Causes and Solutions of Gas Chromatography Peak Tailing(Ⅰ)

When analyzing compounds with gas chromatography (GC) and gas chromatography-mass spectrometry, sometimes you will encounter the problem of chromatographic peak tailing, which is mainly analyzed from the following aspects:

Sample problem

1. The sample concentration is too high

When the sample concentration is too high, the chromatographic peak of the sample will have obvious tailing. In this case, the sample can be diluted, or the sample injection mode can be changed from splitless injection to split injection, or the split injection mode can be changed. Adjust the split ratio higher. For example, the injection split ratio was previously set to 10:1. It can be set to 100:1 according to the actual concentration of the sample.

2. Problems with the nature of the sample

① The compound is too polar

When analyzing polar compounds or active compounds, their active sites tend to adsorb to sites along the way and cause tailing. In this case, the sample analysis system is required to have good inertness, such as using ultra-inert liners and clean split plates and inert low-bleed columns.

② The boiling point of the compound is too low

The components that flow out early are generally those with strong volatility and low boiling points. When such compounds are tailed seriously, the main reason is that the boiling points of the compounds are too low. This may be due to insufficient solvent focusing effect, and the solvent is not completely condensed and partially vaporized. When the sample enters the chromatographic column, compounds with low boiling points enter the chromatographic column first for analysis, resulting in chromatographic peak tailing. In this case, you can lower the temperature of the injection port and adjust the initial temperature of the temperature program to be below the boiling point of the solvent 10-25°C, so that all compounds can enter the chromatographic column uniformly while condensing.

③ The boiling point of the compound is too high

The late eluting chromatographic peaks are generally components with low volatility and high boiling points. The tailing phenomenon of these compounds becomes more serious as the retention time increases. The main reason is that the boiling points of the compounds are too high and the vaporization at the injection port is incomplete. Or the temperature of the chromatographic column and transfer line is too low, causing partial condensation of the sample during the analysis process, resulting in chromatographic peak tailing. In this case, attention should be paid to the boiling point of the compound, and the tailing phenomenon can be improved by appropriately increasing the temperature at the inlet, chromatographic column, transfer line, etc.