Problem with Antioxidant capacity - rescue me!!! (Nov/26/2006 )

I try to test antioxidant capacity by ORAC assay [ oxygen radical absorbance capacity ] using Wallac 1420 victor fluorometer.I want to make a standard concentation curve . But its not work.
the fluorescence value for the blank varies! sometime the sample is less than the blank???

so I clean all my lab glassware , change water [ now I use MilliQ water ] , use new tip , and use brand new reagent
but the result is the same.
what wrong with it?

help me please!!!!



Have someone has a possible explaination/solution, I would be really grateful!

do you use 96- or 384-well microtiterplates for measuring?

I use 96 well plate. and

warm reagent 10 min at 37^C before use.

I once checked the quality (binding capacity) of plates of either different lots of one supplier, as well as quality of different companies; what I strongly recommend is to check each lot before use;
most variations were found at the outer rows but this is not to generalize; if you seriously check you will be astonished how binding capacities differ of even a single plate!