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

Abstract

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 to 10^{-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.