Portable flow-injection analyzer with liquid-core waveguide based fluorescence, luminescence, and long path length absorbance detector Original Research Article

We describe a multifunctional flow analysis instrument that is portable (25 cm×20 cm×11 cm, 2.3 kg) for facile field deployment. Using a 50 cm long Teflon® AF tubing as final reaction and optical measurement conduit, we combine a liquid-core waveguide (LCW) based fluorescence detector that is transversely illuminated by an addressable light emitting diode array, a chemiluminescence (CL) detector and an absorbance detector with a solid-state broadband (400–700 nm) source. Several illustrative experiments have been carried out to test the performance of the instrument in different detection modes. A S/N=3 limit of detection (LOD) of 0.25 μg l−1 for chromium(VI) was established using the diphenylcarbazide chemistry, and an LOD of 5 μg l−1 was similarly established for Al(III), using Pyrocatechol Violet (PCV) as the chelating chromogenic dye, in both cases using long path absorption detection. The LOD for aqueous hydrogen peroxide was 16 nM using a fluorescence method based on the formation of thiochrome from thiamine and 4 nM by a luminol chemiluminescence method. With a Nafion membrane diffusion scrubber (DS), the LOD was 8.0 pptv for gaseous hydrogen peroxide by the fluorescence method.