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- Posts: 70
- Joined: Wed Feb 23, 2005 2:56 pm
Hi there. I have encountered an issue with a contamination peak from my LC system.
I have a Shimadzu UFLC and it has been running fine until the past 2 days when I started to experience a ghost peak at a retention time of app. 5.3 min.
I am using a HILIC column and my standard retention time in the initial stage is app. 5.05min.
However, there is a change in the std peak RT to 5.3min as mentioned earlier ; most probably due to the buffer being prepared. I dont have a concern here.
However, I started to experience a peak at the time of 5.3min and injections for my std peak came out at the same time; this is weird because using the same buffer condition, my std peak came out at app. 5.1 min in the earlier injections; but now, the RT has shifted to about 5.3min.
I have tried to flush the column with 97% water and then with 97% ACN but to no avail. The column pressure has also increased from app. 600psi for 97% ACN to about 780psi.
The ghost peak was suspected to be a carry over of my std; however, I am not sure where does it comes from since we didnt change any buffer, or the conditions; except that we started to see this when we try to inject a blank solvent; and we saw this peak. In the same vial of the same conditions. we didnt see this peak. Hence, its quite strange to see this.
We suspected it might comes from the injection port or the syringe; however, we have rinsing and flush needle mode before and after every injections.
Again, we didnt see this carry over peak for all the earlier samples run of approximately 300 samples using the same conditions; all was fine until the past 2 days when we started to see this carry over peak.
Even by using new vials and ultra pure water , or new solvents ( thinking it might be a contamination on the solvents/vials ) but this didnt solve the issue. We are still experiencing the carry over peaks.
Any kind advise as I have not much idea how this happens. Thanks a lot.
I have a Shimadzu UFLC and it has been running fine until the past 2 days when I started to experience a ghost peak at a retention time of app. 5.3 min.
I am using a HILIC column and my standard retention time in the initial stage is app. 5.05min.
However, there is a change in the std peak RT to 5.3min as mentioned earlier ; most probably due to the buffer being prepared. I dont have a concern here.
However, I started to experience a peak at the time of 5.3min and injections for my std peak came out at the same time; this is weird because using the same buffer condition, my std peak came out at app. 5.1 min in the earlier injections; but now, the RT has shifted to about 5.3min.
I have tried to flush the column with 97% water and then with 97% ACN but to no avail. The column pressure has also increased from app. 600psi for 97% ACN to about 780psi.
The ghost peak was suspected to be a carry over of my std; however, I am not sure where does it comes from since we didnt change any buffer, or the conditions; except that we started to see this when we try to inject a blank solvent; and we saw this peak. In the same vial of the same conditions. we didnt see this peak. Hence, its quite strange to see this.
We suspected it might comes from the injection port or the syringe; however, we have rinsing and flush needle mode before and after every injections.
Again, we didnt see this carry over peak for all the earlier samples run of approximately 300 samples using the same conditions; all was fine until the past 2 days when we started to see this carry over peak.
Even by using new vials and ultra pure water , or new solvents ( thinking it might be a contamination on the solvents/vials ) but this didnt solve the issue. We are still experiencing the carry over peaks.
Any kind advise as I have not much idea how this happens. Thanks a lot.
