Yinzhe Jin

Effect of Concentration of Ionic Liquid 1‐Butyl‐3‐Methylimidazolium, Tetrafuoroborate, for Retention and Separation of Some Amino and Nucleic Acids

Abstract In this paper, three nucleic acids such as cytosine, cytidine, and thymine and two amino acids, such as D‐tryptophan and N‐carbobenzyloxy‐D‐phenylalanine, were chromatographed using ionic liquid as an additive for the mobile phase in high performance liquid chromatography (HPLC). Ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafuloroborate ([BMIm]+ [BF4]−), was used. The nucleic acid eluent was 5 vol. % of the modifier (methanol:acetonitrile=95:5 (vol. %)), in 10 mM of sodium phosphate monobasic, with addition of 0.5, 2.0, and 4.0 mmol/L of ionic liquid. Separation of nucleic acids was obtained on a commercially available octadecyl silica column (4.6×150 mm i.d., and particle size 5 µm). In the case of D‐amino acids, the mobile phase was 65% methanol in water, with additions of 0.5, 1.0, 2.0, 8.0, 12.0, and 15.0 mmol/L of ionic liquid. The experiments were performed on a stainless steel column, 3.9×300 mm i.d., and particle size 15 µm, packed with octadecyl‐bonded silica at the laboratory. Effects of the concentration of ionic liquid for retention and separation of some nucleic and amino acids were discussed. The results showed the potential application of ionic liquid as a mobile phase additive in liquid chromatography.

Adsorption Isotherm of Ibuprofen on Molecular Imprinted Polymer

A molecular imprinted polymer (MIP) using (+)-(S)-2-(4-isobutylphenyl) propionic acid ((+)-(S)-ibuprofen) as the template and 4-vinylpyridine (4-VPY) as the functional monomer was prepared. Chloroform and acetonitrile were used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator. Comparison of ibuprofen adsorption isotherm on molecular imprinted and blank polymers was made by the static method. The adsorption equilibrium data were correlated into the Freundlich, Langmuir, Sips (Langmuir-Freundlich) and Radke-Prausnitz isotherm models, respectively. By a nonlinear regression analysis, the experimental parameters in the equilibrium isotherms were estimated and compared. The calculated data is well fitted with the experimented data. Through the analysis, the ibuprofen imprinted polymer showed higher adsorption ability than blank polymer.

Separation of Catechin Compounds by Retention Theory in RP‐HPLC

Abstract An efficient optimization method was used to separate catechin compounds by RP‐HPLC. In this work, the binary mobile phase of water and acetonitrile was used with the buffer of acetic acid (AA). The elution profiles were calculated by the plate theory based on the linear and quadratic equations of retention factor, lnk=Ink w +SF, lnk=L+MF+NF 2, k=A+B/F, where F was the vol.% of acetonitrile. We modified the retention theory to calculate the elution profile in both isocratic and gradient modes. The final calculated results showed that the first mobile phase composition was water in 0.1% AA/acetonitrile in 0.1% AA, 90/10 vol.%, followed 30 min later by the second composition of mobile phase, which was linearly changed to 70/30 vol.%. In the experimental conditions, the agreement between the experimental data and the calculated values was relatively good. Catechin compounds from Korean and Chinese green tea as potential powers of anticancer and antioxidant components were target materials in this work. The full content of the catechin compounds of EGC, (+) C, EC, EGCG, and ECG in Chinese green tea extracted was 249.92 mg/g, so it was 2.15 times of that from Korean tea.

