Quantitative determination of triacylglycerol profile of structured lipid by capillary supercritical fluid chromatography and high-temperature gas chromatography

Two analytical methods have been developed for the qualitative and quantitative analyses of triacylglycerol profile of structured lipid (SL)-containing medium-chain and long-chain fatty acids. Supercritical fluid chromatography (SFC) was used in the first method. The SL was dissolved in chloroform/methanol, 95:5 (vol/vol), and analyzed directly using a super-critical fluid chromatograph equipped with temperature and density programming capabilities. No derivatization was required for sample preparation. An SB-methyl-100 capillary column (10 m, 100 μ i.d., 0.25 μ film thickness) was used for the separation of the triacylglycerol species and a flame-ionization detector (FID) was used for the detection. Supercritical fluid carbon dioxide was used as the mobile phase. In the second method, the SL was hydrogenated to complete saturation prior to analysis using gas chromatography at high temperatures of up to 375°C. A DB-5HT capillary column (30 m × 0.32 mm i.d., 0.1 μ film thickness) was used for the separation. FID was used for the detection and helium gas was used as mobile phase. The triacylglycerol species were separated and identified based on their equivalent carbon number (ECN), the total carbon number of the acyl side chains. A calibration curve was constructed using a triacylglycerol mixture containing known amounts of monoacyltriacylglycerol standard materials ranging from ECN 18 (trihexanoin) to ECN 66 (tridocosanoin). The novel triacylglycerol species, ECN 32–43, created by the interesterification of medium-chain triacylglycerol (MCT) and long-chain triacylglycerol (LCT) were separated and identified based on their retention times. These triacylglycerols, ECN 32–43, were absent in the physical mixture of MCT and LCT. The unique triacylglycerol specieis, ECN 32-43, were therefore selected as the fingerprinting region for the qualitative identification of the SL. Quantitation of the novel triacylglycerol species in the SL was achieved by using the integrated peak area of the new species. Both methods were employed successfully to distinguish the physical mixture from the corresponding interesterified SL. Results generated by the two methods were compared and found to be in good agreement.     

蛋白质在温度响应性PNIPAAm接枝硅胶表面吸附和解吸过程:分子模拟和实验研究(英文)

Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorption.Molecular dynamics simulation at an all-atom level was performed to illustrate the adsorption/desorption behavior of cytochrome c,the model protein,on PNIPAAm-grafted-silica,a temperature responsive adsorbent.At a temperature above the lower critical solution temperature(LCST),the PNIPAAm chains aggregate on the silica surface,forming a hydrophobic surface that is favorable for the hydrophobic adsorption of cytochrome c,which has a high exposure of hydrophobic patches.At temperatures below the LCST,the PNIPAAm chains stretch,forming hydrophilic surface due to hydrogen bonding between PNIPAAm and surrounding water.Desorption of cytochrome c on the PNIPAAm-grafted-silica surface occurs as a result of competition with water,which forms hydrogen bonds with the protein.The conformational transitions of both cytochrome c and PNIPAAm are monitored,providing molecular insight into this temperature-responsive RPC technique.PNIPAAm-grafted-silica beads were synthesized and used for the adsorption and desorption of cytochrome c at approximately 313 K and 290 K,respectively.The experimental results validate the molecular dynamics simulation.In comparison to conventional RPC,using temperature as a driving force for RPC reduces the risk of protein denaturation caused by exposure to chaotropic solvents.Moreover,it simplifies the separation process by avoiding the buffer exchange operations between the steps.     

铜基催化剂上甲醇合成的动态反应动力学

Adsorption, surface reaction and process dynamics on the surface of a commercial copper-based cata-lyst for methanol synthesis from CO/CO2/H2 were systematically studied by means of temperature programmed desorption (TPD), temperature programmed surface reaction (TPSR), in-situ Fourier transform-inferred spectroecopy(FTIR) and stimulus-response techniques. As a part of results, an elementary step sequence was suggested and a group of ordinary differential equations (ODEs) for describing transient conversations relevant to all species on the catalyst surface and in the gas phase in a micro-fixed-bed reactor was derived. The values of the parameters referred to dynamic kinetics were estimated by fitting the solution of the ODEs with the transient response data obtained by the stimulus-response technique with a FTIR analyzer as an on-line detector.     

