Anodic stripping voltammetry of copper at insonated glassy carbon-based electrodes: application to the determination of copper in beer

The suitability of ultrasound-assisted anodic stripping voltammetry (sono-A SV) for the detection of total copper content in beer using both mercury th in film and glassy carbon electrodes has been investigated. An immersion ho rn probe is introduced into a small thermostatted conventional three electr ode cell (20 cm(3)) opposite the working electrode: an ex situ mercury plat ed Nafion(R)-coated mercury film electrode or a bare glassy carbon electrod e. Minimal sample pre-treatment is required which consists of acidification of the beer with dilute nitric acid and out-gassing with argon. After the deposition of copper (as the metal or its amalgam) on the electrode in the presence of ultrasound, a square wave scan is employed to get the analytica l signal. In the absence of ultrasound, electrode passivation by organic sp ecies and lower rates of mass transport prevent the observation of any meas urable signals. In situ cavitational cleaning of the electrode by insonatio n maintains the electrode activity. Total copper content levels in the rang e of 100 to 300 mu g Cu L-1 were determined by sono-ASV using both electrod e substrates and showed excellent agreement with values provided by an inde pendent method. This highlights the validity of the sono-ASV method as a us eful electroanalytical technique in hostile media.