CN2784920Y - Near field laser thermal lens spectrometry instrument - Google Patents

Abstract

The utility model is a near-field laser thermal lens spectrum analyzer, which is composed of a laser, a beam modulator, a focusing lens, a sample pool, an aperture, a photoelectric receiving device, an amplifier circuit and a readout system. The technical core lies in the connection between the sample pool and A beam expander lens is arranged between the photoelectric receiving devices to complete near-field beam expansion of the laser beam generated by the sample cell to realize near-field laser thermal lens spectral signal detection. Because the utility model uses a beam expander lens to expand the laser beam passing through the sample cell solution in the near field, the detection optical path distance is shortened to 16-28cm, and the detection of the spectral signal of the laser thermal lens in the near field is realized. The photoelectric receiving device of the instrument is assembled with the aperture, which makes the structure of the instrument compact and reasonable. There is no need to adjust the optical path system during the measurement, and the operation is convenient.

Description

Near Field Laser Thermal Lens Spectrum Analyzer

technical field

The utility model relates to a spectrum analyzer, in particular to a near-field laser thermal lens spectrum analyzer.

Background technique

Laser thermal lens spectral analysis is a high-sensitivity laser photothermal spectral analysis technology established and developed based on the thermal lens effect. The basic principle is that when a Gaussian intensity distribution of laser radiation passes through the sample solution to be tested, the molecules of the sample solution absorb the laser radiation of the characteristic wavelength and transition to an excited state, and convert part or all of the absorbed energy in a non-radiative relaxation manner. For heat, a thermal lens effect is generated, which causes a change in the refractive index of the sample solution to be measured and diverges the beam of light. The concentration of the sample solution to be tested can be obtained by measuring the change of the central light intensity in the far field. This analytical method can be applied to high-sensitivity analytical determination and spectral research of trace substances in many fields such as chemistry, physics, life science and environmental science.

At present, the existing laser thermal lens spectrometry (Laser Near Field Thermal Lens Spectrometry, abbreviated as LTLS) is detected in the far-field optical path, that is, at a distance of about 2 meters from the sample cell, the light intensity of the detection center changes to determine the Measure the sample concentration. Due to the long detection optical path of this instrument and the need to adjust the optical path system for each detection, it can only be measured by a laser thermal lens analysis instrument assembled in the laboratory, and there is no commercialized instrument so far. Faubel et al. (German patent Deutschpat.4231214) used optical fiber to transmit light beams, and experimentally developed a near-field laser thermal lens spectrum analyzer for measurement in the near-field. Although this analyzer uses optical fiber to transmit the light beam, which shortens the distance between the sample cell and the detection device, the actual optical path is not shortened, and there are still shortcomings such as the loss of optical fiber transmission.

Contents of the invention

The purpose of the utility model is to provide a near-field laser thermal lens spectrum analyzer, so that the laser thermal lens spectrum signal can be detected by the near-field optical path, so as to overcome the shortcomings of the prior art.

The purpose of this utility model is achieved in that a near-field laser thermal lens spectrum analyzer consists of a laser (1), a beam modulator (2), a focusing lens (3), a sample pool (4), an aperture (6 ), a photoelectric receiving device (7), an amplifying circuit and a readout system (8), it is characterized in that: a beam expander lens (5) is set between the sample pool (4) and the photoelectric receiving device (7), and the sample The laser beam generated by the pool (4) completes near-field beam expansion to realize near-field laser thermal lens spectral signal detection.

The focal length of the beam expander lens (5) of the utility model is 1-4cm.

The layout parameters of each part of the utility model are: the laser (1) and the beam modulator (2) are closely arranged, and the distance between the focusing lens (3) and the focusing lens (3) is between 3-6 centimeters; the focusing lens (3) and the sample pool (4) The distance between the sample cell (4) and the beam expander lens (5) is between 8-10 cm; the distance between the beam expander lens (5) and the diaphragm (6) is between 6.5-8 cm ; The photoelectric receiving device (7) is placed at 0.5-1.5 centimeters behind the diaphragm (6).

The laser (1) of the present utility model can adopt a continuous wave laser or a pulsed laser.

Since the utility model adopts the beam expander lens to expand the laser beam passing through the sample cell solution in the near field, the detection optical path distance is shortened to 16-28cm, and the detection of the spectral signal of the laser thermal lens in the near field is realized; and The photoelectric receiving device of the instrument is assembled with the aperture, which makes the structure of the instrument compact and reasonable, and is integrated. There is no need to adjust the optical path system during the measurement, and the operation is convenient. The utility model near-field laser thermal lens spectrum analyzer can be used for high-sensitivity analysis and measurement and spectrum research in the fields of chemistry, physics, life science, and environmental science, and can be used with analytical instruments such as high-performance liquid chromatography, high-pressure capillary electrophoresis, and flow injection analysis. joint use.

Description of drawings

Accompanying drawing 1 is the structural representation of the utility model.

Accompanying drawing 2 is the measurement curve of Nile Blue, B and C are the measurement results of LTLS in the near field and far field respectively.

Accompanying drawing 3 is the thermal lens signal waveform that the measured Nile blue solution produces.

Detailed ways

Below with reference to accompanying drawing, the utility model is described in detail.

