Transversely illuminated liquid core waveguide based fluorescence detection: Fluorometric flow injection determination of aqueous ammonium/ammonia

The analytical performance of a new type of fluorescence detector, based on a transversely illuminated liquid core waveguide (LCW), has been investigated using the determination of NH3/NH4+ as the 1-sulfonatoisoindole. With a very inexpensive combination of a miniature Hg blacklight as an excitation source, a colored plastic sheet as the emission filter, and an integrated blue sensitized photodiode-operational amplifier as the detector (totaling <$100 in hardware cost), we were able to achieve a limit of detection (LOD) of 35 nM (1.6 pmol) NH3 with a linear dynamic range up to 60 μM NH3. Details of detector construction and performance are given.