The new protocol is based on the following steps (cf. Fig. 1): (1) A
μL-sized sample (e.g., chloride solution) is attached as droplet to an
electrode surface, with the electrode positioned upside-down (in air).
(2) A reagent droplet is added to produce a precipitate (e.g., containing
Ag+ to produce AgCl). (3) The solvent is evaporated in a drying cabinet.
If the precipitate that has not yet formed in step 2, it will form in any
case nowduring solvent evaporation. (4) Then the electrode is inserted
in an appropriate electrolyte solution and the electrochemical measuring
step is commencedwithout delay by (5) a reduction of AgCl to Ag at
−0.7 V, followed by (6) electrochemical dissolution of Ag using DPV,
so that the AgCl precipitate has hardly a chance to dissolve before
its electrochemical conversion providing the signal generation. The
proposed Stripping VoltammetryMicroprobe combines the high sensitivity
of stripping voltammetry withmicrosampling, thus providing a platform
for the determination of low absolute amounts of analytes. The new
protocol is demonstrated here for the case of determination of silver
ions (or chloride ions) in 5 μL droplets.