Practical experience with the Variosens equipment in measuring chlorophyll concentrations and fluorescent tracer substances, like rhodamine, fluorescein, and some new substances

The quantitative measurement of the dispersion of matter in large bodies of water, e.g., in ocean currents [1], needs an optoelectronic fluorometer of very high sensitivity due to the great quantities of the required fluorescent substances like rhodamine B or fluorescein that would otherwise be required. The basis of a new tracer technology of very high sensitivity is the use of pulsed bluish light for excitation [6], [7]. The instrument described here is known as the Variosens. It is able to measure concentrations of fluorescent substances down to10^{-11}and has a logarithmic scale covering a concentration range of about 1:3000. The fluorescence is excited by means of a xenon spark at a frequency of 10/s with stabilized light emission. A wide-band optical filter defines the exact spectral range of the required exciting light. The receiver operates with a narrow-band optical filter by measuring the fluorescent radiation of the tracer substance used. This filter must have a very high blocking factor. Without filters the instrument uses backscatter to measure the quantity of suspended particles in the water in milligrams/liter.     

Fluorometric in situ measurements of water currents and mingling of waters in cases of heavy turbidity as in coastal shoal areas

By means of the in situ pulse-light fluorometer Variosens the fluorescent substance uranin was used to detect small water bodies. In mixture with a big river (Elbe) a quantity of 40-g uranin only was sufficient for tracer activities during 2 h and was a factor of about 50 above basic noise. It has been found that uranin in turbid water is highly superior to all kinds of rhodamine.