拟稳态模型用于间歇萃取精馏的数值模拟

Batch extractive distillation (BED) is a special method used in the distillation process by adding a solvent into the batch distillation column to alter the relative volatility of the components and improve the separation. A comprehensive design and simulation method is required due to the complexity of BED. In this study, a quasi-steady-state model for BED is proposed, the derivation and solution of the model are presented. This shortcut model can be used to simulate the composition and temperature of the reboiler, the top and other plates of the column in a batch extractive distillation operation. The calculated values are in good agreement with the experi-mental data. The results show that the quasi-steady-state model is a practical method because of some advantages such as high precision and fast calculation.     

Adsorption equilibrium for Z-ligustilide on C18-bonded silica from supercritical carbon dioxide

Adsorption equilibrium is of great importance for the preparative supercritical fluid chromatography(pre-SFC) in defining supercritical adsorption behavior and the industrial amplification.This paper presents adsorption isotherms of Z-ligustilide from supercritical carbon dioxide(SC-CO_2) on C18-bonded silica.Adsorption behavior was studied at 305.15 K,313.15 K and 323.15 K with SC-CO_2 density varying from 0.687 g·cm~(-3) to0.863 g·cm~(-3) with the elution by characteristic points(ECP) method.The adsorption amount of Z-ligustilide from SC-CO_2 on C18-bonded silica decreased with the increasing density of the mobile phase as well as the increasing temperature.Adsorption equilibrium data were fitted by Langmuir and Freundlich isotherm models,and the Langmuir isotherm model performed better for describing the whole adsorption process on the column.The monolayer saturation adsorption capacity of Z-ligustilide is in the range of 3.0 × 10~(-4) mg·cm~(-3) to5.5 × 10~(-4) mg·cm~(-3) with an average value of 4.0 × 10~(-4) mg·cm~(-3).     

Analysis of ionogenic surfactants by HPLC with ion-pair extraction detector

A technique for developing a selective and highly sensitive detection method was studied, which responds to particular ionogenic surfactants using a system of connecting the post-column reaction detector with a high performance liquid chromatograph (HPLC). HPLC conditions used for the separation were: column packing and size, TSK-LS410 (5μ) and 6 mm i.d. × 250 mm; mobile phase, a mixture of methanol, water, sodium perchlorate and phosphoric acid. A Technicon AutoAnalyzer II system was used as the post-column reaction detector. Orange II was used to form the hydrophobic ion-pair complexes for cationic and amphoteric surfactants, and Methylene blue for anionic surfactants. By this method, cationic, amphoteric and anionic surfactants were easily identified in the chromatograms. The analytical results of their homolog distributions were in good agreement with those obtained by conventional gas chromatographic (GC) methods.     

Hybridization of metal–organic framework and monodisperse spherical silica for chromatographic separation of xylene isomers

Metal–organic frameworks(MOFs) packed in the column have been a promising candidate as the stationary phase for high performance liquid chromatography(HPLC). However, the direct packing of irregular MOF powder could raise some problems like high back pressure and low column efficiency in the HPLC separation. In this work, UiO-66 capable of separating xylenes was supported effectively on the surface of the monodisperse spherical silica microspheres by one-pot method. The hybridization of Ui O-66 and silica microspheres(termed UiO-66@SiO_2 shell–core composite) was prepared by stirring the suspension of the precursors of Ui O-66 and\\COOH terminated silica in the N,N-dimethylformamide with heating. The shell–core composite material UiO66@SiO_2 was characterized by SEM, TEM, PXRD and FTIR. Then, it was used as a packing material for the chromatographic separation of xylene isomers. Xylene isomers including o-xylene, m-xylene and p-xylene were efficiently separated on the column with high resolution and good reproducibility. Moreover, the Ui O-66@SiO_2 shell–core composites packed column still remained reverse shape selectivity as Ui O-66 possessed, and the retention of xylenes was probably ascribed to the hydrophobic effect between analytes and the aromatic rings of the Ui O-66 shell. The Ui O-66@SiO_2 shell–core composites obtained in this study have some potential for the separation of structural isomers in HPLC.     

