Development of a Sensor Based on Modified Carbon Paste with Com Iron(III) Protoporphyrin Immobilized on SiNbZn Silica Matrix for L-tryptophan Determination

In this work, SiO2/Nb2O5/ZnO prepared by the sol-gel processing method was used as substrate base for immobilization of the protoporphyrin-IX ion. Iron(III) ion was inserted into the porphyrin ring (SiNbZn-PPFe). A simple square wave voltammetry method based on a composite sensor carbon paste electrode of this material,designed as EPC-SiNbZn-PPFe, was developed and validated successfully for the determination of L-tryptophan (Trp). The optimum conditions were obtained by using sensor modified with 18.00mg SiNbZn-PPFe material, 12.00mg graphite powder and 6.0L mineral oil and phosphate buffer 0.3molL(-1) pH7.0. The sensitivity of the sensor was found to be 0.523ALmol(-1), linear range from 10 to 70molL(-1) and limit of detection of 3.28molL(-1). Therefore, the developed method was successfully applied for the Trp determination in real samples of pharmaceutical formulation and can be used for routine quality control pharmaceutical formulations containing Trp.