Instruments that cannot be sanitized must be immersed in what solution for disinfection?

The correct choice specifies that instruments that cannot be sanitized should be immersed in a 70% alcohol solution for at least five minutes for effective disinfection. Using a 70% alcohol solution is optimal because it contains enough water to enhance the penetration of alcohol into cells, allowing it to denature proteins effectively and destroy microbial life.

The five-minute immersion time is crucial; it allows sufficient contact time for the alcohol to actively work on the surfaces of the instruments, thereby ensuring that any pathogens present are adequately eliminated. This method is widely recognized in sanitation protocols for non-critical instruments that cannot withstand heat sterilization.

The other solutions provided would not achieve the same level of efficacy in disinfection. For instance, 50% alcohol lacks the optimal concentration needed for effective disinfection, while 100% alcohol could evaporate too quickly, reducing contact time and effectiveness. Lastly, 30% alcohol does not provide sufficient strength to effectively kill most pathogens. Therefore, using 70% alcohol for at least five minutes strikes the best balance for proper disinfection of instruments that cannot be sanitized.