Nitrate fluorimetric analysis using an active optical fiber

Abstract
With the objective to use a fluorimetric determination of nitrate based on fluorescein as the sensit ive fluorescent indicator, an active optical fiber was elaborated and its response was tested using a specific ally adapted fluorimeter. So, the three required chemical steps to fix fluorescein via a covalent bond on the silica fiber tip will be described, as well as the amount of grafted probe and the stability of the optrode in sulfuric acid (the required medium for the analysis). Then, for the determination of nitrate, the active optr odes were connected to the specially designed optical fiber fluorimeter. The integrating optical fiber sensor response is linear for concentrations between 2 10-6 and 10-5 mol NO3- L-1 (i.e. between 0.12 and 0.62 mg NO3- L-1 in the reactive medium). One optrode has to be used for each analysis (or each set of analyses if all the grafted fluorescein is not consumed).