Development of a Simple Chemiluminometer to Determine Acid Value of Edible Oil Free of the Inner-Filter Effect

摘要

In the determination of an acid value of colored and/or turbid edible oil by chemiluminescence measurement, the chemiluminescence signal is reduced by an inner-filter effect of the sample solution, which leads to a sizable measurement error. To remove this inner-filter effect, we propose a photometric correction scheme that utilizes the sample transmittance as an additional parameter to obtain the true chemiluminescence signal. To this end, a new chemiluminometer that detects simultaneously both the chemiluminescence and the transmittance signals is presented. The performance of the proposed chemiluminometer was evaluated by the chemiluminescence of a turbid luminol-H2O2 solution. The experimental results show the effectiveness of the proposed chemiluminometer in determining the true chemiluminescence signal even in the presence of strong inner-filter effect. Using this chemiluminometer, the relationship between chemiluminescence intensity and the acid value of edible oil (rape-soybean oil) was investigated. The results indicated that the corrected chemiluminescence intensity increased rapidly as the oil oxidation progressed, while the observed chemiluminescence intensity was misleadingly reduced by the strong inner-filter effect.