Characteristic and Molecular Recognition Mechanism of Theophylline Monolithic Molecularly Imprinted Polymer

Yan, Hongyuan,Row, Kyung Ho Taylor Francis 2006 JOURNAL OF LIQUID CHROMATOGRAPHY AND RELATED TECHN Vol.29 No.10

<P> A monolithic molecularly imprinted polymer (MIP) with specific recognition ability for theophylline was prepared by in-situ therm polymerization, using acrylamide as a functional monomer, ethylene glycol dimethacrylate as a cross-linking agent, toluene and dodecanol as porogenic solvents and 2,2'-azobisisobutyronitrile as initiator. Scanning electron microscopy and an accelerated surface area and porosimetry system were used to identify the structural features of the MIP. The results show that the large through-pore structure allows mobile phase to flow through the MIP column with a low back pressure, and the other pores lead to the molecular recognition. Some chromatographic conditions such as the composition of the mobile phase, flow rate, and temperature were characterized and illustrated by a homologous series of xanthine derivatives, theophylline and caffeine. Effects of molecular recognition were also discussed and the possible recognition mechanisms were hydrogen bonding and hydrophobic interactions between the theophylline molecule and the MIP.</P>

Determination of Three Tanshinones from Radix Salvia Miltiorrhiza by Molecularly Imprinted Solid-phase Extraction

Yan, Hongyuan,Tian, Minglei,Row, Kyung Ho WILEY-VCH Verlag 2009 Chinese journal of chemistry Vol.27 No.11

<P>A selective molecularly imprinted solid-phase extraction procedure was developed for the selective separation of tanshinone I, tanshinone IIA, and cryptotanshinone from Radix Salvia Miltiorrhiza samples. Tanshinone IIA imprinted polymers (MIP) synthesized in ethanol-dodecanol system show high affinity to tanshinone IIA and its structure analogs in aqueous environment and the affinity can be controlled by adjusting the intensity of the eluents. By using 60% water-40% methanol (volume ratio) and 99.5% methanol-0.5% trifluoroacetic acid (volume ratio) as washing and eluting solvents, most interferences originating from the salvia matrix were eliminated. The extracts were sufficiently clean enough to be directly injected into HPLC for further chromatographic analysis. Good linearity was obtained from 0.4 to 500.0 mg·L<SUP>−1</SUP> (r<SUP>2</SUP>=0.999) with the relative standard deviations less than 4.2%. The mean recoveries of tanshinone IIA in Radix Salvia Miltiorrhiza were more than 85.6% at three different concentrations and the limits of detection were 0.06–0.09 mg·L<SUP>−1</SUP>. This method is a viable alternative tool to the existing HPLC methods for analyzing the content of the three tanshinones in Radix Salvia Miltiorrhiza samples.</P> <B>Graphic Abstract</B> <P>Tanshione MIP was prepared in ethanol-dodecanol solvents and showed high affinity to tanshinones in an aqueous environment. <img src='wiley_img/1001604X-2009-27-11-CJOC200990371-content.gif' alt='wiley_img/1001604X-2009-27-11-CJOC200990371-content'> </P>

Molecularly Imprinted Solid-Phase Extraction for Determination of Enrofloxacin and Ciprofloxacin in Chicken Muscle

Hongyuan Yan,노경호 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.6

A simple and sensitive high-performance liquid chromatographic method was developed for the simultaneous identification of enrofloxacin and its active metabolite ciprofloxacin in chicken muscle. Norflorxacin imprinted polymers synthesized in water-containing systems show high selectivity to enrofloxacin and ciprofloxacin in an aqueous environment. Using these water-compatible imprinted polymers as selective adsorbents in the solid-phase extraction of enrofloxacin and ciprofloxacin from chicken samples, the remaining biological matrix could be quickly washed out from the imprinted column while enrofloxacin and ciprofloxacin were selectively retained and enriched. Analytical separation was performed on a C18 column using acetonitrile-water as a mobile phase and fluorescence detection. Good linearity was obtained from 0.8 to 500 ng/g (r > 0.998) with relative standard deviation of less than 3.9%. The mean recoveries of enrofloxacin and ciprofloxacin from chicken muscle were 80.6-94.5% and 77.8-91.8% at three different concentrations. The limits of determinations based on S/N=3 were 0.07 ng/g and 0.09 ng/g, which are below the maximum residue limits established in many countries.

Preparation and Characterization of Monolithic Poly(methacrylic acid - ethylene glycol dimethacrylate) Columns for High Performance Liquid Chromatography

Hongyuan Yan,노경호 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.1

Novel molecularly imprinted monolithic column for selective on-line extraction of ciprofloxacin from human urine

Yan, Hongyuan,Row, Kyung Ho John Wiley Sons, Ltd. 2008 Biomedical chromatography Vol.22 No.5

<P>Water-compatible ciprofloxacin-imprinted monolithic columns were synthesized in water-containing systems for selective extraction of ciprofloxacin from human urine samples. Methanol–water (10:3, v/v) was used as a porogenic solvent and the obtained monolithic imprinted polymers reveal high selectivity to ciprofloxacin in an aqueous environment; the affinity can be easily controlled by adjusting the pH of the mobile phase. Owing to the unique porous structure and flow-through channels existing in the network skeleton of the monolithic MIP, urine samples could be directly injected into the column, proteins and other biological matrix were quickly washed out and ciprofloxacin was selectively retained and enriched. Good linearity was obtained from 0.08 to 400 mg/L (r = 0.998) with the relative standard deviations less than 3.6%. The limit of detection of the method was 0.04 mg/L and the recoveries were more than 94.5% at three different concentrations. Moreover, by increasing the injection volume to 2.0 mL, the sensitivity of the method could be improved 100-fold according to the peak height of ciprofloxacin. This expedient greatly simplified the overall procedure, resulting in a rapid and efficient sample analysis while maintaining precision and accuracy. Copyright © 2007 John Wiley & Sons, Ltd.</P>

