Light-scattering Instrument Research Articles

Waters to buy light-scattering instrument maker Wyatt

Waters to buy light-scattering instrument maker Wyatt

Physicochemical characteristics of liposome encapsulation of stingless bees' propolis

Nutraceuticals from natural sources have shown potential new leads in functional food products. Despite a broad range of health-promoting effects, these compounds are easily oxidized and unstable, making their utilization as nutraceutical ingredients limited. In this study, the encapsulated stingless bees' propolis in liposome was prepared using soy phosphatidylcholine and cholesterol by thin-film hydration technique. Three different formulations of phosphatidylcholine composition and cholesterol prepared by weight ratio was conducted to extract high propolis encapsulation. Physicochemical changes in the result of the encapsulation process are briefly discussed using scanning electron microscopy and Fourier Transform Infrared Spectroscopy. A dynamic light-scattering instrument was used to measure the hydrodynamic diameter, polydispersity index, and zeta potential. The increment of the liposomal size was observed when the concentration of extract loaded increased. In comparing three formulations, F2 (8:1 w/w) presented the best formulation as it yielded small nanoparticles of 275.9 nm with high encapsulation efficiency (66.9%). F1 (6:1 w/w) formed large particles of liposomes with 422.8 nm, while F3 (10:1 w/w) showed low encapsulation efficiency with (by) 38.7%. The liposome encapsulation will provide an effective nanocarrier system to protect and deliver the flavonoids extracted from stingless bees' propolis.

Validation of a light-scattering PM2.5 sensor monitor based on the long-term gravimetric measurements in field tests.

BackgroundPortable direct-reading instruments by light-scattering method are increasingly used in airborne fine particulate matter (PM2.5) monitoring. However, there are limited calibration studies on such instruments by applying the gravimetric method as reference method in field tests.MethodsAn 8-month sampling was performed and 96 pairs of PM2.5 data by both the gravimetric method and the simultaneous light-scattering real-time monitoring (QT-50) were obtained from July, 2015 to February, 2016 in Shanghai. Temperature and relative humidity (RH) were recorded. Mann-Whitney U nonparametric test and Spearman correlation were used to investigate the differences between the two measurements. Multiple linear regression (MLR) model was applied to set up the calibration model for the light-scattering device.ResultsThe average PM2.5 concentration (median) was 48.1μg/m3 (min-max 10.4–95.8μg/m3) by the gravimetric method and 58.1μg/m3 (19.2–315.9μg/m3) by the light-scattering method, respectively. By time trend analyses, they were significantly correlated with each other (Spearman correlation coefficient 0.889, P<0.01). By MLR, the calibration model for the light-scattering instrument was Y(calibrated) = 57.45 + 0.47 × X(the QT – 50 measurements) – 0.53 × RH – 0.41 × Temp with both RH and temperature adjusted. The 10-fold cross-validation R2 and the root mean squared error of the calibration model were 0.79 and 11.43 μg/m3, respectively.ConclusionLight-scattering measurements of PM2.5 by QT-50 instrument overestimated the concentration levels and were affected by temperature and RH. The calibration model for QT-50 instrument was firstly set up against the gravimetric method with temperature and RH adjusted.

Ambient and laboratory evaluation of a low-cost particulate matter sensor

Low-cost, light-scattering-based particulate matter (PM) sensors are becoming more widely available and are being increasingly deployed in ambient and indoor environments because of their low cost and ability to provide high spatial and temporal resolution PM information. Researchers have begun to evaluate some of these sensors under laboratory and environmental conditions. In this study, a low-cost, particulate matter sensor (Plantower PMS 1003/3003) used by a community air-quality network is evaluated in a controlled wind-tunnel environment and in the ambient environment during several winter-time, cold-pool events that are associated with high ambient levels of PM. In the wind-tunnel, the PMS sensor performance is compared to two research-grade, light-scattering instruments, and in the ambient tests, the sensor performance is compared to two federal equivalent (one tapered element oscillating microbalance and one beta attenuation monitor) and gravimetric federal reference methods (FEMs/FRMs) as well as one research-grade instrument (GRIMM). The PMS sensor response correlates well with research-grade instruments in the wind-tunnel tests, and its response is linear over the concentration range tested (200–850 μg/m3). In the ambient tests, this PM sensor correlates better with gravimetric methods than previous studies with correlation coefficients of 0.88. However additional measurements under a variety of ambient conditions are needed. Although the PMS sensor correlated as well as the research-grade instrument to the FRM/FEMs in ambient conditions, its response varies with particle properties to a much greater degree than the research-grade instrument. In addition, the PMS sensors overestimate ambient PM concentrations and begin to exhibit a non-linear response when PM2.5 concentrations exceed 40 μg/m3. These results have important implications for communicating results from low-cost sensor networks, and they highlight the importance of using an appropriate correction factor for the target environmental conditions if the user wants to compare the results to FEM/FRMs.

