Quartz crystal microbalance sensor for organic vapor detection based on molecularly imprinted polymers

Molecularly imprinted polymers on quartz crystal microbalances (QCM) are examined for their ability to detect vapors of small organic molecules with greater sensitivity and selectivity than the traditional amorphous polymer coatings. Hydroquinone and phenol serve as noncovalently bound templates that generate shape-selective cavities in a poly(acrylic) or poly(methacrylic) polymer matrix. The imprinted polymers are immobilized on the piezoelectric crystal surface via a precoated poly(isobutylene) layer. The behavior of the imprinted polymer films is characterized by the dynamic and steady-state response of the QCM frequency to pulses of organic vapors in dry air. The apparent partition coefficients are determined for imprinted and nonimprinted polymers prepared by two synthetic methods and for varying mole ratios of template to monomer. The hydroquinone-imprinted polymers and, to a lesser extent, the phenol-imprinted polymers exhibit greater sensitivity and higher selectivity than the nonimprinted polymers toward organic vapors that are structurally related to the templates. These results indicate that molecularly imprinted polymers are promising for the development of selective piezoelectric sensors for organic vapor detection.     

Determination of clenbuterol in bovine liver by combining matrix solid-phase dispersion and molecular imprinted solid-phase extraction followed by liquid chromatography/electrospray ion trap multiple-stage mass spectrometry

Matrix solid-phase dispersion (MSPD) is a new sample pretreatment for solid samples. This technique greatly simplifies sample pretreatment but, nonetheless, the extracts often still require an extra cleanup step that is both laborious and time-consuming. The potential of combining MSPD with molecularly imprinted solid-phase extraction (MISPE) was investigated in this study. Liver samples were ground in a mortar with C18 sorbent and the homogenized mixture packed into an SPE cartridge and placed on top of a MISPE cartridge. Subsequently, clenbuterol was eluted from the MSPD cartridge onto the MISPE cartridge using acetonitrile containing 1% acetic acid. The ability of the molecularly imprinted polymer to selectively adsorb analyte in acetonitrile was exploited for re-extracting clenbuterol directly from this acetonitrile extract via the double cartridge tandem system. The analyte was eluted from the MISPE cartridge using acidified methanol. A clear eluate was obtained, which was subsequently evaporated, redissolved, and analyzed by HPLC electrochemical detection (ECD) or ion trap mass spectrometry (LC/IT-MS). The MISPE cartridge used in this study was imprinted using bromoclenbuterol, a structural analogue of clenbuterol, as the template. These MISPE cartridges showed excellent stability. The complete extraction procedure was rapid, and recoveries exceeded 90% for the target analyte. The method detection limit for the LC/IT-MS procedure was < 0.1 microg/kg. This method, therefore, satisfies the stringent requirements of European Union regulation EEC 2377/90.     

Method for synthesis and screening of large groups of molecularly imprinted polymers

A technique for the synthesis of molecularly imprinted polymers (MIPs) in small scale (～55 mg) coupled with direct in situ processing and batch rebinding evaluation is reported. The primary assessment is based on quantification by HPLC or UV absorbance measurement of the amount of template released from the polymer in a given solvent. This method allows a rapid screening of the parameters of importance to reach a desired level of binding affinity capacity and selectivity for a given target molecule. This was demonstrated for the triazine herbicide terbutylazine, where an initial screening was performed for the type of functional monomer used in the MIP preparation. Thus among the six functional monomers tested, methyl methacrylate, 4-vinylpyridine, and N-vinyl-α-pyrrolidone led to rapid and quantitative extraction whereas methacrylic acid and (trifluoromethyl)acrylic acid led to polymers that retained the template the most. After having established useful functional monomers, a secondary screening for selectivity was performed. In this, nonimprinted blank polymers were prepared and a normal batch rebinding evaluation was performed. The polymer showing the highest selectivity was the one prepared using methacrylic acid as functional monomer. This polymer was shown to strongly retain chlorotriazines including atrazine when a normal-scale batch of the polymer was evaluated in chromatography.     

