On the 15th, Nitride announced that it will use the same amount in the experiment of inactivating the new coronavirus at wavelengths of 222nm, 254nm and 275nm in cooperation with the director of the Virus Center of the Clinical Research Department of the Sendai Medical Center of the National Hospital. In the comparative test of light energy (unit J Joule) irradiating each deep ultraviolet wavelength, the inactivation effect of 275nm is equal to or higher than 254nm.
◆ Background
Since the German physicist Harman Straver discovered in 1901 that ultraviolet lamps can inactivate bacteria and viruses under deep ultraviolet rays, humans have been using mercury-containing ultraviolet lamps as germicidal lamps. Because the ultraviolet lamp does not use chemicals for inactivation, it has achieved fruitful results in the medical field as a safe and reliable inactivation method without residual substances.
In recent years, due to the development of semiconductor technology, the deep ultraviolet light emitting diode UV LED with sufficient illuminance below 300nm and the wavelength light emitted by the excimer lamp of 222 nm have been proved to have the same sterilization effect and have been applied. In order to compare and verify the sterilization efficiency of two kinds of ultraviolet light with wavelengths of 222nm and 275nm, this experiment was carried out, and the traditional 254nm sterilization light source was used as a reference.
◆ Experimental content
Light source of each emission wavelength, wavelength 222nm: excimer lamp, wavelength 254nm: UV (low pressure mercury) lamp, wavelength 275nm: deep ultraviolet LED. Since the illuminance of each light source is different, in order to make the conditions the same, the length of time for illuminating the object is adjusted according to the illuminance of each light source, so that the illuminating light energy (integrated light amount) is the same.
In addition, because many limited test results can be seen in similar verification tests under special circumstances, the distance between the light source and the object is based on the assumption of actual application in the medical environment, and the experimental group set it to 500 mm to obtain practical The inactivation effect.
This figure shows the residual infection effect of OC43 coronavirus attached to the surface over time. The two blue bars in the reference correspond to the standard values of the test conditions. They are the smear samples just after creation. The same sample is placed in a safety cabinet at 22°C 30-35% RH for 12 minutes.
Use the orange, yellow, blue, green, and gray bars of each wavelength in a biological clean room maintained at 20°C and 8-14% RH, and wait until the smear sample is completely dried according to the protocol. The result of light intensity irradiation is orange 0,7 J/m2, yellow 5 J/m2, blue 15 J/m2, green 30 J/m2, gray 60 J/m2, and the light source used is the result of irradiating from a distance of 50 cm from the left. As shown in the figure.
Regarding the change of residual infection rate over time, compared with the 0.0 J/m2 orange bar graph, the shorter the bar length, the higher the inactivation effect. It is worth noting that the 60J/m2 gray bar graph with the largest amount of irradiated light shows the shortest at 275nm, followed by the wavelength at 254nm, and finally at 222nm.
◆ Meaning
Compared with the 254nm wavelength used as the sterilization line wavelength in the past, the result is that the 275nm wavelength has the same or better inactivation effect on the pseudo-new coronavirus. This is in line with the procedures for the complete abolition of mercury stipulated in the United Nations Environment Programme (UNEP) Minamata Convention, which stipulates the complete abolition of mercury and shows that it can be used as an alternative light source.
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