Correcting respirable photometric particulate measurements using a gravimetric sampling method

According to the National Environmental Management: Air Quality Act of 2004 people have the right to clean air and a healthy environment. Particulate matter (PM) emissions pose a significant health threat. Both indoor and ambient air pollution contribute to the burden of disease associated with poor air quality. This is particularly true within the South African setting where low income households make use of different solid fuels for heating and cooking purposes resulting in high levels of PM emissions. This paper focuses on the evaluation mass concentration measurements recorded by continuous photometric PM instruments within KwaDela, a low income settlement in Mpumalanga located on the South African Highveld. Thus, obtaining a photometric calibration factor for both the DustTrak Model 8530 and the SidePak AM510. Sampling took place during August 2014 for a period of seven days. The photometric and gravimetric instruments were collocated within the indoor environment of selected households. These instruments were all fitted with 10mm Dorr-Oliver Cyclone inlets to obtain the respirable (PM4) cut-point. The study found that both instruments tend to overestimate the indoor particulate mass concentrations when compared to the reference gravimetric method. The estimated photometric calibration factors for the DustTrak Model 8530 and SidePak AM510 are 0.14 (95%Cl: 0.09, 0.15) and 0.24 (95%Cl: 0.16, 0.30) respectively. The overestimation of the photometric measurements is rather significant. It is therefore important that the correction factors are applied to data collected in indoor environments prone to the combustion of solid fuels. The correction factors obtained from this and other studies vary as a result of the environment (ambient, indoor etc.) as well as the aerosol size fraction and the origin thereof. Thus, it is important to considered site specific calibration factors when implementing these photometric light-scattering instruments.

Büchi acquires Grace chromatography line

Büchi Labortechnik has acquired W.R. Grace’s portfolio of flash chromatography and evaporative light-scattering detector instruments. Grace built the business under Gregory E. Poling, who recently left to head GCP Applied Technologies, the construction and packaging business spun off of Grace. Büchi says it will integrate the Grace instruments into its chromatography portfolio. Grace will continue to provide silica-based purification media to Büchi and other customers.

광산란 측정장치에 따른 대중교통차량 미세먼지 측정 특성

광산란 측정장치에 따른 대중교통차량 미세먼지 측정 특성

Wyatt Charts Its Own Course

Every year, big companies buy their smaller competitors; it’s the way of the world. In fact, some small companies actively seek larger owners. But that is not the case for 30-year-old Wyatt Technology, a quirky family-owned maker of particle analysis instruments in Santa Barbara, Calif., that vows to stay independent. Wyatt is a maker of instruments for laser light scattering, which is a technique that harnesses lasers and photon detectors and is used by researchers in areas as diverse as polymer design, cement quality control, and drug development. The firm leads the $250 million light-scattering instruments market, logging annual growth rates in the high single-digit percentages, estimates Michael Tice, vice president of instrumentation consulting firm Strategic Directions International. Its competitors, generally larger instrument companies, have been growing at about 5%, Tice says. Wyatt, which claims its scientists were the first to incorporate lasers into commercial light-scattering instruments, doe...

