Final answer:
A 70% isopropyl alcohol solution is recommended and widely used as a low-level disinfectant because it effectively denatures proteins and disrupts cell membranes in pathogens. Higher concentrations are not as effective due to the lack of water necessary for the optimal coagulation and penetration of the cells.
Step-by-step explanation:
The percentage of isopropyl alcohol recommended for use as a low-level disinfectant is typically around a 70% aqueous solution. This concentration is known to be effective in killing bacteria and viruses. The presence of water is crucial because it facilitates the denaturation of proteins, a process necessary for the alcohol to disrupt cell metabolism and cause cell lysis. A 70% isopropanol solution coagulates proteins just enough to allow the alcohol to penetrate the cell and affect the microbes adequately without the rapid coagulation that higher concentrations cause, which could prevent effective penetration.
Furthermore, solutions with higher alcohol content, such as 100% isopropanol, are not as effective at inhibiting microbial growth due to the lack of water needed for the optimal denaturing of proteins. Also, use-dilution tests performed by disinfectant manufacturers and validated by groups such as the Association of Official Agricultural Chemists International (AOAC) typically conform to these concentrations to ensure that the products are effective against pathogens.