Chromatography Forum

If the method used for assay is used for ID and it stipulates for assay "dry the standard" is it necessary to dry the standard for ID.


Also, do you use the dried portion for weighing the standard
Thanks
Liv

The standard has to be dried in order to assign a reliable value to the content of the compound of interests.
If not dried, the water content will contribute to the mass when the standard is weighed and thus resulting in invalid calibration. The latter actually answers you second question – it is the dried portion that should be weighed.
Another way of correcting the standard’s mass is to determine the water content (by Karl- Fischer titration for instance) and calculate the dry mass value. This method is particularly useful when the substance is susceptible to degradation under the drying procedure.

When it comes to the identity - the answer is: No drying needed. The identity procedure you’re dealing with in this situation is simply to obtain the same retention time (plus/minus something) for standard and sample, leaving a minor role for the exact content/concentration. One should of course obtain a similar chromatographic profile for those, meaning that the comparison should be made for the main peaks (both for standard and sample)

Best Regards

Thanks so much that was a comprehensive answer and I fully understand
Liv