Application of a New Iridium Complex as a Chemiluminescence Reagent for the Determination of Tryptophan

Abstract

It was found that a novel iridium complex, [(dpci)(2)Ir(bvbbi)](PF(6)) (dpci = 3,4-diphenylcinnoline, bvbbi = N,N'-bivinyester-(1)H,(1)'H-[2,2'] bibenzimidazole), with Ce(IV) in the presence of sodium sulfite can induce a great chemiluminescence (CL) emission. More importantly, a rapid and sensitive CL method for the determination of tryptophan coupled with a flow-injection analysis (FIA) technique has been developed based on the inhibition effect of the tryptophan to the CL emission of [(dpci)(2)Ir(bvbbi)](PF(6))-Ce(IV)-SO(3)(2-) system. Under the optimum conditions, the decreased CL intensity is proportional with the concentration of tryptophan in the range of 5.0 × 10(-7) to 2.0 × 10(-5) mol L(-1), and the detection limit is 8.2 × 10(-8) mol L(-1) (3σ). The relative standard deviation (RSD) for 11 parallel measurements of 1.0 × 10(-5) mol L(-1) tryptophan is 2.7%. The proposed method has been applied successfully for the determination of tryptophan in its pharmaceutical formulations. Moreover, the possible inhibition mechanism of tryptophan on [(dpci)(2)Ir(bvbbi)](PF(6))-Ce(IV)-SO(3)(2-) CL system was briefly discussed.