while performing DPPH antioxidant assay for my samples I am getting a lower absorbance value for blank when compared to my extracts. DPPH solution- 24mg DPPH mixed with 100mL methanol.
Blank- 50% acetone+ DPPH working solution (10uL+190uL)
Sample- Extract+DPPH working solution (10uL+190uL)
Standard- Trolox 20-250mg/L
I am subtracting blank absorbance from extract absorbance (Blank- Extract) to get the final value for extract absorbance and then using this value to calculate antioxidant capacity in terms of Trolox equivalence.
Could someone please advice why is this happening?
Thanks