Preparation of imprinted polymers at surface of magnetic nanoparticles for the selective extraction of tadalafil from medicines

In this paper, highly selective core-shell molecularly imprinted polymers (MIPs) of tadalafil on the surface of magnetic nanoparticles (MNPs) were prepared. Three widely used functional monomers 2-(trifluoromethyl) acrylic acid (TFMAA), acrylic acid (AA), and methacrylic acid (MAA) were compared theoretically as the candidates for MIP preparation. MIP-coated magnetic nanoparticles (MIP-coated MNPs) showed large adsorption capacity, high recognition ability, and fast binding kinetics for tadalafil. Furthermore, because of the good magnetic properties, MIP-coated MNPs can achieve rapid and efficient separation with an external magnetic field simply. The resulting MIP-coated MNPs were used as dispersive solid-phase extraction (DSPE) materials coupled with HPLC-UV for the selective extraction and detection of tadalafil from medicines (herbal sexual health products). Encouraging results were obtained. The amounts of tadalafil that were detected from the herbal sexual health product was 43.46 nmol g(-1), and the recoveries were in the range of 87.36-90.93% with the RSD < 6.55%.     

Molecularly imprinted polymeric fibers for solid-phase microextraction

Solid-phase microextraction (SPME) is widely used in analytical laboratories for the analysis of organic compounds, thanks to its simplicity and versatility. However, the current commercially available fibers are based on nonselective sorbents, making difficult in some cases the final determination of target compounds by chromatographic techniques. Molecularly imprinted polymers (MIPs) are stable polymers with selective molecular recognition abilities, provided by the template used during their synthesis. In the present work, a simple polymerization strategy allowing the obtainment of molecularly imprinted polymeric fibers to be used in SPME is proposed. Such a strategy is based on the direct synthesis of molecularly imprinted polymeric fibers (monoliths) using silica capillaries as molds, with silica being etched away after polymerization. The system propazine:methacrylic acid was used as a model for the preparation of molecularly imprinted fibers, and its ability to selectively rebind triazines was evaluated. Variables affecting polymer morphology (i.e., polymerization time, fiber thickness) and binding-elution of target analytes (i.e., solvents, time, temperature) were studied in detail. The imprinted fiber showing the best performance in terms of selectivity and affinity for triazines was successfully applied to the extraction of target analytes from environmental and food samples.     

Molecular engineering of fluorescent penicillins for molecularly imprinted polymer assays

The interaction of seven novel fluorescent labeled beta-lactams with a library of six polymer materials molecularly imprinted (MI) with penicillin G (PenG) has been evaluated using both radioactive and fluorescence competitive assays. The highly fluorescent competitors (emission quantum yields of 0.4-0.95) have been molecularly engineered to contain pyrene or dansyl labels while keeping intact the 6-aminopenicillanic acid moiety for efficient recognition by the cross-linked polymers. Pyrenemethylacetamidopenicillanic acid (PAAP) is the tagged antibiotic that provides the highest selectivity when competing with PenG for the specific binding sites in a MI polymer prepared with methacrylic acid and trimethylolpropane trimethacrylate (10:15 molar ratio) in acetonitrile in the presence of PenG. Molecular modeling shows that recognition of the fluorescent analogues of PenG by the MI material is due to a combination of size and shape selectivity and demonstrates how critical the choice of label and tether chain is. PAAP has been applied to the development of a fluorescence competitive assay for PenG analysis with a dynamic range of 3-890 muM in 99:1 acetonitrile-water solution. Competitive binding studies demonstrate various degrees of cross-reactivity for some antibiotics derived from 6-aminopenicillanic acid, particularly amoxicillin, ampicillin, and penicillin V (but not oxacillin, cloxacillin, dicloxacillin, or nafcillin). Other antibiotics, such as chloramphenicol, tetracycline, or cephapirin, do not compete with PAAP for binding to the imprinted polymer. The MI assay has successfully been tested for PenG analysis in a pharmaceutical formulation.     

Chemical grafting of molecularly imprinted homopolymers to the surface of microplates. Application of artificial adrenergic receptor in enzyme-linked assay for beta-agonists determination

A technique for coating of microplate wells with a molecularly imprinted polymer (MIP), specific for epinephrine, is presented. 3-Aminophenylboronic acid was polymerized in the presence of epinephrine using oxidation of the monomer by ammonium persulfate. This process resulted in the grafting of a thin polymer layer onto the polystyrene surface of the microplates. The polymer affinity was determined by an enzyme-linked assay using a conjugate of horseradish peroxidase and norepinephrine (HRP-N). It was found that imprinting resulted in increased affinity of the polymer toward HRP-N and epinephrine. Influence of the buffer pH and concentration on the polymer affinity was analyzed. It was shown that the MIP-coated microplates could be used for assay development and drug screening. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to traditional antibodies or receptors, used in ELISA.     

