Capillary electrophoresis - quick system check

Discussions about CE, MEKC and related topics

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We are performing a CZE method which required a very long analysis time (i.e. 12 hours preconditioning, 2 hours per sample)

Is there any quick way to check, prior to running the actual preconditioning or system suitability samples, that the CE system is ok overall (e.g. lamp ok, capillary window not scratched, buffers prepared correctly)?

For example any simple compound that we can inject during the NaOH rinsing step?
It is not difficult to understand that you would like this... The point of a SST is however to check the whole system, that is, including all the buffer preparation, the capillary and the capillary conditioning. Especially in CE this is true as the flow in the system is not a pumped flow as in LC or GC, but a flow resulting from electro-osmosis, see Separation Science's recent CE Solutions for further explanation. The electro-osmotic flow (EOF) is dependent on the capillary wall and the electrophoresis solution composition. Thus very much dependent on the conditioning.
Normally, this is not such an extended procedure as 12 hours (which reminds me of a certain pharmacopoeial method...). Usually, a pre-sequence conditioning can be around 30 minutes, so then waiting it out is not an issue.

If you do want to check the equipment before preparing to the real analysis, you could check it out with any fast analysis you happen to have around, such as e.g. the Performance Verification test. However, you would not check the capillary that way, as it is best to stick to one application per capillary. As already discussed, the EOF is dependent on the condition of the wall, and flushing through different types of solutions might leave traces you don't want and influence your application that you are really interested in.

A second alternative, somewhere between the above and waiting for the full system suitability check, is to inject a simple compound that migrates quite fast in the buffer of your application (and is not likely to stick to the wall) so that you at least can check with the capillary in place and after the preconditioning.

I usually like to follow the UV signal during rinsing, it also gives quite a good indication that things are OK. If you switch from water to NaOH in the conditioning and watch at low UV wavelength, you see quite a strong chance in the UV responsce when the NaOH hits the detector window. The time it takes for a certain pressure, length and diameter and this jump in baselines are good indicators for the capillary not being blocked and the pressure pump functioning properly.

Better than all of the above would of course be if you use the equipment most of the days, so that you know you can trust it and that it functions properly :) . So extend the application range!

I hope this helps!
Thank you Dr Sanger, we will try this..

Always a pleasure to read your posts !
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