2.3.2. Para-Anisidine Value (p-AV)

Secondary oxidation products in oil samples were measured as p-AV according to the AOCS official method Cd 18–19 [40]. An oil sample of 0.3–0.5 g (g m) was dissolved in 25 mL of isooctane and absorbance was measured at 350 nm (A_b) using a quartz cuvette. One mL of p-anisidine solution (0.25% in glacial acetic acid (w/v)) was added to 5 mL of this mixture and after 10 min in the dark, the absorbance was measured at 350 nm (A_s). A blank was prepared with isooctane and measured the same way as the samples. The following equation was used to calculate p-AV:

where 25 is the volume of isooctane used to dissolve the oil and 1.2 is a correction factor for dilution of sample solution with 1 mL of p-anisidine solution.