The Importance Of A Stable PH Environment in HPLC Detection

In liquid chromatography, buffer solution is often added to the mobile phase, one of the purposes is to make the entire HPLC system charge a stable chemical environment, so that the detection has better reproducibility. If the pH of the system is not stable enough, there will be various problems such as drift of retention time, unreproducible retention time of multiple detections, multi-component peak sequence, inconsistent peak composition and so on.

Especially in the detection of acid and basic components, the pH value has a great influence on its retention and peak shape. Therefore, when these components are detected, the pH stability of the HPLC system is very important. Buffer salts to maintain system stability. For example, the salts we usually use, such as phosphoric acid, have better buffering capacity in the pH range of 1.5-3.5.

Example:

The original mobile phase of a certain component only uses glacial acetic acid to adjust the pH value, but does not add a buffer salt system. Because the pH value of the HPLC system is not stable enough, a certain peak drifts during sample detection, and the results cannot be reproduced after repeated experiments. The problem.

Figure 1: There is no buffer solution in the mobile phase and the pH of the system is unstable

Figure 2: Adding buffer salts to the mobile phase to stabilize the system pH