A 2 mL of the sample was mixed
with 3.7 mL of deionized water and reacts with ferrous chloride (5 mmol/L, 0.1 mL) to which 0.2 mL of 5 mmol/L ferrozine
was added, the solution was mixed to measure the absorbance
at 562 nm employing EDTA as a positive control.