How to evaluate the ultraviolet sterilization effect of uvcld

On January 28th, 2020, the National Health Commission and the State Administration of traditional Chinese Medicine published the fourth edition of the diagnosis and treatment plan for pneumonia infected by novel coronavirus (Trial), which describes that the virus is sensitive to ultraviolet and heat. In other words, ultraviolet light can kill the novel coronavirus (2019 ncov). With the improvement of the power and technology of UV LED, it has gradually replaced the low-power UV mercury lamp in the market by virtue of its safety, environmental protection, compact performance and no chemical residue. Jinjian laboratory found that the brand, lamp type, wavelength, luminous efficiency, irradiation distance, irradiation time, radiation intensity, penetration rate and application field of UV-LED are the influencing factors for the disinfection and sterilization identification results of UV-LED different from that of UV mercury lamp. In this paper, we list three experiments to illustrate the importance of several factors, and suggest customers to evaluate the sterilization effect of UV-LED UV lamp according to different scientific design experimental conditions of product performance and application fields.

 

1、 Comparison of germicidal efficacy of the same product on different strains

A customer entrusted Jinjian laboratory to carry out sterilization test on UV LED lamps. Jinjian engineer tested that the central wavelength of this lamp is 275nm, and its radiation intensity is 98 when the irradiation distance is 1m μ W/cm 2, after vertical irradiation for 15min, compare the blank group to evaluate the bactericidal effect on Candida albicans, Staphylococcus aureus and Escherichia coli. The test results in this test show that although the same kind of UV LED has the same radiation intensity, it has different sterilization effects on different strains.

2、 Comparison of effects of different irradiation times for the same product

A customer entrusted Jinjian laboratory to carry out sterilization comparative test on UV LED lamp beads under different conditions. Jinjian engineer tested that the central wavelength of the sample UV LED lamp bead was 280nm, and the sterilization effect on E. coli was evaluated after 30s, 40s and 50s of vertical irradiation above the culture medium. This test shows that under the same irradiation distance, the sterilization effect of UV LED is significantly enhanced with the increase of irradiation time. This UV LED UV lamp has a good sterilization effect on E. coli after 50s of irradiation. The test results are as follows:

3、 Comparison of effects of different irradiation distances for the same product

A customer entrusted Jinjian laboratory to carry out sterilization test on UV LED lamp beads. Jinjian engineer tested that the central wavelength of this UV LED lamp bead was 275nm. The germicidal efficacy against Staphylococcus aureus was evaluated after 60s of vertical irradiation 5cm, 7cm and 10cm above the culture medium. In this test, under the same irradiation time, the sterilization effect of UV LED UV lamp decreased significantly with the increase of distance; It has a good bactericidal effect on Staphylococcus aureus at a distance of 5cm. The test results are as follows:

Compared with the traditional ultraviolet lamp, Jinjian laboratory believes that the following differences should be considered in the design of UVLED sterilization experiment:

1. wave band: different wave bands have different killing effects on bacteria and viruses.

The traditional UV mercury lamp generates UV radiation with the wavelength of 253.7nm by discharge. However, according to the latest research results, the sterilization effect of UV may be higher near 264 nm. In terms of sterilization and disinfection of deep UV UVC led, standardization faces a series of challenges. For example, the sterilization of UV mercury lamp is mainly at 253.7nm, while the wavelength of UVC LED is mainly distributed at 200-280nm, which brings a series of differences for subsequent application solutions.

2. UV dose: sterilization requires sufficient irradiation intensity, sufficient time and appropriate wave band.

The intensity of UV radiation depends on the luminous intensity of the effective spectrum in the UV light source, the light output angle (beam concentration) of the lamp, the distance between the lamp and the object to be radiated, and other factors. Generally speaking, the higher the radiation intensity, the better the effect; The more concentrated the beam is on the surface of the irradiated object, the better the sterilization effect is; The closer to the object to be radiated, the better the effect; Cumulative radiation time is the total radiation time of the illuminated object under the ultraviolet lamp. The longer the time, the better the effect.

3. luminous efficiency: at present, UV LED cannot completely replace mercury lamp in terms of luminous efficiency.

UVA LED technology is relatively mature, and EQE can reach 50-60%. More work on UVA products in the future will focus on the development of application systems. The external quantum efficiency of UVB and UVC band deep UV LEDs is still relatively low, EQE is generally below 10%, and commercial products are basically 1%~3%.

4. application field: UV LED also has the advantages of small size, portability, environmental protection, safety and easy design, which can give birth to some application requirements different from traditional mercury lamps.

For example, portable electronic disinfection products, elevator handrail sterilizers, and sweeping robots have emerged. This is where the traditional ultraviolet light source is difficult to apply.

