Chromatography Forum

Let me know if somebody had this issue before and how it got fixed. When I do repetitive injections of the same vial of a standard solution that contains more than one component, the area response of one of the components is larger (~30%) than what it is supposed to be. The area for all components in previous injections and further injections is as expected, but suddenly in one of the injections the area for one of the components is larger, but the other components on that injection have expected areas. It only happens with one of our HPLC's. I have the feeling the issue is with the detector, but I am not certain. Any suggestions ?

Let me know if somebody had this issue before and how it got fixed. When I do repetitive injections of the same vial of a standard solution that contains more than one component, the area response of one of the components is larger (~30%) than what it is supposed to be. The area for all components in previous injections and further injections is as expected, but suddenly in one of the injections the area for one of the components is larger, but the other components on that injection have expected areas. It only happens with one of our HPLC's. I have the feeling the issue is with the detector, but I am not certain. Any suggestions ?

It is quite difficult to give a recommendation for you problem but I will try it. The abnormal compound elutes between other components or is there something special?This happens regulare with only one of your hplc (Are there differences to the other hplcs)? I agree with you, if there ist not something special with this abnormal compound, I would also check the detector first.

Do you already have exchanged the lamp with a new one?

Are the retention times of all compounds stable for each injections?
Are you recording the chromatogram at the same wavelenght for each peak? If not, if you have time windows recording the chromatogram at different wavelenght, a shift in retention time can cause the peak to be recorded at a wrong wavelenght and modify the respnse factor.

Is the shape of the unspected larger peak still correct or not?
In isocratic mode, it's possible that a late eluting interference comes out of the column after some injections. This interference can overlap one of your peak of interest but normally this could largelly increase the widht of your peak and give a strange shape!