QCM apparatus

A quartz crystal microbalance, QCM, sensor apparatus comprising:

• a sensor holder having a compartment for receiving a QCM sensor,
• a plurality of sample fluid containers,
• a fluid selector unit for selectively placing one of said sample fluid containers in fluid connection with said compartment, said fluid selector unit having:
• a plurality of inlet ports, each inlet port in fluid connection with a sample fluid container,
• a sensor outlet configured to be in fluid connection with said sensor, and
• a valve arrangement for selectively connecting one of said inlets to said outlet, and
• a thermoelectrical element arranged in thermal connection with the sensor holder,
• wherein said fluid selector unit is sandwiched between the fluid sample containers and the sensor holder, and
• wherein the sensor apparatus further comprises a thermally insulating housing enclosing the sample fluid containers, fluid selector unit and sensor holder, an interior of the compartment having a substantially homogeneous temperature.