Nitrate fluorimetric analysis using an active optical fiber

With the objective to use a fluorimetric determination of nitrate based on fluorescein as the sensitive fluorescent indicator, an active optical fiber was elaborated and its response was rested using a specifically adapted fl uorimeter. So, the three required chemical steps to fix fluorescein via a c ovalent bond on the silica fiber tip will be described, as well as the amou nt 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 optrodes were connected to the specially designed optical fiber fluorimeter. The integrating optical fiber sensor response is linear for co ncentrations between 2 10(-6) and 10(-5) mol NO3- L-1 (i.e. between 0.12 an d 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 ail the grafted fluorescein is no t consumed).