Dynamic Size Range Research Articles

Comparison of a thickness-tapered channel in flow field-flow fractionation with a conventional channel with flow rate programming

The thickness-tapered channel structure in flow field-flow fractionation (FlFFF), recently introduced by constructing a channel with a linear decrease in thickness along its length, demonstrated effectiveness in steric/hyperlayer separation of supramicron particles with improvements in separation speed, elution recovery, and an expanded dynamic size range of separation. In this study, we conducted a comparative analysis of the performance between the impact of field (or crossflow rate) programming or outflow rate programming for the separation of polystyrene latex standards (50 ∼ 800 nm) with a conventional channel having uniform thickness and a thickness-tapered channel without programming. Outlet flow rate and crossflow rate conditions were also varied. Although the particle size resolution of the tapered channel does not surpass that of field programming in uniform thickness channel, it achieves higher-speed separation without a significant loss of resolution and without the need for a complex flow controller system even at a low outflow rate condition. Furthermore, it yielded an improved resolution for particles close to the steric transition regime (400 ∼ 600 nm) in the normal mode of separation. Due to the continuous increase in mean flow velocity down the channel, the tapered channel exhibits flexibility in separating submicron-sized particles at high crossflow rate conditions or low outflow rate conditions, of which the latter can be advantageous when coupled with mass spectrometry in a miniaturized setup.

Separation and characterization of Gastrodia elata polysaccharides based on asymmetrical flow field-flow fractionation: steric transition phenomenon

Asymmetrical flow field-flow fractionation (AF4), a gentle tool for the separation and characterization of particles and macromolecules, has attracted increased interest in recent years owing to its broad dynamic size range and utilization of "open channel" voids in the packing or stationary phase. A steric transition phenomenon in which the sample elution mode change from the normal mode to the steric/hyperlayer mode occurs. Accurate characterization by AF4 requires the absence of steric transition, particularly when the sample has a broad size distribution, because the effect of the combination of different modes is difficult to interpret. In this study, the relative molecular mass (M), radius of gyration (Rg), and conformation of Gastrodia elata polysaccharides (GEPs) were characterized using AF4 coupled with online multi-angle light scattering (MALS) and differential refractive index (dRI) detection (AF4-MALS-dRI). Steric transition was observed during GEP separation by AF4 owing to the broad size distribution of the molecules. This phenomenon would result in the inaccurate characterization of the GEPs in terms of M and Rg because two GEP groups of different sizes may elute together. In this study, the effects of constant and exponentially decaying cross-flow rates, sample mass concentration, and spacer thickness on steric transition were systematically investigated. The results indicated that a high GEP mass concentration (i. e., 0.75 mg/mL) can lead to steric transition. The spacer thickness affected the resolution and retention time of the GEPs and changed the steric transition point (di). An exponentially decaying cross-flow rate not only adjusted the di of the polydisperse GEP samples but also improved the GEP resolution and shortened the analysis time. The influence of steric transition was solved under the following operating conditions: injected GEP mass concentration=0.5 mg/mL; injection volume=50 μL; spacer thickness=350 μm; detector flow rate=1.0 mL/min; and cross-flow rate exponentially decayed from 0.2 to 0.05 mL/min with a half-life of 2 min. Moreover, the influence of GEP origins and ultrasound treatment time on the M and Rg distributions and conformation of GEPs were investigated under the optimized operating conditions. The results showed that the M and Rg distributions of Yunnan and Sichuan GEPs decreased with increasing ultrasound time. When the ultrasound treatment time was 15 min, the Yunnan GEPs had a loosely hyperbranched chain conformation, whereas the Sichuan GEPs had a spherical conformation. When the ultrasound treatment time was increased to 30 or 60 min, the GEPs from both Yunnan and Sichuan had a hyperbranched chain conformation, indicating that ultrasound treatment resulted in GEP degradation. Under the same extraction conditions, GEPs from Yunnan had larger M and Rg values than those from Sichuan. AF4-MALS-dRI showed good repeatability for the characterization of GEPs under the optimized operating conditions. The relative standard deviations of Rg and M were 0.5% and 1.7%, respectively. The data presented in this study can be used as a starting point for in-depth studies on the structural bioactivity of GEPs.

