Chromatography Forum

Hello,

I work in a Quality Control Stability Lab, and I have run across a few methods that require duplicate bracket standard injections. What is the reasoning behind this, because theoretically one should be sufficient???

There are a few reasons I can think of off the top of my head...
1) repeatability between injections
2) if this is a Related Substances run and there isn't a flush performed between sample and bracket you might have some carry over.


Just one mans opinion though...

ABAdam,

1) repeatability is demonstrated with the method SS requirement of replicate of five injections.

2) This method called for duplicate injections for the Assay and Related Substances test.

Tim

Duplicate stds generally provide better confidence in ur calibration curve when both stds are used throughout the run for the calibration curve.

I presume you mean you are having to prepare two standard solutions and have to inject/bracket throughout the run?

If so we do this for all of our HPLC assay methods to ensure you are getting what we call "standard agreement" between the duplicate preparations. If you didn't do this how would you have confidence in the preparation of a singular standard solution?

@Rob Burgess,

Here we also prepare two standard solutions, but no this method is reffering to injecting one solution in duplicate for bracket injections. I always have confidence

@gtma,

I agree with what you are saying(more N = better data), but it isn't used in the calculation for a calibration curve.

Thanks

Tim