Lab 1: DPPH Flashcards
What does DPPH stand for?
2,2-Diphenyl-1-picrylhydrazyl
What is the principle behind the DPPH assay?
The assay measures the antioxidant capacity of a sample by tracking the reduction of the DPPH radical, which causes a decrease in absorbance at ~520 nm.
Why does the DPPH assay change colour?
When antioxidants donate electrons to the DPPH radical, it becomes reduced, leading to a color change from deep purple to yellow.
What is Trolox and why is it used in this experiment?
Lab 1: DPPH Assay
Trolox is a vitamin E analog used as a standard to express antioxidant capacity in Trolox equivalents (TE).
Why must methanol be handled quickly in this lab?
Lab 1: DPPH Assay
Because it evaporates quickly, which could alter sample concentrations.
Why do we prepare a standard curve in this assay?
Lab 1: DPPH Assay
The standard curve allows us to determine the antioxidant capacity of onion extracts by comparing their absorbance to known Trolox concentrations.
What is the role of a blank in the DPPH assay?
The blank (80% methanol) is used to zero the spectrophotometer and account for any background absorbance.
How is the antioxidant capacity of onions reported in the DPPH assay experiment?
In μmol Trolox equivalents (TE) per gram of fresh onion sample.
How do you calculate antioxidant capacity from absorbance values?
DPPH assay
By using the standard curve equation and converting the values to μmol TE/g onion using the formula:
