Institution: | a Gesellschaft für Me- und Systemtechnik mbH, Rudower Chaussee 5, 12489, Berlin, Germany b Geographisches Institut, Humboldt-Universität Berlin, Chausseestrasse 86, 10115, Berlin, Germany |
Abstract: | Optical methods are appropriate tools to detect organic micro-pollutants in fluids. A new technique is introduced which uses the decay of interaction processes like fluorescence and elastically scattered radiation by a fluid. Principally two different parameters are determined: 1. (i) the decay-time of the conventional interaction τC, which occurs at relatively short path-lengths of the incidence beam in the fluid, and 2. (ii) the decay-time τMP of the multi-path-saturation interaction originating at long path-lengths, e.g. in multi-path-reflection cuvettes, where the incidence beam is fully absorbed by the fluid.
A relation between the decay-time and the absorption coefficient of a fluid is theoretically derived. A simple preliminary experiment is performed considering distilled water polluted with non-fluorescent azobenzene and fluorescent quinine-sulphate. A nitrogen laser has been used to generate the fluorescence and scattering signals. The reciprocal value of the difference between the decay-time of the multi-path and conventional signals, 1/(τMP ? τC), yields the total absorption coefficient directly. In comparison to the conventional absorption technique the decay-time method is characterized by a higher sensitivity. |