Bioequivalence and Bioavailability Forum

Dear nvs!

❝ can any one let me know on what is the main differentiation between

❝ selectivity and matrix effect,and main purpose to conduct matrix effect in

❝ validation.

1. Selectivity is the ability of a method to distinguish between the compound of interest (the analyte) and interferences.
   
2. Matrix effects may occur in highly selective (but not necessarily sensitive) analytical methods.
   Examples: LC/MS-MS, and - to a much lesser extent - fluorescence.

Just to give you an example: in a method which is not very selective (e.g., HPLC-UV) it's quite easy to 'see' co-eluting compounds in the chromatogram and adjust the method accordingly.
The opposite is the case in LC/MS-MS, where large amounts of interfering compounds may co-elute with you analyte without being even noticed. Unfortunatelly these compounds may alter (suppress or enhance) the ionization (and therefore the signal) of the analyte.

Making things even worse, not only the current chromatogram may be influenced, but the sensitivity of subsequent ones may also gradually be influenced by some kind of 'memory' of the ion-source.

The lesson we have learned the hard way in the last years was this one:
Contrary to the promises of vendors of MS-instruments (protein precipitation and inject), although LC/MS-MS is a powerful and very selective analytical technique, sample clean-up is even more important than in 'classical' HPLC/GC.