Why is there always a “ghost” in your chromatogram?
What’s Ghost Peaks?
In the chromatographic separation, there are some peaks which appears erratically like ghosts during gradient elution or long-period operation, we call them Ghost Peaks.
The harm of ghost peaks
Ghost Peak is not scary, but he is annoying! Ghost Peak brings the following major hazards:
1. Misjudge the composition of the sample;
2. Overlap with the target peak, affecting the resolution;
3, Do more verification work to determine whether the substance is the target;
4. Pollute instruments.
Where are ghost peaks come from?
1. Gradient change
In the UV detector, the baseline changes to a certain extent with the change of mobile phase ratios, and when the change rate is large, a gradient peak will appear.
2. Sample residue
Sample residue when it is overloaded in the injector;
Sample residue when it is overloaded on the column.
3. Flow dead ends
There are dead ends in the flow path: for example, the T-joint of the pressure gauge, the 90° turning angle of the connecting pipe.
4. The system is polluted
Reagents of insufficient purity were used;
A deteriorated mobile phase was used.
5. Sample preparation
Sample is contaminated during sample preparation;
The utensils are not thoroughly cleaned;
The filter membrane is dissolved;
The solvent dissolves the materials which contact to solvent.
6. There are difficult eluting components in the sample solution
It remains too strong in the column and takes a long time to elute, and the time of stopping collection and injection is inconsistent, resulting in unstable peak time and peak area.
7. Impurities in the water and mobile phase
Water carries impurities in many ways;
Long-term storage of the mobile phase leads to bacterial growth;
Various mobile phase additives, buffer salts, acids, and alkalis are not uniformly mixed; Residual contaminants from long service life of systems.
What to do when meet the ghost peaks?
Fully understand the nature of your sample – stability, composition etc.;
Better cleaning and maintenance of pretreatment vessels, instruments and syringe;
Replace the solvent that causes the ghost peak;
Change the detection wavelength;
Of course, there is a simpler and more effective way!
Use Ghost-Buster Column to catch impurities.
The Ghost-Buster Column developed by Welch can effectively remove weak polar impurities from the system, so as to prevent the impurity peak from interfering with the target peak. Installed between the gradient mixer and the injector, it not only removes impurities from the mobile phase, but also effectively removes impurities from the tubing and mixer.
- Chromatogram with and without GB column
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