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Home > Mall Dynamic > Principle Of Color Measurement By Photometry And Application Of Spectrophotometer
The spectrophotometer is widely used in medical and health, clinical testing, petrochemical, environmental protection, quality control and other departments, is one of the commonly used analytical instruments in industrial production and laboratories, this paper brings you the common visible light spectrophotometer measurement principle and use method.
In the qualitative and quantitative tests of biochemistry, photometry is commonly used. Photometry is an analytical method based on the selective absorption of light by the molecules of a substance, including colorimetry and spectrophotometry. Colorimetric method to compare the color depth of colored solution to determine the content of colored substances: spectrophotometry is a color meter to measure the absorbance of the solution at a certain wavelength to determine the content of measured substances in the solution analysis method, which mainly includes ultraviolet spectrophotometry and visible light spectrophotometry. The commonly used wavelength range is: 200-400nm ultraviolet region; 400-760nm visible region; 2.5-25μm infrared light region. The instruments used are ultraviolet spectrophotometer, visible spectrophotometer (spectrophotometer) and infrared spectrophotometer. In order to ensure the precision and accuracy of the measurement, all instruments shall be calibrated and verified regularly in accordance with the national metrology verification regulations.
Spectrophotometry has the characteristics of high sensitivity, good accuracy, simple equipment requirements, simple operation, rapid determination, etc., so it is widely used.
When a beam of light irradiates to a substance or a solution, particles such as molecules, atoms or ions of the substance interact with photons, and the energy of the photons is transferred, so that these particles transition from a low energy orbit to a high energy orbit, that is, from the ground state to the excited state, this process is the absorption of light by the substance. Since the energy level of a molecule, atom or ion is quantized and discontinuous, it can be absorbed only when the energy of a photon is equal to the difference between the ground state and the excited state energy of the irradiated material particle. The energy difference between the ground state and the excited state of different substances is different, and the energy selected to absorb the photon is also different, that is, the absorption wavelength is different. As molecules, atoms and electrons move, they have energy and absorb energy differently. Measuring the degree of light absorption of substances at different wavelengths, the curve drawn with wavelength as the horizontal coordinate and absorption as the vertical coordinate is called the absorption curve or absorption spectrum.
On the absorption curve, the peak of the absorption curve is called the absorption peak, and its corresponding wavelength is called the maximum absorption wavelength, indicating that the substance has the greatest degree of light absorption at this wavelength. The lowest part between the peak and the peak is called the valley, and the wavelength there is called the minimum absorption wavelength. Different substances and their molecular structure are different, so the shape of the absorption curve is the basis for qualitative identification of substances. According to the absorption curve, we can select the appropriate wavelength to determine the material for quantitative analysis and structural analysis.
1. Turn on the power supply, turn on the instrument switch, lift the cover of the camera obscurum in the sample room, and preheat for 10min.
2, the sensitivity switch to "1" (if the zero regulator can not be adjusted to "0", need to choose higher grade).
3. Turn the wavelength selection button according to the desired wavelength.
4. Pour the blank liquid and the measuring liquid into 3/4 of the colorimetric cup, wipe the outer wall with the mirror wiping paper, put it into the sample room, and align the blank tube with the light path.
5. Adjust the zero adjuster when the camera obscula cover is open, so that the pointer of the reading disk points to t=0.
6, cover the camera lid, adjust the "100" regulator, so that the blank tube t=100, the pointer is stable, gradually pull out the sample rod, read out the optical density value of the measurement tube, and record.
7. After color comparison, turn off the power, take out the color plate and wash it, and wipe the sample room with soft cloth or soft paper.
The instrument should be placed in a dry room, placed on a solid and stable workbench when used, and the indoor lighting should not be too strong. In hot days, the fan can not be used to blow directly to the instrument to prevent the lamp filament from shining unstable.
Before using the instrument, the user should first understand the structure and working principle of the instrument, as well as the function of each control knob. Before the power supply is not pressed, the safety performance of the instrument should be checked, the power connection should be firm, the power should be good, the starting position of each adjustment knob should be correct, and then press the power switch.
When the instrument is not connected to the power supply, the meter pointer must be carved on the "0" line, if this is not the case, it can be adjusted with the correction screw on the meter.
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