WARNING: Chemistry lesson ahead! Embrace the details and (we hope) you will get a whole new appreciation for how this stuff works.  This article is designed to tap into a little more science than normal, so it is going to be a bit longer than our typical articles. Our goal is to concisely explain why hypochlorous is a better choice than sodium hypochlorite “bleach”. We’ve established that HOCl is a non-synthetic and sustainable killing machine, so let’s dive deeper and talk about why it works…


 

Chlorine is Chlorine because it’s an element on the periodic table. However, it takes on different forms, and not all chlorine species are equally effective as disinfectants. Chlorine as a disinfectant is referred to as Free Available Chlorine (FAC). This type of chlorine can be in the form of hypochlorous acid (HOCl) or hypochlorite (OCl-). Both are effective at killing germs, but chemically speaking – hypochlorous acid is actually more effective. In fact, it is suggested that HOCl is 80 to 120 times more effective than sodium hypochlorite. Why is that? Well, it boils down to two main things: molecular charge and pH. 

Molecular Charge: HOCl vs. OCl-

Because HOCl has no charge (notice the lack of + or – in “HOCl”) and has a relatively low molecular weight it is better able than other chlorine-based disinfectants (i.e., hypochlorite ions) to penetrate the cell walls. Conversely, take the chemical compound for hypochlorite ions (OCl-). Notice the little negative (-) symbol in the formula? This indicates a negatively-charged ion. In nature, microbes have a negatively charged wall (e.g., cell wall of bacteria). Remember playing with magnetics as a kid? What happened when you put the same poles (North and North or South and South) together? Right, they repelled. Well, the same thing happens here with hypochlorite and negatively charged germs. Because hypochlorous has a neutral charge, it is NOT repelled and passes through a cell wall to disrupt DNA more easily.

Chlorine and pH Values:

Chlorine will actually change forms, based on its pH. In a typical solution, FAC is a blend of both hypochlorous acid and hypochlorite ions and that blend is weighted one way or another – based on pH (see figure 1). As you can see in figure 1, HOCl is more predominant at lower pH values.  As pH increases – the percentage of hypochlorous decreases – making the solution more hypochlorite ion heavy. And because hypochlorous doesn’t cause germs to run away (remember the magnet example?), having more hypochlorous in solution is a good thing, right? 

Figure 1

The answer is absolutely YES! And because our hypochlorous has a pH similar to water (pH 6-7), germs are fooled into drinking it as a food source (aka, letting it in freely through osmosis). Once inside, the hypochlorous disrupts the DNA and destroys the germ – it is the Trojan Horse of disinfection. 

Additional Points to Note:

You may be wondering why ‘bleach’ has antimicrobial properties if this article shows that hypochlorite ions are repelled by germs. If so, we are proud of you for getting this far! You may have also noticed that ‘bleach’ is called sodium hypochlorite (NaOCl-) and not simply hypochlorite (OCl-) as the article also mentions. Well, let us address both of those points. 

  • Chlorine is an oxidizer, which is unstable and can rapidly ‘gas off’ – rendering it less effective over time. Forcing concentrated amounts of sodium hydroxide (NaOH) into solution causes the pH rise to around 13, which drastically slows this oxidation process – making “concentrated bleach” more shelf stable in a bottle. 
  • This concentrated bleach (13 pH) acts as a “chemical hammer” and will try to bludgeon germs to death (aka crack open the negatively charged cell wall) to allow for the hypochlorite ions to get in and do their thing. So it can work, but it is extremely unsafe to handle.  Bleach can cause adverse effects on human health, hard surfaces and fabrics because of its dangerously high pH. 

References:

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255518/#:~:text=Hypochlorous%20acid%20(HOCl)%20is%20a,yet%20is%20nontoxic%20to%20humans.
  2. https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html

Videos and More!

We are ready for you to make the switch to safer and more effective disinfection, www.annihilare.com. If you want to learn more about the differences between hypochlorous and bleach check out the videos:

Next week – More on how you can become more knowledgeable about the disinfecting chemicals that you use at home, work and school.  It’s time you learn how to read a Safety Data Sheet(SDS) and further understand the myth of the Hazardous Materials Identification System (HMIS).