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By isoboy on Friday, May 14, 2004 - 10:33 am:
I'm new to gradient LC, but my problem is this:
I have a constant ghost peak that elutes at 15min. in an IP-RPLC gradient method. My gradient profile is as follows:
0.1min - 10%B
5min - 10%B
12min - 23%
34min - 26%
54min - 100%
56min - 100%
57min - 10%
B = ethanol. Mobile phase A = a blend of water, hexafluoroisopropanol, EDTA and TEA. The column is a Kromasil 3.5um 150 x 4.6mm C18 at 60deg. C. Flowrate = 0.150ml/min. Wavelenght = 260nm.
The ghost peak is very large (runs off scale), well defined and has excellent symmetry. The peak width of the ghost peak is wider than other peaks near the same retention which leads me to believe that the peak is from carry over from a previous injection. The kicker though is that we see this peak even in multiple, back to back blank injections and in injectionless gradient-only runs in which we bypass the injection port alltogether.
Any help would be greatly appreciated.
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By Anonymous on Friday, May 14, 2004 - 10:54 am:
Often, peaks like this are caused by poor quality water. Organic impurities from the water concentrate on the head of the column and are eluted as the gradient progreses. Impurities from other mobile phase components can also cause this effect.
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By Anonymous on Saturday, May 15, 2004 - 07:08 am:
There have nee many discussions on ghost peak problems. Look for other threads!
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By Henrik Vogelius on Wednesday, May 19, 2004 - 10:48 am:
As an HPLC column ages, the chromatographic peaks will broaden. When the
resolution is no longer acceptable, the column will have to be discarded. Other
causes of broad chromatographic peaks include high viscosity mobile phases and
large injection volumes. If just one peak in the chromatogram appears broad it
may be a late eluter from an earlier injection.
I'm new to gradient LC, but my problem is this:
I have a constant ghost peak that elutes at 15min. in an IP-RPLC gradient method. My gradient profile is as follows:
0.1min - 10%B
5min - 10%B
12min - 23%
34min - 26%
54min - 100%
56min - 100%
57min - 10%
B = ethanol. Mobile phase A = a blend of water, hexafluoroisopropanol, EDTA and TEA. The column is a Kromasil 3.5um 150 x 4.6mm C18 at 60deg. C. Flowrate = 0.150ml/min. Wavelenght = 260nm.
The ghost peak is very large (runs off scale), well defined and has excellent symmetry. The peak width of the ghost peak is wider than other peaks near the same retention which leads me to believe that the peak is from carry over from a previous injection. The kicker though is that we see this peak even in multiple, back to back blank injections and in injectionless gradient-only runs in which we bypass the injection port alltogether.
Any help would be greatly appreciated.
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, May 14, 2004 - 10:54 am:
Often, peaks like this are caused by poor quality water. Organic impurities from the water concentrate on the head of the column and are eluted as the gradient progreses. Impurities from other mobile phase components can also cause this effect.
-------------------------------------------------------------------------------------------------------
By Anonymous on Saturday, May 15, 2004 - 07:08 am:
There have nee many discussions on ghost peak problems. Look for other threads!
-------------------------------------------------------------------------------------------------------
By Henrik Vogelius on Wednesday, May 19, 2004 - 10:48 am:
As an HPLC column ages, the chromatographic peaks will broaden. When the
resolution is no longer acceptable, the column will have to be discarded. Other
causes of broad chromatographic peaks include high viscosity mobile phases and
large injection volumes. If just one peak in the chromatogram appears broad it
may be a late eluter from an earlier injection.