Concentration of mixed acid by electrodialysis for the intensification of absorption process in acrylic acid production

The absorption process in acrylic acid production was water-intensive. The concentration of acrylic acid before distillation process was low, which induced to large amount of wastewater and enormous energy consumption.In this work, a new method was proposed to concentrate the side stream of absorption column and thus increase the concentration in bottom product by electrodialysis. The influence of operating conditions on concentration rate and specific energy consumption were investigated by a laboratory-scale device. When the voltage drop was 1 V·cP~(-1)(1 cP=10~(-3) Pa·s), flow velocity was 3 cm·s~(-1) and the temperature was 35 °C, the concentration rates of acrylic acid and acetic acid could be 203.3% and 156.6% in the continual-ED process. Based on the experimental data, the absorption process combined with ED was simulated, in which the diluted solution from ED process was used as spray water and the concentrated solution was feed back to the absorption column. The results shown that the flow rate of spray water was decreased by 37.1%, and the acrylic acid concentration at the bottom of the tower was increased by 4.56%. The ions exchange membranes before and after use 1200 h were tested by membrane surface morphology(scanning electron microscope), membrane chemical groups(infrared spectra), ion exchange capacity, and membrane area resistance, which indicated the membrane were stable in the acid system. This method provides new method for energy conservation and emission reduction in the traditional chemical industry.     

Physicochemical characterization of galactosyldiglycerides and their quantitation in wheat flour lipids by high performance liquid chromatography

A high performance liquid chromatographic (HPLC) method was developed for analyzing digalactosyldiglycerides (DGDG) and monogalactosyldiglyceride (MGDG) in polar lipids fractionated from lipid extracts of wheat or flour. Wheat lipid samples were prepared by solvent extraction, then fractionated on a silica gel packed open column. A Spherisorb ODS (octadecyl silane) column with methanol/water elution system was used for separation of glycolipids in the polar lipid fractions. The detection limit of the refractive index detector with interferometric optics was 0.25μg for both DGDG and MGDG. Separating on nonpolar bonded phase columns permitted us to differentiate, based on fatty acid composition and position, among components within the specific glycolipid classes. Semipreparative HPLC on analytical columns was used to subfractionate the polar lipids. The glycolipids were collected for functional group characterization. Approximately 35% of each DGDG subfraction was accounted for as carbohydrate. The absence of phosphorus precluded phospholipids. Fatty acid analysis by gas chromatography showed the first DGDG to be linoleic acid, whereas the second DGDG peak was composed of linoleic, oleic and palmitic acids. Mass spectrometric analysis of the first DGDG peak showed linoleic acid in both the SN-1 and 2 positions. Mass spectrometric analysis revealed that palmitic or oleic acid in the second peak was preferentially located on the SN-1 position; linoleic acid was on the SN-2 position. Contribution no. 80-207J, Department of Grain Science and Industry, Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS. Part of a dissertation submitted by T.N. Tweeten in partial fulfillment of the PhD degree. Honored Student Award Presentation at AOCS annual meeting, San Francisco, April 1979.     

Hemicellulose in corn straw:Extracted from alkali solution and produced 5-hydroxymethyl furfural in HCOOH/HCOONa buffer solution☆

Hemicellulose in corn straw is a group of complex heteropolysaccharides which are composed of different sugar units, including mannans, xylans, arabinans and galactans. This study developed a simple and practical process for production of 5-hydroxymethyl furfural(HMF) using hemicellulose that was extracted from corn straw. In the hemicellulose degradation process HCOOH/HCOONa was used as buffer solution, and the optimum conditions for maximum HMF yield were explored. Various extraction conditions including NaOH concentration, reaction time,temperature, solid-to-liquid ratio and precipitant were tested for hemicellulose obtaining, giving the optimum condition of 55 °C, 4 h, solid-to-liquid ratio of 1:10, 1.5 mol·L~(-1) NaOH solution and ethanol as precipitant with the yield of 34.16%. Dehydration of hemicellulose under HCOOH/HCOONa buffer solution process, using solution medium of pH = 0.8 hydrolyzed hemicellulose in corn straw at 190 °C after 190 min and 82% of HMF yield was achieved.     

