Correction to: Asymmetric Flow Field-Flow Fractionation: Current Status,Possibilities, Analytical Limitations and Future Trends

Chromatographia - A correction to this paper has been published: https://doi.org/10.1007/s10337-021-04054-7     

Fractionation and characterization of a protein–polysaccharide complex from Pleurotus tuberregium sclerotia

A water‐soluble sample (TM4b), extracted from sclerotia of Pleurotus tuberregium, was analyzed using elemental analysis, one‐ and two‐dimensional ¹H and ¹³C NMR. The results indicated that TM4b was protein–polysaccharide complex, and the polysaccharide moiety was hyperbranched β‐D ‐glucan with residuals branched at C3, C2, C4, and C6 positions. A preparative size‐exclusion chromatography (SEC) column combined with nonsolvent addition method was used to fractionate TM4b, and nine fractions were obtained. Solution properties of TM4b in 0.15 M aqueous NaCl were studied using static laser light scattering and viscometry at 25 °C. The dependences of intrinsic viscosity ([η]) and radius of gyration (〈S²〉) on weight–average molecular weight (M_w) for TM4b in the M_w range from 1.89 × 10⁴ to 2.58 × 10⁶ were found to be [η] = 0.21M and 〈S²〉 = 3.63M. It indicated that TM4b existed as compact sphere conformation in the aqueous solution. Atomic force microscopy image further confirmed that the TM4b molecules exhibited globular shape in the solution. This work gave valuable information on fractionation and chain conformation characterization of the globular protein–polysaccharide complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2546–2554, 2007     

Fractionation of Poly(butyl methacrylate) by Molecular Topology Using Multidetector Thermal Field‐Flow Fractionation

Thermal field‐flow fractionation (ThFFF) is an interesting alternative to column‐based fractionation being able to address different molecular parameters including size and composition. Until today it has not been shown to be able to fractionate polymers of similar molar masses and chemical compositions by molecular topology. The present study demonstrates that poly(butyl methacrylates) with identical molar masses can be fractionated by ThFFF according to the topology of the butyl group. The influence of the solvent polarity on the thermal diffusion behavior of these polymers is presented and it is shown to have a significant influence on the fractionation of poly(n‐butyl methacrylate) and poly(t‐butyl methacrylate). Fractionation improves with increasing solvent polarity and solvent polarity may have a greater influence on fractionation than solvent viscosity. It is found that the thermal diffusion coefficient, D_T, as well as the hydrodynamic diameter, D_h, exhibit increasing trends with increasing solvent polarity. The solvent quality has a significant influence on the fractionation. It is found that cyclohexane, being a theta solvent for poly(t‐butyl methacrylate) but not for poly(n‐butyl methacrylate), significantly improves the fractionation of the samples by decreasing the diffusion rate of the former but not the latter.

     

磷脂的分离纯化及高效毛细管电泳分析

采用溶剂提取和柱色谱法分离纯化市售大豆粉末磷脂(卵磷脂含量14.05%),得到高纯度的卵磷脂产品(纯度92.80%)。重点建立了磷脂的胶束电动毛细管色谱(MECC)分离分析方法。以分离度和峰面积为优化指标,对表面活性剂及其浓度、电泳缓冲液pH、有机改性剂及其含量、缓冲液浓度、温度等条件进行优化,确定了最优化电泳条件:电泳缓冲液为35 mmol/L脱氧胆酸钠-1 mmol/L 硼砂缓冲液/正丙醇(体积比为57∶43)(pH 8.30),柱温44 ℃,操作电压25 kV,检测波长200 nm;内加法定性磷脂组分;外标法定量卵磷脂。结果表明,MECC法能有效分离5种磷脂组分;0.1～1 g/L的质量浓度范围内卵磷脂的线性关系良好(r=0.9990),平均回收率为98.0%,日内、日间精密度分别为1.36%和3.27%,定性结果与薄层色谱法、红外光谱法的定性结果相符。     

Enhanced Lipidome Coverage in Shotgun Analyses by using Gas-Phase Fractionation

A high resolving power shotgun lipidomics strategy using gas-phase fractionation and data-dependent acquisition (DDA) was applied toward comprehensive characterization of lipids in a hen ovarian tissue in an untargeted fashion. Using this approach, a total of 822 unique lipids across a diverse range of lipid categories and classes were identified based on their MS/MS fragmentation patterns. Classes of glycerophospholipids and glycerolipids, such as glycerophosphocholines (PC), glycerophosphoethanolamines (PE), and triglycerides (TG), are often the most abundant peaks observed in shotgun lipidomics analyses. These ions suppress the signal from low abundance ions and hinder the chances of characterizing low abundant lipids when DDA is used. These issues were circumvented by utilizing gas-phase fractionation, where DDA was performed on narrow m/z ranges instead of a broad m/z range. Employing gas-phase fractionation resulted in an increase in sensitivity by more than an order of magnitude in both positive- and negative-ion modes. Furthermore, the enhanced sensitivity increased the number of lipids identified by a factor of ≈4, and facilitated identification of low abundant lipids from classes such as cardiolipins that are often difficult to observe in untargeted shotgun analyses and require sample-specific preparation steps prior to analysis. This method serves as a resource for comprehensive profiling of lipids from many different categories and classes in an untargeted manner, as well as for targeted and quantitative analyses of individual lipids. Furthermore, this comprehensive analysis of the lipidome can serve as a species- and tissue-specific database for confident identification of other MS-based datasets, such as mass spectrometry imaging.

