硝酸铵水凝胶分子印迹聚合物的制备

目的：目前安全问题成为世界各国的首要问题,尤其是对炸药分子的检测。硝酸铵是硝铵炸药的主要成分。研究水凝胶分子印迹法对硝铵炸药分子的检测。方法：水凝胶分子印迹方法制备硝酸铵水凝胶分子印迹聚合物,运用静态结合实验对其结合率进行了测定。结果：聚合物对硝酸铵具有良好的识别和吸附性能。印迹聚合物的解离常数为4.08g/L,最大吸附量为3.51mg/g。结论：水凝胶分子印迹法可合成水溶性炸药分子印迹聚合物,并且识别及吸附性能良好。     

A urea electrochemical sensor based on molecularly imprinted chitosan film doping with CdS quantum dots

An improved imprinted film-based electrochemical sensor for urea recognition was developed using CdS quantum dots (QDs) doped chitosan as the functional matrix. The microstructure and composition of the imprinted films depicted by scanning electron microscopy (SEM), attenuated total reflection infrared (ATR-IR), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS) indicated the fabricated feasibility of the nanoparticle doped films via in situ electrodeposition. Differential pulse voltammetric responses under the optimal fabrication conditions showed that the sensitivity of CdS QDs-MIP (molecularly imprinted polymer) electrochemical sensor was enhanced from the favorable electron transfer and magnified surface area of CdS QDs with a short adsorption equilibrium time (7 min), wide linear range (5.0 × 10(-12) to 4.0 × 10(-10) M and 5.0 × 10(-10) to 7.0 × 10(-8) M), and low detection limit (1.0 × 10(-12) M). Meanwhile, the fabricated sensor showed excellent specific recognition to template molecule among the structural similarities and coexistence substances. Furthermore, the proposed sensor was applied to determine the urea in human blood serum samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application.     

Molecularly imprinted chitosan-genipin hydrogels with recognition capacity toward o-xylene

A molecularly imprinted material was developed from hydrogels of chitosan (CS) cross-linked with genipin (GNP) using o-xylene as the template molecule. Gelling time, mechanical, and diffusion properties of CS-GNP hydrogels were initially investigated to establish optimal conditions to prepare molecularly imprinted hydrogels (MIHs). The elastic modulus was found to be directly proportional to the degree of cross-linking (R = moles of genipin/moles of glucosamine) while the diffusion of water, as monitored by magnetic resonance imaging, decreased with R. CS-GNP hydrogels of varying R were imprinted with o-xylene (MIH(o-xylene)). The adsorption capacity of o-xylene by MIH(o-xylene) was greater than the corresponding control hydrogels, particularly at R = 0.25. Freundlich isotherms yielded a better fitness than Langmuir ones and afforded n and Q(max)values of 2.55 and 103.3 mg/g, respectively. The imprinted hydrogel showed the highest adsorption capacity for o-xylene; however, the material was not highly selective as it also exhibited the capacity to adsorb m- and p-xylene isomers. In turn, the MIH(o-xylene) showed a low adsorption when 2-fluorotoluene was used in rebinding experiments, suggesting that molecular recognition by the binding sites is influenced by the electronic and steric properties of the analyte molecule, thus effectively confirming the imprinting effect within the MIH(o-xylene) network. This work opens the possibility to future development of materials with the capacity to adsorb o-xylene analogue molecules such as contaminants bearing chlorinated aromatic structures.     

Molecularly imprinted polymer anchored on the surface of denatured bovine serum albumin modified CdTe quantum dots as fluorescent artificial receptor for recognition of target protein

A new type of molecularly imprinted polymer (MIP)-based fluorescent artificial receptor was developed by anchoring MIP on the surface of denatured bovine serum albumin (dBSA) modified CdTe quantum dots (QDs) using the surface molecular imprinting process. The approach combined the merits of molecular imprinting technology and the fluorescent property of the CdTe QDs. The dBSA was used not only to modify the surface defects of the CdTe QDs, but also as assistant monomer to create effective recognition sites. Three different proteins, namely lysozyme (Lyz), cytochrome c (Cyt) and methylated bovine serum albumin (mBSA), were tested as the template molecules and then the receptors were synthesized by sol-gel reaction (imprinting process). The results of fluorescence and binding experiments demonstrated the recognition performance of the receptors toward the corresponding template. Under optimum conditions, the linear range for Lyz was from 1.4×10(-8) to 8.5×10(-6) M, and the detection limit was 6.8 nM. Moreover, the new artificial receptors were applied to separate and detect Lyz in real samples. This fluorescent artificial receptor may serve as a starting point in the design of highly effective synthetic fluorescent receptor for recognition of target protein.     

