PH Influences Solution Stability

When the pH value drops, the stability of the hypochlorite solution drastically diminishes. This is the reason for which industrial NaOCl has added

Fig. 10. Influence of pH on chlorine/hypochlorite solution equilibria.

soda. This increases its stability (not sufficiently for medical use) but significantly reduces its effectiveness and tolerability.

At about 1% concentration (typical of the Alcavis 100 product), the NaOCl solution exhibits a surface tension of 75 dyn/cm, viscosity equal to 0.968 cP, conductivity of 65.5 mS, density of 1.04g/cm3 and humidifying capacity equal to 1 h and 27min. Its mechanism of antimicrobial action can be observed, verifying its chemico-physical characteristics and its reactivity with organic tissues. In fact, the strong antimicrobial effectiveness of NaOCl is based on its high pH (action of the hydroxide ions). This interferes indeed with the integrity of the cytoplasmic membrane, with irreversible enzymatic inhibition, biosynthetic alteration of cellular metabolism and phospholipid degradation observed in the lipidic hyperoxidation. For this reason, NaOCl exhibits antimicrobial activity with action on the enzymatic assets of bacteria, promoting irreversible inactivation originating with the hydroxyl ions and the action of chloramination.

So, considering the high surface tension and the antimicrobial action that can be obtained with less concentrated solutions, the best option is the use of NaOCl solutions with about 1% free chlorine (Alcavis 100 contains about 1.1% of equivalent active chlorine).

The chemico-physical characteristics of NaOCl solutions are important in order to understand their mechanism of action. The reactions of saponification, neutralization of amino acids and chloramination that occur in the presence of microorganisms and organic tissues lead to the antimicrobial process and that of elimination of organic pollutants. Antimicrobial activity is correlated with essential enzymatic sites on the bacteria, on which occurs irreversible inactivation through the hydroxyl ions and the chloramination reaction. Organic dissolution can be observed, instead, in the saponification reaction, when

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NaOCl causes the degradation of lipids and fatty acids, with formation of soaps and glycerol.

NaOCl in high concentrations is very aggressive, while in lower concentrations (0.5-1%) it is biocompatible. In order to consider a substance biocompatible, it must not react or react only weakly with organic tissues for any period of time and have moderate action in the first 7 days, which decreases with time to insignificant values.

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