5. ultraviolet penetrability: the UV LED has a good inactivation effect on the surface of the directly irradiated object, but the penetrability is not strong. It has no obvious effect on the interior and covered parts of the object that cannot be penetrated by light. The traditional UV lamp can make use of the dispersion of ozone generated to make up for the shortcomings that ultraviolet rays only propagate along a straight line and there are dead corners in disinfection.

6. sterilization difference: ultraviolet lamps of different brands and specifications have great differences in sterilization. When purchasing, it is necessary to confirm the radiation wavelength, radiation intensity, protection design, work requirements, etc. of the light source, and select appropriate lamps.

 

As a third-party laboratory specialized in LED quality management, Jinjian laboratory has passed the certification of CMA, CNAs and ISO 9001 quality management system, and has launched the service project of "UV LED ultraviolet sterilization experiment" to the market. According to the brand, lamp type, wavelength, luminous efficiency, irradiation distance, irradiation time, radiation intensity, penetration rate, application field and other factors that affect the disinfection and sterilization identification results, we will jointly design an experimental scheme with customers to scientifically evaluate the sterilization effect of UV-LED UV lamp.

The optimized test scheme:

       1. Comparative test of different strains

       2. Comparative test of germicidal efficacy at different irradiation distances

       3. Comparative test on germicidal efficacy of different irradiation time

       4. Comparative test on germicidal efficacy of different radiation intensities

       5. Comparison test of the same test conditions for different products

       ......

 

 

Test strain:

Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus albus, Mycobacterium Chelonii abscess subspecies, Bacillus subtilis var. niger spores, Candida albicans, etc.

Note: Staphylococcus aureus ATCC 6538 is the representative of pyogenic coccus in bacterial propagules;

E. coli 8099 is the representative of intestinal bacteria in bacterial propagator;

Pseudomonas aeruginosa ATCC 15442 is the most commonly isolated bacterial propagator in hospital infection;

Staphylococcus albus 8032 is the representative of bacteria in the air;

Mycobacterium Chelonii abscess subspecies ATCC 93326 is the representative of human Mycobacterium tuberculosis;

Bacillus subtilis var. niger Spore ATCC 9372 is the representative of bacterial spores;

Candida albicans ATCC 10231 is the representative of pathogenic fungi.

 

Executive standard:

Technical specifications for disinfection, GB 28235-2011 safety and health standard for ultraviolet air disinfectors, hj2522-2012 technical requirements for environmental protection products ultraviolet disinfection devices, wst367-2012 technical specifications for disinfection of medical institutions and enterprise standards of Jinjian laboratory.

 

Appendix:

1、 Advantages of deep UV LED sterilization:

1. high efficiency sterilization: the sterilization and inactivation of bacteria and bacteria are generally completed in a few seconds, almost instantaneous.

2. broad spectrum sterilization: it can effectively kill almost all bacteria and viruses.

3. no secondary pollution: no other chemical pollutants.

 

The germicidal efficacy of deep ultraviolet light on common bacteria and viruses is shown in the table below:

 

 

2、 UV band classification

UV band is divided according to wavelength:

UVA: 315-400nm (near UV nuv365-400nm), and its applications include curing, photocatalytic purification, anti-counterfeiting and other fields.

UVB: 280-315nm, and its applications include light health / medical treatment, light regulation of plant growth, etc.

UVC: 200-280nm (solar blind - "solar blind" ultraviolet), which is used for sterilization and disinfection of water, air, etc.

 

 

3、 Principle of ultraviolet disinfection

UV disinfection technology is based on the research foundation of modern epidemic prevention, medicine and photodynamics, and is realized by using specially designed UVC band UV lamps with high efficiency, high intensity and long life. Ultraviolet radiation damages microorganisms (bacteria, viruses, spores and other pathogens) and destroys the function of nucleic acids, so as to kill microorganisms and achieve the purpose of disinfection and sterilization. The inactivation effect depends on the ultraviolet radiation dose.

 

Microbial structure and UV inactivation mechanism:

 

 

 

4、 Class I and II disinfection products

The national health and Family Planning Commission (the health and Family Planning Commission) has issued corresponding policies, requiring that class I and class II disinfection products need to conduct health and safety evaluation by themselves or by entrusting a third party before they are first marketed, and only disinfection products that pass the evaluation can be marketed. That is, before listing, a third-party testing and evaluation institution shall be entrusted to conduct health and safety evaluation, issue a professional testing report, and put on record by the government before the product can be sold on the market.

 

The first category of disinfection products refers to disinfection products that have high risks and need to be strictly managed to ensure safety and effectiveness. It includes high-level disinfectants and disinfection devices, fungicides and sterilization devices for medical devices, skin and mucous membrane disinfectants, biological indicators and chemical indicators of sterilization effect.

 

The second category of disinfection products refers to the disinfection products with moderate risks that need to be strengthened in management to ensure safety and effectiveness, including disinfectants, disinfection instruments, chemical indicators other than the first category of products, as well as packaging materials of sterilization articles with sterilization marks and anti (anti -) bacterial agents.