Optimum Operational Conditions for Chiral Separation of Tryptophan Enatiomers Using Ligand Exchange Liquid Chromatography

Hongyuan Yan,노경호 한국생물공학회 2007 Biotechnology and Bioprocess Engineering Vol.12 No.3

A simple and precise method for chiral separation of tryptophan enantiomers using high performance liquid chromatography with a ligand exchange mobile phase was developed. Chiral separation was performed on a conventional C18 column, using a mobile phase that consisted of a water-methanol solution (88:12, v/v) containing 10 mmol/L L-leucine and 5 mmol/L copper sulfate as a chiral ligand additive at a flow rate of 1.0 mL/min. This method allowed baseline separation of two enantiomers with a resolution of 1.84 in less than 30 min. The effect of various conditions, including concentration, type of ligand, organic modifier, pH, flow rate, and temperature, on enantioseparation were evaluated and chiral recognition mechanisms were investigated. Thermodynamic data (△△H and △△S) obtained by van’t Hoff plots revealed that enantioseparation is an enthalpy-controlled process.

Synthesis of Water-Compatible Molecularly Imprinted Polymers

노경호,( Hongyuan Yan ) 한국공업화학회 2007 한국공업화학회 연구논문 초록집 Vol.2007 No.1

Molecularly Imprinted Monolithic Stationary Phases for Liquid Chromatographic Separation of Tryptophan and N-CBZ-Phenylalanine Enantiomers

노경호,Hongyuan Yan 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.4

Monolithic molecularly imprinted columns were designed and prepared by an in-situ thermal-initiated copolymerization technique for rapid separation of tryptophan and N-CBZ-phenylalanine enantiomers. The influence of polymerization conditions and separation conditions on the specific molecular recognition ability for enantiomers and diastereomers was investigated. The specious molecular recognition was found to be dependent on the stereo structures and the arrangement of functional groups of the imprinted molecule and the cavities in the molecularly imprinted polymer (MIP). Moreover, hydrogen bonding interactions and hydrophobic interactions played an important role in the retention and separation. Compared to conventional MIP preparation procedures, the present method is very simple, and its macroporous structure has excellent separation properties.

Simultaneous Quantification of Multiple Alkaloids in Sophora Flavescens Ait and Human Urine by HPLC

Junyu Liu,Hongyuan Yan,Kyung Ho Row 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.5

This study developed a simple and sensitive liquid chromatography method to quantify the multiple active alkaloids (matrine, sophocarpine, and sophoridine) from sophora flavescens ait in urine samples simultaneously. The results showed that liquid- liquid extraction using water as the solvent could effectively isolate all the analyses with the lowest matrix effects. A low concentration of diethylamine (0.07%, v/v) in the mobile phase improved dramatically the resolution of all the alkaloids with less interference from the matrix. Good linearity ranging from 0.025 to 1250.0 μg/mL for all analytes was obtained, and the accuracy and precision varied from 73.25 to 87.86% and 1.4 to 2.2%, respectively. Finally, the suitability of the proposed method was demonstrated in the urinary drug excretion of 4 volunteers receiving an oral dose of a sophora flavescens ait extract. The intra and inter RSD were ≤ 1.9% This study developed a simple and sensitive liquid chromatography method to quantify the multiple active alkaloids (matrine, sophocarpine, and sophoridine) from sophora flavescens ait in urine samples simultaneously. The results showed that liquid- liquid extraction using water as the solvent could effectively isolate all the analyses with the lowest matrix effects. A low concentration of diethylamine (0.07%, v/v) in the mobile phase improved dramatically the resolution of all the alkaloids with less interference from the matrix. Good linearity ranging from 0.025 to 1250.0 μg/mL for all analytes was obtained, and the accuracy and precision varied from 73.25 to 87.86% and 1.4 to 2.2%, respectively. Finally, the suitability of the proposed method was demonstrated in the urinary drug excretion of 4 volunteers receiving an oral dose of a sophora flavescens ait extract. The intra and inter RSD were ≤ 1.9%

Simultaneous Extraction and Separation of Liquiritin, Glycyrrhizic Acid, and Glabridin from Licorice Root with Analytical and Preparative Chromatography

Minglei Tian,Hongyuan Yan,노경호 한국생물공학회 2008 Biotechnology and Bioprocess Engineering Vol.13 No.6

Simultaneous extraction and separation of liquiritin, glycyrrhizic acid, and glabridin from licorice were developed by liquid-liquid extraction with liquid chromatography separation. By utilizing different extraction solvents, procedures, and times, the optimum extraction conditions were established. The extracts of licorice were separated and determined using a C₁8 column with a mobile phase consisting of acetonitrile-water (containing 1.0% acetic acid) with a gradient elution of 0~10 min from 20:80 to 60:40 (v/v). Preparative columns with different packing sizes were investigated to isolate the three compounds from the extracts of licorice. The 12 μm chromatographic column showed better separation for the three compounds from licorice. 0.29 mg/g for liquiritin, 1.43 mg/g for glycyrrhizic acid, and 0.07 mg/g for glabridin were obtained and the recoveries were 80.8, 89.7, and 72.5%, respectively.