During pretreatment process for oil sample, charring and ashing processes of oil in AOCS Official Method Ca 12-55 were improved. Oil was pretreated with concentrated sulfuric acid and potassium hydroxide instead of zinc oxide. As a result, soluble phosphate was obtained in a short time, the subsequent steps were also simplified. Firstly, phosphorus contents were measured, then the equivalent phosphatide contents in oil samples were calculated, RSD (relative SD) was only 1.03%. According to the spiking experiments at low, middle and high concentration levels, recoveries were between 97.03 and 100.99%, RSD were all less than 1.57% (n = 5). The method was applied for determining the equivalent phosphatide content of different types of oils. Compared with AOCS Official Method Ca 12-55, the improved method can provide a more effective means for detecting and analyzing the phosphorus or the equivalent phosphatide content in vegetable oils.
Practical applications: In theory, the applicable scope of the improved method should be consistent with that of AOCS Official Method Ca 12-55, that is, the method is also suitable for detecting phosphorus or the equivalent phosphatide content in crude, degummed and refined vegetable oils. However, the promotion of the method should be based on more experimental data from various vegetable oils.