System suitabilty requirements

[Richard.westcott]

How long is a HPLC system "suitable" for once you have run the system suitability tests? Currently we will run the system suitability at the start of a run, which can last up to 3 or 4 days. Is there any requirment for the length of time a system is suitable for?

[danko]

Hi Richard,

The SST’s role is to show/document that the system performed as required during the whole analytical series/sequence. Now I’m not aware of your SST procedure, but a good/valid SST procedure should bracket all the samples thus showing that all the runs – from the firs to the last are run under the same conditions. If you have 30 unknowns for instance, the SST sample could be injected before all unknowns, then after the 15th and finally at the end of the series. There should be some criteria (e.g. to the RSD) built in, thus showing that the whole sequence is consistent. So, if you follow this procedure, you don’t really need to worry about the time span and the validity of your results.

Best Regards

[Dan]

Richard,

It can depend on your system and your method and, most importantly, your SOP.

If your SOP does not cover this, then use a little bit of scientific common sense. Two concerns are: the stability of the system/run and if any changes will/did/can occur during the run.

We would do the normal system suitable testing (as per USP/EP) with injections at the beginning of the run and use injections of calibrations standards throughout the run, bracketing no more than six sample injections. We would have the additional system suitability requirement of an RSD criteria for those bracketing calibration standards.

Our SOP will guide us for long run times and other issues as to when/if we need to redo the initial system suitability injections.

The SOP states to redo the system suitability injections if (1) the total run time exceeds 24 hours or (2) a change occurred to the system.

Two examples of a change to the system:
- a power failure occurred
- you added mobile phase to the system resevoir that was of a NEW batch/preparation of mobile phase

So, in keeping with our SOP, we would be having the system suitability injections run once a day.

The bracketing calibration standard injections would always be used throughout the run. This is in keeping with the USP requirement for establishing the suitability of the run.

Regards,
Dan

[Sunjay]

Dear Richard,

There is a requirement form USP to establish the sys suit throughout the run time. I suggest you to read USP chapter on Chromatography.

We have incorporated in our SOP that after every 12 injection and at the end of sequence, one standard injection should be given and we have RSD requirements for that.

Regards