Ghost peak is one of the common questions in Liquid chromatography, many elements will lead to the ghost peek. Any improper operation in the process of the liquid chromatography will cause the ghost and impact the accuracy of any result. According to the frequency of ghost peaks, the main factors that produce ghost peaks are solvent problems, instrument problems, residual bubbles in the mobile phase, and improper operation.
一、Solvent
1.Organic solvent
Compared with the acetonitrile, the Preparation Process of Methanol is more easy and contains less impurities. But methanol has a wider uv absorption range than acetonitrile. When using a UV detector, especially when the wavelength is low, using methanol as the organic phase will cause too much drift and cause problems.The quality requirement of acetonitrile used for gradient chromatography is relatively high, and the use of imported acetonitrile for gradient chromatography can reduce the appearance of ghost peaks. In addition, if the organic phase is used up and the mobile phase bottle is not replaced with a new one, it may also produce ghost peaks if it is directly added to the old mobile phase bottle.
2.water
To ensure that the water is “clean”, to avoid the water containing more impurities, try to use HPLC-grade pure water and the water phase should be used immediately to avoid microbial growth.
3.Other reagents
Buffer salts, TFA, EDTA and other reagents will also have a great impact on the mobile phase. Try to use high-purity reagents to prepare the mobile phase.
二、Instrument
1.The mobile phase lines in the liquid phase are contaminated
Using a mobile phase with high water content over a long period of time (especially if buffer salts are added), bacteria can easily grow in the pipeline and produce metabolites or cell debris that can cause ghost peaks to appear.
2.Detector sample residue
Some sample components remain in the flow cell of the detector, resulting in ghost peaks. In this case, the flow cell needs to be thoroughly cleaned.
3.Check valve blocked
The system pressure is unstable due to the blockage of the one-way valve, resulting in ghost peaks.
4.Residual components in the column
The chromatographic column can enrich the strongly retained contaminated components in the mobile phase or the system flow path, and will be washed out when the organic proportion changes with the gradient program. The residual contaminated components will lead to the appearance of ghost peaks.
三、Residual bubbles in mobile phase
In this case, the mobile phase ultrasound or He can remove the bubble and open the purge valve, the high flow rate out of the device bubble pipeline, to reduce the bubble caused by ghost peak phenomenon.
四、Operation
1.The mobile phase configuration is contaminated
The main reason is that the container or sample bottle containing the mobile phase is contaminated. This pollution may come from detergent, chromic acid lotion or other residual impurities after the experimenter has used it up.Sometimes fragments of plastic caps from mobile phase containers can be sources of impurities.For the ghost peak in the case of sample bottle contamination, it is easy to eliminate, only need to respectively replace the reagents used for sample dissolution or dilution and the sample injection vial to determine the source of the ghost peak.
3.The sample diluent differs too much from the flow phase polarity or pH
This is also one of the reasons for ghost peaks. This problem is likely to cause the sample to split into two different phases, resulting in double peaks or multiple peaks.
At this point in the discussion, you can see that there are many sources of ghost peaks. In addition to avoiding the appearance of ghost peaks due to experimental operation errors, solvent and instrument errors, the use of ghost peak trapping columns can greatly reduce the appearance of ghost peaks. UPLCS ghost peak also named ghost trap DS.Installing the ghost peak trapping column between the gradient mixer and the autosampler can not only remove impurities in the mobile phase, but also effectively trap impurities in the pipeline and mixer.The cylinder core volume is about 700μL, the pressure resistance>35Mpa, there are many sizes and specifications to choose from.
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Post time: Dec-04-2020
