Zinc detection in oil-polluted marine environment by stripping voltammetry with mercury-free nanoporous gold electrode

Abstract

Detection of Zn(II) in oil-polluted seawater via square-wave anodic stripping voltammetry (SW-ASV) utilizing thin gold electrodes sputtered onto nanoporous poly(acrylic acid)-grafted-poly(vinylidene difluoride) (PAA-g-PVDF) membrane is herein reported. Prior to SW-ASV, PAA grafted nanopores demonstrated to efficiently trap Zn(II) ions at open circuit. This passive adsorption followed a Langmuir law. An affinity constant of 1.41 L [Formula: see text]mol[Formula: see text] and a maximum Zn(II) adsorbed mass q[Formula: see text] of 1.21 [Formula: see text]mol g[Formula: see text] were found. Applied SW-ASV protocol implied an accumulation step (- 1.2 V for 120 s) followed by a stripping step (- 1.2 to 1 V; 25 Hz; step: 4 mV; amplitude: 25 mV; acetate buffer (pH 5.5)). It revealed a Zn redox potential at - 0.8 V (Ag/AgCl pseudo-reference). Multiple measurements in synthetic waters close to the composition of production waters exhibited a decreasing precision with the number of readings R (1.65[Formula: see text] (R = 2) and 6.56[Formula: see text] (R = 3)). These membrane-electrodes should be used as disposable. The intra-batch mean precision was 14[Formula: see text] (n = 3) while inter-batches precision was 20[Formula: see text] (n = 15). Linear and linear-log calibrations allow exploitation of Zn(II) concentrations ranging from 10 to 500 [Formula: see text]g L[Formula: see text] and 100 to 1000 [Formula: see text]g L[Formula: see text] respectively. The LOD was 4.2 [Formula: see text]g L[Formula: see text] (3S/N). Thanks to obtained calibration, a detected Zn(II) content of 1 ppm in a raw production water from North Sea oil platform was determined.