USE OF TIME-RESOLVED LANTHANIDE-SENSITIZED LUMINESCENCE FOR THE KINETIC DETERMINATION OF P-AMINOBENZOIC ACID

Lanthanide-sensitized luminescence was for the first time used to deve lop a simple kinetic method for the determination of p-aminobenzoic ac id. The method is based on the formation of a complex with terbium(III ) in the presence of trioctylphosphine oxide as synergistic agent and Triton X-100 as micellar medium. The high initial rate of the complex formation required the use of stopped-flow mixing technique in order t o make kinetic measurements which, in addition, allows the method to b e automated. Its analytical features compare very favourably with thos e described by using solid-surface room temperature phosphorescence in terms of rapidity, precision and selectivity. The initial rate is obt ained within only 0.2 s after the reactants are mixed, which allows re ady application of the proposed method to routine analyses. The calibr ation graph is linear over the range 0.08-4.0 mu g ml(-1) p-aminobenzo ic acid and the detection limit is 0.02 mu g ml(-1). The relative stan dard deviation is close to 2%. The kinetic methodology avoids the effe ct of the sample matrix allowing the direct determination of this comp ound in pharmaceutical preparations. Analytical recoveries ranged betw een 98.6 and 113.0%. (C) 1998 Elsevier Science B.V.