Separation/enrichment of active natural low content protein using protein imprinted polymer

We describe a new type of protein-imprinted polymer for separation/enrichment of active natural protein present at a relatively low level in cell extracts, with a cloned bacterial protein as template. In this work, cloned pig cyclophilin 18 (pCyP18) was used as template. The template protein was selectively assembled with assistant recognition polymer chains (ARPCs) from their library, which consists of numerous limited length polymer chains with randomly distributed recognition and immobilizing sites. These assemblies of protein and ARPCs were adsorbed by porous polymeric beads and immobilized by cross-linking polymerization. After removing the template, the synthesized imprinted polymer was used to adsorb authentic pCyP18 from cell extract, and its proportional content was enriched 200 times. The assay of peptidyl-prolyl cis-trans-isomerase (PPIase) activity showed that natural pCyP18 is more active than cloned pCyP18 and, in particular, it is much more sensitive to the suppressant cyclosporine A (CsA).     

Combinatorial screening of polymer precursors for preparation of benzo[α] pyrene imprinted polymer: an ab initio computational approach

A combinatorial screening procedure was used for the selection of polymer precursors in the preparation of molecularly imprinted polymer (MIP), which is useful in the detection of the air pollution marker molecule benzo[a]pyrene (BAP). Molecular imprinting is a technique for the preparation of polymer materials with specific molecular recognition receptors. The preparation of imprinted polymers requires polymer precursors such as functional monomer, cross-linking monomer, solvent, an initiator of polymerization and thermal or UV radiation. A virtual library of functional monomers was prepared based on interaction binding scores computed using HyperChem Release 8.0 software. Initially, the possible minimum energy conformation of the monomers and BAP were optimized using the semi-empirical (PM3) quantum method. The binding energy between the functional monomer and the template (BAP) was computed using the Hartree-Fock (HF) method with 6-31 G basis set, which is an ab initio approach based on Moller-Plesset second order perturbation theory (MP2). From the computations, methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were selected for preparation of BAP imprinted polymer. The larger interaction energy (ΔE) represents possibility of more affinity binding sites formation in the polymer, which provides high binding capacity. The theoretical predictions were complimented through adsorption experiments. There is a good agreement between experimental binding results and theoretical computations, which provides further evidence of the validity of the usefulness of computational screening procedures in the selection of appropriate MIP precursors in an experiment-free way.     

A novel electrochemical sensor for determination of dopamine based on AuNPs@SiO(2) core-shell imprinted composite

A novel core-shell composite of gold nanoparticles (AuNPs) and SiO(2) molecularly imprinted polymers (AuNPs@SiO(2)-MIPs) was synthesized through sol-gel technique and applied as a molecular recognition element to construct an electrochemical sensor for determination of dopamine (DA). Compared with previous imprinting recognition, the main advantages of this strategy lie in the introduction and combination of AuNPs and biocompatible porous sol-gel material (SiO(2)). The template molecules (DA) were firstly adsorbed at the AuNPs surface due to their excellent affinity, and subsequently they were further assembled onto the polymer membrane through hydrogen bonds and π-π interactions formed between template molecules and silane monomers. Cyclic voltammetry (CV) was carried out to extract DA molecules from the imprinted membrane, and as a result, DA could be rapidly and effectively removed. The AuNPs@SiO(2)-MIPs was characterized by ultraviolet visible (UV-vis) absorbance spectroscopy, transmission electron microscope (TEM) and Fourier transform infrared spectrometer (FT-IR). The prepared AuNPs@SiO(2)-MIPs sensor exhibited not only high selectivity toward DA in comparison to other interferents, but also a wide linear range over DA concentration from 4.8×10(-8) to 5.0×10(-5)M with a detection limit of 2.0×10(-8)M (S/N=3). Moreover, the new electrochemical sensor was successfully applied to the DA detection in dopamine hydrochloride injection and human urine sample, which proved that it was a versatile sensing tool for the selective detection of DA in real samples.     

