What size membrane filters are generally used to sterilize solutions prepared with nonsterile ingredients?

The use of a 0.2 µm membrane filter is standard practice for sterilizing solutions prepared with nonsterile ingredients. This size is particularly effective in removing bacteria and yeast from solutions, as most bacteria range from about 0.2 to 5.0 µm in diameter. A 0.2 µm filter is capable of trapping these microorganisms while allowing the solution to pass through, thereby ensuring sterility.

Using a filter of 0.2 µm is advantageous for maintaining the integrity of the solution, as it strikes a balance between effective filtration of pathogens and preserving the solution's components. Filters with smaller pore sizes, like 0.1 µm, can also be used but may not be necessary for all applications and could reduce flow rate dramatically. Larger filters, such as 1.0 µm or 5.0 µm, do not provide the level of sterility required since they allow bacteria to pass through, rendering them unsuitable for sterilization purposes.