I have used the microplate reader for DPPH assay. I didn't have the 517 filter. So instead I used 540 filter. I received negative values for results. Could this be because I used a different filter?
No Shanura's reason was not the issue there. We have 490 and 540. Not in between.
I used various sample concentration ranges and received positive values. I am still not sure what the issue is. I didn't store the DPPH solution in -20C. Could that have any effect on the readings?
It might be doing that. But it would be the same for every cell right? Even for the negative control and the blanks I had used. SO would it really make a difference?