The most widespread application of the Sigrist fluorescence instrument is the detection of traces of hydrocarbons in water.
In the laboratory, hydrocarbon determination is carried out by infrared absorption measurement. Because the water itself absorbs the infrared radiation, the hydrocarbons have to be extracted first with a solvent (carbon tetrachloride or a freon). This sample preparation (mixing, separation, drying) excludes continuous measurement and makes it very costly to operate such analyzers in industrial applications. A simple substitute solution now in use is turbidity measurement. Although it does detect tiny suspended oil droplets, it also reacts to other turbidity substances and fails to detect dissolved hydrocarbons.
For these reasons, the measurement of fluorescence has been adopted as direct detection method. It picks up the fluorescing substances regardless of their form (dissolved, emulsified, etc.) specifically and without requiring the use of reagents.
The most important industrial applications are: