Analysis of Influencing Factors on Disinfection Effect of Hydrogen Peroxide Disinfectant
Hydrogen peroxide, also known as hydrogen peroxide and hydrogen dioxide, is a peroxide-based disinfectant. It is the product of certain reducing substances and oxygen in nature. It is rare and only exists in trace amounts in some plants. In juice and rain and snow. The molecular formula of hydrogen peroxide is H2O2 and the molecular weight is 34.015. Oxygen atoms adopt unequal sp3 hybrid orbitals to form bonds, the molecules are covalently polar molecules, and the three-dimensional structure is like two pages of a half-opened book.
Hydrogen peroxide is a strong oxidant, weakly acidic, colorless and odorless transparent liquid. As long as the storage conditions are good and there is no impurity pollution, pure hydrogen peroxide is relatively stable and can be stored for a long time without decomposition. The decomposition rate of hydrogen peroxide in alkaline medium is much faster than that in acidic medium, and the important factors affecting its stability are impurities (many heavy metal ions such as Fe2+, Mn2+, Cu2+, Cr3+), pH value, temperature, light, And the roughness of the inner surface of the storage container, etc. High concentrations of hydrogen peroxide can cause many organic solvents to burn, and can explode when interacting with manganese dioxide. Therefore, hydrogen peroxide should be sealed in a plastic container and stored in a cool place. It is strictly forbidden to expose it to the sun, and to avoid contamination and violent shaking.
Hydrogen peroxide is a highly efficient chemical disinfectant. A certain concentration of hydrogen peroxide solution can kill microorganisms including bacterial propagules, spores, fungi and viruses.
# mechanism of action
1. Hydrogen peroxide is decomposed under the catalysis of photochemistry, ionizing radiation, heavy metals and convertible metal ions to generate various chemical groups, such as active oxygen and derivatives, OH groups, etc., which have a strong killing effect on microorganisms. effect. By changing the permeability barrier of microorganisms, the protein enzymes, amino acids and nucleic acids of microorganisms are destroyed, resulting in the death of microorganisms.
2 . Hydrogen peroxide is an oxidant, which can ionize the molecules or atoms of bacterial cells and cause the breakage of lipid chains on the cell wall, thereby destroying the cell wall.
3. Hydrogen peroxide can oxidize enzymes containing SH groups, so that the function of metabolic activation enzymes is lost, resulting in cell division and reproduction disorders.
4. After entering the bacterial cell, it produces toxic OH group, which acts on the phosphodiester bond of DNA and breaks it.
# Factors Affecting Disinfection
The bactericidal effect of hydrogen peroxide is affected by factors such as action time, concentration, pH value, relative humidity, organic matter protection, and physical and chemical factors.
2.1 Action time
The bactericidal effect increases with time. With 10% hydrogen peroxide acting on the spores of Bacillus subtilis var. black, the longer the action time, the more the bacterial spores die.
The bactericidal effect was enhanced as the concentration of hydrogen peroxide increased. Some studies have shown that the spores of Bacillus subtilis var. niger were killed by different concentrations of hydrogen peroxide at 20°C. The higher the concentration of hydrogen peroxide, the shorter the sterilization time. Whether in liquid or gas form, there is a proportional relationship between the bactericidal effect and concentration of hydrogen peroxide. Studies have shown that the n value (concentration coefficient or dilution coefficient, used to indicate the effect of chemical disinfectant concentration on the disinfection effect, the larger the n value, the more obvious the effect of concentration changes on the disinfection effect) is 0.5, the dilution factor for killing Bacillus subtilis spores is 0.7~0.9. Zhang Wenfu et al. conducted killing tests on Bacillus subtilis var. nigricans spores with different concentrations of hydrogen peroxide at 20°C. The results showed that the higher the concentration, the shorter the killing time, and the logarithm of the concentration and the action time. There was a linear negative correlation (Y=2.944-1.134X, r=-0.989, P < 0.01).
