Sammanfattning: The quartz crystal microbalance (QCM) is an ultra-sensitive weighing device. It consists of a piezoelectric quartz crystal, often in the form of a disk, which is sandwiched between a pair of evaporated electrodes. When these are connected to an electronic oscillator, the crystal can be made to oscillate in a very stable manner at its resonant frequency, f, due to the piezoelectric effect. If a thin, rigid film is deposited evenly over one or both of the electrode surfaces in such a way that it does not slip on the surface, the resonant frequency decreases proportionally to the mass of the film. By measuring the resonant frequency, masses well below 1 ng/cm can be gauged. Traditionally, the QCM has been used in gaseous or vacuum environments but has lately been employed as a mass sensor in liquids. However, in a liquid, several other factors besides the deposited mass may influence the resonant frequency, and the linear mass to frequency relationship might no longer hold.