The analysis of aqueous solutions with ethanol-soluble reagents in a flow injection system

A spectrophotometric method for the determination of uranium is adapted to flow injection analysis. The reagent, 2(5-bromo-2-pyridylazo)-5-diethylaminophenol, forms a complex with uranyl ions, with an absorbance maximum at 578 nm. The detection limit of the procedure is 0.15 mg l^?1 uranium and 60 samples can be analyzed per hour. Iron, calcium, ammonium, sulphate and fluoridedo not interfere; phosphate interferes even at moderate levels and carbonate interferes at high concentrations. Difficulties encountered in mixing the aqueous stream carrying the sample with the ethanol reagent stream initiated an investigation of different kinds of mixers in flow systems. A tight coil of teflon tubing proved to be the most efficient mixer, i.e., the one yielding the least baseline noise without excessive dispersion.