Abstract
Fixation in a traditional sense means the immersion of biological material into a chemical fluid. For permanent preservation (1) the fixative is always supplied in excess of the cell sample, and (2) the process of fixation is influenced by chemical impurities of the fixative fluid. Both factors influence the subsequent staining of cells. In order to avoid these uncontrolled influences, a new technology for controlled cell fixation has to be developed, whereby freshly prepared formaldehyde gas in an "inert" gas-flow of helium was applied to thin membranes by use of a capillary flow-in technique. The amount of fixative gas supplied, adsorbed, absorbed, diffused, and desorbed after saturation of the membranes could be reliably measured with an on-line operating "inert" mass spectrometer of the Omegatron type.