Calculated according to the following concentration coefficient formula: n = [(lgT2 – lgT1)/(lgC1-lgC2)], when the concentration of hydrogen peroxide varies between 5% and 25%, its concentration coefficient (n) is 1.13, according to this According to the calculation of the concentration coefficient, within the range of the experimental value, the concentration of hydrogen peroxide is reduced by half, and the required action time is prolonged by 2.19 times.
Other conditions remain unchanged, the bactericidal effect of the hydrogen peroxide liquid increases with increasing temperature. Tested with 10% hydrogen peroxide to kill Bacillus subtilis var. black spores, the solution temperature has a linear negative correlation with the logarithm of the time required to kill the bacterial spores. At 70°C, 10% hydrogen peroxide can kill all the spores in just 1 minute, while it takes 205 minutes to achieve the same effect at 10°C.
2.4 Relative humidity
If the relative humidity in the air is too low or too high, it will adversely affect the bactericidal effect of hydrogen peroxide. In the sterilization test of the air disinfectant with hydrogen peroxide as the main component to kill Staphylococcus albus, the results show that the killing rate is 91.13% when the relative humidity is 52% to 54% after 10 minutes of action; the relative humidity is 72%. When the relative humidity is 90% to 92%, the killing rate is 68.98%.
Both pure hydrogen peroxide and hydrogen peroxide synergized with other components such as potassium iodide show that the bactericidal ability in an acidic environment is stronger than that in an alkaline environment.
The protection of organic matter has a certain influence on the bactericidal effect of hydrogen peroxide. When killing microorganisms contaminated by blood, pus, sputum and urine, the action time needs to be prolonged. However, some studies have pointed out that it has little effect on the sterilization effect of high concentration hydrogen peroxide, especially the sterilization effect in high temperature environment is not obvious.
Research results in recent years have shown that various physical and chemical factors such as ultraviolet rays, metal ions, and negative ions have synergistic effects on the bactericidal effect of hydrogen peroxide.
(1) Ultraviolet rays have a synergistic effect on hydrogen peroxide sterilization. Ultraviolet radiation can promote the decomposition of hydrogen peroxide to generate free radicals, which act on the spore protein and cortex, causing rapid death of microorganisms. Studies have shown that when 3% hydrogen peroxide and 70uw/cm2 ultraviolet rays are used synergistically for 5 minutes, the killing rate of Bacillus subtilis var. with 99.20%.
(2) The bactericidal and synergistic effect of potassium iodide on hydrogen peroxide has been proved at home and abroad. The synergy coefficient of 0.125% hydrogen peroxide and 0.125% potassium iodide for 3 minutes was higher than that of 0.250% hydrogen peroxide and 0.250% potassium iodide for the same time. The larger the synergy coefficient, the stronger the effect.
(3) The mixture of hydrogen peroxide and glutaraldehyde produces aldehyde peroxide, which can improve the bactericidal effect. Studies have shown that when 5% hydrogen peroxide and 0.5% glutaraldehyde act synergistically for 10 to 30 minutes, the killing rate of Bacillus subtilis var. The sterilization rates were 60.12% and 88.18%, respectively.
(4) Hydrogen peroxide and ultrasound are synergistic. It is reported that high-intensity ultrasound and 6% hydrogen peroxide are used to kill Bacillus cereus spores and Candida albicans synergistically in only 10 minutes, while ultrasonic or hydrogen peroxide is used alone for 30 minutes. , still not enough to kill it.
(5) The synergy between hydrogen peroxide and plasma, and the synergistic sterilization effect is due to the fact that hydrogen peroxide is easily decomposed to produce various free active groups in the plasma state.
(6) Hydrogen peroxide cooperates with metal ions (Fe2+, Cu2+, Ag+), and metal ions can also promote the decomposition of hydrogen peroxide to generate free radicals and accelerate the death of microorganisms.
(7) Hydrogen peroxide is synergistic with surfactants. Studies have found that adding surfactant D-33 or Sulfonol during hydrogen peroxide sol disinfection can reduce the diameter of the aerosol, thereby improving the sterilization effect.