• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.65-70
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• 2002

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1549-1553
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• 2008

A molecular imprinted polymer (MIP) using (+)catechin ((+)C) as a template and acrylamide (AM) as a functional monomer was prepared. Acetonitrile was used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The adsorption isotherms in the MIP were measured and the parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation for original concentration and adsorpted concentrations was then expressed, and the adsorption equilibrium data were correlated into Langmuir, Freundlich, quadratic, and Langmuir Extension isotherm models. The mixture compounds of (+)C and epicatechin (EC) show competitive adsorption on specific binding sites of the (+)catechin-MIP. The adsorption concentrations of (+)C, epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), on the (+)catechin-molecular imprinted polymer were compared. Through the analysis, the (+)catechin-molecular imprinted polymer showed higher adsorption ability than blank polymer which was synthesized molecular imprinted polymer without (+)catechin. Furthermore, the competitive Langmuir isotherms were applied to the mixture compounds of (+)C and EC.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.1
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• pp.47-51
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• 2004

Ceramide III was prepared by the cultivation of Saccharomyces cerevisiae. Ceramide III was partitioned from the cell extracts by solvent extraction and analyzed by Normal Phase High Performance Liquid Chromatography (NP-HPLC) using Evaporative Light Scattering Detector (ELSD). We experimentally determined the mobile phase composition to separate ceramide III with NP-HPLC. Three binary mobile phases of n-hexane/ethanol, n-hexane/lsoprophyl Alcohol(IPA) and n-hexane/n-butanol and one ternary mobile phase of n-hexane/IPA/methanol were demonstrated. For the binary mobile phase of n-hexane/ethanol, the first mobile phase composition, 95/5(v/v), was step-increased to 72/23(v/v) at 3 min. In the binary mobile phase, the retention time of ceramide III was 7.87min, while it was 4.11 min respectively in the ternary system, where the mobile phase composition of n-hexane/IPA/methanol, 85/7/8(v/v/v), was step-increased to 75/10/15(v/v/v) at 3 min. However, in the ternary mobile phase, the more peak area of ceramide III was observed.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.5
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• pp.331-338
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• 2004

The Separation of two amino acids, phenylalanine and tryptophan, was carried out using laboratory simulated moving bed (SMB) chromatography. The SMB process consisted of four zones, with each zone having 2 columns. The triangle theory was used to obtain the operating conditions for the SMB. The mass transfer coefficients of the two amino acids were obtained from the best-fit values by comparing simulated and experimental pulse data. The competitive adsorption isotherms of the two amino acids were obtained by single and binary frontal analyses, taking into consideration the competition between the two components. A competitive Langmuir isotherm, obtained from single-component frontal chromatography, was used in the first run, and the isotherm from binary frontal chromatography in the second, with the flow rate of zone 1 modified to improve the purity. Compared to the first and second runs, the competitive Langmuir isotherm from the binary frontal chromatography Showed good agreement with the experimental results. Also, adjusting the flow rate in zone 1 increased the purity of the products. The purities of the phenylalanine in the raffinate and the tryptophan in the extract were 99.84 and $99.99\%$, respectively.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.5
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• pp.362-368
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• 2004

A new one-column chromatography process, analogous to a four-zone simulated moving bed (SMB), was presented. The basic principle of the process was identical to that of a four-zone SMB. The process consisted of one chromatographic column and four tanks, instead of the four columns in the four-zone SMB (1-1-1-1), and has been used for the separation of two amino acids, phenylalanine and tryptophan, using an ion exchange resin. The operating parameters for the one-column process and four-zone SMB were obtained from equilibrium theory. Computer simulations were used to compare the performances of the new one column process to that of the general four-zone SMB, using Aspen $Chromatography^{TM}$ v 11.1. The differences between the one-column and SMB processes in terms of the purities and yields of phenylalanine and tryptophan were less than 4 and about $6\%$, respectively. The lower purities of the one-column process were due to the loss of the developed concentration profiles in the column when the liquid was stored in tanks. The one-column process gave great flexibility, and would be useful for reconstructing an existing conventional chromatography process to one of a SMB.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.3
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• pp.179-182
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• 2001

