A new compact holder for either 5-or 10-MHz AT-cut quartz crystal resonator of an electrochemical quartz crystal microbalance was designed, fabricated and characterized. The holder is a hydrodynamically controlled thin-layer radial-flow microelectrochemical cell. Its unique feature consists of (i) a micrometer-screw adjustable distance between the movable coaxial assembly of the Ag/Ag þ pseudoreference electrode and the inlet capillary nozzle with respect to the metal-film working electrode of the quartz crystal resonator, and (ii) a U-clamp mountable resonator, easily accessible for change without using any tools. The inlet solution stream is centered axially against the working electrode. The holder performance was tested under different flow conditions. These include hydrodynamic voltammetry measurements on the Fe(CN) 4À 6 /Fe(CN) 3À 6 couple, i.e., a redox system with no mass transfer across the solution -electrode interface, as well as simultaneous chronoamperometry and chronoelectrogravimetry measurements under flow injection analysis (FIA) conditions on the Ag/Ag þ couple, i.e., a system with electrodeposition of a rigid metallic film. Moreover, simultaneous changes of resonant frequency and dynamic resistance were measured under FIA conditions for a glycerol solution, i.e., an electroinactive viscous medium. For the 30 < F m < 180 mL min À1 volume flow rate of solution and 50 < d < 250 mm nozzle-to-resonator distance, the holder operates in a thin-layer radial-flow regime at a fully developed laminar flow. For F m ¼ 30 mL min À1 and d ¼ 100 mm, both mass and charge conversion accompanying silver electrodeposition is appreciably high and close to 35%. Simultaneous measurements of the resonant frequency change and current-potential or current-time transients allowed investigations of electrochemical processes involving mass changes of rigid deposits while those of the frequency change and dynamic resistance change involve changes of viscoelastic properties of medium.

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