Electrochemical sensor based on molecularly imprinted membranes at platinum nanoparticles-modified electrode for determination of 17β-estradiol

In this paper, an electrochemical sensor for 17β-estradiol (E2) based on the molecular imprinting polymer (MIP) membranes had been constructed. 6-mercaptonicotinic acid (MNA) and E2 were first assembled on the surface of platinum nanoparticles-modified glassy carbon electrode (PtNPs/GCE) by the formation of Pt-S bonds and hydrogen-bonding interactions, and subsequently the polymer membranes were formed by electropolymerization. Finally, a novel molecularly imprinted sensor (MIS) was obtained after removal of E2. Experimental parameters such as deposition time, scan cycles, pH value and accumulation condition were optimized. Under optimal conditions, the MIS exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of 3.0×10(-8)-5.0×10(-5)molL(-1) (r=0.996) with an estimated detection limit of 1.6×10(-8)molL(-1). MIS had been successfully used to analyze E2 in water samples without complex pretreatment. Meanwhile, the average recoveries were higher than 93.9% with RSD<3.7%. All results above reveal that MIS is an effective electrochemical technique to determine E2 real-time in complicated matrix.     

Molecular imprinted polymer with cloned bacterial protein template enriches authentic target in cell extract

Here we describe a new method for preparing a protein-imprinted polymer with a cloned bacterial protein template, which recognizes/adsorbs authentic target protein present at a relatively low level in cell extract. In this work, cloned pig cyclophilin 18 (pCyP18) was used as a template. The template protein was selectively assembled with memory molecules from their library, which consists of numerous limited length polymer chains with randomly distributed recognition sites and immobilizing sites. These assemblies of protein and memory molecules were adsorbed by porous polymeric beads and immobilized by cross-linking polymerization. After removing the template, binding sites that were complementary to the target protein in size, shape and the position of recognition groups were exposed, and their confirmation was preserved by the cross-linked structure. The synthesized imprinted polymer was used to adsorb authentic pCyP18 from cell extract, and its proportional content was enriched 300 times.     

Quartz crystal microbalance for the determination of daminozide using molecularly imprinted polymers as recognition element

As the daminozide (DM) and its metabolite have been identified to be potentially carcinogenic, rapid detection method for them is necessary for food safety. A type of piezoelectric crystal sensor has been prepared by using a molecularly imprinted polymer (MIP) as recognition element. The molecularly imprinted polymer was prepared by hot-induced precipitation polymerization, and then the polymer particles were fixed on the surface of the electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to evaluate the obtained imprinted polymer particles and the MIP sensitive film coated on the electrode. The results showed that a typical time-response curve of the MIP-coated crystal to the DM solution had been given, frequency shifts versus logarithm changes of DM showed good linear correlation within the concentration range of 1.0x10(-9) to 10(-6) mg/mL (y=11.38 lg x+115.45, r=0.9872) and 1.0x10(-6) to 10(-1) mg/mL (y=25.22lgx+209.44, r=0.9938), respectively. The detection limit was 5.0x10(-8) mg/mL (S/N=3), which is lower than that of conventional methods. Further, computer simulation technology was employed to investigate the interaction between methacrylic acid and DM for elucidating the recognition mechanism. The influencing factor pH has also been investigated. The injection experiments of DM structurally related compounds indicated that the obtained sensor has high sensitivity, excellent selectivity, low cost, good reproducibility, and reusable property by combining with piezoelectric crystal and molecularly imprinted polymer.     

Use of molecule imprinting-chemiluminescence method for the determination of tamoxifen in breast cancer sufferers' urine.