农药对硫磷分子印迹聚合物合成及亲和性评价

对硫磷为模板分子,甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,热引发沉淀聚合法合成对硫磷分子印迹聚合物(MIP)。通过计算机模拟和紫外分析阐述模板与功能单体的分子间作用;通过电镜观察和平衡吸附试验讨论引发剂用量与聚合物性质关系;通过吸附试验Scatchard分析测得最大吸附量为3.92μmol/g,平衡解离常数为91.7μmol/L,且具有较好的吸附特异性。该分子印迹聚合物性能优良,有望应用于环境中对硫磷的富集和检测。     

Probing the recognition of molecularly imprinted polymer beads

A facile, robust and cost-effective suspension polymerisation methodology for the generation of ibuprofen molecularly imprinted polymers in bead formats was evaluated. Mineral oil was employed as the continuous phase whereby microdroplets of the pre-polymerisation mixture were formed through vigorous agitation, followed by photo-polymerisation resulting in formation of imprinted beads. For comparison purposes, irregular particles were also prepared from monolith polymers. Physical characteristics of the imprinted polymers were investigated using scanning electron microscope, particle size distribution, nitrogen sorption porosimetry and solvent swelling ratios, with subsequent correlation of these parameters to analyte rebinding performance. Overall, an increase in affinity was observed with decreasing the degree of cross-linking, however, specific rebinding was compromised. An inverse relationship between polymer affinity for the template and surface area was identified, while solvent swelling ratios were directly related to polymer affinity. Correlation between pre-polymerisation studies and polymer binding performance highlighted the significance of employing the polymerisation solvent in template rebinding in order to achieve superior recognition capabilities. Additionally, shape selectivity of binding sites was demonstrated by the decreased binding performance of template structural analogues to the imprinted polymer.     

Analysis of nicotine and its oxidation products in nicotine chewing gum by a molecularly imprinted solid-phase extraction

Chromatographic stationary phases showing exceptional selectivity for nicotine can be prepared by the technique of molecular imprinting. Such phases were used in the search for a rapid cleanup step for nicotine and some of its oxidation products in chewing gum formulations. Thus, using an organic mobile phase, the nicotine analytes from chewing gums dissolved in nonpolar solvent were retained, whereas the nonpolar matrix eluted close to the void peak. A subsequent switch to an acidic mobile phase resulted in elution of the analytes as one sharp peak. Due to weak binding of the less basic oxidation products, other imprinted polymers were tested, and the solid-phase extraction procedure was optimized. Polymers were prepared using various functional and cross-linking monomers, templates, porogens and thermal treatments. This resulted in phases that, when compared with a nonimprinted or a C18 reversed-phase column, showed significantly higher recoveries of the analytes. Furthermore, no bleeding of template from the phases could be detected. The cleanup step was coupled off-line to reversed-phase HPLC, and the efficiency of the analysis was compared with and without the cleanup step. Three out of four analytes were quantitatively recovered using the imprinted phase, whereas, using the nonimprinted phase, only nicotine was recovered. Without the cleanup step, none of the analytes could be determined using the reversed-phase HPLC method.     

Extraction and purification of penicillin G from fermentation broth by water-compatible molecularly imprinted polymers

Highly selective molecularly imprinted polymer (MIP) was synthesized by using methacrylic acid as functional monomer, trimethylolpropane trimethacrylate as cross-linker, chloroform as porogen and penicillin G potassium as template molecule. These imprinted polymers were used as solid-phase extraction sorbent for the selective extraction of penicillin G from the fermentation broth samples. Various parameters affecting the extraction efficiency of the MIP particles such as; effects of pH, wash and eluent solutions were evaluated. Molecular recognition properties and selectivity of these MIPs were estimated and the obtained results revealed high affinity for the target antibiotic. Equilibrium binding experiments were done to assess the performance of the MIP relative to non imprinted polymer (NIP). After optimizing the extraction parameters in molecularly imprinted solid-phase extraction (MISPE), successful imprinting was confirmed by comparison of the recoveries from the fermentation broth, ranging between 24–26% (RSD 4.1–4.5%, n = 4) for the NIPs and 83–88% (RSD 3.1–3.4%, n = 4) for the MIPs.     

