DETERMINATION OF TRACE AMOUNTS OF UREA BY USING FLOW-INJECTION WITH CHEMILUMINESCENCE DETECTION

Reaction between urea and hypobromite in alkaline solution was found t o produce chemiluminescence with a maximum wavelength at 510 nm. A sim ple chemiluminescence detection method was used for the determination of urea in human urine and natural aqueous samples, which combined thi s chemiluminescence reaction wtih a flow injection analysis system. Th e relative standard deviation for 5 x 10(-7) mol dm(-3) urea is 1.9% ( n = 6), and the detection limit is 9.0 x 10(-8) mol dm(-3) (3 s(r)). A s this chemiluminescence reaction is very fast, a double concentric tu be mixer connected directly to the chemiluminescence cell was used to mix urea solution and hypobromite solution. Alkylamines, carboxylic ac ids and most amino acids do not interfere in the determination. Ammoni um ion interferes, but the sensitivity for ammonium ion is only 1% of that for urea. The interference from ammonium ion was removed sufficie ntly by using an on-line cation-exchange column.