Inertial Spectrometer Research Articles

Holographic imaging platform for particle discrimination based on simultaneous mass density and refractive index measurements.

Real-time detection, classification and identification of aerosol particles is crucial in various industries and public health areas. In order to circumvent the limitations of existing particle analysis methods for efficient discrimination, we demonstrate a compact digital in-line holographic microscopy platform with an inertial spectrometer for simultaneous measurement of two independent fingerprint parameters at single species level. In particular, by interrogating the particle location and size captured with the platform, particle mass density can be estimated. Furthermore, by employing Monte Carlo fitting to the Lorenz-Mie theory, the refractive index of each particle can also be extracted from the interference patterns. It is demonstrated that the combination of mass density and optical density characterization unambiguously enhances the discriminatory power of the system, especially when dealing with particles that exhibit similar mass densities but distinctive refractive indices or vice versa. This innovative approach represents a significant advancement in particle characterization and composition identification, with potential applications in various industrial, scientific, and research domains. An iOS-based app interface is then customized for wireless controlling of the CMOS imager, image acquisition, reconstruction, and data analysis. The imaging platform proposed in this work has prominent advantages including compactness, accuracy, efficiency, high throughput, and remote sensing capability, which is especially relevant for applications where on-site/remote metrology and identification of particles is required.

Particulate matter size distribution and associated polycyclic aromatic hydrocarbon content from indirect and direct injection diesel engines

Within the framework of atmospheric aerosol study, evaluation of the contribution of the particle source to global atmospheric pollution is a challenge that requires an improvement in the knowledge of particulate matter. As a part of this knowledge improvement, this study has been focused on particles emitted from diesel vehicles. Two light-duty diesel vehicles were studied for particulate matter size distribution and associated polycyclic aromatic hydrocarbon (PAH) content. A diffusional and inertial spectrometer was used, allowing particles from 7.5 nm to 15 μm to be collected and analysed. Teflon-coated glass fibre filters were employed as collector substrates, and weighed prior to and after sampling. Each of them was extracted with methylene chloride in an accelerated solvent extractor, cleaned on a silica gel micro-column and analysed for PAH by gas chromatography/mass spectrometry using internal standards for quantitation. Both analytical and sampling methods were validated. The highest particle mass was found to be emitted at 0.2 μm for the direct injection engine and 0.07 μm for the indirect injection engine. PAHs were found to be essentially distributed on particles in the accumulation mode, at about 0.2 μm, and high molecular weight PAH distributions were found to be bimodal or trimodal, depending on the engine injection.

Mineral Fibre Sampling and Size Selection

Potential health hazards due to fibre inhalation are only evaluated in a limited way by simple optical microscopy examination of the membrane filters on which the fibres have been collected. One must consider the amount of fibres deposited and persisting in the most vulnerable organ compartments. Exposure evaluated in this way must take account of the deposition efficiency and relative clearance efficiency of different regions of the respiratory tract, which depends mainly on the diameter and length distribution of the fibres. The fibre diameter roughly indicates the deposition site in the respiratory tract, while the length is mainly connected with toxicity. For these reasons, at international level, special samplers have been recently proposed, capable of distinguishing the fibre sizes, in order to separate the so-called 'thoracic fraction' (the total fibres which penetrate beyond the larynx) and the 'respirable fraction' (only the fibres reaching the non ciliated respiratory area), which represent the most interesting sizes as far as health effects are concerned. Our purpose in this context is to explore the feasibility of using the Inertial Spectrometer (INSPEC) as a sampler that separates the fibres according to their aerodynamic diameter. The optical and electron microscope observations of the samples demonstrate a satisfactory size separation of the fibres and alignment along the flow lines. Therefore, INSPEC is successful in restricting the microscopic analyses to the potentially noxious fibres and in assessing specific concentrations for each diameter interval.