A Computer-Controlled Whole-Body Inhalation Exposure System for the Oil Dispersant COREXIT EC9500A

An automated whole-body inhalation exposure system capable of exposing 12 individually housed rats was designed to examine the potential adverse health effects of the oil dispersant COREXIT EC9500A, used extensively during the Deepwater Horizon oil spill. A computer-controlled syringe pump injected the COREXIT EC9500A into an atomizer where droplets and vapor were formed and mixed with diluent air. The aerosolized COREXIT EC9500A was passed into a customized exposure chamber where a calibrated light-scattering instrument estimated the real-time particle mass concentration of the aerosol in the chamber. Software feedback loops controlled the chamber aerosol concentration and pressure throughout each exposure. The particle size distribution of the dispersant aerosol was measured and shown to have a count median aerodynamic diameter of 285 nm with a geometric standard deviation of 1.7. The total chamber concentration (particulate + vapor) was determined using a modification of the acidified methylene blue spectrophotometric assay for anionic surfactants. Tests were conducted to show the effectiveness of closed loop control of chamber concentration and to verify chamber concentration homogeneity. Five automated 5-h animal exposures were performed that produced controlled and consistent COREXIT EC9500A concentrations (27.1 ± 2.9 mg/m3, mean ± SD).

Development of a Standard Method for Nanoparticle Sizing by Using the Angular Dependence of Dynamic Light Scattering

A standard method for nanoparticle sizing based on the angular dependence of dynamic light scattering was developed. The dependences of the diffusion coefficients for aqueous suspensions of polystyrene latex on the concentration and scattering angle were accurately measured by using a high-resolution dynamic light-scattering instrument. Precise measurements of the short-time correlation function at seven scattering angles and five concentrations were made for suspensions of polystyrene latex particles with diameters from 30 to 100 nm. The apparent diffusion coefficients obtained at various angles and concentrations showed properties characteristic of polystyrene latex particles with electrostatic interactions. A simulation was used to calculate a dynamic structure factor representing the long-range interactions between particles. Extrapolations to infinite dilution and to low angles gave accurate particle sizes by eliminating the effects of long-range interactions. The resulting particle sizes were consistent with those measured by using a differential mobility analyzer and those obtained by pulsed-field gradient nuclear magnetic resonance measurements.

Preparation of poly( N-vinylcarbazole) (PVK) nanoparticles by emulsion polymerization and PVK hollow particles

PVK nanoparticles were obtained by oil-in-water emulsion polymerization of N-vinylcarbazole (VCz). VCz is a white crystalline material with a melting point of 65 °C, which is an unsuitable monomer for conventional emulsion polymerization because of its crystallinity. However, we could successfully synthesize PVK nanoparticles by emulsion polymerization from VCz solution with organic solvent. And then, we found that the concentration of VCz influenced the particle size. PVK hollow particles were also obtained by etching of PMMA core from PMMA/PVK core–shell particles, and the size of a hollow particle was enlarged by two times compared with a core–shell particle due to the swelling process. PVK nanoparticles were probed by UV–vis absorption and fluorescence spectrometers, and hollow particles were characterized by FT-IR spectra. Both of them were confirmed by TEM, and the light-scattering instrument.

An inexpensive light-scattering particle monitor: field validation

We have developed a small, light, passive, inexpensive, datalogging particle monitor called the "UCB" (University of California Berkeley particle monitor). Following previously published laboratory assessments, we present here results of tests of its performance in field settings at high particle concentrations. We demonstrate the mass sensitivity of the UCB in relation to gravimetric filter-based PM(2.5) mass estimates as well as commercial light-scattering instruments co-located in field chamber tests and in kitchens of wood-burning households. The coefficient of variation of the unadjusted UCB mass response in relation to gravimetric estimates was 15%. Although requiring adjustment for differences in sensitivity, inter-monitor performance was consistently high (r(2) > 0.99). Moreover, the UCB can consistently estimate PM(2.5) mass concentrations in wood-burning kitchens (Pearson r(2) = 0.89; N = 99), with good agreement between duplicate measures (Pearson r(2) = 0.94; N = 88). In addition, with appropriate cleaning of the sensing chamber, UCB mass sensitivity does not decrease with time when used intensively in open woodfire kitchens, demonstrating the significant potential of this monitor.

