Fluorescence is derived from fluorite (CaF2). Like many other minerals, this mineral is capable of spontaneously emitting light, shortly after it has been stimulated with energy-richer light. This behavior of short-wave light absorption and the resulting emission of longer-wave light are known as fluorescence. Fluorescences have a very low light transmitting power and are therefore outshone by the more intense light of a microscope, making them no longer visible. However, the use of a particular filter makes it possible to separate the bright excitation light and the weak fluorescent light in the beam path (fluorescence microscope). As a result, only the fluorescent light is used for the image generation.
The determination of the total number of live microorganisms in a sample of water, waste water, beverages and food is one typical use. The pre-treated sample is filtered through a TRAKETCH PET or PC membrane by means of the membrane filtration method. The use of a specific fluorescent stain and an epifluorescence microscope makes it possible to distinguish the live from the inactive microorganisms and to subsequently count them, because the fluorescent light is emitted with different wavelengths. However, this fluorescence is only visible if the filter membrane is stained e.g. black, in order to drastically reduce its intrinsic fluorescence. ”TRAKETCH® PET Black“ by SABEU is characterized by very low intrinsic fluorescence and is therefore very suitable to determine live microorganisms for quality control in bacteriology.