Whether you will encounter such a strange situation in the daily detection experiment. An abnormal peak suddenly appears in the spectrum of a sample. If the experiment is repeated under the same conditions, it may not appear again. The abnormal peaks can be big or small. Facing such abnormalities, are you confused, angry and unable to start? We will take you through the “ghost busting” in chromatographic analysis today.
Ghost peak Description: In the process of chromatographic separation, especially when gradient elution or the instrument is used for too long, it is easy to produce chromatographic peaks that sometimes do not exist, which is commonly known as ghost peak.
Source of ghost peak:
● water can bring impurities in many ways
● purification system itself
● the introduction and placement of storage containers for too long leads to bacterial growth
● various mobile phase additives, salts, acids and bases
● the instrument system is no longer pure for a long time
● organic pollutants, etc
So, how do we check the ghost peak?
In case of ghost peak, first check whether the pollution comes from the injection system through the function of “direct sample injection” or “direct standard sample injection” in the liquid chromatography instrument software. This function has no injection action and only records the mobile phase baseline under the current chromatographic conditions. Re injection 0 μ L (with injection action), the possible source of ghost peak can be checked.
|Operation mode||Abnormal peak||Abnormal peak||Abnormal peak|
|Injection 0 μ L||No||Yes||Yes|
|Direct sample injection without injection action||No||No||Yes|
|Check the Reason||Sample contamination||Contamination of injection system||Mobile phase or chromatographic column or other systemic problems|
Investigation of sample contamination
Sample contamination can be divided into contamination or degradation of the sample itself, contamination of the sample solvent, and degradation of the sample solution when it is placed in the sample bottle. For the contamination or degradation of the sample itself, it is possible to check and compare the detection conditions of different sample batches or fresh samples; for sample solvent contamination, a new diluent can be prepared; if the sample solution degrades when placed in the sample bottle, it is necessary to The stability of the samples in different diluents and different material vials or vials of different brands was investigated.
Contamination of the sampling system
It is recommended to replace the Needle Wash with better solubility for the sample, such as 90% methanol or acetonitrile in water.
Mobile phase contamination
If the mobile phase is contaminated, it is necessary to check whether the source of ghost peaks comes from buffer salts, additives, water or organic reagents in the mobile phase.
For example, if the method mobile phase contains a buffered salt phase:
● Remove the buffer salt and run the empty needle. If there is no ghost peak, the buffer salt contains impurities;
● If there are ghost peaks, extend the high-proportion water phase operation, run empty needles, and the ghost peaks will become larger, that is, the pollution comes from the water phase;
● If the ghost peaks do not become larger, they are from the organic phase.
If the chromatographic column is contaminated, it is first recommended to perform daily or abnormal flushing of the chromatographic column according to the instructions of the chromatographic column. At the same time, the column cleaning method can be adjusted according to the chromatographic conditions and sample properties. If in the reversed-phase chromatography conditions, the highest proportion of the organic phase in the analytical method is low (for example, only to 40%), it is recommended that the column be gradient flushed every 30-40 needles.
Ghost peaks caused by other systemic problems
Ghost peaks caused by other systemic problems, such as in the UV detector, the change of the two-phase ratio of the gradient method, the baseline has a certain change, should try to avoid the gradient ghost peak caused by the excessive gradient change rate. Another example, the T-joint of the pressure gauge, the 90° turning angle of the connecting pipeline, etc., will also easily produce ghost peaks, and the pipeline should be avoided as much as possible.
If the above investigations can’t solve the problem of Ghost Peak, what should I do! ! Come and take a look at the most powerful method for collecting ghost peaks, Ghost-Buster Column impurity trapping column, which can effectively adsorb and remove impurities with weak polarity in the system, thereby preventing the impurity peak in the system from affecting the target peak. interference. It is installed between the gradient mixer and the injector, which can not only remove impurities in the mobile phase, but also effectively remove impurities in the pipeline and mixer.
|Ghost-Buster HP Column||06100-31021||2.1×33mm||100MPa||UHPLC|
|Ghost-Buster Column kit||GBKIT-01||four point six × 50 mm, with 4 joints and 2 sections of pipeline||40MPa||HPLC|
|Ghost-Buster Column kit||GBKIT-02||seven point eight × 50 mm, with 4 joints and 2 sections of pipeline||40MPa||HPLC|
|Ghost-Buster Column II||06100-31008||4.0×50mm||40MPa||HPLC|
|Ghost-Buster Column II||06100-31016||3.0×50mm||40MPa||HPLC|