Final answer:
Ethyl alcohol is most effective as a disinfectant at a concentration of approximately 70% aqueous solution, due to its ability to denature proteins and disrupt cell membranes without rapid coagulation that would occur at higher concentrations.
Step-by-step explanation:
The effectiveness of ethyl alcohol as a low level disinfectant is optimal at a concentration of about 70% aqueous solution. In this form, it rapidly denatures proteins and disrupts cell membranes, which results in cell lysis. A 70% concentration is preferred over a 100% concentration because the presence of water allows for the alcohol to penetrate cells more effectively before the outer proteins coagulate, which would otherwise prevent penetration. Ethanol is a common active ingredient in hand sanitizer formulations, often found in concentrations ranging from 60% to 80%, with additives such as ethylene or glycerin to maintain skin softness.
As a disinfectant, alcohol's advantages include its affordability and broad effectiveness against vegetative microbes. However, due to its high volatility, the disinfecting action of alcohol is limited to the time immediately after application. For consistent effectiveness and to meet regulatory standards, manufacturers adhere to protocols such as those established by the Association of Official Agricultural Chemists International (AOAC) when validating the efficacy of disinfectant products.