High performance liquid chromatography-size exclusion chromatography for rapid analysis of total polar compounds in used frying oils.

摘要

Analysis of used frying oil samples by high performance liquid chromatography-size exclusion chromatography (HPLC-SEC or HPSEC) was compared to AOCS Official Method Cd 20-91 (silica gel column chromatography) for the purpose of developing a rapid analysis of total polar compounds (TPC). In a direct comparison of the two analytical methods using four different sets of used frying oils (21 total oil samples) ranging from fresh to discard quality (4.3 to 35.4% TPC by column chromatography), the weight percent total polar compounds (%TPC) determined by HPLC-SEC averaged 0.71% higher than the values by silica gel column chromatography. Reproducibility of the HPLC-SEC method of s_r = 0.30 and RSD_r% = 1.22 compares to the variability of s_r = 0.29 and RSD_r = 1.3 for samples of approximately the same %TPC, reported in AOCS Method Cd 20-91. Because the rapid method does not separate pure (non-polar) triacylglycerol (TAG) and polar, oxidized TAG (OX-TAG), a high concentration of OX-TAG will quantitatively affect the results. This places practical limits on the types of studies to which the method may be applied if a separate analysis for the OX-TAG is not performed. Advantages of the HPLC-SEC method include the following. It uses about 75% less solvent than standard column chromatography methods for determination of %TPC. This HPLC-SEC method is very similar to AOCS Official Method Cd 22-91, and thus, also separates and quantifies polymerized triacylglycerols. The HPLC-SEC method determines both TAG polymer concentration and %TPC of used frying oils in about 1 h