What is a “ghost peak”? What causes it? How to eliminate it?

Spurious peaks are chromatographic peaks that appear in places where they should not be; they generally do not occur during normal testing, but can show up if temperature control is poor or if the sample preparation is incomplete. The appearance of spurious peaks during testing poses a significant challenge to the analysts. If the spurious peaks are caused by electrical signal interference, then factors in the external environment need to be considered: installing a voltage stabilizer, removing the oxidation layer from the electrical connection wires, isolating the device from large electrical appliances in the vicinity, and improving the grounding conditions of the instrument ； If spurious peaks appear during the chromatographic separation process, it is necessary to consider the chromatographic conditions: the time interval between two injections should be as long as possible, or the chromatographic conditions should be changed so that all components in the sample elute; additionally, a gas purifier can be used and the detector can be cleaned.

An unknown peak that appears at the wrong time and in the wrong place. There are various reasons that lead to this phenomenon.

If temperature control is poor or the sample preparation is incomplete, spurious peaks may appear. The key is to control the chromatography conditions and to prevent impurities from entering the sample; the detector also needs to be cleaned

Common possibilities for the appearance of ghost peaks: 1. Impurity components in the sample or gas source； 2. Residuals in the chromatography column ； 3. Detector contamination ； 4. Changes in chromatographic parameter conditions (including sample derivatization and fragmentation) ； 5. Electromagnetic and power supply interference ； 6. Sample contamination ； Based on the possible scenarios mentioned above, it’s sufficient to take preventive measures. If there is a problem in the analysis, the first step is to determine which type it belongs to. Then it becomes much simpler to handle.

　 Spurious peak: In chromatographic analysis, peaks that are not produced by the sample are called spurious peaks. Also known as false peaks or spurious peaks; the memory effect also falls under the category of spurious peaks. 　Reasons for the appearance of ghost peaks/and ways to eliminate them: 1. Residual peaks from the injection valve – Clean the valve with a strong solvent after each use, and improve the cleaning process for both the valve and the sample ； 2. The column is unbalanced; rebalance the column using the mobile phase as the sample solvent ； 3. Check whether the mobile phase is pure. 4. Reduce the injection volume

•Contaminants accumulate on the column head; bake the column and then run it without a sample. • Loss of the injection pad – use high-quality injection pads; bake the oven chamber at the highest temperature required for the method to be used, throughout the night. • Contamination of the injection port – residues from previous injections remaining in the injection port or liner. • Impure carrier gas. • Reactions between contaminants in the stationary phase and the carrier gas – use high-quality gases and gas filters, replacing them regularly. • If split/splitless injection is used, the sealing gasket at the bottom of the injection port may react with the sample. • Overheating of the injection port can cause degradation of the sample components; reduce the temperature of the injection port by 20 degrees each time to see if the peaks disappear. • Reaction between the liner and the sample – use deactivated liners. • The filler material in the liner is reactive; remove the filler or use liners without fillers. • The sample remains in the injection port for too long – increase the column flow rate. • Unstable sample components

O. So that’s what Ghost Peak is like, then. Thank you everyone. I get it now. ×2 thanks.

At excessively high temperatures, the loss of the stationary phase can also cause spurious peaks.