Modification of glassy carbon electrode with a polymer/mediator composite and its application for the electrochemical detection of iodate.

A modified glassy carbon electrode was prepared by depositing a composite of polymer and mediator on a glassy carbon electrode (GCE). The mediator, flavin adenine dinucleotide (FAD) and the polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) were electrochemically deposited as a composite on the GCE by applying cyclic voltammetry (CV). This modified electrode is hereafter designated as GCE/PEDOT/FAD. FAD was found to significantly enhance the growth of PEDOT. Electrochemical quartz crystal microbalance (EQCM) analysis was performed to study the mass changes in the electrode during the electrodeposition of PEDOT, with and without the addition of FAD. The optimal cycle number for preparing the modified electrode was determined to be 9, and the corresponding surface coverage of FAD (Γ(FAD)) was ca. 5.11×10(-10)mol cm(-2). The amperometric detection of iodate was performed in a 100 mM buffer solution (pH 1.5). The GCE/PEDOT/FAD showed a sensitivity of 0.78 µA µM(-1) cm(-2), a linear range of 4-140 µM, and a limit of detection of 0.16 µM for iodate. The interference effects of 250-fold Na(+), Mg(2+), Ca(2+), Zn(2+), Fe(2+), Cl(-), NO(3)(-), I(-), SO(4)(2-) and SO(3)(2-), with reference to the concentration of iodate were negligible. The long-term stability of GCE/PEDOT/FAD was also investigated. The GCE/PEDOT/FAD electrode retained 82% of its initial amperometric response to iodate after 7 days. The GCE/PEDOT/FAD was also applied to determine iodate in a commercial salt.

Preparation of a novel molecularly imprinted polymer by the sol-gel process for sensing creatinine.

A novel molecularly imprinted polymer (MIP) was prepared and used as an artificial receptor for creatinine (Cre). A sol-gel process was used to prepare the MIP. Tetraethoxysilane (TEOS) was employed as the crosslinker for the formation of a silica matrix for the MIP. Aluminum ion (Al(3+)) was chosen as the dopant to generate Lewis acid sites in the silica matrix for interactions with Cre. Through the sol-gel process, a polymeric matrix with memory sites for Cre was obtained, and this is mentioned here as the molecularly imprinted polymer for creatinine (MIP(Cre)). The imprinting efficiency of MIP(Cre) was evaluated by contrasting the adsorbed amount of Cre by MIP(Cre) with that by the corresponding non-imprinted polymer (NIP). Creatine (Cn), N-hydroxysuccinimide (NHS), and L-tyrosine (L-tyr) were selected as interferences to study the selectivity of the MIP(Cre). The interference studies were also conducted using binary mixtures, such as Cre/Cn, Cre/NHS, and Cre/L-tyr. All these studies reveal that the MIP(Cre) possess a remarkable affinity for Cre. The crucial role of Al(3+) in this system is discussed in detail. Furthermore, the effects of concentrations of Al(3+) and TEOS on the adsorbed amount of Cre by MIP(Cre) were also investigated.