高效液相色谱法测定三烯丙基异氰尿酸酯的含量

建立了高效液相色谱测定三烯丙基异氰尿酸酯含量的分析方法。通过实验确定了最佳色谱条件,色谱柱:Ultmate-C18柱(250 mm×4.6 mm,5μm);柱温:25℃;流动相:V(甲醇)∶V(0.1 mol/L磷酸-磷酸二氢钠缓冲溶液(pH为3.0))=60∶40;检测波长:210 nm;流速:1.0 mL/min。结果表明,三烯丙基异氰尿酸酯的浓度在1.0～200.0 mg/L范围内线性良好,相关系数为0.999 9,平均回收率为99.33%,相对标准偏差为1.81%,最低检出限为0.2 mg/L,最低定量限为1.2mg/L。本法简便、快速、准确,重复性好,可有效测定三烯丙基异氰尿酸酯的含量。     

基质固相分散-高效液相色谱法测定烟草中的茄呢醇

研究了用基质固相分散-高效液相色谱法测定烟草中的茄呢醇。将m(烟草样品)/m(硅胶)=1∶4充分研磨后装柱,用环己烷-二氯甲烷洗脱样品中的茄呢醇,然后以ZORBAX Stable Bound(4.6×10 mm,1.8μm)C18快速分离柱为固定相,甲醇-四氢呋喃为流动相分离,蒸发光散射检测器检测;样品中的茄呢醇在0.8min内可达到基线分离。方法标准回收率为97%～102%,RSD为1.6%～2.2%。     

高效液相色谱法测定白酒中纽甜含量

建立了一种高效液相色谱法(HPLC)测定白酒中纽甜含量的方法。沸水浴加热除去乙醇,纯水定容至相应体积,采用二极管阵列检测器(DAD),Agilent Eclipse XDB-C18柱(4.6 mm×250mm,5μm),流动相为乙腈-离子对缓冲溶液(体积比25∶75),进样量20μL,柱温30℃,检测波长218nm进行检测,外标法定量。添加回收率范围为97%～102%。     

粉唑醇GC和HPLC分析方法

采用气相色谱法和液相色谱法分别对粉唑醇进行了定性和定量分析。气相色谱法中以正二十烷为内标物,色谱柱采用3%OV-101 chromosorb AW DMCS 150-177μm1m×3mm玻璃柱,柱温为195℃,汽化温和检测温均为230℃,方法回收率为99.2%～100.9%,变异系数为0.262%。高效液相色谱法中Nova-PaK C18 250 mm×4.6mm色谱柱,以v(甲醇)+v(水)=851∶5为流动相,检测波长为262nm。方法回收率为98.9%～99.4%,变异系数为0.505%。     

莽草酸发酵液的快速检测方法

建立了采用高效液相色谱法快速测定发酵液中蔗糖、莽草酸和芳香族氨基酸含量的方法,为微生物发酵生产莽草酸的工艺控制提供便捷. 色谱条件为：Hypersil APS-2色谱柱(5 mm, 250 mm×4.6 mm),检测波长215 nm,示差检测器和紫外检测器联用,流动相为pH 2.5的磷酸水溶液和乙腈(体积比20:80),柱温30℃,流速1.0 mL/min,进样量10 mL. 在该条件下所测各物质的线性回归方程相关系数均大于0.9986,加样回收率为95%~105%,相对标准偏差均小于2.0%.     

高效液相色谱-二极管阵列检测法测定马来酸和乙醛酸

建立了高效液相色谱-二极管阵列法同时测定乙醛酸和马来酸的高效液相色谱方法。色谱条件为:Shim-pack VP.ODS柱(250 mm×4.6 mm I.D.,5μm);二极管阵列检测器;流动相为甲醇/磷酸盐缓冲溶液(NaH2PO4浓度为0.1 mol/L,H3PO4调节至pH=2.98),体积比为5∶95,流速为1.0 mL/min,检测波长为195 nm,柱温为40℃。线性范围分别为79.6～26 660 mg/L和9.3～7 864 mg/L,检出限分别为39.4 mg/L和4.7 mg/L;日内、日间测定的相对标准偏差(RSD):乙醛酸为0.22%和0.46%,马来酸为0.02%和0.03%。     

