Fabrication of acrylate monolith using photopolymerization: Effect of light intensity on electrochromatographic performance

A hexyl acrylate monolith was prepared via photopolymerization into a cyclic olefin copolymer micro-device for reversed-phase electrochromatography purposes. This work deals with the influence of the irradiation conditions (irradiation time and light intensity) used during synthesis on the electrochromatographic performances of the monolithic column obtained. Up to day, the monolith structure was often controlled by means of irradiation time at constant light intensity, but the effect of light intensity (irradiance) on the monolith structure was scarcely considered. This study shows a strong effect of light intensity on electrochromatographic efficiency. Using an optimal light intensity of 4.7 mW/cm(2) and an irradiation time of a few minutes allows obtaining heights equivalent to a theoretical plate reaching down to 5 μm for the reversed-phase separation of six polycyclic aromatic hydrocarbons.     

Numerical simulation to correlate photopolymerization kinetics monitoring by RT-NIR spectroscopy and photocalorimetry

Photocalorimetry (DSC) and real time infrared (RTIR) spectroscopy are the two usual methods used to follow photopolymerization reactions. Kinetics obtained by DSC on thin samples and kinetics obtained by real time near-infrared (RT-NIR) spectroscopy on thick samples are not the same. The heat release during the photopolymerization induced a high temperature increase in thick samples because of the absence of temperature control. We think that this temperature offset is the main cause of this kinetic difference. In this paper, we want to verify this assumption. To reach this aim, conversion and temperature evolutions versus time were numerically simulated for a sample placed in the thermal conditions of NIR analysis by using experimental kinetic data obtained by photocalorimetry in isothermal mode. The boundary conditions were determined such as the simulated evolution of the sample temperature is the same as the experimental one. At last, conversion curves simulated to obtain these temperature profiles were compared to experimental results obtained by RT-NIR.     

Temperature depending light scattering measurements of aqueous gelatin and alginate solutions and their mixtures

Highly diluted solutions of an alkaline treated pig bone gelatin and a seaweed alginate of Macrocystis pyrifera have been investigated by means of static light scattering at various temperatures. With these results the thermodynamic properties found by other authors and us before can be verified. Furthermore, diluted mixtures of both polymers with different ratios of composition have been investigated. These measurements show that both polymers in all mixtures behave quasi-binarily in the investigated temperature range. They maintain their association phenomena of the pure polymer solutions.     

Characterization of gold nanoparticle bioconjugation by resonance light scattering correlation spectroscopy

<正>Gold nanoparticles(GNPs) have been widely used as probes and nanomaterials in certain biological and biomedical fields thanks to its special physical and chemical properties.However,it is still difficult to characterize GNPs-bioconjugates in solution,which has greatly limited further bioapplications of GNPs.In this study,we reported a single particle method for characterizing GNPsbiomolecules in solution using resonance light scattering correlation spectroscopy(RLSCS).The interaction of GNPs with bovine serum albumin(BSA) and thiol-modified oligonucletides were investigated.     

青霉素类药物的共振光散射光谱分析

本文研究了青霉素钠-碱性品红缔合物的共振散射光谱,建立了pH =7.5的C-L缓冲溶液中,共振光散射法测定青霉素钠的新方法.线性回归方程△IRu=1.74+5.17C,相关系数R=0.9981,检测限3.16×10-7mol/L.该方法简单快速,灵敏度高,对实际样品进行了测定,得到了令人满意的结果.     

光散射分析技术测定盐酸环丙沙星含量

在pH 4.6的乙酸-乙酸钠缓冲溶液中,环丙沙星能与四苯硼钠作用生成沉淀产生光散射信号(LS)能应用普通荧光分光光度计检测,从而建立了环丙沙星的光散射分析法.LS光谱在385.0 nm处,具有特征散射峰,且增强的光散射强度(ΔILS)与0.03～0.2 μg/mL,0.2～2.5 μg/mL两个范围内的环丙沙星溶液呈线性关系,相对应的检出限分别为7.4,2.7 ng/mL.本实验中研究了酸度、聚乙二醇600溶液的浓度、四苯硼酸钠溶液的浓度以及共存物质对LS强度的影响.方法已用于盐酸环丙沙星片剂中环丙沙星的测定,RSD为0.3%～0.6%.     