Flow Field-Flow Fractionation with a Thickness-Tapered Channel.

This study introduces the thickness-tapered channel design for flow field-flow fractionation (FlFFF) for the first time. In this design, the channel thickness linearly decreases along the channel axis such that the flow velocity increases down the channel. Channel thickness is an important variable for controlling retention time and resolution in field-flow fractionation. Especially, in the steric/hyperlayer mode of FlFFF, in which particles (>1 μm) migrate at elevated heights above the channel wall owing to hydrodynamic lift forces, the migration of long-retaining smaller-sized particles can be enhanced in a relatively thin channel or by increasing the migration flow rate; however, an upper size limit that can be resolved is simultaneously sacrificed. A thickness-tapered channel was constructed without a channel spacer by carving the surface of a channel block such that the channel inlet was deeper than the outlet (w = 400 → 200 μm). The performance of a thickness-tapered channel was evaluated using polystyrene standards and compared to that of a channel of uniform thickness (w = 300 μm) with a similar effective channel volume in terms of sample recovery, dynamic size range of separation, and steric transition under different flow rate conditions. The thickness-tapered channel can be an alternative to maintain the resolving power for particles with an upper large-diameter limit, faster separation of particles with a lower limit, and higher elution recovery without implementing the additional field-programming option.

Three-Dimensional Imaging Lidar for Characterizing Particle Fields and Organisms in the Mesopelagic Zone

The ocean’s mesopelagic zone is largely uncharacterized despite its vital role in sustaining ocean ecosystems. The composition, cycling, and fate of particle fields in the mesopelagic lacks an integrative multi-scale understanding of organism migration patterns, distribution, and diversity. This problem is addressed by combining complementary technologies with overlapping size spectra, including profiler mounted optical scattering sensors, profiler, and ship mounted acoustic devices, and a custom Unobtrusive Multi-Static Lidar Imager (UMSLI). This unique sensor suite can observe distributions of particles including organisms over a six order of magnitude dynamic size range, from microns to meters. Overlapping size ranges between different methods allows for cross-validation. This work focuses on the lidar imaging measurements and optical backscattering and attenuation, covering a combined particle size range of 0.1 mm to several cm. Particles at the small end of this range are sized using an existing backscattering time series inversion method after Briggs et al. (2013). Larger particles are resolved with UMSLI over an expanding volume using three-dimensional photo-realistic laser serial imaging. UMSLI’s image rectifying ability over time allows for derivation of particle concentration, size, and spatial distribution. Technical details on the development and post-processing methods for the novel UMSLI system are provided. Image resolved particle size distributions (PSDs) revealed a size shift from smaller to larger particles (>0.5 mm) as indicated by flatter slopes from dawn (slope = 2.6) to dusk (slope = 3.0). PSD trends are supported by an optical backscatter and transmissometer time series inversion analysis. Size shifts in the particle field are largely attributed to aggregation effects. Images support evidence of temporal variation between dusk and dawn stations through statistical analysis of particle concentrations for particle sizes 0.50–5.41 mm. Spatial analysis of the particle field revealed a dominantly uniform distributed marine snow background. The importance and potential of integrated approaches to studying particle and organism dynamics in ocean environments are discussed.

Rapid measurement of sub-micrometer aerosol size distribution using a fast integrated mobility spectrometer