Porcine liver esterase was immobilized in polyacrylamide gel for the enantioselective production of levofloxacin from ofloxacin butyl ester. The initial activity of immobilized esterase was found to be significantly affected by the polyacrylamide gel composition. The optimum concentrations of monomer and crosslinker were determined to be 20% and 8.3%, respectively. The activity of immobilized esterase was 55.4% compared to a free enzyme. Enantiomeric excess was maintained at 60%, almost the same level as that of free enzyme. In addition, the immobilized esterase could be used repeatedly up to 10 times without experiencing any severe loss of activity and enantioselectivity.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.1
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• pp.16-20
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• 2002

Parameter estimations were made for the reversed-phase adsorption of perillyl alcohol (POH), a potent anti-cancer agent, on octadecylsilyl-silica gel (ODS). The average particle diameter of ODS was about $15\;{\mu}m$, and the particles were packed in the column $(3.9\;\times\;300mm)$. The mobile phase used was a mixture of acetonitrile and water, in which the acetonitrile ranged between 50 and $70\;(v/v\;\%)$. The first absolute moment and the second central moment were determined from the chromatographic elution curves by moment analysis. Experiments were carried out using POH solutions within the linear adsorption range. The fluid-to-particle mass transfer coefficient was estimated using the Wilson-Geankoplis equation. The axial dispersion coefficient and the intra particle diffusivity were determined from the slope and intercept of a plot of H vs $1/u_0$, respectively. The contributions of each mass-transfer step were axial dispersion, fluid-to-particle mass transfer, and intraparticle diffusion.

• Bulletin of the Korean Chemical Society
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• v.27 no.2
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• pp.211-218
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• 2006

This work deals with 24 substances composed of nitrogen-containing heterocycles. The relationships between the chromatographic retention factor (k) and those physicochemical properties which are relevant in quantitative structure-properties relationship (QSPR) studies, such as the polarizability $(\alpha)$, molar refractivity (MR), lipophilicity (logP), dipole moment $(\mu)$, total energy $(E_{tot})$, heat of formation $(\Delta H_f)$, molecular surface area $(S_M)$, and binding energy $(E_b)$, were investigated. The accuracy of the simple linear regressions between the chromatographic retention and the descriptors for all of the compounds was satisfactory (correlation coefficient, $0.8 \leq r \leq 1.0$). The QSPR models of these nitrogen-containing heterocyclic compounds could be predicted with a multiple linear regression equation having the statistical index, r = 1.000. This work demonstrated the successful application of the multiple linear approaches through the development of accurate predictive equations for retention factors in liquid chromatography.

• Bulletin of the Korean Chemical Society
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• v.25 no.3
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• pp.357-360
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• 2004

We developed in the present study molecular imprinted polymers (MIPs), using single templates (pentoxifylline, caffeine and theophylline) and mixed-templates (pentoxifylline-caffeine, pentoxifylline-theophylline and caffeine-theophylline). The MIPs were prepared with methacrylic acid (MAA) as the monomer, ethylene glycol dimetharylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The obtained polymer particles (particle size after grinding was about 25-35 ${\mu}$m) were packed into a HPLC column (3.9 mm i.d. ${\times}$ 150 mm). The selectivity and chromatographic characteristics of the MIPs were studied using acetonitrile as the mobile phase at a flow rate of 0.8 mL/min. UV detector wavelength was set at 270 nm. Different single template MIPs showed different molecular recognitions to the templates and the structurally analogues, according to the rigidity and steric hindrance of the compounds. Recognition was improved on the mixed-template MIPs as a result of the cooperation or sum effect of the templates, whereas on the pentoxifylline-theophylline imprinted polymer, the highest selectivity and affinity were obtained. Separations of the test compounds on different polymers were also investigated.

• KSBB Journal
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• v.15 no.6
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• pp.605-608
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• 2000

Oligodeoxynucleotides (ODNs) were separated by high-performance membrane chromatography (HPMC), a combined system of chromatography and membrane. The separation mechanism involved anion-exchange, and the stationary phase was cation CIM (Convective Interaction Media) DEAE disk (16${\times}$3 mm). Two types of mobile phase were used, buffer A (20mM Tris-HCl, pH 7.4) and buffer B (buffer A + 1M NaCl). As the amount of NaCl dissolved in buffer linearly increased, the retention time shortened, which enabled a gradient elution mode. Based on the number of theoretical plates and resolution observed, the optimum mobile phase and operating condition (Buffer A/Buffer B=50/50 - 20/80 vol%, gradient time 2 min) were experimentally determined. In this experimental condition, ODNs were separated within 2 min at a mobile phase flow rate of 6 ml/min.