title: Rotating sample system: an equivalent of a rotating electrode for microliter samples.
abstract: Voltammetric experiments in sample droplets of 20 microL volume were carried out with gold ring electrodes microfabricated on Pyrex substrates. The droplet studied was centered and kept in place by a hydrophobic ring deposited on the substrate around the ring electrode, which also ensured that each sample assume a semispherical shape. A small hole in the center of the substrate filled with an agar gel membrane served as a junction. A mild jet of humidified nitrogen gas directed tangentially at the droplet caused it to rotate at a high rate. Cyclic voltammetry and constant-potential electrolysis of potassium ferricyanide were used to characterize this rotating sample system and to calculate diffusion layer thickness. The results clearly demonstrate that rotating of a semispherical microsample placed above a stationary ring electrode with a mild gas jet can be as effective as a rotating electrode system. As a practical example, voltammetric stripping analysis of 20-120 pmol mercuric nitrate samples was performed with a calibration of good linearity (r2 = 0.988) and a time constant for exhaustive electrolysis of approximately 2 min.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
authors.forename: A
authors.initials: A
authors.lastname: Cserey
authors.forename: M
authors.initials: M
authors.lastname: Gratzl
mesh_terms: D004563:Electrochemistry; D017669:Mercury Compounds / Q000032:analysis; D008839:Microelectrodes; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D009566:Nitrates / Q000032:analysis; D012399:Rotation
chemical_list: D017669:Mercury Compounds; D009566:Nitrates; C029948:mercury nitrate