Uncertainty and other metrological parameters of peroxide value determination in vegetable oils

Measurement uncertainty in the proposed redox-potentiometric methods for peroxide value (PV) determination in vegetable oils is evaluated in comparison with uncertainty in the standard methods. The methods determine all peroxides in oils, in terms of milliequivalents per kg of sample (meq/kg), that oxidize potassium iodide (KI) under the conditions of the test. The standard methods are based on KI oxidation by the oil test portion and volumetric titration of the liberated iodine, while the proposed methods are using redox-potentiometric iodine determination without titration. As far as fresh refined oils have PV≤0.5 meq/kg, the limit of detection (LOD) and limit of quantitation (LOQ) of the methods are important. An approach to assess the LOD and LOQ using uncertainty calculation was applied. It is shown how important is the influence of the solvents purity on the values of LOD and LOQ.