I am trying to get a standard graph for antioxidant activity of ascorbic acid using 0.1 mM DPPH solution. I had used 100 ug/ml stock and serial dilutions were from 1 ug/ml to 10 ug/ml. All of the absorbance values were negative at 517 nm. I used methanol as a solvent for making both DPPH and ascorbic acid stock. Blank was taken as (DPPH + methanol) in equal parts. what should i do?
* Try to use higher levels of AA for standard curve, for example from 1 to 0.01 mg/ml.
* you can use Trolox instead of AA.
Kindly check this out
Guidelines for antioxidant assays for food components
The antioxidant capacity of the antioxidants can be ... The standard commonly used in this method is ... Stock solution of DCFH‐DA (20.00 mmol/l) was ...
https://onlinelibrary.wiley.com/doi/full/10.1002/fft2.10
Check your calculations carefully.
The percentage of DPPH scavenging effect can be calculated by following equation.
DPPH scavenging effect (%)/% Inhibition=A0-A1/A0 × 100
Where A0=The absorbance of control.
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