NACE‐ESI‐TOF MS to reveal phenolic compounds from olive oil: Introducing enriched olive oil directly inside capillary

Abstract Most CE methods for the analysis of phenols from olive oil use an aqueous electrolyte separation medium, although the importance of NACE is obvious, as this kind of CE seems to be more compatible with the hydrophobic olive oil matrix and could facilitate its direct injection. In the current work we develop a method involving SPE and NACE coupled to ESI‐TOF MS. All the CE and ESI‐TOF MS parameters were optimized in order to maximize the number of phenolic compounds detected and the sensitivity in their determination. Electrophoretic separation was carried out using a CE buffer system consisting of 25 mM NH 4 OAc/AcH in methanol/ACN (1/1 v/v) at an apparent pH value of 5.0. We studied in depth the effect of the nature and concentration of different electrolytes dissolved in different organic solvents and other experimental and instrumental CE variables. The results were compared with those obtained by CZE (with aqueous buffers) coupled to ESI‐TOF MS; both methods offered to the analyst the chance to study phenolic compounds of different families (such as phenolic alcohols, lignans, complex phenols, flavonoids, etc .) from virgin olive oil by injecting methanolic extracts with efficient and fast CE separations. In the case of NACE method, we also studied the direct injection of the investigated matrix introducing a plug of olive oil directly into the capillary.