The invention relates to an ionization chamber for connection to a mass spectrometer. The ionization chamber has a temperature-control block with a gas inlet and a gas channel which starts at the gas inlet and leads into a gas outlet. A temperature-control device is positioned along the gas channel and ensures that a gas flowing in the gas channel is brought to a specific temperature, i.e. it is heated or cooled, before it enters the ionization chamber. The temperature-control block has a formed part into which a structure of the gas channel is incorporated and which is fabricated by means of a sol-gel process, for example out of a glass or ceramic material.