A multi-pumping flow system for chemiluminescent determination of ammonium in natural waters

Abstract

A multi-pumping flow system with improved mixing conditions is proposed for chemiluminescent determination of ammonium in natural waters. The system includes a gas-diffusion unit, a Y-connector made of sintered glass particles (100–200 mesh), and a chemiluminometric detector. System configuration, flow rates, reagent concentrations, pH, and reactor lengths were optimized. The analytical curve is linear from 0.3 to 5.0 mg L⁻¹ N-NH₄, and the detection limit is estimated as 0.02 mg L⁻¹ at the 99.7% confidence level. The system handles about 50 samples per hour, requires 3.1 µg of active chlorine and 0.11 mg of luminol per determination, and yields precise results (RSD<1.2%, n = 10) in agreement with those obtained by the spectrophotometric indophenol blue method.

Keywords:

• Flow analysis
• Ammonium
• Multi-pumping
• Chemiluminescence
• Water analysis

Acknowledgements

Partial support from the CNPq/GRICES bi-national consortium is greatly appreciated. K.L. Marques thanks FCT for a PhD grant (FSE–IIIQCA).