Chromatography Forum

Hi,

I would like to run a gradient in an HPLC method. The problem is, however, that the detection is electrochemical, which is not compatible with gradient elution. The HPLC system is Dionex and Chromeleon is the software. Does anyone know, if it is possible to circumvent the detector automatically via a set up in Chromeleon? Of course, I can pull out the capillary of the detector, but that is not feasible, if I aim at analysing 100 samples in an analytical run with the method.

Thanks in advance,
Anne.

Hi,

I would like to run a gradient in an HPLC method. The problem is, however, that the detection is electrochemical, which is not compatible with gradient elution. The HPLC system is Dionex and Chromeleon is the software. Does anyone know, if it is possible to circumvent the detector automatically via a set up in Chromeleon? Of course, I can pull out the capillary of the detector, but that is not feasible, if I aim at analysing 100 samples in an analytical run with the method.

Thanks in advance,
Anne.

But do you really need to bypass this detector ? Will gradient deteriorate or damage detector ?
If NO, then ignore this detector, don't save signal generated by it.
However you will need another detector connected in series with your system.

OK. Thanks for the reply.

But be aware that every unused detector will cause peak broadening to some extent due to the volume of the flow cell. If you really need sharp peaks, bypass it instead of ignoring it.

What hardware are you using? What detector will you use instead of the ECD? Some Dionex/Thermo hardware has extra valving that you could use to switch between detectors. The program dictates the waveform and could then be used to turn off the ECD when not in use. I'm not sure your peaks won't be better off than in the previous comment with two detectors in serial though so it may be moot.

Thanks for the responses.
I would not run another detector, since the peaks arising in that retention window are not interesting for me. I use a combination of Agilent and Dionex hardware, a Dionex ECD. But could I switch between a detector and a drain?
But now, I am thinking more in terms of sample clean up, so I will try to get rid of these matrix peaks, before injecting the samples in to the HPLC system.

I switch between an MS and a drain so I don't see a major reason you couldn't switch between an ECD and one. It might be worth plumbing a little flow to the ECD while the eluent stream is diverted to the drain to keep the electrodes in good shape.

But be aware that every unused detector will cause peak broadening to some extent due to the volume of the flow cell. If you really need sharp peaks, bypass it instead of ignoring it.

Not every. IF it is the last in series then even very large volume od the flow cell won't affect peak shapes.