Bioequivalence and Bioavailability Forum

Hi stdev!

❝ nice way to write my nickname by the way

Could not resist.

❝ Yes, I am working with daily prepared calibrators and QCs and I see low/no response for my lowest QC sample as well.

OK, that fits into the picture. I was hoping that you are working with a batch of deep-frozen QCs and prepare only calibrators daily. Have you considered adsorption? Does your system require multiple (to many) injections of matrix-extracts in order to achieve good sensitivity (typical for some LC/MS-MS conditions) or did it work “right away”? Maybe the system is overloaded with matrix components which chews up low concentrations. Only if your system does not require “pre-loading” consider cleaning (I know, I know…). We once had a stupid case of adsorption in the sample loop!