Daily maintenance and maintenance of infrared spectrometer

Infrared spectrometers are divided into two types: raster scanning and Michelson interferometer scanning. Among them, Michelson interference scanning is currently widely used. It is also called Fourier transform infrared spectroscopy. It is used in dyeing and weaving industry, environmental science, biology, material science, polymer chemistry, catalysis, coal structure research, petroleum Industry, biomedicine, biochemistry, pharmacy, basic research of inorganic and organic chemistry, semiconductor materials, daily chemical industry and other research fields.Infrared spectrometer is an instrument that uses the absorption characteristics of different wavelengths of infrared radiation to perform molecular structure and chemical composition analysis. Infrared spectrometer is usually composed of light source, monochromator, detector and computer processing information system. According to the different spectroscopic devices, it is divided into dispersion type and interference type. For the dispersive dual-path optical zero balance infrared spectrophotometer, when the sample absorbs a certain frequency of infrared radiation, the vibrational energy level of the molecule undergoes a transition, and the light of the corresponding frequency in the transmitted beam is weakened, resulting in a reference The intensity difference of the corresponding radiation between the light path and the sample light path is used to obtain the infrared spectrum of the tested sample.The Fourier transform infrared spectrometer is called the third generation infrared spectrometer. It uses the Michelson interferometer to interfere with two beams of complex infrared light whose optical path difference changes at a certain speed to form interference light, which then interacts with the sample. The detector sends the obtained interference signal to the computer for the mathematical processing of Fourier change, and restores the interferogram into a spectrogram. This article introduces the maintenance precautions of the infrared spectrometer instrument in daily use.Precautions for installation and placement of infrared spectrometer1. Installation conditionsThe infrared spectrometer requires a single-phase power supply with a voltage of 220V. The single-phase power supply is connected to the live wire and the neutral wire. But the infrared spectrometer also requires a ground wire. If the ground wire is not connected, when the instrument leaks, it will not be able to protect the instrument. In addition to a well-grounded ground wire for the power supply of the infrared spectrometer, a leakage protection device should be installed on the power distribution line. Once there is a leakage phenomenon, the circuit will automatically cut off the power supply.In order to prevent the sudden power failure and the call immediately on the instrument from adversely affecting the instrument, a magnetic starter can be installed on the power supply line. With a magnetic starter, you must press the start button to transmit power after a power failure, which can reduce damage to the instrument.In addition, the infrared spectrometer should also be equipped with a regulated power supply to prevent too much voltage fluctuations that will affect the strength of the light source output light signal and the sensitivity of the instrument, resulting in inaccurate measurement results and damage to the instrument. If there is only an infrared host and a computer, a 1kW stabilized power supply is sufficient. If it is also equipped with an infrared microscope or Raman accessories, it should be equipped with a 2kW regulated power supply. If it is the color-red combination accessory and the thermorecombination use, it should be equipped with a more powerful regulated power supply.2. Environmental requirements for instrument placementThe infrared spectrometer should be placed in a constant temperature and humidity room with a clean environment, no strong vibration, no corrosive gas, and no electromagnetic interference. Air conditioning and dehumidifiers should be installed indoors. The temperature of the room should be controlled at 17～27℃. For a long-time sample measurement process, temperature changes have a great influence on the measurement results. It is required that the temperature fluctuation should not exceed 1℃ per hour and 2℃ per day.The indoor relative humidity is maintained at about 50%. If the humidity is too low, it is easy to generate static electricity, and if the humidity is too high, the parts of the instrument are easily damaged. However, the indoor humidity is difficult to control. Generally, the indoor relative humidity is slightly lower in winter, while the annual relative humidity in the south is usually higher than 50%, so the dehumidifier should always be turned on. In the rainy season or summer, the air conditioner and dehumidifier must be always on.Not only that, but also pay attention to regularly check whether the water tank of the dehumidifier is full of water, and dump it in time, otherwise the dehumidifier will stop working and it will not be able to dehumidify. If conditions permit, drill a small hole in the wall and use a rubber tube to drain the water drawn from the dehumidifier to the outdoors, which can reduce the work of the water tank. Because when the humidity is high, the dehumidifier will draw out a box of water a day.In the summer vacation, the workload of checking whether the water tank is full and pouring water every day is still relatively large. But pay attention when drilling holes in the wall, the size of the hole should match the size of the rubber tube. If the hole is too large, there will be a gap between the two, and the outdoor water vapor will diffuse into the room, making it more difficult to control the indoor humidity.The windows of the infrared room are equipped with double glazing. Double-layer glass can effectively prevent outdoor dust from entering the room, reduce noise, and keep indoor temperature changes little. Normally, indoor windows must be closed tightly.The infrared room is also separated from the chemical laboratory. Because the gases