voltammetry
/ vol-TAM-uh-tree /
Imagine slowly turning up a dial that controls how strongly you tug at the electrons in a solution, and watching for the moment a particular molecule gives in and reacts. At that moment a current flows. Voltammetry is exactly this: you sweep the voltage applied to an electrode and record the resulting current, and the shape of that current-versus-voltage curve fingerprints what is in the solution and how much.
Formally, voltammetry is a family of electroanalytical methods in which the potential of a working electrode is varied in a controlled way while the resulting current is measured. Each substance reacts (is oxidized or reduced) at a characteristic potential, producing a current peak or wave; the position of that feature tells you what the substance is, and its height tells you the concentration.
It matters because voltammetry can be very sensitive, can detect several species in one scan, and uses small, inexpensive electrodes suited to portable and trace work. The caveat is that the current includes not just the useful reaction (faradaic) current but also a background charging current and contributions from how fast molecules diffuse to the electrode, so careful technique and a clean, well-defined electrode surface are essential.
To check a river sample for trace lead and cadmium, an analyst runs a voltammetric scan: each metal plates onto the electrode and then strips off at its own voltage, giving two separate current peaks whose heights reveal each metal's concentration.
Sweep the voltage, read the current: peak position identifies, peak height quantifies.
Voltammetry is the opposite measurement of potentiometry: here you control the voltage and measure the current, whereas in potentiometry you measure the voltage at near-zero current. Amperometry and polarography are members of the voltammetry family.