Rapid measurement of submicron particle size distributions enables the characterization of aerosols with fast changing properties, and is often necessary for measurements onboard mobile platforms (e.g., research aircraft). Aerosol mobility size distribution is commonly measured by a scanning mobility particle sizer (SMPS), which relies on voltage scanning or stepping to classify particles of different sizes, and may take about 1 minute or longer to obtain a complete size spectrum of aerosol particles. The recently developed fast integrated mobility spectrometer (FIMS) with enhanced dynamic size range separates and detects particles from 10 to ~600 nm simultaneously, allowing submicron aerosol mobility size distributions to be captured at a time resolution of 1 s.In this study, we present a detailed data inversion routine for deriving aerosol size distribution from FIMS measurements of aerosols with a wide size range. The inversion routine takes into consideration the FIMS transfer function, particle penetration efficiency in the FIMS, and multiple charging of aerosols. The accuracy of the FIMS measurement is demonstrated by comparing parallel FIMS and SMPS measurements of stable aerosols with a wide range of size spectrum shapes, including ambient aerosols and aerosols classified by a differential mobility analyzer (DMA). The FIMS and SMPS-derived size distributions show excellent agreements for all aerosols tested. In addition, total number concentrations of ambient aerosols were integrated from 1 Hz FIMS size distributions, and compared with those directly measured by a condensation particle counter (CPC) operated in parallel. The integrated and measured total particle concentrations agree well within 6.5%.

A water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range

ABSTRACTA water-based fast integrated mobility spectrometer (WFIMS) with enhanced dynamic size range is developed. The WFIMS builds on two established technologies: the fast integrated mobility spectrometer and laminar flow water-based condensation methodology. Inside WFIMS, particles of differing electrical mobility are separated in a drift tube and subsequently enlarged through water condensation. Particle size and concentration are measured via digital imaging at a frame rate of 10 Hz. By measuring particles of different mobilities simultaneously, the WFIMS resolves particle diameters ranging from 8 to 580 nm within 1 s or less. The performance of WFIMS was characterized with differential mobility analyzer (DMA) classified (NH4)2SO2 particles with diameters ranging from 8 to 265 nm. The mean particle diameters measured by WFIMS were found to be in excellent agreement with DMA centroid diameters. Furthermore, detection efficiency of WFIMS was characterized using a condensation particle counter as a refe...

A Fast Integrated Mobility Spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part II: Experimental characterization

A Fast Integrated Mobility Spectrometer (FIMS) with a wide dynamic size range has been developed for rapid aerosol size distribution measurements. The design and model evaluation of the FIMS are presented in the preceding paper (Paper I, Wang et al., 2017), and this paper focuses on the experimental characterization of the FIMS. Monodisperse aerosol with diameter ranging from 8 to 600nm was generated using a Differential Mobility Analyzer (DMA), and was measured by the FIMS in parallel with a Condensation Particle Counter (CPC). The mean particle diameter measured by the FIMS is in good agreement with the DMA centroid diameter. Comparison of the particle concentrations measured by the FIMS and CPC indicates the FIMS detection efficiency is essentially 100% for particles with diameters of 8nm or larger. For particles smaller than 20nm or larger than 200nm, FIMS transfer function and mobility resolution can be well represented by the calculated ones based on simulated particle trajectories in the FIMS. For particles between 20 and 200nm, the FIMS transfer function is boarder than the calculated, likely due to non-ideality of the electric field, including edge effects near the end of the electrode, which are not represented by the 2-D electric field used to simulate particle trajectories.

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part I: Design and model evaluation

A fast integrated mobility spectrometer (FIMS) was previously developed to characterize submicron aerosol size distributions at a frequency of 1Hz and with high size resolution and counting statistics (Kulkarni & Wang, 2006a, 2006b; Olfert, Kulkarni, & Wang, 2008). However, the dynamic size range of the FIMS was limited to one decade in particle electrical mobility. It was proposed that the FIMS dynamic size range can be greatly increased by using a spatially varying electric field (Wang, 2009). This electric field creates regions with drastically different field strengths in the separator, such that particles of a wide diameter range can be simultaneously classified and subsequently measured. A FIMS incorporating this spatially varying electric field is developed. This paper describes the theoretical frame work and numerical simulations of the FIMS with extended dynamic size range, including the spatially varying electric field, particle trajectories, activation of separated particles in the condenser, and the transfer function, transmission efficiency, and mobility resolution. The influences of the particle Brownian motion on FIMS transfer function and mobility resolution are examined. The simulation results indicate that the FIMS incorporating the spatially varying electric field is capable of measuring aerosol size distribution from 8 to 600nm with high time resolution. The experimental characterization of the FIMS is presented in an accompanying paper.

