The PBS protocol above says to adjust pH to 7.4 with HCl. What does this imply on the pH of 10x PBS before adjusting the pH, would it be greater or smaller than 7.4?

since HCL will be going down, the original pH has to be greater. HCl is likely 2.0 pH

To determine whether the pH of 10x PBS before adjustment is greater or smaller than 7.4, let's first understand what PBS is and how it relates to pH.

PBS stands for Phosphate Buffered Saline, and it is a commonly used buffer solution in biological and biochemical experiments. It consists of a phosphate buffer component, which helps maintain a stable pH, and a saline component, which provides the necessary salt concentration.

The "10x" indicates that the PBS solution is prepared at 10 times the desired concentration. This means that you need to dilute the 10x PBS to bring it to the desired concentration before use.

Now, the pH of the 10x PBS before adjustment can vary depending on the specific recipe used to make it. However, typically, the pH of 10x PBS is higher than 7.4. This is because phosphate buffers are usually prepared at a slightly alkaline pH to ensure stability and prevent pH changes during dilution.

Therefore, in most cases, the pH of 10x PBS before adjustment would be greater than 7.4. The addition of HCl (hydrochloric acid), a strong acid, is required to lower the pH to the desired level of 7.4. HCl is added dropwise until the pH reaches the target value, at which point the solution is considered to be pH adjusted.

It is worth noting that the actual pH of the 10x PBS before adjustment can vary depending on factors such as the specific recipe used, storage conditions, and any impurities present. Therefore, it is always recommended to use a pH meter or litmus paper to verify and adjust the pH as required.