|
Ghost
(Unknown “Phantom”) Peaks
in
HPLC analysis
|
Ghost (“Phantom”) peaks
are not real samples peaks; they are contaminant peaks that can appear even
when no sample is injected.
Ghost peaks can easily misidentified when they are close to
peaks of interest and can leads to erroneous result. Ghost peak can be resulted
from impurities in instrument, impurities in sample or impurities in mobile
phase.
Probable Causes of Ghost
peaks
· Laboratory
sample contamination
· Column
contamination
· System
contamination
· Contamination
from Glassware and Filtration of Reagents
· Contamination
from mobile phase
· Cary
over from the previous injection
The most common reason for ghost peaks originating in the
instrument is carryover attributable to the auto-sampler (or manual injector).
When the needle is dipped into the vial to aspirate the sample, substances in
the sample, which become the source of carryover, are adsorbed to the inside
and outside surfaces of the needle. Those substances which are not eliminated
even after needle rinsing are carried over to the next analysis, and appear as
ghost peaks.
Ghost peak can occur due to degradation of the sample, and such
degradation can be inhibited by using an auto-sampler with a vial cooling
feature.
Ghost peaks can also be generated from the mobile phase in
various ways, including, generation of organic substances in mobile phase due
to prolonged use, or dissolution of organic substances from the air in the
mobile phase. Mobile phase vial contamination due to topping off existing
mobile phase with new mobile phase over a long period of time instead of
preparing a fresh bottle each day or for each set of samples. Usage of
contaminated organic solvent and/or water to prepare mobile phase.
A good instrument for removing ghost peaks in gradient HPLC is the use of a trap column like the Ghost-Guard-LC:
ReplyDeleteThe Ghost-Guard-LC increases reliability of gradient trace impurity analysis by eliminating Ghost Peaks caused by mobile Phase or hardware components.
In gradient elution analysis using a HPLC system, impurities from the mobile phase solvents, mobile phase containers, flow lines, pump, gradient mixer etc., can cause peaks to appear in chromatograms. If such ghost peaks appear, it can be difficult to distinguish them from peaks corresponding to trace sample components, reducing analysis reliability.
Furthermore, identifying the source of ghost peaks can be extremely time-consuming, and has been a source of frustration for chromatographers, particularly in trace analysis work. The Ghost-Guard-LC column enabled efficient removal of impurities from mobile phase solvents and other sources by adsorption to easily avoid the effects of ghost peaks in analysis.
Ghost-Guard-LC columns can be used to efficiently adsorb impurities in both aqueous and organic solvents. Using the Ghost-Guard-LC in reverse-phase gradient elution, which is widely used in liquid chromatography, allows adsorbing and removing all components that cause ghost peaks from mobile phases and their flow lines. This can significantly increase the analytical accuracy of trace analysis. Previously, if ghost peaking interfered with analysis, it was necessary to identify the causes and implement countermeasures, which was extremely time-consuming. In contrast, using the Ghost-Guard-LC easily removes the causes without any need to investigate their source.
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ReplyDeleteIn waters system whaw is reason to comecghost peak in sample
ReplyDelete