Voltammetric sensing of E,E-dienestrol in fish tissue by combining a cathodically pretreated boron-doped diamond electrode and QuEChERS extraction method

Abstract

Food quality control has been a pressing issue in recent years and demands the development of efficient and versatile analytical methods. This paper describes a promising voltammetric assay to monitor the synthetic estrogen E,E-dienestrol (E,E-DNL) in fish tissue, using a cathodically pretreated boron-doped diamond (Cpt-BDD) electrode in combination with QuEChERS extraction method. The electrochemical reactivity of E,E-DNL on Cpt-BDD electrode is strongly pH-dependent, so that a well-defined anodic peak (≈ 0.97 V vs. Ag/AgCl) was recorded in Britton-Robinson buffer (pH = 2.0) due to oxidation of estrogen to quinone. This behavior became much more evident after cathodic pretreatment of the working electrode, since the hydrogen-terminations produced on the active surface improve the charge-transfer process, signal-to-background ratio and fouling resistance. When estrogen oxidation current was observed by square-wave voltammetry under optimum conditions, it was found a linear relationship from 2.30 × 10–7 to 9.69 × 10–6 mol L–1E,E-DNL, with high data correlation (R2 = 0.9987), sensitivity (detection limit of 5.43 × 10–8 mol L–1) and precision (RSD < 5.0% for repeatability and reproducibility tests) of the measurements. The procedure was successfully applied to quantify E,E-DNL in QuEChERS extracts from Nile Tilapia (Oreochromis niloticus) liver tissue (92.3–98.8% recovery), proving its high potential for the quality control of this estrogen in aquatic origin foods.