Amperometric detection at carbon felt electrodes. Application to the determination of nitro musk derivatives and phenolic endocrine disruptors

Abstract

The use of a carbon-felt electrode (CFE) of small dimensions for the amperometric detection of various nitro musk fragrances and phenolic compounds with endocrine disrupting properties is reported. The electrode material is composed of multiple disordered carbon fibres of micrometre diameter. The use of CFE for the detection of nitro musk derivatives implied the electrochemical activation by applying successive SW voltammetric scans between 0.0 and +2.6 V vs. Ag/AgCl in 0.1 M PBS of pH 7.0. At the activated CFE (aCFE), cyclic voltammograms for nitro musks derivatives in 0.1 M PBS of pH 7.0, showed a non-reversible behaviour with two or three cathodic peaks corresponding to the number of nitro groups present in the molecule. Hydrodynamic voltammograms from nitro musk solutions obtained under flow injection conditions at the aCFE led to the selection of a cathodic potential of −800 mV vs. Ag/AgCl as the value to be applied for the amperometric detection of these compounds. A calibration graph for musk ketone was obtained between 0.1 and 10 μg mL⁻¹ with a detection limit of 50 ng mL⁻¹. A RSD value of 3.7% was calculated for 10 successive measurements of 500 ng mL⁻¹ musk ketone with no need for cleaning the electrode surface. Similar results to those obtained by GC-MS were found for the analysis of incense samples by FI with amperometric detection at the activated CFE. FI hydrodynamic voltammograms for estrogenic phenols at non-activated CFE exhibited current anodic plateaux from which a detection potential of +700 mV was chosen. Liquid chromatography with amperometric detection at the CFE was accomplished to analyze mixtures of estrogenic compounds. A mobile phase consisting of 40 : 60 (v/v) acetonitrile : 0.05 M PBS of pH 7.0 was employed. Detection limits ranging between 102 nM for bisphenol A (BPA) and 182 nM for 17α-ethynylestradiol (EE2) were achieved. Good recoveries were obtained in the analysis of well water and tap water samples spiked with five phenolic estrogenic compounds at a 14 nM each concentration level.