Flow injection manifolds for liquid–liquid extraction without phase separation assisted by ultrasound Original Research Article

Flow injection (FI) manifolds based on iterative change of the flow direction have been designed to study the influence of auxiliary energy on continuous liquid–liquid extraction without phase separation and compare it with the non-assisted process in a single experiment. In order to demonstrate the utility of ultrasounds as auxiliary energy for the extraction of polyphenols from an organic phase, the approach has been applied to samples of extra virgin olive oil, using an alkaline aqueous phase as extractant and subsequent derivatization with the Folin–Ciocalteu reagent. The proposed method provides results similar to those from the official method-recoveries between 97 and 100%. The sensitivity of the proposed method is 3.5 times higher than that of the non-ultrasound-assisted method. The precision, expressed as relative standard deviation (R.S.D.) for n=5, was within 1–5% and the relative errors for the irradiated and non-irradiated method were within 3 and 5%, respectively. The repeatability and within-laboratory reproducibility, studied at two concentration levels (379 and 813 μg ml−1) ranged between 0.7–4.4% and 0.6–4.8%, respectively. The proposed manifolds can also be applied to either other type of auxiliary energies—microwave, thermal—or two different types of auxiliary energies at the same time.