Peroxide Value Method
Weigh 0.01 mg oil into test tube and record exact weight .
Solid fat should be melted first .
Samples with high PV may need to be serially diluted in working solvent .
Make sure to record dilution factor if so .
Up to 0.10 g can be used for samples with very low PV .
Immediately add 3 mL working solvent and vortex to dissolve - make sure it is fully dissolved .
Prepare a blank tube ( solvent in place of sample ) .
Add 15 μl ammonium thiocyanate to all tubes , and vortex 2 - 4 sec .
Add 15 μl ferrous chloride to all tubes , and vortex 2 - 4 sec .
Let sit at room temperature 20 min .
Keep out of bright light .
Read absorbance on spectrophotometer set to 510 nm .
Determine PV using the following calculations :
a . PV ( meq peroxide per kg sample ) = ( As – Ab ) x m / ( 55.84 x m0 x 2 ) As = absorbance of sampleAb = absorbance of blankm = slope of standard curvem0 = mass in grams of the sample55.84 = atomic weight of iron
