There is a common misconception that sodium hypochlorite (often known as “84 disinfectant”) and hypochlorous acid are the same, and people often express concerns about their potential respiratory irritation and toxicity. Even some medical professionals are not entirely clear about the distinction between the two. This article aims to explain the fundamental chemical differences between them in a way that even individuals without a chemistry background can comprehend.
84 Disinfectant originated in 1984 and was developed by the First Infectious Disease Hospital in Beijing. It is known for its potent ability to kill hepatitis viruses. This product, in existence for nearly 40 years, primarily consists of sodium hypochlorite.
Misconception Source: Definition of Chlorine-Containing Disinfectants
First and foremost, let’s clarify the definition of “chlorine-containing disinfectants.” These are substances that, when dissolved in water, can generate hypochlorous acid, which possesses bactericidal properties. Various substances, including sodium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate, and trichloroisocyanuric acid, fall under the category of chlorine-containing disinfectants. However, these disinfectants exhibit significant differences in their physical and chemical properties, much like the distinction between vans and sports cars, both being vehicles but with notable disparities.
Chemical Property Differences
1. pH Level Discrepancy
- Sodium hypochlorite typically exhibits strong alkalinity. When used, its pH value usually exceeds 10, making it highly corrosive and unsuitable for skin contact. Mixing it with substances like hydrochloric acid can even generate toxic chlorine gas.
- In contrast, hypochlorous acid maintains a pH of around 6 under normal usage concentrations, falling within the range of weak acidity. It closely resembles the pH of human skin, thus causing no irritation, making it suitable for use in child-friendly no-rinse disinfectants. You can easily detect these differences using pH test strips.
2. Varied Bactericidal Capacity
The surfaces of cell membranes generally carry a negative charge, which makes it difficult for hypochlorite ions (ClO-) to penetrate into the interior of cells. Conversely, hypochlorous acid (HClO) is a neutral, small molecule that can easily pass through cell membranes, enter the cell interior, and react with DNA and mitochondria inside, causing the death of bacteria. Consequently, the concentration of hypochlorous acid molecules to some extent determines the bactericidal capacity of chlorine-containing disinfectants, with the solution’s pH value directly affecting the concentration of hypochlorous acid molecules.
3. Disparate Irritation Levels
Due to varying bactericidal effectiveness, the concentration of sodium hypochlorite is significantly higher than that of hypochlorous acid. As a result, the former exhibits considerably higher irritation. In line with the hygiene requirements specified in GB/T 36758-2018, sodium hypochlorite should not be used on air, hands, skin, or mucous membranes, whereas hypochlorous acid is not subject to such restrictions.
4. Residual Effects
During the bactericidal process, sodium hypochlorite can generate harmful substances such as chloroform, urea, and cytotoxins. In contrast, hypochlorous acid not only eliminates bacteria but also completely decomposes residual toxins, underscoring the thoroughness of hypochlorous acid. Furthermore, hypochlorous acid serves as the first line of defense in the human immune system. When pathogens invade, white blood cells produce hypochlorous acid to exterminate the invaders. Because it shares similarities with the human immune system and exhibits biocompatibility, it poses minimal harm to human health.
Safety and Environmental Considerations
Taking various factors into account, hypochlorous acid currently stands as one of the best disinfectants in the market, particularly suitable for households concerned about safety, such as those with infants or pets. It has a mild odor and does not irritate the skin, respiratory tract, or eyes.
Product Selection and Usage Recommendations
1. Hypochlorous Acid Disinfectant Solution
- Product labels generally indicate a shelf life of one year, but the actual situation may vary.
- The stability of hypochlorous acid disinfectant solution depends on the packaging. For example, 500ml bottles typically employ PET material, ensuring stability for up to one year. Once opened, it is advisable to use the solution within two months to ensure effectiveness.
- In the case of 5L container packaging, commonly made of HDPE or PE material, the unopened shelf life is typically six months. Once opened, it is recommended to use it within one month. Consequently, if you cannot finish a 5L container within a month, it is not advisable to purchase it, and you can opt for 500ml bottle packaging or use hypochlorous acid disinfectant tablets.
2. Hypochlorous Acid Disinfectant Tablets
- Hypochlorous acid disinfectant tablets dissolve in water to produce hypochlorous acid disinfectant solution. They have several advantages over directly purchasing container-packaged hypochlorous acid:
- A longer shelf life, lasting up to two years before dissolution.
- Relatively lower prices.
- Convenient for storage and transportation.
- However, hypochlorous acid disinfectant tablets also have certain disadvantages, such as a shorter shelf life. Typically, it is recommended to use the solution produced from dissolving the tablets within 15 days because stabilizing agents cannot be added, as in the case of container-packaged products.
To ensure effectiveness, it is recommended to select reputable brands with a strong track record.
Considering aspects of safety, disinfection efficacy, applicability, and environmental friendliness, hypochlorous acid stands as one of the best disinfectants on the market. This is especially true for households concerned about safety, such as those with infants or pets. Through proper selection and storage, you can maximize the benefits of this disinfectant, creating a safer and healthier environment for your home.