Late Pleistocene glacial–interglacial shell-size–isotope variability in planktonic foraminifera as a function of local hydrography

Abstract. So-called "vital effects" are a collective term for a suite of physiologically and metabolically induced variability in oxygen (δ18O) and carbon (δ13C) isotope ratios of planktonic foraminifer shells that hamper precise quantitative reconstruction of past ocean parameters. Correction for potential isotopic offsets from equilibrium or the expected value is paramount, as too is the ability to define a comparable life stage for each species that allows for direct comparison. Past research has focused upon finding a specific size range for individual species in lieu of other identifiable features, thus allowing ocean parameters from a particular constant (i.e. a specific depth or season) to be reconstructed. Single-shell isotope analysis of fossil shells from a mid-latitude North Atlantic Ocean piston core covering Termination III (200 to 250 ka) highlight the advantage of using a dynamic size range, i.e. utilising measurements from multiple narrow sieve size fractions spanning a large range of total body sizes, in studies of palaeoclimate. Using this methodology, we show that isotopic offsets between specimens in successive size fractions of Globorotalia inflata and Globorotalia truncatulinoides are not constant over time, contrary to previous findings. For δ18O in smaller-sized globorotalids (212–250 μm) it is suggested that the offset from other size fractions may reflect a shallower habitat in an early ontogenetic stage. A reduction in the difference between small and large specimens of G. inflata between insolation minima and maxima is interpreted to relate to a prolonged period of reduced water column stratification. For the shallow-dwelling species Globigerina bulloides, no size–isotope difference between size fractions is observed, and the variability in the oxygen isotopic values is shown to correlate well with the seasonal insolation patterns. As such, patterns in oxygen isotope variability of fossil populations may be used to reconstruct past seasonality changes.

Capabilities of Single Particle Inductively Coupled Plasma Mass Spectrometry for the Size Measurement of Nanoparticles: A Case Study on Gold Nanoparticles

The increasing application of engineered nanomaterials (ENMs) in consumer and medical products has motivated the development of single-particle inductively coupled plasma mass spectrometry (spICP-MS) for characterizing nanoparticles under realistic environmental exposure conditions. Recent studies have established a set of metrological criteria and evaluated the feasibility of spICP-MS for sizing or quantifying various highly commercialized ENMs. However, less is known about the performance of spICP-MS for detecting nanoparticles with sizes greater than 80 nm. This paper presents a systematic study on spICP-MS for accurate size measurement of gold nanoparticles from 10 to 200 nm. We show that dwell time contributes significantly to the quality of data, with the optimal dwell time that limits split particle events, particle coincidences and false positives being 10 ms. A simple approach to correct for split particle events is demonstrated. We show that transient features of single particle events can be temporally resolved on a conventional quadrupole ICP-MS system using a sufficiently short dwell time (0.1 ms). We propose an intensity-size diagram for estimating the linear dynamic size range and guiding the selection of ICP-MS operating conditions. The linear dynamic size range of the ICP-MS system under standard (highest) sensitivity conditions is 10 to 70 nm but can be further extended to 200 nm by operating in less sensitive modes. Finally, the ability of spICP-MS to characterize heterogeneous forms of metal containing nanoparticles is evaluated in mixtures containing both dissolved and poly disperse nanoparticulate Au.

A methodological approach for direct quantification of the activated sludge floc size distribution by using different techniques

The activated sludge floc size distribution (FSD) is investigated by using different measurement techniques in order to gain insight in FSD assessment as well as to detect the strengths and limitations of each technique. A second objective was to determine the experimental conditions that allow a representative and accurate measurement of activated sludge floc size distributions. Laser diffraction, Time Of Transition (TOT) and Dynamic Image Analysis (DIA) devices were connected in series. The sample dilution liquid, the dilution factor and hydraulic flow conditions avoiding flocculation proved to be important. All methods had certain advantages and limitations. The MastersizerS has a broader dynamic size range and provides accurate results at high concentrations. However, it suffers from an imprecise evaluation of small size flocs and is susceptible to particle shape effects. TOT suffers less from size overestimation for non-spherical particles. However, care should be taken with the settings of the transparency check. Being primarily a counting technique, DIA suffers from a limited size detection range but is an excellent technique for process visualization. All evaluated techniques turned out to be reliable methods to quantify the floc size distribution. Selection of a certain method depends on the purpose of the measurement.