The reaction between soluble Mn(IV) and tamoxifen can produce chemiluminescence and formaldehyde can enhance this chemiluminescence reaction. A tamoxifen molecular imprinted polymer (MIP) was synthesized and its adsorption selectivity to tamoxifen in aqueous solution was evaluated. Using a synthesized tamoxifen MIP as the recognition material and a soluble Mn(IV)-formaldehyde-tamoxifen chemiluminesence system as the detection system, a new molecule imprinting-chemiluminesence method of determination of tamoxifen was established. The response range of this method was 1.0 x 10(-7)-6.0 x 10(-6) g/mL, with a linear correlation coefficient of 0.997. The detection limit was 4 x 10(-8) g/mL. The relative standard deviation for 5.0 x 10(-7) g/mL tamoxifen solution was 4.1% (n = 9).     

Nanostructured conducting molecularly imprinted polymer for selective uptake/release of naproxen by the electrochemically controlled sorbent

A conducting molecularly imprinted polymer (CMIP) film, based on polypyrrole, was electrosynthesized for selective uptake/release and determination of naproxen. The film was prepared by incorporation of a template anion (naproxen) during the electropolymerization of pyrrole into a platinum electrode using the cyclic voltammetry method. Overoxidized polypyrrole films with cavities complementary to the template were used as a potential-induced selective recognition element in the solid-phase sorbent. Various important fabricating factors, which control the performance of the CMIP film, were investigated using fluorescence spectroscopy. The measured fluorescence intensities of released solutions were related to the concentrations of naproxen taken up into the films. Several key parameters such as applied potential and time for uptake and release were varied to achieve the optimal sorption procedure. The film template with naproxen exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5×10(-8) to 3×10(-7)molml(-1) and 7×10(-6) to 8×10(-4)molml(-1), and the limit of detection was 1×10(-8)molml(-1). The CMIP films, as the electrochemically controlled solid-phase sorbent, were applied for the selective cleanup and quantification of trace amounts of naproxen from physiological samples. Scanning electron microscopy confirmed the nanostructure morphology of the films.     

Detection of organophosphorus compounds using a molecularly imprinted photonic crystal

A label free molecularly imprinted photonic crystal (MIPC) was developed to detect the degradation product of nerve agents. Mono-dispersed poly-methyl methacrylate colloidal particles with the diameter of 280 nm were used to fabricate a closely packed colloidal crystal array (CCA), and a methyl phosphonic acid (MPA) imprinted hydrogel was prepared within the CCA using 2-hydroxyethyl-methacrylate and N-isopropylacrylamide as monomers, ethyleneglycol dimethacrylate and N, N'-methylenebisacrylamide as cross-linkers, a mixture of n-octanol and acetonitrile as porogen. The diffraction intensity of the MIPC decreased significantly upon the MPA adsorption with a limit of detection (LOD) of 10(-6) molL(-1). Furthermore, the diffraction intensity decreased and blue shifted with the increase of temperature, decreased and red shifted with the increase of ionic strength. At higher pH, the diffraction intensity increased without obvious diffraction shift. The MIPC provides an indirect path to detect nerve agents (Sarin, Soman, VX and R-VX) by monitoring the MPA released from the hydrolysis of nerve agents, with LODs of 3.5 × 10(-6) molL(-1), 2.5 × 10(-5) molL(-1), 7.5 × 10(-5) molL(-1) and 7.5 × 10(-5) molL(-1) for Sarin, Soman, VX and R-VX, respectively.     

Electrochemical sensor for dopamine based on a novel graphene-molecular imprinted polymers composite recognition element

A novel composite of graphene sheets/Congo red-molecular imprinted polymers (GSCR-MIPs) was synthesized through free radical polymerization (FRP) and applied as a molecular recognition element to construct dopamine (DA) electrochemical sensor. The template molecules (DA) were firstly absorbed at the GSCR surface due to their excellent affinity, and subsequently, selective copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) was further achieved at the GSCR surface. Potential scanning was presented to extract DA molecules from the imprinted polymers film, and as a result, DA could be rapidly and completely removed by this way. With regard to the traditional MIPs, the GSCR-MIPs not only possessed a faster desorption and adsorption dynamics, but also exhibited a higher selectivity and binding capacity toward DA molecule. As a consequence, an electrochemical sensor for highly sensitive and selective detection of DA was successfully constructed as demonstration based on the synthesized GSCR-MIPs nanocomposites. Under experimental conditions, selective detection of DA in a linear concentration range of 1.0 × 10(-7)-8.3 × 10(-4)M was obtained, which revealed a lower limit of detection and wider linear response compared to some previously reported DA electrochemical MIPs sensors. The new DA electrochemical sensor based on GSCR-MIPs composites also exhibited excellent repeatability, which expressed as relative standard deviation (RSD) was about 2.50% for 30 repeated analyses of 20 μM DA.     

