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 Introduction of Sodium hypochlorite

Sodium hypochlorite (NaOCl) in solution exhibits broad-spectrum anti-microbial ( bacteria, virus, fungi, and parasites)  activity and is widely used in healthcare facilities in a variety of settings. It is usually diluted in water depending on its intended use. “Strong chlorine solution” is a 0.5% solution of hypochlorite (containing approximately 5000 ppm free chlorine) used for disinfecting areas contaminated with body fluids, including large blood spills (the area is first cleaned with detergent before being disinfected). It is also known as bleach and the most common disinfectant used in medical laboratories.

Chlorine

Reactions for free chlorine formation:

Cl2 (g) + H2O <=> HOCl + Cl- + H+

HOCl <=> OCl- + H+ (at pH >7.6)

Three different methods of application

Cl2 (gas)

NaOCl (liquid)

Ca(OCl)2 (solid)

Chloramine formation

HOCl + NH3 <=> NH2Cl (monochloramine) + H2O

NH2Cl + HOCl <=> NHCl2 (dichloramine) + H2O

NHCl2 + HOCl <=> NCl3 (trichloramine) + H2O

  Preparation of  working Sodium hypochlorite

Sodium hypochlorite is also called bleach.

It is prepared by following methods

Given,

concentrated-4%

Should be diluted: 0.5%

amount of water to be added to 1 part of concentrated hypochlorite= Concentrated/dilution-1

=4/0.5-1

=7

i.e. 7 parts water and 1 part concentrated  hypochlorite

It means 7 glass water and 1 glass concentrated hypochlorite.

Here,

C1= Concentrated hypochlorite or stock

V1= Volume of required stock

C2=Concentration of working solution which is required i.e. 0.5%

V1=Volume to be prepared i.e.Known-2000ml

then, C1ΧV1=C2V2

V1= 0.5Χ2000/4

=250 ml

It means 1750 ml water and 250 ml concentrated hypochlorite and final volume 20000 ml i.e. working hypochlorite.

Uses of Sodium hypochlorite

Chlorine is used in free, hypochlorite as well as chloramine forms.

1. It kills vegetative bacteria.
2. It kills viruses like the human immunodeficiency virus(HIV) and hepatitis B virus (HBV).
3. It is very effective against HBV and HIV viruses, therefore its use is recommended at 1:10 dilution for disinfection of blood spills.
4.  It is not much use against spores.
5. Chlorine and its compounds have been used as disinfectants in water supplies and swimming pools.

Further Reading on Sodium hypochlorite

1. Rutala WA, Weber DJ (15 February 2017) [2008]. “Guideline for Disinfection and Sterilization in Healthcare Facilities” (PDF). www.cdc.gov. Retrieved 29 August 2017
2. Textbook of Medical Laboratory Technology by Praful B. Godkar, Darshan P. Godkar
3. Textbook of  Medical Laboratory Technology by Sood
4. http://www.forp.usp.br/bdj/bdj13(2)/v13n2a07/v13n2a07.html
5. https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-hypochlorite#section=Effects-of-Short-Term-Exposure
6. https://www.oxy.com/OurBusinesses/Chemicals/Products/Documents/sodiumhypochlorite/bleach.pdf