Desenvolvimento de um sensor à base de pasta de carbono modificada com protoporfirina de ferro(III) imobilizada em matriz de sílica visando a determinação de L-Triptofano

The tryptophan (Trp) is an essential amino acid for humans. This compound is a precursor of serotonin (a neurotransmitter). When improperly metabolized, it creates a waste product in the brain that is toxic, causing hallucinations and delusions[1,2]. Therefore, the determination of Trp in pharmaceutical formulations is extremely important. In this context, a sensitive and selective sensor wasdeveloped for the Trp voltammetric determination in pharmaceutical formulation employing a device based carbon paste electrode (CPE) modified with iron(III) protoporphyrin previouslyimmobilizedon silica matrix(SiNbZn-PPFe) prepared by sol-gel process, which was denominated EPC-SiNbZn-PPFe. Scanning Electron Microscopy, InfraredSpectroscopy Fourier Transformand UV-Vis spectrophotometrywere used to characterize the materials and composite formed. The Trp oxidation employing the EPC-SiNbZn-PPFe composite was investigated by Cyclic Voltammetry, Differential Pulse Voltammetry and Square Wave Voltammetry. The optimum conditions were obtained by using (sensor) modified with 18.00 mg SiNbZn-PPFe, 12.00 mg graphite powder and 6.0 μL mineral oil, phosphate buffer 0.3 mol L-1pH 7.0. Considering the conditions adopted for the study of the validation method for determination of Trp at pharmaceutical formulations the a oxidation currents obtained by Square Wave Voltammetry showed good linearity for the concentreation of Trp in the range from 10 to 70 μmol L-1, detection limit of 3.28 μmol L-1and quantification limit of 10.9 μmol L-1. The results obtained for the determination of Trp in real samples of pharmaceutical formulation presented with small relative error,showing the good performance of the method developed.