Prediction of the Elution Profile of Aromatic Compounds in RP‐HPLC

Abstract An efficient prediction method for the elution profile was used to separate aromatic compounds such as benzene, toluene, chlorobenzene, o‐xylene, and 1,2‐dichlorobenzene by RP‐HPLC. The retention factor and bandwidth were predicted under linear‐gradient condition with the three retention models. The elution profiles were calculated based on the linear and quadratic equations of retention factor, lnk=lnk w +Sϕ, lnk=L+Mϕ+Nϕ2, k=A+B/ϕ, where ϕ was the vol.% of methanol. The elution profiles were calculated by the Gaussian distribution with obtained retention factor and bandwidth. Two kinds of experiments were performed; one is the isocratic runs to estimate the coefficients of three retention models, and the other is the linear gradient runs that were carried out with same initial mobile phase composition (water/methanol=96/4, vol.%), two final mobile phase compositions (water/methanol=24/76 and 40/60, vol.%), and three gradient times (20, 40, and 60 min). The predicted elution profiles by the three retention models and new prediction method have good agreement with experimental data in the employed gradient conditions. The minimum average errors of calculated and experimental results of aromatic compounds were lower than 3.5% by Bi‐poly equation.

Extraction and Purification of Depigmenting Agents from Chinese Plants

Depigmenting agents were solvent-extracted and purified by preparative and analytical HPLC from three Chinese plants; Chrysanthemum morifolium Ramat (Xizang Caijuhua), Rhodiola sachalinensis , and Terminalia chebula Retzius . Four fractions obtained from the ethyl ether layer of C. m. Rama and two fractions from the ethyl acetate layer of Rhodiola salientness show depigmenting effects. At δ 200, the ethyl acetate layers of Chrysanthemum morifolium Ramat, Rhodiola sachalinensis and the methanol extract of Terminalia chebula Retzius , can inhibit the melanin production of mouse B16 melanoma cells by 92%, 60% and 90%, respectively, whereas 46% inhibition was observed by commercially available depigmenting agents (arbutin). These results show the potential of these three Chinese plants as a novel resource for depigmenting agents in the cosmetic industry.

Adsorption Isotherms of Quercetin and Catechin Compounds on Quercetin-MIP

A molecular imprinted polymer(MIP) was prepared with quercetin as the template and methacrylic acid(MAA) as the functional monomer. Acetonitrile and methanol were used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator. The experimental parameters of the equilibrium isotherms were estimated via linear and nonlinear regression analyses. The linear equation as the functions of the adsorption concentration of the single compound in its solution and the competitive adsorption of the single compound in its mixed compounds solution was then expressed, and the adsorption equilibrium data were correlated to Langmuir and Freundlich isotherm models. The mixture compounds show competitive adsorption on the specific binding sites of quercetin-MIP. Furthermore, the competitive Langmuir isotherms were applied to the mixture compounds. The adsorption concentrations of quercetin, (+) catechin (+C), and (-) epicatechin (EC) on the quercetin molecular imprinted polymer were compared. The quercetin-imprinted polymer shows extraordinarily higher adsorption ability for quercetin than for the two catechin compounds that were also assessed.

Dielectric properties of Antarctic krill (Euphausia superba) and white shrimp (Penaeus vannamei) during microwave thawing and heating

ABSTRACT Dielectric properties of Antarctic krill and white shrimp were measured across the microwave frequency range 300–3000 MHz in a temperature range of −20 to 20 °C. To shorten thawing time, the effects of salt, sucrose and moisture contents on dielectric properties at 915 and 2450 MHz were also studied during microwave thawing (MT) and microwave heating (MH). The results indicate that the change in sucrose content had a smaller effect on dielectric properties, and only addition of salt had a significant influence (p < 0.05) on dielectric properties during MT. Moreover, when these shrimps with addition of a salt–sucrose mixture at 3% w/w were thawed and heated to 20 °C, the microwave processing time was no more than 130 s. Compared with the samples without any additives, thawing time shortened significantly when salt and sucrose were simultaneously added to the samples. Besides, the centre temperature and temperature distribution within the cross section of shrimps confirmed effects of various additives on dielectric properties, suggesting that MT and MH can be applied to the processing of freshwater and oceanic shrimp, and that addition of only salt or the salt–sucrose mixture can further quicken thawing and heating rates to optimize the industrial processing of shrimp.