Nanomole silver detection in chloride-free phosphate buffer using platinum and gold micro- And nanoelectrodes

The electrochemical determination of ultra-low concentrations of silver requires reliable, reproducible measurements using sensitive analytical techniques. To date, the electrochemical determination of silver in biological buffers and pH neutral media has not been successful in terms of reproducibility. In this work, we report on the determination of ultra-low concentrations of silver in chloride-free phosphate buffer solution (PB, pH 7.4). Detection was conducted at gold and platinum micro and nanoelectrodes using anodic stripping voltammetry (ASV). The micro and nanoelectrodes were fabricated using a Sutter P-2000 laser puller, with physical and electrochemical characterization revealing flat disk-shaped working surfaces of 10-15 μm (microelectrode) and 10-100 nm (nanoelectrodes) in radius. These dimensions were calculated from steady-state limiting currents and confirmed using FE-SEM. The laser pulled electrodes exhibit excellent electrochemical activity when characterized using ferrocene, without the addition of supporting electrolyte, and reproducible stripping voltammetric profiles for the determination of silver, with a LoD of 1.3 pM (1.8%) were obtained in 0.1 M chloride-free phosphate at platinum nanoelectrode. Determination of ultra-low concentrations of silver in chloride-free PB provides the scope to explore the mechanism of action of bioinorganic silver-based anti-bacterial, anti-fungal and anti-cancer drugs in cell media for in vitro and, potentially, in vivo analysis.