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Fractionation of lyophilized MIBI kit for99mTc labeling

Summary The lyophilized MIBI kit was dissolved in 1 ml sterile saline or 250<span style='font-size: 12.0pt;font-family:Symbol;mso-bidi-font-family:Symbol'>mg/ml ascorbic acid and dispensed into 0.2 ml fractions, which were stored at -20 °C for 12 days. The solution was prepared by using two different protection methods. In the first method evacuated vials were used for storage of fractionated solution while in the second method an antioxidant agent, ascorbic acid was employed. The radiochemical impurity of ^99mTc-MIBI in the unprotected fractions rises with time. Exclusion of air as well addition of ascorbic acid in fractionated solutions gave very good results. The labeling efficiency and biodistribution of fractionated solutions was the same as the lyophilized kit even after 12 days.     

Application of the Numerical Fractionation Approach to the Design of Biofunctional PEG Hydrogel Membranes

A mathematical model is described for surface‐initiated photopolymerization of PEG‐DA forming crosslinked biofunctional PEG hydrogel membranes based on the NF technique. The model includes an additional monomer with biological functionality, which is a common experimental strategy for the design of ECM mimics in tissue engineering in order to direct signaling pathways, and considers concentration‐dependent VP propagation and reaction diffusion termination. The influence of these features on the crosslink density of the soluble and gel phases, the progression through gelation, sol/gel fraction, and molecular weight distribution of biofunctional PEG hydrogel are studied using the NF model. This model may be useful for specific applications of tissue engineering.

     

Thermal Field-Flow Fractionation as a Powerful Tool for the Fractionation of Complex Synthetic Polymers: A Perspective

Chromatographia - Synthetic polymers have complex molecular structures with distributions in molar mass, chemical composition, functionality and molecular topology. For the comprehensive analysis...     

Reconstruction of the Chain Length Distribution for Vinyl‐Divinyl Copolymerization Using the Numerical Fractionation Technique

A proposed theory for evaluating the chain length distribution (CLD) using the numerical fractionation (NF) technique was extended to the vinyl‐divinyl (VDV) copolymerization. The CLD is reconstructed for this system, in which pendant double bond propagation leads to crosslinking and gel formation. The method was earlier developed for a non‐linear free‐radical polymerization scheme where chain transfer to polymer and termination by combination resulted in gel formation. The VDV study presented indicates that the proposed method of weighted summation (WS) accurately predicts the resulting CLDs evaluated using NF.

Comparison of the overall polymer NF and the direct solution CLDs near the gel point.     

Tutorial: Field-Flow Fractionation

A simple model of a crystalline solid that leads to an electronic band structure is presented. The development requires no quantum mechanics beyond that taught in most physical chemistry courses and can be taught in a single one-hour lecture.     

Branched versus linear polyisoprene: Fractionation and phase behavior

Branched polyisoprene (PI) was prepared from PI-macromonomers. Linear byproducts of the synthesized polymer were removed by means of inverse spin fractionation, using the solvent cyclohexane (CH) and the precipitant acetone (AC). A well-defined fraction (M_w = 17.5 kg/mol, M_w/M_n = 1.8) of the branched polyisoprene obtained in this manner was used to determine different phase diagrams with branched and/or linear PI in the mixed solvent CH/AC at 25 °C. For comparable molar masses of the polymers the two-phase area is smallest for the branched PI and slightly larger for the linear PI; in the case of the unfractionated original sample of the branched polymer one observes a pronounced peninsula of immiscibility extending into the region of high CH concentrations. This feature is attributed to a large miscibility gap between the branched and the linear polymer, which was studied in more detail for the ternary system CH/branched PI/linear PI.     

Fractionation of Cynara cardunculus (cardoon) biomass by dilute-acid pretreatment

Cynara cardunculus L. (cardoon) is a Mediterranean perennial herb offering good potential as substrate for sustainable production of bioethanol. In this work the first approach to the study of dilute-acid pretreatment of cardoon biomass for biological conversion was made. The influence of temperature (160-200 degrees C), acid concentration (0-0.2% [w/w]), and solid concentration (5-10% [w/v]) in the formation of free sugars and sugar decomposition products in the prehydrolyzate was studied using a response surface methodology. Results show a negative interaction effect between acid concentration and temperature in xylose recovery yield in prehydrolyzate, whereas dry matter concentration does not exert a significant effect. Xylose recovery yield reaches a maximum of about 80% of the content in dry untreated raw material at 180 degrees C and 0.1 or 0.2% acid addition. At these conditions the ratio of monomers found in prehydrolyzate in relation to total sugar yield for xylose is close to 100%. Furfural concentration, the major furan determined in the prehydrolyzate, increases as pretreatment severity rises. Maximum furfural yield of 4.2 g/100 g dry untreated raw material was found at 200 degrees C and 0.2% acid concentration. The yield of furfural at the conditions in which maximum xylose recovery is attained is substantially lower, less than 2 g/100 g dry untreated raw material. This fact supports the idea of using moderate temperatures in dilute-acid processes, which at the same time provides reasonably high sugar recovery yield and avoids high inhibitory products formation.     