The near-field laser thermal lens spectrum analyzer of the present utility model is composed of a laser (1), a beam modulator (2), a focusing lens (3), a sample pool (4), a beam expanding lens (5), and a diaphragm (6) And a photoelectric receiving device (7), an amplification circuit and a readout system (8). The laser beam output by the laser (1) is modulated by the beam modulator (2) into a beam of a certain frequency (depending on the specific test sample), and the focusing lens (3) (f=3-6cm) is focused and incident on the sample cell (4) Medium sample solution. The sample solution absorbs the incident laser radiation, creating a thermal lensing effect. After the laser beam passing through the sample solution is expanded by the beam expander lens (5) (f=1-4cm), it is incident on the aperture (6), and the photoelectric conversion of the measurement signal is completed by the photoelectric receiving device (7), and the amplifier and readout The display system (8) enlarges and displays the spectral signal intensity of the readout laser thermal lens.

Example 1. Thermal lens signal waveform and measurement sensitivity

The near-field laser thermal lens spectrometer uses a He-Ne laser as the light source with a wavelength of 632.8nm. The He-Ne laser and the beam modulator are closely placed, 3 cm from the focusing lens; 3 cm from the focusing lens and the sample cell; 8 cm from the sample cell to the beam expander lens; 6.5 cm from the beam expander lens to the diaphragm; photoelectric receiving device 1 cm behind the aperture.

Accurately prepare 1.0×10 ^-5 mol/L Nile blue solution, measure it on the near-field laser thermal lens spectrometer, and use a digital storage oscilloscope to record the thermal lens signal waveform generated by the solution, which is different from that usually measured in the far field The measurement results of the laser thermal lens spectrometer device were compared. The signal waveform and sensitivity of the two thermal lenses are exactly the same (Figure 2, Figure 3).

Example 2. Dopamine near-field laser thermal lens spectroscopic analysis and determination

The near-field laser thermal lens spectrometer uses an Ar ⁺ laser as the light source with a wavelength of 488nm. The Ar ⁺ laser and the beam modulator are closely placed, 5 cm away from the focusing lens; 4 cm away from the focusing lens; 10 cm away from the beam expander lens between the sample cell; 0.5 cm behind the aperture.

Accurately prepare 20 μg/mL dopamine hydrochloride and 3X 10 ^-4 mol/L chloranil ethanol solutions respectively, and generate corresponding complexes based on the charge-transfer reaction between dopamine and chloranil, and use the near-field laser thermal lens spectrometer To measure. The concentration of dopamine in the range of 0-20μg/10mL has a linear relationship with the signal intensity of the laser thermal lens. It is applied to the determination of dopamine content in dopamine hydrochloride injection. The results are consistent with the results of the pharmacopoeia method and the measurement results of the usual laser thermal lens spectral analysis instrument.

Example 3. Catalytic Kinetics Method Determination

The near-field laser thermal lens spectrometer uses a He-Ne laser as the light source with a wavelength of 632.8nm. The He-Ne laser and the beam modulator are closely placed, 6 cm away from the focusing lens; 5 cm away from the focusing lens and the sample cell; 9 cm away from the beam expander lens between the sample cell; 7 cm away from the beam expander lens; the photoelectric receiving device 0.5 cm behind the aperture.

In the presence of surfactant Triton X-100, silver (I) catalyzes the kinetic reaction of sodium persulfate to oxidize bromocresol green, and the ultra-trace silver is determined by the near-field laser thermal lens spectrometer. The silver (I) concentration was linear in the range of 0-1.6μg/mL, and the detection limit was 2×10 ^-7 ng/mL. It is applied to the determination of silver in the crude lead standard sample, and the result is consistent with the standard value of silver (I) content in the crude lead standard sample.

Example 4. Cyclohexane absorption coefficient determination

The near-field laser thermal lens spectrometer uses a Nd:YAG pumped dye laser as the light source, the laser dye is DCM, the frequency is 10Hz, and the wavelength is 646nm. The laser and the beam modulator are closely placed, 5 cm from the focusing lens; 4 cm from the focusing lens and the sample cell; 8 cm from the sample cell to the beam expander lens; 7 cm from the beam expander lens to the diaphragm; 0.5 cm behind the appendix. The measured absorption coefficient of cyclohexane overtone (v=6) is 1×10 ^-3 cm ^-1 , which is completely consistent with the results reported by MS Burberry et al. (MS Burberry et al. J. Chem. Phys. 1979, 70, 5522.)

Claims (4)

1. A near-field laser thermal lens spectrum analyzer, consisting of a laser (1), a beam modulator (2), a focusing lens (3), a sample cell (4), an aperture (6), and a photoelectric receiving device (7) Composed of an amplification circuit and a readout system (8), it is characterized in that: a beam expander lens (5) is set between the sample cell (4) and the photoelectric receiving device (7), and a thermal lens effect will be generated through the sample cell (4) The laser beam completes the near-field beam expansion, and realizes the spectral signal detection of the near-field laser thermal lens. 2. The near-field laser thermal lens spectrum analyzer according to claim 1, characterized in that: the focal length of the beam expander lens (5) is 1-4cm. 3. The near-field laser thermal lens spectrum analyzer according to claim 1 is characterized in that: the laser (1) and the beam modulator (2) are closely arranged, and the distance between it and the focusing lens (3) is between 3-6 centimeters The distance between focusing lens (3) and sample cell (4) is between 2.5-5 centimeters; the distance between sample cell (4) and beam expander lens (5) is between 8-10 cm; beam expander lens (5) and light The distance between the diaphragm (6) is 6.5-8 centimeters; the photoelectric receiving device (7) is placed 0.5-1.5 centimeters behind the diaphragm (6). 4. The near-field laser thermal lens spectrum analyzer according to claim 1, characterized in that: the laser (1) can be a continuous wave laser or a pulsed laser.

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