Time-resolved spectroscopy of long-path fluorescence and scattering for measuring total absorption of fluids

✍ Scribed by K.-H. Mittenzwey; G. Sinn

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 468 KB
• Volume: 330
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(96)00168-7

✦ Synopsis

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: (i) the decay-time of the conventional interaction ro, which occurs at relatively short path-lengths of the incidence beam in the fluid, and (ii) the decay-time rMp of the multi-path-saturation interaction originating at long pathlengths, 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, l/(7 MP-rc), yields the total absorption coefficient directly. In comparison to the conventional absorption technique the decay-time method is characterized by a higher sensitivity.