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1、 Acid molecularly imprinted membrane electrochemical biosensor Of: Li Huai-Fen Hsieh Cheng-Gen Xie Chunyan Zhou Hankun Abstract salicylic acid as the template molecule, using cyclic voltammetry, the formation of polypyrrole electropolymerization to a fixed potential of molecular imprinting removed b
2、y peroxide, salicylic acid was prepared by molecular imprinting membrane electrode. The imprinted electrode can promote the water Yang acid electro-oxidation process, effectively avoid structural analogs (such as the determination of benzoic acid to its interference. Cyclic voltammetry for electroch
3、emical detection, when the enrichment time was 10 min, phosphate buffer solution of pH = 6.86 when In the 1.0 10-6 2.0 10-3 mol / L concentration range, the oxidation peak current and the concentration of salicylic acid showed a good linear relationship, the detection limit was 0.8 mol / L, with the
4、 increase of molecular imprinted membrane electrode Standard samples were analyzed, recoveries were 94.6% 103.4%. Keywords: salicylic acid, molecular imprinting, electro pyrrole, modified electrode, the sensor Abstract Molecular imprinted film modified glassy carbon electrode was prepared by electro
5、chemical polymerization of pyrrole with the cyclic voltammetry in the presence of template molecular, salicylic acid. The template molecules were removed from the modified electrode surface by over oxidized at 1.3V in the solution of 0.2 mol / L Na2HPO4 for 10 min. The modified electrodes can effect
6、ively promote electrochemical oxidation process of salicylic acid in the surface of electrode and avoid interference of structural similar substance such as benzoic acid. Cyclic voltammetry was employed in the electrochemical measurements. The experimental results show that the optimum acidity of ba
7、ckground solution is pH 6.86 and the optimum incubation is 10 min. The linear response curve was obtained from 1.0 10-6 mol / L to 2.0 10-3 mol / L, with the detection limit of 8.0 10-7 mol / L. The imprinted electrode has been applied to the analysis of salicylic acid in the simulated samples with
8、recovery rates ranging from 94.6% to 103.4%. Keywords Salicylic acid, molecular imprinted polymer, electrochemical polymerization of pyrrole, modified electrode, sensor 1 Introduction Molecular imprinting is a template molecule and functional monomer by covalent or non-covalent role in the polymeriz
9、ation process will be fixed in the cross-linked template polymer network, remove the template molecules, leaving the shape with the template molecule and function-based matching holes formed in the synthesis of materials with high affinity and high selectivity of molecular recognition sites 1 4. As
10、the molecular imprinted polymer with the structure-activity predetermination, specific recognition and wide availability, etc. advantages, so that in the adsorption and separation, chemical and biological sensors, selective catalysts are widely used in research 5,6. Salicylic acid is a used in medic
11、ine, spices, dyes and pesticides, and other aspects of important organic chemical raw materials. Establish a highly efficient method for rapid detection of salicylic acid content is important. At present, the main methods for determination of salicylic acid photometric , fluorescence, HPLC and biose
12、nsor method. by chemical polymerization of salicylic acid salicylic acid imprinted materials have been used in the separation and detection 7,8, the use of electronic molecular imprinting polymerization membrane sensor has been reported 9 11, but electricity polymerization acid molecularly imprinted
13、 membrane sensor is also rarely reported. In this study, molecular imprinting technique, using cyclic voltammetry at a glassy carbon electrode prepared by the salicylaldehyde acid as the template molecule imprinted polypyrrole film electrode was investigated imprinted electrodes and structural analo
14、gues of salicylic acid electrochemical behavior, the establishment of a highly selective detection of salicylic acid analysis. 2 Experimental part 2.1 Instruments and reagents LK98B Electrochemical Analysis System (Tianjin blue LeCroy Corporation, a three-electrode system to glassy carbon electrode
15、( = 2 mm, or molecularly imprinted film modified glassy carbon electrode as working electrode, saturated calomel electrode as reference electrode, platinum wire electrode as the counter electrode. pyrrole (AR distilled before use, salicylic acid, benzoic acid and other reagents were of analytical gr
16、ade, double distilled water experiments. 2.2 Preparation of imprinted membrane electrode 0.3 m Al2O3 powder with a glassy carbon electrode polished to a mirror, then followed by ultrasonic cleaning with ethanol and water. Will be placed in three-electrode system containing 0.05 mol / L pyrrole, 0.01
17、mol / L salicylic acid and 0.1 mol / L KCl 0.05 mol / L phosphate buffer (pH 6.86 in the. pass after 10 min of nitrogen in the potential range of -1.0 1.0 V within 10 laps cyclic voltammetry, scan rate of 0.05 V / s. 0.2 and then placed on modified electrode mol / L Na2HPO4 solution, under constant
18、potential electrolysis at 1.3 V 10 min, carried out on the polypyrrole oxidation treatment to remove the molecular imprinted polypyrrole films, which are acid molecularly imprinted membrane electrode. In addition to polymer solution without acid, the non-imprinted membrane electrode membrane electro
19、de process and the same blot. 2.3 Electrochemical measurements Peroxide treatment, the molecular imprinted membrane electrodes were placed 0.1 mol / L KCl 0.05 mol / L phosphate buffer (pH 6.86, at -1.0 1.0 V potential range for cyclic voltammetry, to restore the polypyrrole skeleton The positive na
20、ture, and then blot the electrode immersed in a certain concentration of salicylic acid containing 0.05 mol / L phosphate buffer (pH 6.86 in the enrichment of 10 min, the electrode re-combination of salicylic acid, rinse the electrode with phosphate buffer solution, -1.0 1.0 V in the potential range
21、 to 0.05 V / s scan rate for cyclic voltammetry, the redox peak current record. 3 Results and discussion 3.1 acid blotting membrane electrode material Figure 1 is a salicylic acid imprinted membrane electrode cyclic voltammetry curves at -0.8 V appears only in an irreversible reduction peak and the