Stored Ca2+ Depletion-induced Oligomerization of Stromal Interaction Molecule 1 (STIM1) via the EF-SAM Region

Stromal interaction molecule 1 (STIM1) has recently been identified as a key player in store-operated Ca2+ entry. Endoplasmic reticulum (ER) luminal Ca2+ depletion results in STIM1 redistribution from ER membrane homogeneity to distinctly localized aggregates near the plasma membrane; these changes precede and are linked to cytoplasmic Ca2+ influx via Ca2+ release-activated channels (CRACs). The molecular mechanisms initiating ER STIM1 redistribution and plasma membrane CRAC activity are not well understood. We recombinantly expressed the Ca2+-sensing region of STIM1 consisting of the EF-hand together with the sterile alpha-motif (SAM) domain (EF-SAM) to investigate its Ca2+-related conformational and biochemical features. We demonstrate that Ca2+-loaded EF-SAM (holo) contains high alpha-helicity, whereas EF-SAM in the absence of Ca2+ (apo) is much less compact. Accordingly, the melting temperature (Tm) of the holoform is approximately 25 degrees C higher than apoform; heat and urea-derived thermodynamic parameters indicate a Ca2+-induced stabilization of 3.2 kcal mol(-1). We show that holoEF-SAM exists as a monomer, whereas apoEF-SAM readily forms a dimer and/or oligomer, and that oligomer to monomer transitions and vice versa are at least in part mediated by changes in surface hydrophobicity. Additionally, we find that the Ca2+ binding affinity of EF-SAM is relatively low with an apparent dissociation constant (Kd) of approximately 0.2-0.6 mM and a binding stoichiometry of 1. Our results suggest that EF-SAM actively participates in and is the likely the molecular trigger initiating STIM1 punctae formation via large conformational changes. The low Ca2+ affinity of EF-SAM is reconciled with the confirmed role of STIM1 as an ER Ca2+ sensor.

Dynamic light scattering in turbid colloidal dispersions: A comparison between the modified flat-cell light-scattering instrument and 3D dynamic light-scattering instrument

It remains a challenge to measure dynamics in dense colloidal systems. Multiple scattering and low light-transmission rates often hinder measurements in such systems. One of the well-established techniques for overcoming the problem of multiple scattering is cross-correlation techniques such as 3D dynamic light scattering (3D-DLS). However, a high degree of multiple scattering, i.e., vanishing single-scattering contribution in the signal, limits the use of the 3D-DLS technique. We present another approach to measure turbid media by way of upgrading our flat-cell light-scattering instrument (FCLSI). This instrument was originally designed for static light-scattering (SLS) experiments and is similar to a Fraunhofer setup, which features a flat sample cell. The thickness of the flat sample cell can be varied from 13 μm to 5 mm. The small thickness increases the transmission, reduces multiple scattering to a negligible amount, and therefore enables the investigation of dense colloidal systems. We upgraded this instrument for DLS measurements by the installation of an optical single-mode fiber detector in the forward scattering regime. We present our instrumentation and subsequently test its limits using a concentration series of a turbid colloidal suspension. We compare the performances of our modified flat-cell light-scattering instrument with that of standard DLS and with that of 3D-DLS. We show that 3D-DLS and FCLSI only have a comparable performance if the length of the light path in the sample using the 3D-DLS is reduced to a minimum. Otherwise, the FCLSI has some advantage.

Characterization of Fine Particles from Machining in Automotive Plants

Sampling of the full range of particle sizes was carried out on 16 processes in six different General Motors plants over a period of 2.5 years. This article deals with particle characterization from five of the processes that relate to machining, specifically, wet machining with water-based fluids from old and new technology processes, grinding with straight oils from old and new technology processes, and dry machining. The concentrations measured by different instruments were in reasonable agreement, although the light-scattering instrument generally produced higher values than filters. Of the processes studied, the old technology grinding using straight oils generated the highest particle concentrations. The new technology controls (enclosed, vented machines) were highly effective but more so for large particles than small particles. The particle size distribution was shifted to smaller particles with enclosed processes. Dry machining generated the largest particles of all processes studied.

Small-angle static light scattering of concentrated silica suspensions during in situ destabilization

