Simultaneous extraction and analysis of apple pomace by gradient pressurized liquid extraction coupled in-line with solid-phase extraction and on-line with HPLC

Due to the complex characteristics and variable composition of apple pomace, sample preparation for chromatographic analysis is a great challenge. To solve this problem, we proposed using a solvent gradient using Pressurized Liquid Extraction (PLE), where the solvent gradually changes from water to ethanol during the extraction. Different dynamic gradients, static time, and temperatures were evaluated and showed relevant effects on the yields of target analytes. It was possible to improve extraction yields of compounds with different characteristics using the extraction solvent gradient. By coupling solid-phase extraction in-line, it was possible to separate compounds into fractions, where furfural, HMF, and chlorogenic acid gradually eluted from the adsorbent. At the same time, flavonoids were retained and eluted in the later fractions. On-line analysis by HPLC provided real-time information about the process and permitted the creation of a 3D chromatogram of the sample.