Molecularly imprinted polymers as antibody mimics in automated on-line fluorescent competitive assays

An automated molecularly imprinted sorbent based assay (MIA) for the rapid and sensitive analysis of penicillin-type beta-lactam antibiotics (BLAs) has been developed and optimized. The polymers were prepared using penicillin G procaine salt as template (PENGp) and a stoichiometric quantity of a urea-based functional monomer to target the single oxyanionic species in the template molecule. Highly fluorescent competitors (emission quantum yields of 0.4-0.95), molecularly engineered to contain pyrene labels while keeping intact the 6-aminopenicillanic acid moiety for efficient recognition by the cross-linked polymers, have been tested as analyte analogues in the competitive assay. Pyrenemethylacetamido penicillanic acid (PAAP) was the tagged antibiotic providing for the highest selectivity when competing with PenG for the specific binding sites in the molecularly imprinted polymer (MIP). Upon desorption from the MIP, the emission signal generated by the PAAP was related to the antibiotic concentration in the sample. The 50% binding inhibition concentration of penicillin G standard curves was at 1.81 x 10(-6) M PENG, and the detection limit was 1.97 x 10(-7) M. The sensor showed a dynamic range (normalized signal in the 20 to 80% range) from 6.80 x 10(-7) to 7.21 x 10(-6) M (20-80% binding inhibition) PENG in acetonitrile:HEPES buffer 0.1 M at pH 7.5 (40:60, v/v) solutions. Competitive binding studies demonstrated various degrees of cross-reactivity with penicillin-type beta-lactam antibiotics such as ampicillin (71%), oxacillin (66%), penicillin V (56%), amoxicillin (13%), and nafcillin (46%) and a lower response to other isoxazolyl penicillins such as cloxacillin (27%) and dicloxacillin (16%). The total analysis time was 14 min per determination, and the MIP reactor could be reused for more than 150 cycles without significant loss of recognition. The automatic MIA has been successfully applied to the direct analysis of penicillin G in spiked urine samples with excellent recoveries (mean value 92%). Results displayed by comparative analysis of the optimized MIA with a chromatographic procedure for penicillin G showed excellent agreement between both methods.     

Adsorption on molecularly imprinted polymers of structural analogues of a template. Single-component adsorption isotherm data

The equilibrium adsorption isotherms on two otherwise identical polymers, one imprinted with Fmoc-L-tryptophan (Fmoc-L-Trp) (MIP), the other nonimprinted (NIP), of compounds that are structural analogues of the template were acquired by frontal analysis (FA) in an acetonitrile/acetic acid (99/1 v/v) mobile phase, over a wide concentration range (from 0.005 to 50 mM). These analogues were Fmoc-L-tyrosine, Fmoc-L-serine, Fmoc-L-phenyalanine, Fmoc-glycine (Fmoc-Gly), Fmoc-L-tryptophan pentafluorophenyl ester (Fmoc-L-Trp(OPfp)), and their antipodes. These substrates have different numbers of functional groups able to interact with the 4-vinylpyridine groups of the polymer. For a given number of the functional groups, these substrates have different hydrophobicities of their side groups (as indicated by their partition coefficients (log P(ow)) in the octanol-water system (e.g., from 4.74 for Fmoc-Trp to 2.53 for Fmoc-Gly)). Statistical results from the fitting of the FA data to Langmuirian isotherm models, the calculation of the affinity energy distribution, and the comparison of calculated and experimental band profiles show that all these sets of FA data are best accounted for by a tri-Langmuir isotherm model, except for the data of Fmoc-L-Trp(OPfp) that are best modeled by a simple Langmuir isotherm. So, all compounds but Fmoc-L-Trp(OPfp) find three different types of adsorption sites on both the MIP and the NIP. The properties of these different types of sites were studied systematically. The results show that the affinity of the structural analogues for the NIP is controlled mostly by the number of the functional groups on the substrates and somewhat by the hydrophobicity of their side groups. These two factors control also the MIP affinity toward the enantiomers of the structural analogues that have a stereochemistry different from that of the template. In contrast, the affinity of the highest affinity sites of the MIP toward the enantiomers of these structural analogues that have the same stereochemistry as the template is highest for the imprinted molecule (Fmoc-L-Trp). The separation of the template from the substrates with the same stereochemistry is influenced by the number of the functional groups on the substrates that can interact with the highest affinity sites on the MIP. The separation of the enantiomers of the analogues of the substrates was also achieved on the MIP, and these enantiomeric separations are influenced by the hydrophobicity of the substrates.     

