Hi,
It seems that doing a final suitability test is quite fashionable, now a days. In fact it is usefull to demonstrate the suitability of the equipment and the method, however, what to do if it fails and the end of the analysis?. Is the whole analysis wrong?

I would like some comments about this new issue.
Thanks a lot

Why should you perform a suitability test at the end of the analysis? When your column is well equilibrated and you inject your system suitability sample, you should get the same result like when you inject the suitability sample after your analysis. If this is not, you may have a clean up problem, but that is a discussion that's already passed.

Anonymous,

In our lab, we perform a suitability check before the analysis of samples. We also have a requirement that after the run is finished, the RSD of all standards in the run used to quantitate the samples must be within the same specs as at the beginning (usually NMT 2.0%). Basically, this is used to show that there has not been a change in the chromatographic system during the analysis. If the final RSD does fail, we determine at which bracketing standard the RSD fails and repeat the analysis of the samples which were bracketed by those standards.

Hope this helps.

Hi Anonymous

We also use pre and post stds to validate our run. The %RSD on our pre-std=N.M.T 1.0% and the overall RSD of all our stds during the run is N.M.T 2.0%. If our overall RSD is more than 2.0% our run would be invalid. If these results are to be used a "planned deviation" would be raised. During the method validation sample/std stability would be done to determine how stable the samples/std is. If the sample/std is not stable a minimum time would be put in the method eg. inject sample/std within 4hrs. If we have long runs ± 24hrs we would inject stds at regular intervals to ensure that the system is ok. eg. every 4hrs/24 injs.
I hope 2 cents worth helps.
Mike

The answer depends on the context of the assay. If the assay is for measuring the impurity on the tail of the active a resolution solution at the end may be indicated. However if the assay is for potency and the all impurities are less than 0.1% then the stability of the standards throughout the run is probably most appropriate. I would like to caution you aginst using a parameter like RSD for all standard throughout the run because it can hide intermittent problems. Take as an example 11 standards total. 10 of the standards have a value of 99.9 and 1 has a value of 95. RSD for the run would be 1.5% but if the assay has a 97-103% specification all points around the 95 are suspect. The ultimate rule is that the system suitability should be based upon what the requirements are for the desired result and the historical(developmental) knowledge of the assay