电还原邻硝基苯酚合成邻氨基苯酚的高效液相色谱分析法

建立了一种反相高效液相色谱法同时测定邻硝基苯酚和邻氨基苯酚的新方法。采用Shim-pack VP-ODS(250 mm×4.6 mm,4.6μm)色谱柱,选用纯甲醇为流动相,以285 nm为检测波长,流速为0.8 m L/min,柱温为35℃,以外标法进行定量分析。实验结果表明,邻硝基苯酚和邻氨基苯酚的质量浓度在1.0~40.0μg/m L范围内呈良好的线性关系,其相关系数分别为r=0.999 5(n=9)和r=0.999 8(n=9),测定其在10.0、20.0和30.0μg/m L这3个不同质量浓度下的方法精密度,其相对标准偏差分别≤1.28%和≤1.04%。将本方法应用于以邻硝基苯酚为原料电解合成邻氨基苯酚反应液的分析,其加标回收率分别在93.0%~105.6%和90.6%~106.2%之间,相对标准偏差分别≤3.75%和≤1.44%。实验结果表明,该方法可用于邻硝基苯酚和邻氨基苯酚两种组分的同时测定。     

HPLC法测定生姜提取液中6-姜酚含量的研究

建立了测定生姜提取液中6-姜酚含量的高效液相色谱方法。采用Agilent ODS C18(250 mm×4.6 mm,5μm)色谱柱,以纯水-乙腈(体积比为58∶42)为流动相,流速为1.2 mL/min,柱温35℃,在282 nm用紫外检测器进行检测。结果表明,重复测定结果的相对标准偏差在0.77%,回收率在95%~105%范围内。该方法的灵敏度高,准确性和重现性良好,有效消除了样品中其他组分对目标峰的干扰,线性范围宽,分离度好,可用来准确分析生姜提取液中6-姜酚的含量。     

二甲戊灵的GC和HPLC分析方法研究

采用气相色谱法和高效液相色谱法两种方法分别对二甲戊灵原药进行定量分析,气相色谱法以邻苯二甲酸二戊酯为内标物,采用HP-5石英毛细管色谱柱（30．0m×320μm×0．25μm）和FID检测器,色谱条件为柱箱采用程序升温,200℃保持0．5min,以10℃／min速率升至240℃,保持2．5min;进样口温度260℃,检测器温度250℃,气体流速为载气（N2）1ml／min,燃气（Hz）30ml／min,助燃气（Air）350ml／min,分流比1：40．本方法的变异系数、平均回收率、线性相关系数分别为0．0779％、100．06％、0．9999。高效液相色谱法中使用ZORBOX Eclipse XDB-C18150mm×4．6mm（i．d）不锈钢柱色谱柱,DAD检测器,以甲醇＋水=80＋20（V＋V）为流动相,检测波长为236nm。二甲戊灵的平均回收率为99．08％,方法变异系数为0．112%;,线性相关系数为0．9999。     

3-甲基-γ-辛内酯超临界流体色谱立体异构性制备拆分

用填充柱超临界流体色谱制备性拆分香料3-甲基-γ-辛内酯4个光学立体异构体。3-甲基-γ-辛内酯(合成的)首先在硅胶柱上制备拆分得其cis-、trans-异构体。然后,在分析模式下,考察手性柱种类、改性剂种类、改性剂含量、柱温、柱压的影响,获得拆分cis-、trans-异构体的较佳超临界流体色谱条件,cis-异构体:手性柱Chiralpak AD-H,柱温30℃,柱压9 MPa,改性剂甲醇体积分数4.0%,流动相流速1.5 mL/min,分离度1.45;trans-异构体:手性柱Chiralpak AD-H,柱温30℃,柱压10 MPa,改性剂甲醇体积分数4.5%,分离度2.24。在较佳的条件下对cis-、trans-异构体进行制备规模手性拆分得mg级4个光学立体异构体产品,光学纯度(对映体过量e.e)均为100%。