Development And Application Of Several Molecularly Imprinted Electrochemical Sensors

Recently, molecular imprinting technology, which is known as a method for preparation of polymeric materials liked molecularly imprinted polymers (MIPs) and molecularly imprinted membranes (MIMs), has become a well-established analytical tool. Because the molecular imprinting process can introduce the recognition properties into synthetic materials by using appropriate template, MIPs/MIMs own the surface cavities complementary to the template molecule and have high selective recognition to the template molecules over its structurally related compounds. This advantage together with its other advantages over the biological recognition element, liked stability, reusability, simplicity and low cost in preparation, make MIPs/MIMs become ideal candidates as recognition elements for sensors.At present, the literatures of electrochemical sensor based on molecules or ions imprinted polymers (MIPs)/membrane have quite a few reports, but their preparation methods are lack. Moreover, sensitivity, especially imprinted sensors by imprinting on bare electrode directly needs to be improved. At the same time, the researches of imprinted sensors about a lot of important analysis objects, such as cholesterol, anti-cancer active ingredients of artemisinin, colchicine, podophyllotoxin and platinum group metal ions such as Pt(IV), Pd(II), Rh(III) have not been reported. Therefore, this paper chose the artemisinin, colchicine, podophyllotoxin and Pt(IV), Pd(II) and Rh(III) as the research objects, and through the introduction of nano materials and nano composite materials such as grapheme/gold nanoparticles composites improving the conductivity and specific surface area of sensors. A series of molecules/ions electrochemical sensors were constructed by different preparation methods. Meanwhile, the recognition mechanism of these sensors was preliminary discussed, and their application were conducted the system research. The main contents are listed as follows:1. A novel electrochemical sensor was constructed by in-situ polymerization of ART- imprinted membranes (ART-MIMs) on the surface of graphene (G) modified glassy carbon electrode (GCE) using acrylamide (AM) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent after the experimental parameters for the preparation of ART-MIMs such as functional monomer, molar ratio of template, monomer and cross-linking agent together with extraction condition were optimized. Under the optimal conditions, the sensor named as ART-MIM/G/GCE exhibited a good selectivity, high sensitivity and considerably better resistance against some analogues of artemisinin such as dihydroartemisinin (DHA), artemether (ARM) and artesunate (ARTS). The calibration graph for the determination of artemisinin by the sensor was linear in the range of1.0×10-8mol L-1to4.0×10-5mol L-1with the detection limit of2.0×10-9mol L-1. Meanwhile, this sensor possessed of good regeneration, stability and practicability. The sensor had been successfully used to analyze artemisinin in annua samples, and the average recoveries were between100.0%～110.5%with RSD<3.1%.2. An imprinted electrochemical sensor based on G/AuNPs compound material and molecular imprinting polymer (MIP) membranes for sensitive detection of colchicines was presented.The film formed by in-situ polymerization of colchicines imprinted membranes on the surface of G/AuNPs modified glassy carbon electrode (GCE) using methyl acrylic acid (MAA) as functional monomer. Under optimal conditions, the MIPs sensor exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of1.2×10-8～1.0×10-4mol L-1with the detection limit of4.8x10-9mol L-1. The sensor had been successfully used to analyze colchicines in drug samples without complex pretreatment. Meanwhile, the average recoveries were higher than97.5%with RSD<3.1%.3. An electrochemical sensor for podophyllotoxin (PPT) based on the molecular imprinting polymer (MIP) membranes had been constructed. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of PPT as template, and then removing the template by immersing the modified GCE in ethanol. Experimental parameters such as the types of monomer, scan cycles, concentration of o-PD and extraction condition were optimized. Under optimal conditions, the sensor exhibited a good selectivity and high selectivity. A good linearity was obtained in the range of4×1-8mol-1to3.2×10-5mol L-1with an estimated detection limit of4.8×10-9mol L-1. The sensor had been applied to the determination of PPT in podophyllum hexandrum and human serum samples with satisfactory results.4. An electrochemical sensor for cholesterol based on the grephene and molecular imprinting polymer (MIP) membranes had been constructed. Molecularly imprinted polymers (MIPs) were synthesized by electropolymerization using cholesterol as the template, and phenol as the monomer. The surface feature of the modified electrode was characterized by cyclic voltammetry (CV). The proposed sensor was tested by differential pulse voltammetry (DPV). Several important parameters controlling the performance of the molecularly imprinted sensor were investigated and optimized. The results showed that the grephene films showed improved conductivity and electrochemical performances. Under the optimal conditions, a linear ranging from8.0×10-8mol L-1to2.0×10-4mol L-1for the detection of cholesterol was observed with the detection limit of5.6×10-8mol L-1(S/N=3). This imprinted electrochemical sensor was successfully employed to detect cholesterol in real samples and the average recoveries were between99.8%～102.0%with RSD<2.9%.5. To develop a convenient method for sensitive and selective determination of platinum in complicated matrices, an electrochemical sensor was studied by in-situ polymerization of Pt(IV) ion-imprinted membranes (Pt(IV)-IIMs) on the surface of glassy carbon electrode (GCE). After the experimental parameters for the preparation of Pt(IV)-IIMs such as functional monomer, molar ratio of template, monomer and cross-linking agent together with extraction condition were optimized, a sensor with good regeneration, high stability and specific recognition to Pt(IV) was obtained by modifying GCE with Pt(IV)-IIMs prepared in acetonitrile using allyluread (NAU) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent, azobisisobutyronitrile (AIBN) as initiator under the molar ratio of template (H2PtCl6), NAU and EGDMA as1:4:40. The resulting sensor named as Pt(IV)-IIMs/GCE exhibits high response sensitivity to Pt(IV) in phosphate buffer (pH5.29). The calibration graph for the determination of Pt(IV) by this sensor is linear in the range of2.0×10-8～2.5×l0-4mol L-1with the detection limit of4.0×10-9mol L-1. There is no metal ions tested at the concentration25times higher than that of Pt(IV) interfered in the determination. The sensor was successfully applied to determine platinum in catalyst and plant samples with RSD of less than3.0%(n=5) and recoveries in the range of97.8-103.6%.6. This work reports an amperometric sensor for selective recognition and sensitive determination of palladium ions using glassy carbon (GC) electrode modified with a novel ion imprinted polymeric nanobeads (IIP) and graphene. The ion imprinted polymers film was prepared by in-situ polymerization in acetonitrile using allyluread (NAU) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent, azobisisobutyronitrile (AIBN) as initiator under the molar ratio of template (PdCl2), NAU and EGDMA as1:4:40. Amperometric i-t curve method was applied as the determination technique. The designed modified electrode was shown a linear response in the range of2.0×10-8-2.0×10-4mol L-1of Pd(II) ion with a detection limit of6.4×10-9mol L-1. The sensor was successfully applied to determine palladium in catalyst and plant samples with RSD of less than3.3%(n=5) and recoveries in the range of99.2-106.5%.7. In this work, a new nano-structured ion imprinted polymer (IIP) was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. A carbon paste electrode modified with IIP-nanoparticles was used for fabrication of a Rh(III) sensitive electrode. The IIP modified electrode showed a considerably higher response, compared bedded with non-imprinted polymer (NIP). The introduced sensor showed a linear range of1.00x10-8～3.0x10-5mol L-1and detection limit of6.0nmol L-1(S/N=3). The sensor was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than3.3%(n=5) and recoveries in the range of95.5-1.02.5%.