Structural and dynamic properties of colloidal liquids and gases of silica spheres (29 nm in diameter) as studied by the light scattering measurements

Static and dynamic light-scattering measurements are made for colloidal-liquids and -gases of silica spheres (29 nm in diameter) in the exhaustively deionized aqueous suspension and in the presence of sodium chloride. Single broad peak is observed in the light-scattering curve and the liquid-like and gas-like distributions have been observed. Colloidal crystals are not formed at any sphere concentrations. The nearest-neighbored interparticle distances of colloidal liquids, l _obs , agree excellently with the effective diameters of spheres (d _eff ) including the electrical double layers in the effective soft-sphere model and also with the mean intersphere distances, l _o , calculated from the sphere concentration, i.e., l _obs ≈d _eff ≈ l _o . This relation supports the importance of the electrostatic interparticle repulsive interaction. Two dynamic processes have been extracted separately from the time profiles of autocorrelation function of colloidal liquids. Decay curves of colloidal gases are characterized by the single translational diffusion coefficients, which are always lower than the calculation from the Stokes-Einstein equation using true diameter of spheres and increase as ionic concentration increases. These experimental results emphasize the importance of the expanded electrical double layers and the electrostatic intersphere repulsion on the structural and dynamic properties of the colloidal liquids and gases. Electronic Publication     

Thermal transitions in associating aqueous block copolymers: light scattering,rheology and spectroscopy

Solutions containing a polyoxy-ethylene/polyoxy-propylene/polyoxy-ethylene (PEO–PPO–PEO) block copolymer, indicated as F68, in water were investigated as a function of composition and temperature. Hydrogen nuclear magnetic resonance (¹H NMR) line width, chemical shift, self-diffusion, spin-lattice relaxation times, laser light scattering and rheological methods were used. The monomer–micelle equilibrium and the micelle–liquid crystalline phase transitions depend on the F68 content in the mixture and temperature. Significant changes in light scattering intensity and apparent hydrodynamic radius are associated to micelle formation above the critical micellar temperature (CMT). According to a Contin analysis, this behaviour is reflected in the presence of two populations in the intensity–intensity autocorrelation functions. The contributions due to molecules and micelles can be evaluated separately. No such effects are observed below the CMT. Micelle onset is also associated to variations in ¹H NMR spectra, affecting the chemical shift, line width and spin-lattice relaxation time of the PPO methyl protons and self-diffusion, as well. Spin-lattice relaxation times of PEO chains, conversely, change significantly at temperatures close to the micelle–liquid crystalline thermal transition. Similar results were obtained from the line width of ²H NMR spectra as a function of T. Significant changes in both viscous and elastic modulus were also observed and ascribed to PPO dehydration, at the CMT, as well as to squeezing and dehydration of PEO units in liquid crystal formation, respectively.     

Determination of soluble phosphates in water samples using ytterbium(III) and dynamic measurements of light scattering intensity at long wavelength

A selective and fast method has been developed for the determination of phosphates by measuring the formation of ytterbium(III) phosphate through the variation of the light scattering intensity with time. The low solubility of this compound causes an efficient dispersion of the radiation at 490 nm, which is measured at 980 nm using the second-order grating effect. This approach minimizes potential background signals from the sample matrix. The initial rate of the system is automatically obtained in only 0.5 s by stopped-flow mixing technique. The variable optimization study has been carried out using univariate and multivariate methods. The dynamic range of the calibration graph is 0.09–7.9 mmol L⁻¹ (Pearson's correlation coefficient = 0.9999) and the detection limit is 0.03 mmol L⁻¹. The precision of the method, expressed as relative standard deviation, is 2.3%. The study of the potential interference of different inorganic anions showed that arsenate is the main interferent, although it is tolerated in a molar ratio of 5.5. The method has been satisfactorily applied to the determination of soluble phosphates in tap, ground and river water using a previous preconcentration step with a Dowex 1 (1 × 4–400) anionic resin. A 500-fold concentration has been achieved, which has allowed to decrease the detection limit up to 60 mmol L⁻¹. The recovery range is 97.5–102.5%. The results obtained are consistent with those obtained with the standard molybdenum blue method.     

