Study On Four New Imprinted Electrochemical Sensors

Molecularly imprinted Polymers (MIPs) are becoming an important class of synthetic materials for provided with characters such as predetermination, specific recognition and practicability, high selectivity, stability and durability against harsh chemical environments. Modified electrode, refers to the electrode whose surface has been chemically treated. In general, molecules, ions, polymers and nano-materials with special chemical properties are used to modify the electrode’s surface. After modification, it could offer good sensitivity and at low cost, with Possibility of easy design, manufacture, automation and miniaturization. To overcome some of the difficulties, applied the advantages of MIT being to the electrode, for the detection of specific molecular or ion are constructed successfully.The details are as follows:1. To develop a convenient method for sensitive and selective determination of palladium in complicated matrices, a novel electrochemical sensor based on a Pd(Ⅱ)-imprinted membrane was fabricated on glassy carbon electrode (GCE) by in situ polymerization with Pd(Ⅱ) as template, allylurea (NAU) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross linking agent at the mole ratio of Pd(Ⅱ), NAU and EGDMA as1:4:40. Various factors, known to affect the response behavior of selective electrode were investigated and optimized. Under the optimal conditions, the sensor exhibits a good stability, reproducibility and selectivity together with high sensitivity. A good linearity for the determination of Pd(Ⅱ) was obtained in the range of0.25～184.0μmol L-1with the detection limit of8.43×10-8mol· L-1. The sensor was applied to the determination of Pd(Ⅱ) in real samples with the relative standard deviation below4.1%, and recovery in the range of101.4～105.8%.2. After the interaction between Ir(Ⅲ) and2-(allylthio)nicotinic acid (ANA) or acrylamide (AM), α-methacrylic acid (MAA),2-acetamidoacrylic acid (AAA) was studied and the amount of crosslinking agent was optimized, a new ion-imprinted carbon paste sensor (ⅡP-CPE) for determination of Ir(Ⅲ) was constructed by mixing Ir(III) ion-imprinted polymers, which was prepared using ANA as functional monomer, and graphite powder with the mass ratio of1:2. The obtained IIP-CPE exhibited good regeneration, stability and selectivity. The response current of this sensor to the other noble metal ions and some common metal ions can be ignored compared with that to Ir(Ⅲ). The relative standard deviation (RSD) of the response currents in the same IIP-CPE after used92times or stored at room temperature for36days was less than5.9%. Under the optimum conditions, the calibration graph for the determination of Ir(Ⅲ) with this sensor by chronoamperometry was linear in the range of2.85×10-8～2.31×10-5mol/L with the detection limit (S/N=3) of7.84nmol/L. The sensor was successfully applied to determine iridium in automobile catalyst and plant samples with the relative standard deviation of less than4.8%and recoveries in the range of101.8-103.7%.3. A novel electrochemical sensor for the determination of podophyllotoxin (PPT) was obtained by modifying a PPT-imprinted membrane, which was synthesized by in situ polymerization with PPT as template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross linking agent at the molar ratio of PPT/MAA/EGDMA as1:2:100, on glassy carbon electrode (GCE) followed by eluting PPT from the modified GCE with methanol/acetic acid (v/v=1:1). The properties of the electrochemical sensor modified with PPT-imprinted membrane (PPT-MECS) was characterized by scanning electron microscope (SEM), infrared spectroscopy(IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and so on. Under the optimum conditions, it was found that the response of peak currents was linear to the concentration of PPT in range of1.0-120μmol/L with the detection limit of0.47μmol/L. The sensor not only shows high selectivity, but also exhibits good stability and reproducibility. It can be used at least85times or stored at room temperature for28days without losing its response sensitivity. The sensor was satisfactorily applied to the determination of PPT in podophyllum hexandrum and human serum samples with the relative standard deviation (RSD) below3.9%and recovery ranging from95.0%to103.3%.4. A new electrochemical sensor for the determination of allantoin (ALL) was prepared. The graphene was first coated on a glassy carbon electrode, and then the sensor was prepared by electropolymerizing ophenylenediamine (o-PD) on the graphene modified glassy carbon electrode (G/GCE) in the presence of ALL as template. The structure and properties of the electrochemical sensor was characterized by scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and so on. After the experimental parameters was optimized, the modified GCE can be used for the determination of allantoin in the range of0.0222～122μmol/L with the detection limit of6.79nmol/L. In brief, the ALL-MIM/G/GCE has the advantages as simple preparation, good reproducibility and high stability, thus, it is suitable for sensitive detection of allantoin in complex matrix.