Mineral Fibre Sampling and Size Selection

Potential health hazards due to fibre inhalation are only evaluated in a limited way by simple optical microscopy examination of the membrane filters on which the fibres have been collected. One must consider the amount of fibres deposited and persisting in the most vulnerable organ compartments. Exposure evaluated in this way must take account of the deposition efficiency and relative clearance efficiency of different regions of the respiratory tract, which depends mainly on the diameter and length distribution of the fibres. The fibre diameter roughly indicates the deposition site in the respiratory tract, while the length is mainly connected with toxicity. For these reasons, at international level, special samplers have been recently proposed, capable of distinguishing the fibre sizes, in order to separate the so-called thoracic fraction (the total fibres which penetrate beyond the larynx) and the respirable fraction (only the fibres reaching the non ciliated respiratory area), which represent the most interesting sizes as far as health effects are concerned. Our purpose in this context is to explore the feasibility of using the Inertial Spectrometer (INSPEC) as a sampler that separates the fibres according to their aerodynamic diameter. The optical and electron microscope observations of the samples demonstrate a satisfactory size separation of the fibres and alignment along the flow lines. Therefore, INSPEC is successful in restricting the microscopic analyses to the potentially noxious fibres and in assessing specific concentrations for each diameter interval.

Optical characterization of size separated aerosol particles of different composition and morphology with a polar nephelometer

A new technique for the determination of the complex refractive index of aerosol particles has been developed. The particles are deposited on a membrane filter by means of an aerosol inertial spectrometer, in order to have fixed and size-separated particles. The filter is then made transparent by exposure to acetone vapours and the sample inspected with a laser beam. Scattering data are then analysed and the complex refractive index is obtained. Data and results are presented for a number of materials.

Separation, dispersion, humidification and transport of fibres in a physical lung model

Due to the health hazards of asbestos fibres, industry is searching hard for safe fibrous substitutes. The question however remains if these new fibres endanger health not just as much. So it is important to investigate the relation between different fibre parameters and their health hazards. One of the first objectives is to gain information on the transport and deposition of fibres in the lung. For this purpose a physical lung model has been designed and built, simulating as much as possible the actual conditions in the human lung. For the experiments, well designed uniform fibres are highly desirable. To obtain these it was necessary to add an extra separation step with a large inertial spectrometer (LASPEC), designed by Prodi et al (1984), to the production process of the fibres. This production process was developed at the Delft University of Technology by Buwalda et al. (1990). The dispersion of these fibres into the system proved to be possible with a spinning top aerosol generator (STAG). The lung model itself consists of glass tubes according to a model designed by Yeh and Schum (1980) with electric conducting inner coating. A newly designed humidification system creates a near saturated atmosphere in the lung model.

Aerodynamic High-Temperature Particle Characterization

For the purpose of in situ sampling at high temperatures the INertial SPECtrometer (INSPEC) has been modified by the adoption of appropriate materials (stainless steel and mineral seals). Since membrane filters suitable for this environment are not easy to find, the INSPEC architecture has been changed in order to allow quartz fiber filters to be used: because of their surface roughness, they are used downstream of a grid that has the purpose of flow confinement; the filter mat captures the particles and controls the flow rate in each grid slot. The particles are separated with a resolution of 2%–6%, in the aerodynamic size range, 0.5–10 or 1–20 μm, according to the total flow rate. The sampling flow rate ranges from a few tens of milliliters per minute to 0.5 L/min, with some sacrifice in resolution at higher values. The relationship between deposition distance and size can be drawn with a confidence of above 3%. The filter can be subjected to scanning electron microscopic measurement of the geometric si...

Experimental Assessment and Calibration of an Inertial Spectrometer

An experimental assessment has been made of the performance of an inertial spectrometer to measure the aerodynamic diameter of aerosol particles. These studies have included a determination of the optimum operating conditions for good size resolution, and the calibration of the instrument with monodisperse aerosol particles. Sampling conditions had to be chosen with care in order to ensure that the instrument operated correctly and separated particles on the basis of their aerodynamic size. When the instrument was upright, the calibration curves agreed closely with those of the manufacturer. However, when the spectrometer was inverted, the calibration curves were slightly displaced due to the change in direction of the gravitational force with respect to the other forces acting on the particles as they passed through the spectrometer.

Particle separation in a shallow channel inertial spectrometer

Particle separation in a shallow channel inertial spectrometer

The effect of gravity on deposition distances in an inertial particle spectrometer

Abstract An algorithm for calculating deposition distances of spherical particles in an inertial spectrometer was tested. The air flow field was approximated by a two-dimensional model, and calculated as a numerical solution of the incompressible Navier-Stokes equations. Deposition distances of given spherical particles exposed to that flow field were calculated and the effects of particle size and operating conditions were studied. Calibration curves predicted by the model are similar in shape to those based on experimental data, however, the slopes are different. The effect of external (gravitational) force directions—longer deposition distances for an inverted spectrometer as compared to a normally positioned one—was expected by the model, and has been clearly demonstrated by our experimental results.

