COBALT(II)-CATALYZED CHEMILUMINESCENCE IN A DIOCTADECYLDIMETHYLAMMONIUM CHLORIDE BILAYER MEMBRANOUS MEDIUM FOR THE FLOW-INJECTION DETERMINATION OF PHENYLPYRUVIC ACID

A novel chemiluminescence system is described for the flow injection determination of phenylpyruvic acid (PPA). The presence of both ordered surfactant molecular assemblies and a metal ion catalyst in the system is essential for the phosphorescence of benzaldehyde (emitter) produced by the aerobic oxidation of PPA in alkaline solution. Dioctadecyl-dimethylammonium chloride bilayer aggregates and cobalt(II) allows PPA to be selectively determined down to 1 x 10(-7) M. The linearity is 2 orders of magnitude with a relative standard deviation 3.1% (n = 10) for 1 x 10(-6) M PPA. Of 28 other species (1 x 10(-3) M) tested, only 4-hydroxymanderic acid, 4-hydroxyphenylpyruvic acid, 2,5-dihydroxyphenylacetic acid, and 4-hydroxy-3-methoxyphenylpyruvic acid provided signals 2-13 times more intense than that for 1 x 10(-6) M PPA. PPA present at 10(-3)-10(-2) M levels in urine from patients with phenylketonuria can be determined with no special sample pretreatment by using this CL procedure. The mechanistic study of the present luminescent reaction are also undertaken in detail. The bilayer aggregates were found to contribute favorably both to the production of key intermediates and to the efficient phosphorescence emission.