NaOH and HCl are strong base and acid so will give very poor buffering capacity and will absorb CO2 from the air and will not store well or be any good as a buffering solution

Hello Salman Almashtoub,

1. Is it scientifically valid to use non-buffered NaOH/HCl-adjusted solutions and for how much time they are stable?

Using non-buffered NaOH/HCl-adjusted solutions can be scientifically valid, but their stability is limited. Buffer solutions are designed to resist changes in pH when small amounts of acid or base are added. On the other hand, NaOH/HCl-adjusted solutions, without a buffering agent, do not possess this capacity to resist pH changes. They are simply solutions where the pH has been adjusted by adding a strong acid like HCl or a strong base like NaOH. Their effectiveness in maintaining a stable pH is minimal, and they are susceptible to changes due to atmospheric carbon dioxide or other contaminants. Despite their limited buffering capacity, you may use non-buffered NaOH/HCl solutions for certain applications where a specific pH is required for a short period, and where minor pH fluctuations are not critical. For instance, in some chemical reactions, a specific pH is needed for the reaction to proceed, and a non-buffered solution might be sufficient if the reaction is not sensitive to minor pH changes.

2. If I do use a buffer, would the pH stay more stable long-term, and for how long can I expect them to remain accurate?

While buffers are designed to resist pH changes, their effectiveness is not indefinite. A buffer solution will maintain a stable pH for a period of time determined by its composition, concentration, and the conditions it is subjected to. There are factors like the buffer's capacity, the strength and concentration of the added acid or base, and environmental conditions (temperature, etc.) which can influence how long the pH will remain stable.

Generally, the shelf life of an unopened buffer solution is 2-5 years. However, the stability of an opened buffer solution is more variable. Some manufacturers recommend using them within a few weeks to a few months. Open buffers can be susceptible to microbial growth, which can affect their pH and stability.

I recommend the use of buffer for your experiment.

Best,

There are literatures that use HCl or NaOH to directly adjust the pH value of the solution to test the stability of phages. Although it is feasible to directly adjust the pH with acid or alkali, a buffer system is usually used as the basic medium in experiments. Buffers can reduce the drastic fluctuations in local pH and avoid damage to phages caused by instantaneous extreme pH due to the addition of strong acids and alkalis.