amperometry
/ am-puh-ROM-uh-tree /
Imagine setting your faucet to one fixed opening and then just watching how fast the water flows out — the flow tells you something about the pressure behind it. Amperometry does the electrical version: you hold the electrode at one fixed voltage and simply watch the current. The size of that steady current tracks how much of your analyte is reaching the electrode and reacting.
Formally, amperometry measures the current at a working electrode held at a constant, chosen potential, where that current is proportional to the concentration of the analyte being oxidized or reduced. Unlike full voltammetry, the voltage is not swept — it is parked at a value where the target reaction runs cleanly, so the current becomes a simple, continuous concentration signal.
It matters because a fixed-voltage current is easy to read continuously and in real time, which makes amperometry ideal for sensors and for detectors at the end of a separation. The home glucose meter and the dissolved-oxygen probe are amperometric. The caveat is that any other substance that also reacts at that same fixed voltage will add to the current, so selectivity must come from the chemistry — often an enzyme or a membrane — rather than from the voltage alone.
A home blood-glucose strip is amperometric: an enzyme on the strip turns glucose into a product that reacts at the electrode held at a set voltage, and the resulting current — proportional to glucose — is what the meter converts into your reading.
Hold the voltage fixed; the steady current measures concentration.
Amperometry is best thought of as voltammetry frozen at one point: instead of scanning the whole current-voltage curve, you sit at a single useful potential and read current over time. It is a workhorse detector in liquid chromatography and electrochemical biosensors.