The aggregation of concentrated aqueous silica suspensions is characterized by means of static light scattering. We use an in situ destabilization mechanism based on the enzyme-catalyzed hydrolysis of urea. This method enables us to continuously and homogeneously change the interparticle potential from repulsive to attractive without disturbing the aggregation process. Moreover, our electrostatically stabilized suspensions can be destabilized by two different methods. In the first method, the pH is shifted toward the isoelectric point of the particles (ΔpH method), thereby leading to a decrease of their surface charge. In the second method, the ionic strength is continuously increased at constant pH (Δ I method), leading to a compression of the electrical double layer around the charged particles. A laboratory-built flat-cell light-scattering instrument is used, which allows fast data acquisition and an adjustment of the sample cell thickness. To circumvent multiple scattering effects, we use a very small sample thickness (≈13 μm). In addition, the refractive index difference between the aqueous phase and the particles is reduced by adding sucrose to the liquid phase of our suspensions. We are able to characterize the structural changes at the very early stages of the destabilization process, where no significant effects are yet detected in macroscopic rheological measurements. While during the ΔpH destabilization, the scattering curve shows significant changes only after some characteristic delay time, it changes continuously during the Δ I destabilization. The latter is attributed to the formation of a weak pre-gel structure in the suspensions, as a shallow secondary minimum appears in the interparticle potential. Data are evaluated by using a HMSA square-well structure factor model. Results are in good agreement with those predicted from DLVO theory.

Room‐temperature preparation and characterization of poly (ethylene glycol)‐coated silica nanoparticles for biomedical applications

Monodisperse, spherical, polyethylene glycol (PEG)-coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50-350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field-flow fractionation (AFFF) multiangle static light-scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG-coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein-binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG-coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG-coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems.

Novel Liquid Crystalline Block Copolymers by ATRP and ROMP

Two new liquid crystalline block copolymers have been synthesized: a side-on liquid crystalline/isotropic (LC/Iso) triblock copolymer ABA (B = LC) by ATRP and a side-on LC/Iso diblock copolymer AB‘ (B‘ = LC) by first synthesizing the LC block (B‘) using ROMP and then the Iso block using ATRP. Absolute values of molar masses of the homopolymers and of the block copolymers were determined using SEC with an on-line light-scattering instrument: Mn = 1.43 × 104, Mw/Mn = 1.04 for homopolymer B, Mn = 3.47 × 104, Mw/Mn = 1.32 for triblock copolymer ABA, Mn = 2.29 × 104, Mw/Mn = 1.06 for homopolymer B‘, and Mn = 3.61 × 104, Mw/Mn = 1.28 for diblock copolymer AB‘. The di and triblock copolymers self-assemble into lamellar mesophases in which the LC blocks undergo transitions similar to those of the homopolymers. Lamellar structures were studied as a function of temperature by polarized optical microscopy, DSC and X-ray diffraction. Those new liquid crystalline block copolymers could be used as model systems for “artificial muscles”.

Light-scattering instrument to detect thromboemboli in blood.

The characteristics and capabilities of a light-scattering microemboli detector (LSMD) are delineated by detailing its state-of-the-art configuration, by discussing the theoretical and empirical aspects of instrument calibration, and by summarizing various experimental studies that have benefited from this instrument. In the past, thromboembolism, which often results when blood contacts medical devices, has eluded scientific scrutiny due to the absence of instruments that could detect and quantify thromboemboli in circulating blood. More recently, the ability of the LSMD to provide continuous, noninvasive detection of thromboemboli in whole blood (meaning that the LSMD probe does not contact the blood) was exploited in various in vitro and ex vivo models to explore thromboembolic phenomena. Through this work, the LSMD evolved as a sensitive and an economical research tool for the study of thromboembolic phenomena.

Measurements on Concentrated Oil in Water Emulsions Using Static Light Scattering

The characterization of uncharged, micrometer-sized, concentrated oil in water emulsion droplets in terms of size and interaction with static light scattering is the main part of this work. We combined the preparation of monodisperse emulsions with an oil with a low refractive index ratio (close to the matchpoint), the measurements in a light-scattering instrument with variable sample thickness down to about 12 μm (all to ensure that the measurements were carried out in the Rayleigh–Debye–Gans (RDG) single scattering regime), and the evaluation procedure for simultaneous calculation of the form factor and the structure factor. In addition, we studied the major types of influences of the deviation from the RDG single scattering theory and picture their effects on the scattering behavior and the evaluation procedures. We were able to calculate from the structure factor the correct oil content in a concentration series up to a volume fraction of 50%. Entering the multiple RDG scattering regime, one yields scattering curves with increasingly smeared minima and maxima. When the contrast of the droplets changes, we see with increasing contrast an apparent growth of the particles due to the influence of Lorenz–Mie (LM) scattering. The study of the influence of salt to charged emulsions shows that large particles are very sensitive to added salt. Even very low salt concentration led to effective hard-sphere behavior.