Chong Ho Lee

Separation of amino acids by simulated moving bed using competitive Langmuir isotherm

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 I 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 I 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.

Design and Sensitivity Analysis of Simulated Moving Bed Chromatography to Separate Sugar Alcohols

Abstract As the advanced unit operation of batch chromatography, the simulated moving bed (SMB) chromatography is widely used in sugar industries with the ion exchange resin as the stationary phase. The conventional SMB process is composed of 4 zones which have different roles. We considered the SMB process to separate two sugar alcohols, xylitol, and maltitol, which are commercially used as alternative sweeteners. To decide the optimum operating condition of the SMB process, we consider the migration velocities of solutes in each zone. The migration velocity of a solute is dependent on the adsorption isotherm and velocity ratio of the mobile phase and the simulated stationary phase velocities. The total concentration of a sugar alcohol mixture in a feed stream and length of the column (10 cm, 15 cm, 20 cm, and 30 cm) were changed to find the optimum column length and operation sensitivities of the feed condition. The adsorption behaviors of two sugar alcohols were the linear isotherms. The isotherm parameters were determined by the single step frontal analysis. The robust operating condition and optimum column length were decided by considering the sensitivities of purity and yield of products.

Extraction of Perillyl Alcohol in Korean Orange Peel by Supercritical CO2

Supercritical fluid extraction (SFE) in a pilot plant was carried out to extract perillyl alcohol (POH) from Korean orange peel. The extract from the powder of Korean orange peel was obtained by supercritical CO2 at operating conditions of 50°C, 200 bar, and 6 CO2 kg/h/kg sample. Most of the POH was extracted within 14 hours in the experiment. The yield of extract containing POH was 2.5% based on the dry powder of the orange peel. The content of POH in the extracts was 2.8 × 10−3 (wt%) by GC analysis based on the dry powder, which indicated that SFE was approximately 30 times more efficient than the solvent-extraction method previously reported. A brief comparison of SFE and solvent extraction was made. The SFE extracts were further purified by open tubular chromatography to confirm POH in the extracts.

Optimum solvent selectivity and gradient mode for deoxyribonucleosides in reversed-phase high-performance liquid chromatography

The separation condition for five deoxyribonucleosides (dCyd, dUrd, dGuo, dThd, and dAdo) was determined by the optimization of mobile phase conditions. In this work, the binary system of water and methanol was applied in RP-HPLC. The elution profiles were calculated using plate theory based on the quadratic equation of retention factor, ln k=A+BF+CF2, and F was the volume percent of methanol. We modified the plate theory to calculate elution profile in both step and linear gradient mode. The optimal mobile phase composition was obtained by comparing the resolutions of the five deoxyribonucleosides and the separation times of last-eluting solute (dAdo) in step gradient elution. Also, in linear gradient elution, resolutions and separation time could be predicted by a slight modification of the relationship used in step gradient mode. The final calculated result for the resolution of five deoxyribonucleosides suggested that the appropriate first mobile phase composition was water/methanol 88/12 vol.%, then after 7 min the second composition of water/methanol, 65/35 vol.% was step-changed. Under experimental conditions, the agreement between the experimental data and the calculated values was relatively good.

Parameter estimation of perillyl alcohol in RP-HPLC by moment analysis

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 μm, and the particles were packed in the column (3.9 × 300 mm). 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 intraparticle diffusivity were determined from the slope and intercept of a plot ofH vs 1/u0, respectively. The contributions of each mass-transfer step were axial dispersion, fluid-toparticle mass transfer, and intraparticle diffusion.

Mobile phase compositions for ceramide III by normal phase high performance liquid chromatography

Ceramide III was prepared by the cultivation ofSaccharomyces 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/Isoprophyl Alcohol (IPA) andn-hexane/n-butanol and one ternary mobile phase ofn-hexane/IPA/methanol were demonstrated. For the binary mobile phase ofn-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 7.87 min, while it was 4.11 min respectively in the ternary system, where the mobile phase composition ofn-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.

Sensitivity analysis of amino acids in simulated moving bed chromatography

We conducted a sensitivity analysis of the simulated moving bed (SMB) chromatography with the case model of the separation of two amino acids phenylalanine and tryptophan. We consider a four-zone SMB chromatography where the triangle theory is used to determine the operating conditions. Competitive Langmuir isotherm model was used to determine the adsorption isotherm. The finite difference method is used to solve nonlinear partial differential equation (PDE) systems numerically. We examined the effects of alterations in the operating conditions (feed-extract, feed-raffinate, eluent-extract, eluent-raffinate, recycle, and switching time) and the adsorption isotherm parameters (Langmuir isotherm parametersa andb) on SMB efficiency. The variation range of operating conditions and Langmuir isotherma was between −50 and 50% of original value and the variation range of the Langmuir isothermb was between 2.25−5 and 2.255 times of original value.

Correlation of HETP and experimental variables in preparative liquid chromatography

HETP (Height Equivalent to a Theoretical Plate) is widely designated as the column efficiency in Chromatographic separations. The effects of experimental variables such as concentration, injection volume, flow rate and composition of the mobile phase, column diameter, and column length on HETP were investigated by preparative liquid chromatography. Water and methanol as an organic modifier were used as the mobile phase. A sample of thymidine was injected into C18 columns with different dimensions. From fifty experimental runs, it was shown that the larger amounts of sample and higher flow rates increased HETP and an optimum HETP existed at a column diameter of 7.8 mm for preparative packings used in this experiment. The experimental values of HETP were correlated into a quadratic equation with the interaction terms based on the logarithmic experimental values of the experimental variables ; its regression coefficient was 0.952. The experimental variables were simulated from the correlation equation, and their effects on HETP were discussed.

SUPERCRITICAL FLUID EXTRACTION OF PERILLYL ALCOHOL IN KOREAN ORANGE PEEL

A series of experiments for supercritical fluid extraction (SFE) were carried out to extract the perillyl alcohol (POH) from Korean orange peel. The yield of extract from the Korean orange peel powder was investigated under the temperatures of 30–60°C, the pressures of 150–200 bar, and the CO2 flow rates of 1.5–3.5 L/min. It was found that the yield of SFE extract containing POH was obtained as 1% of the dry powder of the orange peel. By GC-analysis of the peel oils obtained by SFE in the experimental ranges, the content of POH was 2.8 × 10−3 (%, wt.) based on the dry powder, which indicated that SFE was approximately 30 times more efficient than the solvent-extraction method previously reported. The SFE-extracts were further purified by gravity-flow packed column chromatography to confirm POH in the extracts.

Comparing the performance of one-column process and four-zone simulated moving bed by computer simulation

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™ 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.