Macromolecular size of polyelectrolytes containing ammonium and sulfonic acid groups, as determined by light scattering

The macromolecular dimensions of fractionated polyelectrolytes poly(4-vinylpyridine) quaternized (PVPyQ), poly[(3-methacryloylamino) propyltrimethyl ammonium chloride] (PMPTA), poly(diallyl dimethyl ammonium chloride) (PDDA), and poly[(3-methacryloylamino) propyltrimethyl ammonium chloride-co-2-acrylamido-2-methyl-1-propanesulfonic acid] P(MPTA-co-APSA), were determined by light scattering, using aqueous electrolyte as solvent. PVPyQ, PMPTA, and P(MPTA-co-APSA) of various comonomer compositions were synthesized by radical polymerization. All polymers were fractionated by membrane ultrafiltration. Light scattering measurements on dialyzed solutions give good Zimm plots from which the average molecular weight, , mean squared radius of gyration, 〈s²〉, and second virial coefficient, A₂, were determined. No significant selective sorption of the electrolyte by the polyelectrolytes was detected. Positive A₂ values are obtained in all cases, corresponding to good solvent conditions, however, the interpenetration function, Ψ, has low values (0.01-0.10), showing that the excluded volume effect is relatively low. In PDDA, the dependence of 〈s²〉 on suggests that the coil of this polyelectrolyte is contracted by branching. In the ammonium-sulfonic copolymers, the comonomer stoichiometric feed 1:1 yields an insoluble copolymer (possible complex formation between amino and sulfonic groups). The soluble copolymers (with unbalanced comonomer compositions) have dimensions similar to the homopolymers, and not appreciably dependent on composition; hence no contraction due to complex formation is detected in these copolymers.     

Detection of aggregate formation during production of human immunoglobulin G by means of light scattering

In human immunoglobulin preparations with a concentration of 50 mg/ml aggregate formation below 0.3% is difficult to quantify. Such small traces may later be responsible for reduced stability and therefore this generation during the process must be prevented. The influence of process conditions on the conformational changes and subsequent aggregation of immunoglobulins were assessed by size-exclusion chromatography (SEC), UV and static light scattering (LS) detection. This work focused on pH-adjustment experiments since several pH adjustments are required during the production of intravenous immunoglobulin G. Experiments in a labscale were made varying process conditions in a narrow range. It was possible to detect differences concerning the formation of aggregates dependent on these small variations of process conditions.     

圣草次苷-CTAB-DNA三元体系共振光散射光谱研究及应用

基于圣草次苷和十六烷基三甲基溴化胺(CTAB)的二元体系增强DNA的共振光散射(resonance light scattering,RLS)信号,提出了一种测定纳克级小牛胸腺DNA(ctDNA)的新方法.研究了圣草次苷、CTAB与DNA的结合方式并讨论了三元体系的最佳反应条件.增强的RLS信号与DNA浓度具有良好的线性关系,线性方程为ΔIRLS=28.33+1241c,r=0.9953.采用该方法对合成样品进行了分析测定,回收率和RSD分别为96.51%~101.38%和2.56%~3.90%,检出限为1.942μg·L^-1.     

Proposed performance qualification and calibration method for evaporative light scattering detectors

Summary A method for the performance testing of Sedex 55 Evaporative Light Scattering Detectors (ELSD) has been developed as part of our regulatory compliance programme. The method uses a readily available chromatographic column, caffeine as the test probe and can be completed in less than one hour.     

Resonance scattering spectroscopy of gold nanoparticle

The gold nanoparticles in diameter of 10-95 nm have been prepared by Frens procedure, all of which exhibit a resonance scattering peak at 580 nm. The mechanism of resonance scattering for gold nanoparticle has been considered according to the wave motion theory of nanoparticle in liquid. The principle of superamolecular interface energy band(SIEB) has been set up and utilized to explain the relationship between the diameter and colors for gold nanoparticle in liquid. A novel spectrophotometric ruler for the determination of the diameter has been proposed according to the relationship of the maximum absorption wavelength and diameter.     

In-situ surface-enhanced Raman scattering and FT-Raman spectroscopy of black prints

The black inkjet and laser prints were analysed with regard to application in forensic analysis of questioned documents. The purpose of this work was to study spectral properties and compare the suitability of surface-enhanced Raman scattering (SERS) with Fourier transform Raman spectra of prints. This work aimed to find optimal surface-enhanced Raman spectroscopic approach for the future analysis of documents using statistical methods. In this work, we analysed eight prints of four laser and four inkjet devices. The samples were measured using two dispersive Raman devices; (DXR Raman microscope with excitation line 532 nm, Foram 685-2 spectrometer − 685 nm) and FT-Raman device (Bruker Spectrometer MultiRAM with excitation line 1064 nm). The silver nanoparticles (AgNPs) colloid for SERS experiment were synthesised and checked by UV–vis spectroscopy and scanning electron microscopy (SEM). The remarkable differences caused by centrifugation of silver colloid were observed just in the SEM images. The main contribution of this paper is to propose the novel approach achieving sufficient SERS signal intensity of black prints using the both, laser and inkjet printers. Moreover, this method is based on just a single metal colloid, and the analysis can be performed in-situ, i.e. directly on the printed sample surface. We consider the SERS could by highly promising and universal for applications in the forensic analysis of printed documents with the combination of statistical method when conventional methods are not effective.     

