1200 series hplc device

Encapsulation efficiency and partitioning behaviour of the main OLE phenolic compounds into alginate microparticles were assessed by HPLC-DAD. OLE loaded alginate microparticles were initially dissolved with 10% (w/v) sodium citrate solution (Flamminii et al., 2020a (link)). The solution containing the broken microbeads was properly centrifuged at 13,000 rpm for 5 min, diluted and filtered with 0.22 mm nylon filters prior the injection into the chromatographic system. The elution was conducted by an Agilent 1200 series HPLC device (Agilent, Santa Clara, USA) with a photodiode array detector (Agilent, Santa Clara, USA). The separation was performed on a Kinetex C18, (250 mm length x 4,6 mm i.d, 5 μm particle size) using a mobile phase consisting of (A) acetic acid 2.5% (v/v) and (B) acetonitrile at a constant flow rate of 0.8 ml/min in a gradient mode. Chromatograms were acquired at 280 nm for Oleuropein and Hydroxytyrosol and 330 nm for Verbascoside which were used as standards for the preparation of the calibration curves. Results were expressed as mg of standard/mg of microparticle powder as dry matter (dm). Encapsulation efficiency (EE%) for each phenolic compound (pc) was evaluated as follow (Eq. (1)): were (mg_pc/mg_dm)_cs represent the phenolic content of the citrate solution (cs) and (mg_pc/mg_dm)_is represent the phenolic content of the initial encapsulant solution (is).