Error 1: HPLC column cannot be recoil
In general, the pressure value of the liquid chromatography column is much higher than the maximum operating pressure (about 2 times). Therefore, for a stable packed bed, if a suitable mobile phase and a reasonable time distribution are used, a well-filled column can bow from left to right. In turn, the reasons for using the HPLC column are as follows: recoil when changing the column, clean the substances strongly adsorbed on the column head, and wash out the residual substances to prevent the pressure from increasing.
Error 2: all C18 (L1) columns are the same
In the early HPLC system, C18 was the only binding stationary phase of reverse chromatography, so C18 was used as the standard of reverse chromatography column and many pioneers were willing to use it. Because HPLC was first used in the pharmaceutical industry, and the management organization was not willing to make new designs. FDA and USP also provide the classification of analysis methods designed when submitting new drug applications. The HPLC column given C18 is classified as “L” because most of the C18 columns are used as the method columns for submitting new drugs, so C18 becomes L1, which is the first standard column. But more fixed phases appear, named after the new L value. (L7 = C8, L10 cyano, L11 phenyl).
Error 3: protecting the column does not affect the separation effect
If the selection of the stationary phase is wrong, the protective column has an effect on separation, but the protective column is used to protect the analytical column from being polluted by high residual components. Therefore, if the retention of the stationary phase is strong (such as high carbon load and mixed-phase), it can make the retention cheap and affect separation, even lead to different selectivity. If the retention is weak, the problem is not so obvious unless the stationary phase affects the selectivity of the whole system.