Monodisperse lignin fractions as standards in size-exclusion analysis: Comparison with polystyrene standards

The difficulty of preparing monodisperse lignin fractions on a large scale is a limiting factor in many applications. The present paper addresses this problem by examining the properties and size-exclusion behavior of lignin isolated by the acetosolv pulping process from post-extraction crushed sugarcane bagasse. The isolated lignin was subjected to a solvent pretreatment, followed by preparative gel permeation chromatography fractionation. The fractions were analyzed by high-performance size-exclusion chromatography (HPSEC) and these samples showed a great decrease in polydispersity, compared to the original acetosolv lignin. Several fractions of very low polydispersity, close to unity, were employed as calibration curve standards in HPSEC analysis. This original analytical approach allowed calibration with these lignin fractions to be compared with the polystyrene standards that are universally employed for lignin molecular mass determination. This led to a noteworthy result, namely that the lignin fractions and polystyrene standards showed very similar behavior over a large range of molecular masses in a typical HPSEC analysis of acetosolv lignin.     

磁性纳米粒子在生物传感器中的应用研究进展

磁性纳米粒子是一种新型纳米材料,可应用于各种生物活性物质如蛋白质、DNA等的富集和分离,药物的磁靶向,以及疾病的诊断和治疗等许多领域。由于磁性纳米粒子有着独特的化学和物理性能,已经成功应用到磁控生物传感器、DNA传感器、蛋白质传感器、酶传感器以及其它类型的生物传感器中,并显著提高了生物传感器检测的灵敏度、缩短了生化反应的时间和提高检测的通量,为生物传感器领域开辟了广阔的应用前景。本文概述了磁性纳米粒子在生物传感器中的应用研究进展。     

Thermoresponsive magnetic colloids

The combination of magnetic nanoparticles with thermoresponsive polymer systems leads to the formation of hybrid particle dispersions or composites with a variety of interesting properties and perspectives, including instant dispensability, thermoreversible formation of magnetic fluids, and novel magnetoresponsive properties. Special interest is gained by the magnetic heatability of magnetic particles that allows the activation of thermal effects by the application of a high-frequency electromagnetic field. This review summarizes the recent developments in this young field of research with application potential for magnetic separation, drug release systems, and for sensor and actuator purposes.     

功能化磁性纳米粒子在乳状液制备及破乳中的应用及作用机制

功能化磁性纳米粒子因其独特的理化性质,在乳状液制备与破乳领域的应用受到广泛关注。本文归纳了功能化磁性纳米粒子的制备方法、合成结构与特征性质,阐述了其在乳状液制备及破乳中的应用过程,重点分析了磁性纳米粒子在溶液中良好分散、稳定吸附于油水界面排布为膜结构的作用行为,尤其是磁性纳米粒子的磁响应特征对乳状液中界面性质、液滴形貌及运动状态的影响,并进一步总结出其表面性质及作用行为对稳定乳状液或使乳状液破乳的规律。针对磁性纳米粒子对乳状液稳定性影响规律的探究可为其在应用领域提供理论支持。最后本文就功能化磁性纳米粒子研究中亟待解决的新问题作出展望。     

Planar chromatographic separation of petroleum residues and coal-derived liquids

Vacuum distillation residues from two petroleum crudes, a coal liquefaction extract and a coal tar pitch have been fractionated by planar chromatography (PC) using two solvent sequences: pyridine–acetonitrile and tetrahydrofuran (THF)–toluene. Fractions recovered from PC were examined by UV-fluorescence spectroscopy (UV-F), size-exclusion chromatography (SEC). UV-F and SEC of the whole samples showed differences in aromatic cluster size and molecular mass (MM) ranges which could be related to the different origins of the samples. The MM ranges indicated by SEC were greater for the vacuum residues than for coal-derived materials. However, the UV-F spectra of the fractions indicated that the petroleum residue fractions contained similar aromatic types, whereas the fractions from coal liquids contained significantly different aromatic types. SEC profiles of the fractions indicated a separation of coal-derived samples by increasing molecular size with increasing immobility in PC, whereas for petroleum fractions, the same trend was not apparent. MALDI-mass spectra of the set of original samples showed broadly similar ranges of MM distributions but additional work is necessary to identify appropriate matrices and procedures in order to improve the MALDI spectra.     

