Bartier Disinfection Index

[chem geek]

With regard to HOCl vs. OCl- as a sanitizer, there appears to be valid science to back the notion of HOCl being the more powerful sanitizer for certain kinds of bugs. This is because most pathogens have cell walls that are negatively charged as follows:

1) Gram-Positive bacterial cells (so named due to a positive result from a stain test developed by Hans Christian Gram) have teichoic acids (phosphate groups joined by glycerol or ribitol) that give a negative charge to the outer cell wall.
2) Gram-Negative bacterial cells have lipopolysaccharides that give a negative charge to the outer cell well.
3) Many, but not all, viruses have a net negative electrical charge since their viral envelopes often come from host cells (which have a negative charge on their cell wall). Viruses enter cells at specific binding sites that overcome the electrostatic repulsion.

Since HOCl is neutral, it is more readily able to enter cells than OCl-. Polar molecules and ions generaly only enter cells through specific channels that only allow ions of certain sizes and shapes generally blocking OCl-. On the other hand, algae have different types of cell walls like cellulose that does not appear to be charged. So while HOCl may be a more effective sanitizer for bacteria and viruses, it may not be more effective for algae, but I cannot confirm that.

(See WHO water sanitation document)

Once inside a cell, the mechanism of sanitation appears to come down to two different mechanisms though this appears to be somewhat speculative:

1) Chlorine substitution where the HOCl substitutes its chlorine with hydrogen from an organic compound (a protein, typically an enzyme). This substituion inteferes with the enzyme's function (folding of protein, intereference of active site, etc.).
2) Chlorine oxidation of organics (typically from production of free radical oxygen O• from HOCl or OCl-). This can destroy proteins (including enzymes) as well as DNA (typically during cell division).

The dependence of Oxidation-Reduction Potential (ORP) on pH that follows the concentration of HOCl plus my analysis of the commerical spas study (Oregon) data using HOCl lead me to believe that HOCl is indeed the effective sanitizer against bacteria. I couldn't find scientifically valid information on algae to know whether HOCl or OCl- is more effective, but in any event I would doubt that OCl- is more effective than HOCl even for algae (though it might be about equally effective -- I just don't know).