Bioelectrochemical evaluation of the total phenols content in olive oil mill wastewaters using a tyrosinase–colloidal gold–graphite–Teflon biosensor

The use of a robust tyrosinase biosensor, fabricated from graphite–Teflon rigid electrode matrices modified with gold nanoparticles, for the estimation of the total phenols content in olive oil mill wastewaters (OMW), is proposed. The performance of this bioelectrode using both continuous stirring and flow-injection amperometry was studied. A potential value of −0.10 V was selected for the sensitive and stable detection of various phenolic compounds present in OMW samples: catechol, 3,4-dihydroxycinnamic acid (caffeic acid), 3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxyphenylacetic acid, 4-hydroxyphenylethanol (tyrosol), and 4-hydroxyphenylpropionic acid. Using catechol as the target phenol, linear calibration graphs were obtained in the 1.0 × 10−8 − 8.0 × 10−6 mol L−1 (batch) and 1.0 × 10−7 − 1.0 × 10−5 mol L−1 (FI) concentration ranges, with slope values of 750 mA L mol−1 and 103 mA L mol−1, respectively. Batch amperometry was chosen for the analysis of real samples because of its higher sensitivity...