The flow-through oxygen minisensor (FTC) is a miniaturized chemical optical sensor integrated in a flow-through cell. It is connected to the transmitter by an optical fiber. A glass tube with an inner diameter of 2 mm is coated with an oxygen sensor at its inner wall. The volume for liquid inside the FTC is about 100 (±10) microliter. The standard flow-through cell can be easily connected via Luer-Lock adapters to external tubings.