[Practical] Use and precautions of ultraviolet light in scientific instruments
What is ultraviolet light
Ultraviolet light refers to the general term for radiation in the electromagnetic spectrum from 10 nm to 400 nm, which does not cause people's vision. In 1801, the German physicist Ritter discovered that the outer side of the purple end of the daylight spectrum was able to sensitize the photographic film containing silver bromide, thus discovering the presence of ultraviolet light. Ultraviolet light can be used to sterilize, and excessive UV rays entering the body can cause skin cancer in the human body.
Application of ultraviolet light in biological safety cabinet
UV sterilization is widely used as the most common sterilization method in biological safety cabinets, but it is affected by many factors during the use process, especially the low radiation intensity of the lamp and improper application will affect the disinfection and sterilization effect.
First, the scope of application
1. Ultraviolet rays can kill various microorganisms, including bacterial propagules, spores, mycobacteria, viruses, fungi, rickettsia and mycoplasma. Any surface contaminated by the above microorganisms, water and air can be disinfected by ultraviolet rays.
2. The ultraviolet radiation energy is low and the penetrating power is weak. It can only kill the microorganisms directly irradiated. Therefore, the disinfection site must be fully exposed to ultraviolet rays during disinfection.
3. The most suitable temperature range for UV disinfection is 20 ~ 40 °C. If the temperature is too high or too low, the disinfection effect will be affected. The disinfection time can be extended appropriately. When used for air disinfection, the relative humidity of the disinfection environment is better than 80%. Otherwise, the exposure time should be extended appropriately.
4. When using ultraviolet light to kill microorganisms protected by organic matter, the dose should be increased. Suspended particles in air and water can also affect disinfection.
Second, the ultraviolet radiation tube radiation intensity problem
The bio-safety cabinet UV lamp new lamp tube is not less than 100μw/cm2, 70 uw/cm2 is almost 50_80%. According to the requirements of the Ministry of Health disinfection technical specifications, the pass rate is less than 50%. Some units use ultraviolet germicidal lamps with an intensity of less than 70uw/cm2. Some even use less than 40uw/cm2. It is known that each microorganism has its specific UV killing dose threshold. The germicidal dose (K) is irradiation. The product of the intensity (I) and the irradiation time (t), K = It. It can be seen from the formula that high intensity short time or low intensity long time irradiation can obtain the same sterilization effect. However, if the ultraviolet intensity is less than 40 uw / Cm2, then extend the irradiation time can not achieve satisfactory sterilization effect, there is a microbial damage repair problem, deliberately to improve the illumination intensity.
Third, matters needing attention
1. Dust and grease on the surface of the UV lamp will hinder the penetration of UV rays. During use, the lamp should be wiped and cleaned. Before using the new lamp, it can be wiped with a 75% alcohol cotton ball. Wipe every 2 weeks during use. When it is found that there is dust or oil on the surface of the lamp, it should be wiped at any time to keep the lamp clean and transparent, so as not to affect the penetration of UV rays and the radiation intensity.
2. When disinfecting the surface of the object with ultraviolet light, the irradiated surface should be directly irradiated with ultraviolet rays, and a sufficient dose of radiation should be achieved.
3. The ultraviolet intensity meter is calibrated at least once a year, less than 40uw/cm2, and the service life of the ultraviolet germicidal lamp should be no less than 1000h. Light tubes with insufficient strength should be replaced immediately. Ultraviolet light is non-visible light, and the purple-blue light in the low-pressure discharge lamp is *vapor pressure. Although the intensity of the vapor pressure is still related to ultraviolet light, it does not directly represent the intensity of ultraviolet light. Therefore, it is impossible to judge the intensity of ultraviolet rays by the intensity of the purple-blue light in the visible light band. That is to say, the intensity of ultraviolet rays cannot be judged by the naked eye.
4, the use of ultraviolet germicidal lamps should also pay attention to prevent ultraviolet radiation damage: mainly to prevent ultraviolet radiation on the eyes, face damage, especially attention to the radiation damage of the conjunctiva. After the face is damaged by radiation, the eyes are red and swollen, tears , tingling, more serious than electro-optic eye damage. Can be cured after three or four days. (In case the conjunctiva is damaged by ultraviolet radiation, human eye drops can be used, once every half an hour, three to four times better.)
Application of UV lamps in ultra-clean workbench
Wipe the outer surface of the UV germicidal lamp before use to keep the surface clean, otherwise it will affect the sterilization effect.
When using the workbench, it should be turned on one hour in advance, and the ultraviolet sterilization lamp should be turned on at the same time to process the accumulated microorganisms on the surface of the operation area, and the ultraviolet lamp is turned off after 30 minutes.
Precautions
If the UV lamp is turned on synchronously with the ventilation, although the fan is beneficial to pump away the bacteria, it is not conducive to the bactericidal effect of the ozone produced by the ultraviolet lamp. Therefore, the best way is to sterilize the UV lamp first, and then turn on the fan 15 minutes to 20 minutes before the experiment to make the clean area clean. When the staff starts working, be sure to turn off the UV germicidal lamp, otherwise it will burn the work. The eyes and skin of the person.
When the ultra-clean workbench is UV-sterilized, the fluorescent lamp in the room should not be turned on as much as possible. Because the light has a revitalization effect, if the light is irradiated during the ultraviolet sterilization process, the cells after the ultraviolet irradiation are immediately exposed to visible light, and the survival is performed. The rate has increased significantly. However, this light repair process is relatively slow, and the UV has killed most of the bacteria, and the resurrection will not have much impact.
Safe use of UV lamps
The working principle of the ultraviolet lamp is to use the ultraviolet light of the appropriate wavelength to destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of the microorganism, causing growth cell death and/or regenerative cell death. The effect of sterilization.
The UV light switch should be awake to avoid confusion with the fluorescent switch.
The surface of the UV lamp should be kept clean and wiped with an alcohol cotton ball (95%) every 1-2 weeks to keep the UV lamp clean, free of dust and oil.
Ultraviolet rays have certain irritation and damage to human skin and mucous membranes. When disinfecting indoor air, the doors and windows must be closed, and all personnel should be withdrawn. When disinfecting, people should not be directly exposed to avoid damage. After disinfection, turn off the UV lamp, open the door and window and ventilate the air before entering the room.
The UV lamp is used to detect the UV lamp every month, and the failed UV lamp needs to be replaced. After the UV lamp has been used for more than 2000 hours (or according to the manufacturer's instructions), it should be replaced.
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