Spray Droplet Size, Drift Potential, and Risks to Nontarget Organisms from Aerially Applied Glyphosate for Coca Control in Colombia

A wind tunnel atomization study was conducted to measure the emission droplet size spectra for water and Glyphos (a glyphosate formulation sold in Colombia) + Cosmo-flux sprays for aerial application to control coca and poppy crops in Colombia. The droplet size spectra were measured in a wind tunnel for an Accu-Flo nozzle (with 16 size 0.085 [2.16 mm] orifices), under appropriate simulated aircraft speeds (up to 333 km/h), using a laser diffraction instrument covering a dynamic size range for droplets of 0.5 to 3,500 μm. The spray drift potential of the glyphosate was modeled using the AGDISP spray application and drift model, using input parameters representative of those occurring in Colombia for typical aerial application operations. The droplet size spectra for tank mixes containing glyphosate and Cosmo-Flux were considerably finer than water and became finer with higher aircraft speeds. The tank mix with 44% glyphosate had a D v0.5 of 128 μm, while the value at the 4.9% glyphosate rate was 140 μm. These are classified as very fine to fine sprays. Despite being relatively fine, modeling showed that the droplets would not evaporate as rapidly as most similarly sized agricultural sprays because the nonvolatile proportion of the tank mix (active and inert adjuvant ingredients) was large. Thus, longer range drift is small and most drift that does occur will deposit relatively close to the application area. Drift will only occur downwind and, with winds of velocity less than the modeled maximum of 9 km/h, the drift distance would be substantially reduced. Spray drift potential might be additionally reduced through various practices such as the selection of nozzles, tank mix adjuvants, aircraft speeds, and spray pressures that would produce coarser sprays. Species sensitivity distributions to glyphosate were constructed for plants and amphibians. Based on modeled drift and 5th centile concentrations, appropriate no-spray buffer zones (distance from the end of the spray boom as recorded electronically ±5%) for protection of sensitive plants were 50–120 m for coca spray scenarios and considerably lower for poppy spray scenarios. The equivalent buffer zone for amphibia was 5 m. The low toxicity of glyphosate to humans suggests that these aerial applications are not a concern for human health.

A fast integrated mobility spectrometer with wide dynamic size range: Theoretical analysis and numerical simulation

A fast integrated mobility spectrometer with wide size range (WSR-FIMS) is described. The WSR-FIMS greatly enhances the dynamic size range of the original FIMS [Kulkarni, P., & Wang, J. (2006a). New fast integrated mobility spectrometer for real-time measurement of aerosol size distribution—I: Concept and theory. Journal of Aerosol Science, 37, 1303—1325; Kulkarni, P., & Wang, J. (2006b). New fast integrated mobility spectrometer for real-time measurement of aerosol size distribution—II: Design, calibration, and performance characterization. Journal of Aerosol Science, 37, 1326—1339] by employing a non-uniform electric field. The strength of this electric field varies over three orders of magnitude along the width of the separator, allowing particles of a much wider size range to be classified and measured simultaneously. A theoretical framework is developed to derive the transfer function, resolution, and transmission efficiency of the WSR-FIMS. Two representative operation configurations are simulated, and the results show the WSR-FIMS can simultaneously measure particles ranging from 10 to 1470 nm, therefore greatly reducing the measurement time from minutes required by scanning mobility particle sizer (SMPS) to 1 s or less. The WSR-FIMS also has a higher size resolution than typical SMPS over most of its measurement size range. For typical ambient aerosols, the simulations show that 1 s measurements using the WSR-FIMS provide good counting statistics.