Magnetoanalysis of micro/nanoparticles: a review

Application of magnetic field on the separation and analysis of nano/microparticles is a growing subject in analytical separation chemistry. The migration phenomenon of a particle under inhomogeneous magnetic field is called magnetophoresis. The migration velocity depends on the magnetic susceptibility and the size of a particle. Therefore, magnetophoresis allows us to determine the magnetic susceptibility of particles, and to separate particles based on the magnetic properties. Magnetic separation of ferromagnetic particles in liquid has been utilized for a long time. For example, a high gradient magnetic separation under the non-uniform magnetic field generated by ferromagnetic mesh has been utilized in a wide region from chemical industry to bioscience. Recent progress on magnetic nanoparticles and microfluidic devices has made it possible to extend the range of application. Furthermore, it has been demonstrated that the very sensitive measurement of the magnetic susceptibility of microparticles can be performed by observing magnetophoretic velocity. In this review, we mainly introduce novel separation and detection methods based on magnetophoresis, which have been invented in this decade, and then new principles of particle migration under magnetic field are presented.     

Application of magnetic solid phase extraction in separation and enrichment of glycoproteins and glycopeptides

The analysis of endogenous glycoproteins and glycopeptides in human body fluids is of great importance for screening and discovering disease biomarkers with clinical significance. However, the presence of interfering substances makes the direct quantitative detection of low-abundance glycoproteins and glycopeptides in human body fluids one of the great challenges in analytical chemistry. Magnetic solid phase extraction (MSPE) has the advantages of easy preparation, low cost and good magnetic responsiveness. Magnetic adsorbents are the core of MSPE technology, and magnetic adsorbents based on different functional materials are widely used in the quantitative analysis of glycoproteins and glycopeptides in human body fluids, making it possible to analyze glycoproteins and glycopeptides with low abundance as well as multiple types, which provides a technical platform for screening and evaluating glycoproteins and glycopeptides in body fluids as disease biomarkers. In this paper, we focus on the recent advances in the application of MSPE technology and magnetic adsorbents for the separation and enrichment of glycoproteins and glycopeptides in human body fluids, and the future trends and application prospects in this field are also presented.     

Methodology for determination of magnetic force of polymeric nanocomposites

Magnetic nanocomposites present several interesting uses. They are very useful in environmental recovery, drug delivery and sensor applications. However, sophisticated magnetic measurements are very complex and present high costs, which may sometimes prevent research on these materials. Therefore, this paper presents a magnetic force test, which can be performed at relatively low cost and produces interesting results, which are very useful to support the development of these magnetic materials. Specifically, polylactic acid (PLA)/maghemite nanocomposites were prepared and characterized using Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS) and size-exclusion chromatography (SEC). Our results demonstrate that nanocomposites, were obtained, which were also subjected to the magnetic force and magnetic susceptibility tests. The results of these latter tests were found to be linearly related, which proves the utility of the magnetic force test as a practical characterization technique.     

Speciation of nickel,copper, zinc,and manganese in different edible nuts: a comparative study of molecular size distribution by SEC–UV–ICP–MS

Molecular size distribution patterns of Cu, Mn, Ni, and Zn were determined in several nut species by size-exclusion liquid chromatography (SEC) coupled on-line to UV and inductively coupled plasma mass spectrometry (ICP–MS) for detection. The molecular weight (MW) fractionation of the different metals was performed with a Superdex Peptide column, injecting 100 L of the extracted solutions. The association of the elements with different MW fractions was observed with sequential detection by UV and ICP–MS. Various separation conditions were evaluated to obtain proper resolution and reproducible results with the size-exclusion column. Complete MW information of the elemental fractions in the nut samples was obtained within a retention time of 30 min. Fractionation of the above mentioned elements was done in nine different nut species commonly found in commercial markets. Variability of the fractionation patterns for two different extraction media, 0.05 mol L^–1 NaOH and 0.05 mol L^–1 HCl, was evaluated for every nut sample. Differences in the elemental fractionation patterns were found depending on the extraction procedure, nut species, and the type of element studied. It was also observed that the elements studied showed predominant association with high MW fractions when extracted with basic solution whereas with acidic extraction media only low MW fractions were obtained.     

