A portable and low cost equipment for flow injection chemiluminescence measurements

A compact, reliable and low cost flow injection chemiluminescence system is described. The flow system consists of a set of solenoid micro-pumps that can dispense reproductive micro-volumes of solutions. The luminometer was based on a coiled cell constructed from polyethylene tubing that was sandwiched between two large area photodiodes. The whole equipment costs about US$ 750 and weights ca. 3 kg. Equipment performance was evaluated by measuring low concentrations of hydrogen peroxide by oxidation of luminol and for the determination of ammonium, based on its inhibition of the luminescence provided by the reaction of luminol and sodium hypochlorite. Linear responses were achieved within 1.0-80 micromol L(-1) H(2)O(2) and 0.6-60 micromol L(-1) NH(4)(+) with detection limits estimated as 400 nmol L(-1) H(2)O(2) and 60 nmol L(-1) NH(4)(+) at the 99.7% confidence level. Coefficients of variation were 1.0 and 1.8%, estimated for 20 micromol L(-1) H(2)O(2) and 15 micromol L(-1) NH(4)(+) (n=20), respectively. Reagent consumption of 55 microg luminol, effluent volume of 950 microL per determination and sampling rate of 120 samples per hour were also achieved.