Reason for the sudden interest in HOCl/ Electrolyzed water?

Is Hypochlorous Acid the newfound disinfectant? Why is everyone talking about HOCl (Hypochlorous Acid) nowadays? And how is it different from Electrolyzed Water?

Are these new discoveries? Or has the need for an effective disinfectant during the Coronavirus pandemic led people to rediscover an age-old disinfectant?

Actually, Hypochlorous Acid had been in use for decades, right from the time Chlorine gas was discovered to kill microorganisms. Chlorine Gas, that is Cl2, when injected in water (H2O), forms HOCl. This Hypochlorous Acid is what kills the bacteria. Hypochlorous Acid is called by different names such as Electrolyzed Water, Slightly Acidic Electrolyzed Water, Electrolyzed Oxidizing Water, Electro-activated Water, Electro-chemically Activated Water Solution, Hypochlorous Solution. Irrespective of which of these names are used, the power to disinfect and the many advantages remain the same. Now, before getting down to the different methods of making HOCl, let us look at some of the advantages of HOCl.

Advantages of HOCl/Electrolyzed Water

1.Disinfection of Water: untreated drinking water contains many pathogens that cause innumerable water-borne diseases. The main process of water treatment i.e. the killing of bacteria, viruses, and other harmful pathogens, is called disinfection. It was a health revolution when we started using chlorine gas as a disinfectant almost 125 years back in the year 1895. Since then, several types of research have been conducted to understand the bactericidal mechanism of chlorine in the water. In a nutshell, the process is, when Chlorine dissolves in water, it converts to a mixture of Chlorine, Hypochlorous Acid (HOCl), and Hydrochloric Acid (HCl).
Cl2+ H2O ⇌ HOCl + HCl.

In an acidic solution, Cl2 and HOCl are present, whereas, in an alkaline solution, only OCl− (hypochlorite ion) is present. It is this Hypochlorous Acid that kills the bacteria and other living organisms by penetrating the cell wall of the organism or making them incapable of reproducing. The traces of HOCl that is present in water remains in water as residual chlorine to be later converted to HOCl and kill any bacteria that might re-enter the water.

2.Surface Disinfection: During an epidemic, the diseases causing organisms, be it bacteria or a deadly virus, spread through contact with an infected person. Most often the contact need not be direct, it can also be through surfaces that the infected person has contaminated. So, it is essential to disinfect the surfaces of possible contamination. The disinfectant employed to perform this task of sanitizing the surfaces has to be broad-spectrum, quick-acting, and inert to surfaces. HOCl is one such disinfectant.

Unlike in the case of water disinfection, surface disinfection does not have water to convert chlorine into Hypochlorous Solution. Hence for surface disinfection, it is essential to use a pre-converted chlorine solution. The water solution of chlorine forms HOCL, which immediately kills viruses and Bacteria. The HOCl after killing the microorganisms gets converted to harmless water, thereby leaving no residue on the surface.

3. Disinfection of Wounds: Two critical factors important in wound healing are infection and cellular interaction. Infection is a major problem in wound healing, and chronic wounds can get contaminated by surrounding skin, local environment, and endogenous sources. Chronic wounds offer ideal conditions for biofilm production. Biofilm is a primary impediment to the healing of chronic wounds as it forms a physical barrier to bacteria from an external environment. It provides a means for bacteria to communicate with each other, leading to an increase in virulence and antibiotic resistance and provides an escape for bacteria from immune recognition.

Hypochlorous acid (HOCl), a major inorganic bactericidal compound of innate immunity, is effective against a broad range of microorganisms and prevents this biofilm formation.

4. Decontamination of Fruits and Vegetables: The fruits and vegetables are exposed to many organic substances. The chances of them getting contaminated is very high and some of the vegetables harbor harmful bacteria and viruses. All the Food and Beverage Industry use Sodium Hypochlorite as a disinfectant to clean the vegetable before processing, for example, a Tomato Ketchup manufacturer washes the tomatoes in a Hypo solution to kill all the microorganisms, if this not done then the end product will be prone to fungus and will have a very short shelf life.

Even in our homes, washing the vegetables with Hypochlorous Solution before or after cutting will kill all the pathogens. HOCL or Electrolyzed Water does not leave any smell in the water. Hypochlorous Solution (Slightly Acidic Electrolyzed water) converts into plain water after killing the harmful pathogens.

5.Hospital Disinfection: Hospital-acquired infections, and hospital-associated infections, are infections that are not present in the patient at the time of admission to the hospital but develop during the course of the stay in the hospital. There is increasing interest in the link between cleaning and hospital-acquired infections (HAI). Hypochlorous based disinfection is recommended by the WHO as the preferred disinfectant to kill harmful and difficult to treat bacteria like Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C.Difficle).

The various applications of Hypochlorous Solution include disinfection of countertops, floors, tonometer heads, needles, syringes, laundry, dental appliances, hydrotherapy tanks, water distribution instruments in hemodialysis instruments, and regulated medical waste prior to disposal. It is recommended that the disinfectant solution be made fresh every day and as per the concentration required.

The above-mentioned applications are some of the important areas where Hypochlorous Solution or Electrolyzed Water is being used to kill the microorganisms. There are much more applications which we shall discuss in future blog posts.

Methods of generating HOCl

Now let us look at the different methods of synthesizing Hypochlorous Solution (or Electrolyzed Water, Slightly Acidic Electrolyzed Water, Electrolyzed Oxidizing Water, Electro-activated Water or Electrochemically Activated Water Solution)

HOCl can be synthesized by one of the three methods:

(a) Hydrolysis of chlorine gas: Cl2 + H2O → HOCl + H+ + Cl−

(b) Electrolysis of salt solution: 2Cl− + 2e− → Cl2 (I) Cl2 + H2O → HOCl + H+ + Cl− (II)

(c) Acidification of hypochlorite: OCl− + H+ → HOCl

If understanding the complex chemistry is too much, then you can buy any one of the equipments that can help you produce HOCL. There are easy operate and user-friendly equipment available in the market that can produce the required HOCL at your site. This equipment apart from disinfecting various areas is also convenient and cost-saving.