Development and characterization of molecularly imprinted polymers for controlled release of citalopram

In this work, the use of molecularly imprinted polymers (MIPs) for citalolpram as anti-depressant drug was studied. Imprinted polymers were prepared from methacrylic acid (MAA; functional monomer), ethylene glycol dimethacrylate (EGDMA; cross-linker), and citalopram (as a drug template) using bulk polymerization method. The polymeric devices were further characterized by FT-IR, thermogravimetric analysis, scanning electron microscopy, and binding experiments. The dissolution media employed in controlled release studies were hydrochloric acid at the pH level of 4.3 and phosphate buffers, at pH levels of 7.2 and 10.1, maintained at 37.0 and 25.0 ± 0.5°C. Results showed the ability of MIP polymers to control the release of citalopram. In all cases, the imprinted polymers showed a higher affinity for citalopram and a slower release rate than the nonimprinted polymers. At the pH level of 4.3 and at the temperature of 25°C, slower release of citalopram imprinted polymer occurred.     

Nanoporous organosilicas as preconcentration materials for the electrochemical detection of trinitrotoluene

We describe the use of nanoporous organosilicas for rapid preconcentration and extraction of trinitrotoluene (TNT) for electrochemical analysis and demonstrate the effect of template-directed molecular imprinting on TNT adsorption. The relative effects of the benzene (BENZ)- and diethylbenzene (DEB)-bridged organic-inorganic polymers, having narrow or broad pore size distributions, respectively, on electrochemical response and desorption behavior were examined. Sample volumes of 0.5-10 mL containing 5-1000 ppb TNT in a phosphate-buffered saline buffer were preconcentrated in-line before the detector using a microcolumn containing 10 mg of imprinted BENZ or DEB. Square-wave voltammetry was used to detect the first reduction peak of TNT in an electrochemical flow cell using a carbon working electrode and a Ag/AgCl reference electrode. Imprinted BENZ released TNT faster than imprinted DEB with considerably less peak tailing and displayed enhanced sensitivity and an improvement in the limit of detection (LOD) owing to more rapid elution of TNT from that material with increasing signal amplitude. For imprinted BENZ, the slope of signal versus concentration scaled linearly with increasing preconcentration volume, and for preconcentrating 10 mL of sample, the LOD for TNT was estimated to be 5 ppb. Template-directed molecularly imprinted DEB (TDMI-DEB) was 7-fold more efficient in adsorption of TNT from aqueous contaminated soil extract than nonimprinted DEB.     

Molecular recognition in a propazine-imprinted polymer and its application to the determination of triazines in environmental samples.

An analytical methodology for the determination of triazines in environmental samples incorporating a molecularly imprinted solid-phase extraction (MISPE) process using a propazine-imprinted polymer was developed. Two different polymers were prepared using acetonitrile or toluene as porogen, and their optimum loading, washing, and elution conditions were established. Although both polymers were able to recognize several chlorotriazines (propazine, atrazine, simazine, desethylatrazine, and desisopropylatrazine), the polymer prepared in toluene showed the best performance and was also capable of recognizing a methylthiotriazine (prometryn). A binding study carried out in this polymer demonstrated that it possesses heterogeneous binding sites with different binding abilities. From this study, it was also concluded that desethylatrazine and desisopropylatrazine displace the other triazines at high concentrations, including the template molecule. The accuracy and selectivity of the MISPE process developed was verified using a certified reference material for drinking water containing atrazine and simazine among other commonly used pesticides. Finally, the MISPE procedure was successfully applied to the cleanup of drinking and groundwater, soil, and corn sample extracts, and the triazines were determined by micellar electrokinetic chromatography.     