and volatile solvents produced in chemical experiments will corrode the parts of the instrument and shorten the service life of the instrument. The semi-transparent coating of the He-Ne laser on the beam splitter and the window material of the MCT detector are both ZnSe. ZnSe is very sensitive to halide gas, so it is necessary to prevent halide gas from entering the optical table.The experimental table or bench on which the infrared spectrometer is placed must be strong and stable. The desktop cannot be deformed due to long-term placement, otherwise it will cause the light path to deviate from the original direction, weaken the signal reaching the detector, or fail to detect the signal, which will affect the normal use of the instrument. In addition, a proper distance should be left around the instrument to facilitate the inspection and maintenance of the instrument.Daily maintenance and maintenance of infrared spectrometerThe infrared spectrometer must be managed and maintained by a dedicated person, and a technical file and experimental record book for the special infrared spectrometer must be built. Operators must be specially trained, and carefully read the instruction manual and operating procedures to ensure that they have a full understanding of the instrument and can only operate independently after passing the assessment.During use, the operator should strictly abide by the operating procedures. If the instrument fails, immediately exit the detection state and report to the custodian or the person in charge of the department to find out the cause and deal with it in a timely manner. Do not "repair" without authorization. At the same time, make use and failure registration and laboratory records. If the hardware of the instrument is damaged, please ask the maintenance engineer of the instrument company to deal with it in time. If it is not a hardware problem, it should be resolved in accordance with the specific conditions, common failures, failure causes and treatment methods.In case of operating system failure, you can check whether the reading of the signal meets the requirements when entering the OPUS operating software after the self-check of the instrument. If it is conventional infrared transmission, the signal can reach about 24000, if it is attenuated total reflection (ATR), the signal is about 15000, while the diffuse reflection signal is only about 8000, and the mirror reflection signal is only about 800. Therefore, it is necessary to check the signal reading according to the specific test method. If the required signal value is not reached, check whether the sample rack is properly configured, whether the parameter settings are correct, and so on.Infrared spectrometer is an instrument that can work continuously. The instrument can be stabilized soon after turning on, and the sample can be measured after 0 minutes after the light source is powered on. However, the power transformer, infrared light source, HE-Ne condenser and other components of the infrared spectrometer have a service life. Therefore, in order to prolong the service life of the instrument, the instrument should be shut down when it is not in use.The humidity of the air has a great influence on the normal use and daily maintenance of the instrument. Among the components of the infrared spectrometer, the beam splitter is easily damaged, followed by the DTGS detector. The matrix of the mid-infrared beam splitter and the window material of the DTGS detector are made of potassium bromide or cesium iodide crystals, which are very water-absorbing, and are afraid of moisture. After these parts and materials absorb moisture, they are damaged and the instrument cannot work normally. The replacement cost of imported instrument parts is very high, so it is very important to do a good job of daily maintenance.If the instrument is used frequently, the air humidity will not have much influence on the internal parts of the instrument. But in summer, especially summer vacation, the instrument is not used for a long time, and the air humidity can easily damage the instrument. In order to keep the air in the instrument and the instrument room dry, the instrument should be energized for at least a few hours a week to drive out the moisture in the internal parts of the instrument. The dehumidifier and air conditioner in the instrument room must be turned on every day, and the color of the desiccant in the sample chamber and the electronic humidity indicator of the instrument should be observed at any time, and the expired desiccant should be replaced in time to ensure a dry atmosphere in the optical table. When the electronic humidity indicator on the upper right corner of the infrared meter flashes red, the desiccant in the sample compartment and the interferometer compartment should be replaced immediately.The precautions for replacement and regeneration of the infrared spectrometer desiccant are as follows:(1) Open the cover of the instrument with a tool, carefully take out the drying tube in the sample compartment and the interferometer compartment, put the dried spare desiccant into the drying tube, close the sealing cap, and then carefully insert the sample compartment and interferometer Warehouse;(2) Pour the expired molecular sieve desiccant into the disk, put it in a drying oven, and heat and dry it at 150°C for 24 hours;(3) Cool the dried desiccant in a dry atmosphere to below 50°C, then put it into a sealed bottle, close the sealed cap, and store it in a desiccator for later use (remember not to put the high-temperature desiccant into the instrument immediately In, otherwise it will damage the infrared spectrometer).(4) Dust should not be attached to the plane mirror in the optical table and the parabolic mirror for focusing. Once the dust is attached, it can only be blown with an ear-washing ball. The dust that cannot be blown off can not be cleaned with organic solvents, let alone wiped with lens paper, otherwise it will reduce the reflectivity of the mirror surface, so you must pay special attention to dust during normal maintenance. When the instrument is not in use, it should be covered with a dust cloth or dust cover.