Fractionation of chlorinated and brominated persistent organic pollutants in several food samples by pyrenyl-silica liquid chromatography prior to GC-MS determination

A high-performance liquid chromatography (HPLC) method using a column of 2-(1-pyrenyl) ethyldimethylsilylated silica was developed in this work in order to achieve satisfactory and reproducible fractionation of polychlorinated biphenyls (PCBs) from brominated flame retardants (BFRs) (polybrominated diphenylethers, PBDEs; and polybrominated biphenyls, PBBs). After the study of different chromatographic parameters (mobile phase composition and separation temperature were the most important) an isocratic elution with isooctane:toluene (98:2, v/v) at a flow-rate of 1 mL/min, a temperature of 45 °C, and UV-detection at 225 nm was selected for fractionation of PCBs (time region, 4.0-5.8 min) from PBDEs (5.8-9.0 min) and from PBBs (5.8-11.0 min). The applicability of this method to food samples was demonstrated by fractionating PCBs from PBDEs in three food samples (cheese, milk, and fish). Interferences from PCBs (present in real samples at much higher concentrations than PBDEs) were removed in this way. In addition, by analysing these samples by gas chromatography-mass spectrometry (GC-MS) with and without previous fractionation we were able to observe an improvement in detection sensitivity for PBDEs after HPLC fractionation.     

Multidetector Thermal Field‐Flow Fractionation as a Novel Tool for the Microstructure Separation of Polyisoprene and Polybutadiene

For the first time, it is demonstrated that thermal field‐flow fractionation (ThFFF) is an efficient tool for the fractionation of polyisoprene (PI) and polybutadiene (PB) with regard to molecular microstructure. ThFFF analysis of 1,4‐ and 3,4‐PI as well as 1,4‐ and 1,2‐PB samples in tetrahydrofuran (THF), THF/cyclohexane, and cyclohexane reveals that isomers of the same polymer family having similar molar masses exhibit different Soret coefficients depending on microstructure for each solvent. The separation according to microstructure is found to be based on the cooperative influence of the normal and the thermal diffusion coefficient. Of the three solvents, cyclohexane has the greatest influence on the fractionation of the isomers. In order to determine the distribution of isomeric structures in the PI and PB samples, the samples are fractionated by ThFFF in cyclohexane and subsequently analyzed by ¹H NMR. The isomeric distributions determined from NMR data correlate well with ThFFF retention data of the samples and thus further highlight the unique fractionating capabilities of ThFFF. The interplay of the normal and thermal diffusion coefficients that are influenced by temperature and the mobile phase opens the way to highly selective fractionations without the drawbacks of column‐based separation methods.

     

Cross Fractionation of Styrene-Butadiene Copolymer

A sample of styrene-butadiene copolymer was fractionated by successive precipitation (one-direction fractionation) in cyclohexane/isooctane and benzene/methyl ethyl ketone systems. The chemical composition and molecular weight distributions of the sample were constructed from the fractionation data. The results obtained in both systems were nearly identical for the chemical composition distribution, but were different for the molecular weight distribution. The same sample was fractionated by cross fractionation using both solvent/nonsolvent systems. Comparing the results of cross fractionation with the results of one-direction fractionation, the first gave broader molecular weight and chemical composition distribution curves than the second. However, only cross fractionation showed that the chemical composition distribution curve has a long tail not only at the right side but also at the left side of the distribution maximum.

The superiority of cross fractionation over one-direction fractionation seems clear from the present work. It is also clear that even if the chemical composition distribution curves obtained by one-direction fractionation in different systems are identical with one another, the curves do not always show the true distribution.     

Fractionation of apple procyanidins by size-exclusion chromatography.

Oligomeric constituents of apple procyanidins were fractionated by size-exclusion chromatography using a TSKgel Toyopearl HW-40F column. The best separation was obtained using a mobile phase of acetone-8 M urea (6:4; adjusted to pH 2) at a flow-rate of 1.0 ml/min. In this chromatographic system, the use of 8 M urea in the mobile phase resulted in a molecular sieve effect without any surface affinity interaction between the gel beads and the procyanidin molecules. Each fraction obtained was examined by reversed-phase high-performance liquid chromatography and time-of-flight mass spectrometry. The order of elution of the procyanidins from the column was coincident with their degree of polymerization.     

Advances in Crystallization Elution Fractionation

Summary: Crystallization Elution Fractionation has been optimized to improve resolution power and reduce co-crystallization. Most important step to be optimized is the first separation cycle of Dynamic Crystallization which can be investigated with the help of Crystallization Analysis Fractionation experiments. A new approach to reduce co-crystallization and improve resolution is presented by applying successive cooling and heating cycles in a long column. The new process known as Multiple Crystallization Elution Fractionation adds extended separation at each cooling and heating cycles.