Structural basis of recognition of pathogen-associated molecular patterns and inhibition of proinflammatory cytokines by camel peptidoglycan recognition protein

Peptidoglycan recognition proteins (PGRPs) are involved in the recognition of pathogen-associated molecular patterns. The well known pathogen-associated molecular patterns include LPS from Gram-negative bacteria and lipoteichoic acid (LTA) from Gram-positive bacteria. In this work, the crystal structures of two complexes of the short form of camel PGRP (CPGRP-S) with LPS and LTA determined at 1.7- and 2.1-? resolutions, respectively, are reported. Both compounds were held firmly inside the complex formed with four CPGRP-S molecules designated A, B, C, and D. The binding cleft is located at the interface of molecules C and D, which is extendable to the interface of molecules A and C. The interface of molecules A and B is tightly packed, whereas that of molecules B and D forms a wide channel. The hydrophilic moieties of these compounds occupy a common region, whereas hydrophobic chains interact with distinct regions in the binding site. The binding studies showed that CPGRP-S binds to LPS and LTA with affinities of 1.6 × 10(-9) and 2.4 × 10(-8) M, respectively. The flow cytometric studies showed that both LPS- and LTA-induced expression of the proinflammatory cytokines TNF-α and IL-6 was inhibited by CPGRP-S. The results of animal studies using mouse models indicated that both LPS- and LTA-induced mortality rates decreased drastically when CPGRP-S was administered. The recognition of both LPS and LTA, their high binding affinities for CPGRP-S, the significant decrease in the production of LPS- and LTA-induced TNF-α and IL-6, and the drastic reduction in the mortality rates in mice by CPGRP-S indicate its useful properties as an antibiotic agent.     

Enhanced selectivity of a molecularly imprinted polymer toward the target molecule via esterification of non‐specific binding sites with diazomethane

Diazomethane (CH₂N₂) was used to methylate the non‐specific binding sites after molecularly imprinted polymer particles were prepared using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker and bisphenol A (BPA) as the template. After diazomethane treatment and subsequent removal of BPA by triethylamine, the treated molecularly imprinted polymer (TMIP) particles were tested for binding selectivity toward BPA and other organic compounds by capillary electrophoresis with ultraviolet detection. Even in the presence of compounds that were positively charged, neutral or negatively charged in the background electrolyte, BPA was selectively bound with the highest efficiency. A significant decrease in the affinity for metformin (MF, a positively charged compound), along with ¹³C nuclear magnetic resonance spectra and electrophoretic mobility data, provided strong evidence for the elimination of non‐specific –COOH binding sites in the TMIP particles. Only 8% of MF and 16% of diclofenac sodium salt (a negatively charged compound) remained as non‐specific bindings because of hydrophobic interactions. Further comparison with poly(methyl methacrylate) revealed the true merits of the TMIP, which exhibited minimal non‐specific bindings while preserving a high level of specific binding owing to molecular recognition. Copyright © 2014 John Wiley & Sons, Ltd.     

MOLECULARLY IMPRINTED POLYMERS FOR SOME REACTIVE DYES

Depending upon their structure, azo- and anthraquinonic dyes are the two major classes and together represent 90% of all organic colorants. Adsorption of dye molecules onto a sorbent can be an effective, low-cost method of color removal. Most of the techniques used for removal of dyes are of high production cost, and the regeneration also makes them uneconomical. There is much interest in the development of cheaper and effective newer materials for use as adsorbents. Molecular imprinting is a new kind of materials that can be alternative adsorbents. In this study, molecularly imprinted polymers of three textile dyes (Cibacron Orange P-4R, Cibacron Red P-4B, Cibacron Black PSG) were prepared. Methacrylic acid was used as a monomer for red and orange dyes and acrylamide was used for black dye. Methanol:acetonitrile was used as a porogen. The selective recognition ability of the molecularly imprinted polymers was studied by an equilibrium–adsorption batch method. The adsorption data are for Cibacron Black PSG 65% and nonimprinted polymer (NIP) 25%; Cibacron Red P-4B 72% and NIP 18%; and Cibacron Orange P-4R 45% and NIP 10%, respectively. Dye-imprinted polymers were used as a solid-phase extraction material for selective adsorption from wastewater of textile factory.     