Synthesis and surface engineering of magnetic nanoparticles for environmental cleanup and pesticide residue analysis: A review

In recent years, water pollution and pesticide accumulation in the food chain have become a serious environmental and health hazard problem. Direct determination of these contaminants is a difficult task due to their low concentration level and the matrix interferences. Therefore, an efficient separation and preconcentration procedure is often required prior to the analysis. With the advancement in nanotechnology, various types of magnetic core–shell nanoparticles have successfully been synthesized and received considerable attention as sorbents for decontamination of diverse matrices. Magnetic core–shell nanoparticles with surface modifications have the advantages of large surface‐area‐to‐volume ratio, high number of surface active sites, no secondary pollutant, and high magnetic properties. Due to their physicochemical properties, surface‐modified magnetic core–shell nanoparticles exhibit high adsorption efficiency, high rate of removal of contaminants, and easy as well as rapid separation of adsorbent from solution via external magnetic field. Such facile separation is essential to improve the operation efficiency. In addition, reuse of nanoparticles would substantially reduce the treatment cost. In this review article, we have attempted to summarize recent studies that address the preconcentration methods of pesticide residue analysis and removal of toxic contaminants from aquatic systems using magnetic core–shell nanoparticles as adsorbents.     

Magnetic hyperthermia: Potentials and limitations

Despite the fact that the magnetic hyperthermia (MH) has been known for more than 75 years, it is still debated in its clinical applications. The generation of a higher temperature at a tumor is called hyperthermia. There is a different of temperature ranges going from 39 to 40 ?°C up to such high temperatures as 80–90 ?°C. However, due to its high potential, MH is used along with nanoparticles as heat intermediaries in the treatment of cancer. Many Magnetic Nanoparticles (MNPs) with several properties and morphological metallic structures have been useful to magnetics hyperthermia therapy. These MNPs are categorized into two groups; magnetic alloy nanoparticles (MANPs) and magnetic metal oxide nanoparticles (MMONPs). The principal challenges of this method are the control of local tumoral temperature and the increase in nanoparticles heating power. The hyperthermia agents derived from magnetic nanoparticles along with magnetic field. In the recent study, hyperthermia thought, dissimilar types of magnetic nanoparticles for hyperthermia, efficacy for cancer therapy, advances, challenges, and future chances have been examined.     

Heterostructured magnetic nanoparticles: their versatility and high performance capabilities

Magnetic nanoparticles exhibit unique nanoscale properties and their utilization for various magnetic systems is of significant interest. Especially, heterostructured magnetic nanoparticles are emerging as next-generation materials due to their synergistically enhanced magnetism and potential multifunctionalities. Herein, we overview the recent advances in the development of magnetic nanoparticles with a focus on multicomponent heterostructured nanoparticles including alloys, core-shells, and binary superlattices synthesized via nonhydrolytic methods. Their multifunctionalites and high performance capabilities are demonstrated for applications in high density magnetic storages, chemical catalysis, and biomedical separation and diagnostics.     

Analytical fractionation of aquatic humic substances by metal affinity chromatography on iron(III)-coated cellulose

The chromatographic fractionation of aquatic humic substances (HS) onto iron(III)-coated cellulose (Cell-Fe(III)) as a metal-loaded adsorbent is described, analogously to the separation principle of the well-established metal affinity chromatography (MAC). For that purpose the sorption of HS from different aquatic origin on that collector was characterized by their kinetics and equilibrium distribution coefficients Kd. Based on Kd values of 10³ to 10⁴,mL/g, and fast sorption kinetics a preparative HPLC procedure, using stepwise increased pH-values (pH 8–12.5, borate buffer) as an eluent, was developed for the fractionation of dissolved HS (up to 7 fractions of different amount). The fractions obtained by this MAC procedure from selected aquatic HS samples were different in their Cu(II) complexation capacity, absorbance ratio E_{265 nm}/E_{365 nm} and Fourier transform infrared spectra. Received: 14 June 1999 / Revised: 6 August 1999 / Accepted: 10 August 1999     

Analytical fractionation of aquatic humic substances by metal affinity chromatography on iron(III)-coated cellulose