22、peak current decreases, the value of the peak potential shifted to positive potential scan rate (scan rate ) 0.05 V / s. not imprinted electrode cyclic voltammetry was no reduction at -0.8 V at the peak. Therefore, this reduction peak is due to the formation of acid reduction. As in the phosphate bu
23、ffer solution (pH 6.86 in mainly negative electrical properties of salicylic acid, salicylic acid with a negatively charged molecules through electrostatic interaction with positive charge can be embedded in polypyrrole skeleton, with the power polymerization reaction, embedded in polypyrrole skelet
24、on is embedded in the salicylic acid in polypyrrole in the formation of salicylic acid imprinted loci. 3.2 salicylic acid at a bare glassy carbon electrode on the electrochemical behavior Figure 2 shows the acid at a bare glassy carbon electrode the cyclic voltammogram. When the bottom liquid oxygen
25、 through N2 10 min, 1 circle scan, the cyclic voltammetry curves of 0.9 and -0.7 V in oxidation and reduction occurring at the current peak, when the scan after 5, -0.7 V reduction peak current at the stable, and 0.9 V at the oxidation peak current decreases to almost disappear. This is due to aroma
26、tic compounds containing hydroxyl groups in the more positive Under the oxidation potential is similar to the structure of phenoxy anion, and then transformed into benzoquinone structure, the occurrence of dimeric or oligomeric 10. oligomers further growth of polymer chain growth, leading to contami
27、nation of the electrode is the peak current decrease Meanwhile, the oligomers can be lower than the polymer material prior to oxidation potentials, the CV curves in 0.2 V oxidation peak appears at smaller (as shown in Figure 2. Links to free paper download .com 3.3 acid blotting membrane electrode i
28、n the electrochemical behavior Figure 3 curves a and b, respectively, of salicylic acid in the imprinted and non-imprinted membrane electrode membrane electrode cyclic voltammetry. With the bare electrode is different when using the imprinted membrane electrode, the cyclic voltammograms at -0.3 and
29、- near the 0.5 V oxidation peak current of the larger peak and reduction peak, rather than the imprinted membrane electrode -0.5 V appears only in the smaller peak current of the reduction peak. relative to the bare electrode and non-imprinted electrode, the imprinted membrane electrode containing a
30、 substantial amount of salicylic acid template to match the shape, size, and a suitable functional group interaction of the hole, making it easier for Selective Adsorption of salicylic acid molecules and the imprinted membrane electrode embedded in the hole, so that the electrode surface imprinted w
31、ith salicylic acid concentration was significantly increased, the peak current is also increased, In addition, because the structure of salicylic acid molecules embedded in the hole match, you can effectively inhibit the oxidation of salicylic acid in the electrochemical polymerization process of th
32、e occurrence of side effects, so that the water Yang acid in the imprinted membrane electrode more susceptible to oxidation and reduction reactions. Therefore, compared with bare electrodes, salicylic acid in the oxidation peak potential blot on the negative electrode to the move, the reduction peak
33、 potential moving forward. Figure 3c that after peroxide molecule Cyclic voltammetry curves of imprinted membrane, almost no redox peaks. This shows that molecular imprinted membrane electrode template molecule can be fully peroxide treatment and elution. Experiments show that the imprinted membrane
34、 electrode reused 30 times, the oxidation peak current change <10%. Imprinted membrane electrode selectivity of 3.4 Structurally similar to salicylic acid as disruptor substances investigated imprinted membrane electrode and bare electrode selectivity of salicylic acid. Benzoate bare glassy carbo
35、n electrode in the electrochemical behavior of salicylic acid is very similar (Figure 4A, curve a, at 0.9 V at both the emergence of a distinct oxidation peak, and therefore the bare glassy carbon electrode determination of salicylic acid molecules with significant interference. The imprinted membra
36、ne electrode using salicylic acid, benzoic acid is almost not imprinted electrode electrochemical oxidation reduction reaction occurs, cyclic voltammetry curves almost no corresponding redox peaks (Fig. 4B, curve b, while the spatial structure and structural analogues of benzoic acid does not match
37、the force is weak. modification of salicylic acid Molecular imprinted membrane with selective recognition ability of salicylic acid to effectively prevent the molecular structure of salicylic acid analogues interfere with the determination to achieve high selectivity in the detection of salicylic ac
38、id. 3.5 Western blot analysis of membrane electrode application Figure 5 shows the imprinted membrane electrode in different concentrations of salicylic acid in the concentration 10 min after the cyclic voltammetry (arrow indicated the direction of becoming a small concentration of salicylic acid wi
39、th salicylic acid concentration, the oxidation and reduction peak currents were gradually increasing. Under the optimized experimental conditions, the salicylic acid concentration 1.0 10-6 2.0 10-3 mol / L range and its peak current showed a good linear relationship (Figure 5 illustration, the linea
40、r regression equation the ipa (A) = 26 + 1.1 105C (mol / L), correlation coefficient r = 0.9997, detection limit was 0.8 mol / L (S / N = 3. of 4.0 10-4 mol / L salicylic parallel determination of acid 7, the relative standard deviation (RSD) was 3.5%. In order to further verify the imprinted membra
41、ne electrode for the analysis of the feasibility of salicylic acid in 5.0 10-4 mol / L benzoic acid were added 5.0 10 -6, 5.0 10-5 and 5.0 10-4 mol / L salicylic acid for recycling experiments, recoveries were 94.6%, 103.4% and 98.6%. References 1 Xie CG, Liu BH, Wang ZY, Gao DM, Guan GJ, Zhang Z P.
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