PREPARATION OF GLUTATHIONE IMPRINTED POLYMER

Glutathione imprinted polymer was prepared using 1-vinyl imidazole and ethylene glycol dimethacrylate as the functional monomer and crosslinker, respectively, in dimethyl sulfoxide. The adsorption selectivity of glutathione-imprinted polymer was tested by reduced glutathione, oxidized glutathione, and L-Gly-Leu-Tyr in 30% phosphate buffer (0.01 M, pH 5.0)–70% acetonitrile and binding affinity values were compared. Reusability of molecularly imprinted polymer particles was also investigated. Molecularly imprinted polymer particles were found to be stable and to maintain glutathione adsorption capacity at 95% when washed with methanol–acetic acid (10%) after seven usages. Functional monomer 1-vinyl imidazole and cross linker ethylene glycol dimethacrylate-based glutathione imprinted polymer could be used as solid phase extraction material for recognition of glutathione in biological samples.     

New biomedical devices with selective peptide recognition properties. Part 1: Characterization and cytotoxicity of molecularly imprinted polymers

Molecular imprinting is a technique for the synthesis of polymers capable to bind target molecules selectively. The imprinting of large proteins, such as cell adhesion proteins or cell receptors, opens the way to important and innovative biomedical applications. However, such molecules can incur into important conformational changes during the preparation of the imprinted polymer impairing the specificity of the recognition cavities. The "epitope approach" can overcome this limit by adopting, as template, a short peptide sequence representative of an accessible fragment of a larger protein. The resulting imprinted polymer can recognize both the template and the whole molecule thanks to the specific cavities for the epitope. In this work two molecularly imprinted polymer formulations (a macroporous monolith and nanospheres) were obtained using the protected peptide Z-Thr-Ala-Ala-OMe, as template, and Z-Thr-Ile-Leu-OMe, as analogue for the selectivity evaluation, methacrylic acid, as functional monomer, and trimethylolpropane trimethacrylate and pentaerythritol triacrylate (PETRA), as cross-linkers. Polymers were synthesized by precipitation polymerization and characterized by standard techniques. Polymerization and rebinding solutions were analyzed by high performance liquid chromatography. The highly cross-linked polymers retained about 70% of the total template amount, against (20% for the less cross-linked ones). The extracted template amount and the rebinding capacity decreased with the cross-linking degree, while the selectivity showed the opposite behaviour. The PETRA cross-linked polymers showed the best recognition (MIP 2-, alpha=1.71) and selectivity (MIP 2+, alpha'=5.58) capabilities. The cytotoxicity tests showed normal adhesion and proliferation of fibroblasts cultured in the medium that was put in contact with the imprinted polymers.     

Electrochemical imprinted sensor for determination of oleanic acid based on poly (sodium 4-styrenesulfonate-co-acrylic acid)-grafted multi-walled carbon nanotubes-chitosan and cobalt hexacyanoferrate nanoparticles

A novel sensitive and selective imprinted electrochemical sensor for the determination of oleanic acid was constructed on a carbon electrode by stepwise modification of functional multi-walled carbon nanotubes, cobalt hexacyanoferrate nanoparticles and a thin imprinted sol-gel film. The fabrication of a homogeneous porous poly (sodium 4-styrenesulfonate-co-acrylic acid)-grafted multi-walled carbon nanotubes/SiO(2)-chitosan nanocomposite film was conducted by controllable electrodeposition technology. The surface morphologies of the modified electrodes were characterized by scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy in detail. The imprinted sensor displayed high sensitivity and selectivity towards oleanic acid. A linear relationship between the sensor response signal and the logarithm of oleanic acid concentrations ranging from 1.0×10(-8) to 1.0×10(-3) mol L(-1) was obtained with a detection limit of 2.0×10(-9) mol L(-1). It was applied to the determination of oleanic acid in real capsule samples successfully.