Okay, I have a validated procedure incorporating a test sample to show the LOD. A normal sample is injected and is below the LOD. An increased sample increased the good peak heights about a multiple of 7.
The below LOD sample now shows a peak on MS that can be used to ID the component. My thoughts are that the original below LOD sample says stop the analysis. My friend says he can ID the component. What are your thoughts on this -- can increasing the sample size overcome the violation of the validated method.
The reality is that the LOD is nothing more than how you originally define the on column amount ( usually in ug) that is injected. If your method specifies injecting 10 ul and now you are injected say 50 ul, you are altering the method validation.
If the MS ID is simply a "one-off" experiment to show that the analyte is what is is purported to be then it doesn't matter.
If you intend to routinely inject more , then you need to re-validate the method.
It ia not the volume that was increased, it was the amount of solid sample increased. The issue is the amount of the sampling from bulk that was increased but the volume of injection was not altered. The SOP states if below the test sample, stop the analysis. But it was continued with the increase in the solute amount.
Not really. The LOD is based on the linearity curve (standard deviation) and comes with the unique analytical method. By increasing the sample size or injecting more on the column you may be injecting more interferences or reducing the baseline resolution between peaks that the original method did not have. It would be easier to report '
As I mentioned earlier, it's the amount of material that is being put on the column.
You can get there a number of ways but it comes down to concentration of sample (ug/ul ) x amount injected (ul) = ug injected on column. If that differs from
your original validation amount, then I agree with Bruce, it's a deviation from the method.
Thank you both. That is my opinion also but needed that reasoning you provided.
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