Different approaches to synthesize carnosine selective imprinted polymers

Selective recognition of proteins by synthetic molecularly imprinted polymers is one of the interesting topics in biosciences. Carnosine (β-alanyl-l-histidine) and related histidine containing peptides are distributed in a wide range of tissues in vertebrate organisms. These peptides have been extensively studied because of their important physiological properties besides their metal chelation property. In this study, preparation of carnosine specific imprinted polymers (MIPs) for the recognition of imidazole containing peptides with and without copper ion is reported. Carnosine and copper–carnosine complex were employed as template molecules where 4-vinylpyridine and ethylenglycol dimethacrylate were chosen as monomer and crosslinker, respectively. The selectivity and binding studies of copper–carnosine imprinted polymer showed high selectivity toward both carnosine (template peptide) and the cupric ion. The selectivity of copper–carnosine imprinted polymer was 65% and carnosine imprinted polymer was approximately 40%. These results indicate that specific recognition of carnosine is depending on the basis of metal coordination     

Controlled fabrication of theophylline imprinted polymers on multiwalled carbon nanotubes via atom transfer radical polymerization

Theophylline imprinted polymers were synthesized on the surface of multiwalled carbon nanotubes via atom transfer radical polymerization using brominated multiwalled carbon nanotubes as an initiator. The nanotube-based initiator was prepared by directly reacting acyl chloride-modified multiwalled carbon nanotubes with 2-hydroxylethyl-2'-bromoisobutyrate. The grafting copolymerization of 2-hydroxyethyl-2-methyl-2-propenoate and ethylene glycol dimethacrylate in the presence of template theophylline led to thin molecularly imprinted polymer films coating multiwalled carbon nanotubes. The thickness of molecularly imprinted polymer films prepared in this study was about 5 nm as determined by transmission electron microscopy. Fourier-transform infrared spectroscopy was utilized to follow the introduction of initiator groups as well as polymers on the carbon nanotube surfaces. Thermogravimetric analysis indicated that the molecularly imprinted polymers were successfully grown from the carbon nanotube surfaces, with the final products having a polymer weight percentage of ca. 50 wt%. The adsorption properties, such as adsorption dynamics, special binding and selective recognition capacity, of the as-prepared molecularly imprinted polymer films were evaluated. The results demonstrated that the composite of molecularly imprinted polymers and multiwalled carbon nanotubes not only possessed a rapid dynamics but also exhibited a good selectivity toward theophylline, compared to caffeine.     

Interactions of bupivacaine with a molecularly imprinted polymer in a monolithic format studied by NMR

A trimethylolpropane trimethacrylate-based monolith of dimensions carefully chosen to fit exactly in a standard 4-mm solid-state CP/MAS NMR rotor was photopolymerized and subsequently molecularly imprinted with bupivacaine using a grafting protocol with methacrylic acid and ethylene dimethacrylate as monomers. As no crushing or grinding of the monolith was necessary, additional unspecific surface area was not created. This procedure ascertains that differences observed between imprinted and nonimprinted polymers are due only to graft imprinted surfaces and give therefore better results in NMR spectroscopy due to less unspecific interactions between analyte and monolith. This improves the comparability to chromatographic evaluations where uncrushed monolithic columns are also used. To track interactions between analyte and stationary phase, the saturation transfer difference (STD) technique was applied on the polymer in the suspended state using the same solvent as in the chromatographic evaluation. This relatively new NMR method has to our knowledge not been used on chromatographic materials before. By using STD NMR on pristine monoliths, it was possible to measure large differences between the imprinted or nonimprinted polymers and the analyte indicating significant differences in the interaction mechanisms. These could be directly correlated with retention differences observed in chromatographic evaluations.     

Atrazine sensor based on molecularly imprinted polymer-modified gold electrode

Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed an atrazine sensor based on a MIP layer selective for atrazine and its electrochemical reduction on gold electrode. The atrazine sensor was fabricated by directly polymerizing the atrazine-imprinted polymer composed from methacrylic acid and ethylene glycol dimethacrylate onto the surface of a gold electrode. By introducing LiCl into the MIP, atrazine was reduced below -800 mV vs Ag/AgCl reference electrode, at pH 3. The cathodic current of atrazine depended on the concentration of atrazine at the range of 1-10 microM. The sensor exhibited a selective response to atrazine. A nonimprinted polymer-modified electrode did not show selective response to atrazine, thus implying that the imprinted polymer acts as recognition element of atrazine sensor.