A new instrument for the measurement of very small electrophoretic mobilities using phase analysis light scattering (PALS)

A new instrument based on the principles of phase analysis light scattering (PALS) applied to the measurement of electrophoretic mobilities has been produced. Such measurements are particularly useful in the study of dispersions in non-polar media since for a given zeta potential, the mobility is proportional to the dielectric constant. It is also potentially useful where mobilities are low and the use of high electric fields (a traditional remedy) is inappropriate. This is the case when the ionic concentration and hence conductivity of the medium is high. The PALS configuration has been shown to be able to measure mobilities at least two orders of magnitudes lower than conventional LDE. The device is based on developments reported elsewhere (J. Miller et al., J. Colloid Interface Sci. 143 (2) (1991) [1]), but has a number of new features. In particular, all the signal processing is digital and the optical system a reference beam configuration.     

Direct visual detection of DNA based on the light scattering of silica nanoparticles on a human papillomavirus DNA chip

A detection system for a human papillomavirus (HPV) DNA chip based on the light scattering of aggregated silica nanoparticle probes is presented. In the assay, a target HPV DNA is sandwiched between the capture DNA immobilized on the chip and the probe DNA immobilized on the plain silica nanoparticle. The spot where the sandwich reaction occurs appears bright white and is readily distinguishable to the naked eye. Scanning electron microscopy images clearly show the aggregation of the silica nanoparticle probes. When three different sized (55 nm, 137 nm, 286 nm) plain silica nanoparticles were compared, probes of the larger silica nanoparticles showed a higher scattering intensity. Using 286-nm silica nanoparticles, the spots obtained with 200 pM of target DNA were visually detectable. The demonstrated capability to detect a disease related target DNA with direct visualization without using a complex detection instrument provides the prerequisite for the development of portable testing kits for genotyping.     

Single-particle light scattering study of polyethyleneglycol-grafted poly(ureaurethane) microcapsule in ethanol

Microcapsules having polyethyleneglycol-grafted poly(ureaurethane) (PUU) membrane and di-2ethylhexyl phthalate core have been prepared, and the structure when they were suspended in dispersing ethanol have been studied by means of single-particle light scattering method. The PUU membrane was synthesized from monomers with aromatic functional groups (microcapsule MC110) and hexamethylene functional groups (microcapsule MC160). Because the outer and inner solvent passed through the membrane easily, the outside and inside of the membrane were the same at the equilibrium state. The thickness of the wall membrane was significantly smaller than that calculated from the overall weight ratio of the wall-forming material and the core solvents. It was attributed to low affinity of PUU membranes and ethanol.     

Influence of hydrophobe content and salt concentration on dilute solution behaviour of hydrophobically modified ionic polymers from diallylammonium salts/sulfur dioxide cyclocopolymerization: Light scattering and fluorescence spectroscopy

Novel hydrophobically modified polyelectrolytes were synthesized using the cyclocopolymerization of sulfur dioxide, N,N-diallyl-N-carboethoxymethylammonium chloride and the hydrophobic monomer N,N-diallyl-N-octadecylammonium chloride. Aggregation of these polymers in aqueous solutions was characterized in the dilute regime by static light scattering and fluorescence spectroscopy as a function of hydrophobe content and NaCl concentration. Copolymers were observed to associate at very low concentrations (0.005 wt%). The copolymer is capable of associating at this very low polymer concentration because of the extended length of the hydrophobic monomer (C₁₈) that can reach far enough from the backbone to avoid electrostatic repulsion. Aggregation of the polymers increased with increasing hydrophobe content. Upon addition of salt, the apparent molecular weight of polymer aggregates decreased as a result of neutralization of the charges. At high salt concentrations, the size of the polymer aggregates was observed to increase again as a result of increased polarity of the solvent that resulted in more hydrophobic association.     

Polymer analysis by fractionation with on-line light scattering detectors

Summary The classical method for the determination of the molecular weight distribution (MWD) curve of a polymer requires fractionation according to the molecular weight and prior calibration of the separator. It is shown that the use of a dual detection system which includes a molecular mass sensitive detector eliminates the need for prior calibration. The principles of operation of a low-angle light scattering photometer, working as such a detector, are presented, as well as the basic equations for determination of the MWD curve from the elution curve and of the average molecular weights. Then the performances of the light scattering photometer are discussed with special emphasis on the various sources of errors and unaccuracies in these determinations.