The chromatographic fractionation of aquatic humic substances (HS) onto iron(III)-coated cellulose (Cell-Fe(III)) as a metal-loaded adsorbent is described, analogously to the separation principle of the well-established metal affinity chromatography (MAC). For that purpose the sorption of HS from different aquatic origin on that collector was characterized by their kinetics and equilibrium distribution coefficients Kd. Based on Kd values of 10³ to 10⁴,mL/g, and fast sorption kinetics a preparative HPLC procedure, using stepwise increased pH-values (pH 8–12.5, borate buffer) as an eluent, was developed for the fractionation of dissolved HS (up to 7 fractions of different amount). The fractions obtained by this MAC procedure from selected aquatic HS samples were different in their Cu(II) complexation capacity, absorbance ratio E_{265 nm}/E_{365 nm} and Fourier transform infrared spectra. Received: 14 June 1999 / Revised: 6 August 1999 / Accepted: 10 August 1999     

Characterization of Diamond Nanoparticles by High-Speed Micro-Thermal Field-Flow Fractionation

Micro-thermal field-flow fractionation was used to characterize the particle size distribution of nanometer-sized diamond nanoparticles. Although the experimental conditions were chosen to perform high-speed separation, and, consequently, the resolution achieved experimentally was not very high, the application of the original correction method for the zone spreading allowed for obtaining of very good calculated particle size distribution or, explicitly, a true polydispersity index of the diamond nanoparticle sample. The future use of several samples of diamond nanoparticles of different average sizes and different surface chemistries should allow deeper insight into the effect of these particulate characteristics on the retention in micro-thermal field-flow fractionation.     

Magnetic solids in analytical chemistry: A review

Magnetic solids are widely used in detection and analytical systems because of the performance advantages they offer compared to similar solids that lack magnetic properties. These solids can be used to pre-concentrate analytes and for the magnetic separation and molecular identification of biomolecules, and organic and inorganic species. Magnetic solid separation techniques also offer benefits over centrifugation, filtration, and solid-phase extraction. In this review, we describe the synthesis, characterization and applications of a series of solids including silica supports, carbon nanotubes, alumina, organic polymers and other materials, mostly containing magnetite or paramagnetic metals. Also addressed are the future perspectives of magnetic solid applications.     

Characterization of the microstructure of impact polypropylene alloys by preparative temperature rising elution fractionation

Two polypropylene alloys (Samples A and B), as impact polypropylene (PP) with similar ethylene contents and melt indices but different impact properties at low temperatures, are fractionated into eight fractions using preparative temperature rising elution fractionation. The microstructure of the original samples and their fractions are studied using high-temperature gel permeation chromatography, Fourier transform infrared spectroscopy, ¹³C nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. The results indicate that the two alloys are mainly composed of four portions: ethylene–propylene random copolymer (EPR), ethylene–propylene segmented copolymer, ethylene–propylene block copolymer, and propylene homopolymer. Sample A contains more EPR and more fractions with higher isotacticity eluted at 120 and 140 °C than Sample B. The difference in the microstructure distributions of both PP alloys results in observable differences in their mechanical properties: Sample A has better impact toughness and possesses higher rigidity than Sample B. Sample A also exhibits better balance between toughness and stiffness.     

Synthesis,physico‐chemical and biological study of trialkylsiloxyalkyl amine coated iron oxide/oleic acid magnetic nanoparticles for the treatment of cancer

New original water‐soluble magnetic nanoparticles based on natural components, magnetite–oleic acid–biologically active silyl modified alkanolamine, were synthesized. Physico‐chemical characterization, i.e. magnetic properties, concentration of magnetite, size of iron oxide core, of the nanoparticles synthesized and the corresponding magnetic fluids obtained, was carried out. Magnetic fluids were screened for in vitro cytotoxicity concerning human fibrosarcoma (HT‐1080), mouse hepatoma (MG‐22A) monolayer tumour cell lines and normal mouse fibroblasts (NIH 3T3). They possess low or moderate cytotoxic effects, are non‐toxic, exhibit high NO‐induction ability and strongly change tumour cell morphology. Copyright © 2008 John Wiley & Sons, Ltd.     

Magnetic Nanoparticles and Biosciences

Summary.  Magnetic nanoparticles represent an interesting material both present in various living organisms and usable for a variety of bioapplications. This review paper will summarize the information about biogenic magnetic nanoparticles, the ways to synthesize biocompatible magnetic nano- particles and complexes containing them, and the applications of magnetic nanoparticles in various areas of biosciences and biotechnologies. Received October 4, 2001. Accepted November 19, 2001     

Analytical methods for separating and isolating magnetic nanoparticles

Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. In this review, we summarize the separation techniques that have been initially used for this purpose. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. Further development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes.