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 opto-electronic fluorimeter of very high sensitivity due to the great quantities of the required fluorescent substances like Rhodamine B or Fluorescein. The basis of a new tracer technology of very high sensitivity is the use of pulsed bluish light for excitation [6, 7]. This instrument is known as the VARIOSENS. Due to R&D work, especially on filters, it is able to measure concentrations of fluorescent substances down to10^-12. It 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 and a wide band optical filter which 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 mg/litre.