamp.

Clarification of drawings

The device for narrowing the spectral half-width and selecting the exact wavelength of the detector for LED chromatography according to the invention will be described in more detail in a specific exemplary embodiment with the aid of the accompanying drawings, in which FIG. 1 is a circuit diagram, and FIG. 2 is a mechanical diagram of this device.

-1 CZ 309152 B6

Examples of embodiments of the invention

The device for narrowing the spectral half-width and selecting the exact wavelength of the detector for LED chromatography has behind the LEDs 3 slits 2, behind which is a concave mirror 1. In front of the concave mirror 1 there is a holographic grating 9 and a focusing slit 4, behind which is a distributor 5 beams for reflecting the beam to the reference diode 8 and via the cuvette 6 to the measuring diode 7.

The principle of the detector is shown in Fig. 1. The light from the LEDs 3 located in the first order of the spread spectrum passes through the slits 2 to the concave mirror 1, which reflects the rays to the holographic grating 9. Because the holographic grating 9 functions here in the inverse function of the diode array of detectors, consists of beams of different wavelengths from LEDs 3 into one beam, which is focused by reusing the concave mirror 1 into the focusing slit 4. After passing through the focusing slit 4, part of the light is reflected by the beam splitter 5 to the reference diode 8 and the larger part passes through the cuvette 6 through which the measured liquid sample flows, further to the measuring diode 7.

The signal from the measuring diode 7 is used to measure the absorbance according to Lambert-Beer's law by comparing the light intensity after passing through the cuvette 6 with the carrier mobile phase and subsequently with the measured sample. When using several LEDs 3 as light sources, these are lit alternately, which results in an absorbance value at different wavelengths.

The mechanical design of the functional prototype is shown in Fig. 2.

Industrial applicability

The device according to this technical solution finds application in the construction of detectors for liquid chromatography, where a precise wavelength and a narrow spectrum of the light source is required.

Claims (1)

PATENT CLAIMS Device for narrowing the spectral half-width and selecting the exact wavelength of a detector for 5 chromatography with LEDs, characterized in that behind the LEDs (3) behind the slits (2) there is a concave mirror (1), in front of which is a holographic grating ( 9) and a focusing slit (4), behind which is a beam splitter (5) for reflecting the beam to the reference diode (8) and via the cuvette (6) to the measuring diode (7).