Particle deposition within the inertial spectrometer

A model of the particle deposition within the Inertial Spectrometer based on laminar flow and particle Stokes regime, is presented. A remarkable agreement with experimental data is obtained by using a boundary layer approximation along the external curvature of the bend. The particles with masses high enough to penetrate this boundary layer are affected by a slower velocity and so they experience a lower separation than has been calculated previously without consideration of the boundary layer. Through some simplifications it is possible to obtain a relationship between the aerodynamic diameter of different calibration curves. This enables us to extend the comparison with several experimental curves and to predict other calibration curves from a given one.

Conjunction of PIXE with the inertial spectrometer aerosol sampler to permit quantitative, contiguous, narrow resolution particle size measurement

We have developed a protocol using PIXE analysis whereby aerosol samples collected by an inertial spectrometer sampler can be simultaneously characterized for elemental concentration and aerodynamic particle size. Quantitative collection and analysis of ambient aerosols over a wide aerodynamic size range is possible, with an average of 0.08 μ mad size fractionation resolution. The inertial spectrometer sampler has a throat whose sides converge to a rectangular channel which bends through 90°. Clean air is drawn through the throat, and a thin ambient aerosol sheath is injected in front of the channel close to the inner wall of the throat. The surface past the bend consists of a Nuclepore membrane filter through which the air is drawn. Because of their curved path through the bend, the particles are separated according to their size and this separation is magnified by projection onto the filter. Exposed Nuclepore is analysed by PIXE in a He filled chamber. A pulsed proton beam from a Tandetron accelerator is homogenized by an X − Y sweep and collimated to 0.5 mm width using carbon slits. Nuclepore targets are placed at 45° and tracked in 0.9 mm steps across the beam using a directly coupled stepping motor. Position corresponds to particle size. Approximately 2 μC charge is collected at 1.58 MeV and 30 μC at 2.52 MeV with a polystyrene absorber at a 2 μA cm −2 beam current. The distribution of elemental concentrations with aerosol particle size for an urban indoor air samples is measured and the detail observed is demonstrated in examples given of calcium and iron concentrations obtained by 33 approximate 0.08 μ mad “steps” across a ≤ 0.30 μ mad- ≥ 8.0 μ mad particle size range. The sampling method may be extended into the sub-micrometer size range, further enhancing analytical versatility. Because of the sampling simplicity and the resolution and accuracy of analysis, this method can have widespread application.

Calculation of the deposition distance in the inertial spectrometer

Calculation of the deposition distance in the inertial spectrometer

The interpretation of alpha energy spectra from particulate sources

This paper examines the possibilities for using alpha energy spectrometry to determine the particle size characteristics of radioactive aerosols. Results are given of Monte Carlo calculations of the energy spectra of spherical and ellipsoidal particles as a function of particle size and orientation. The spectra for log-normal distributions of spherical particles as a function of the mass median diameter, MMD, and the geometric standard deviation, σ g, are also given. The materials considered are (U, Pu)O 2 and (U, Pu)C. Two simple empirical parameters are used to relate peak shape and peak broadening to particle size, shape and orientation. For log-normal distributions, both MMD and σ g are derived uniquely using these two parameters. Experimental alpha spectrometry results on a log-normal distribution of (U, Pu)O 2 particles are compared with the calculations and with inertial spectrometer and optical counter results.

The aerodynamic size distribution of nuclear fuel aerosols measured with an inertial spectrometer

The aerodynamic size distribution of nuclear fuel aerosols measured with an inertial spectrometer

Characterization of the particulate emission by a large oil fuel fired power plant

The particulate matter in the stack effluents of an oil-fired power plant at different loads was collected and fractionated with an in-stack cascade impactor and a particle inertial spectrometer. The concentration, the size distribution and the particle density of the aerosols sampled have been determined. The elemental composition was measured as a function of particle size by means of proton induced x-ray emission (PIXE) and atomic absorption spectroscopy (AAS). The morphological characteristics (shape, surface feature) and the mineralogical compositions of single particles have been performed by scanning electron microscope (SEM), mineralogical microscope (MM) and X-ray diffractometer (XRD): spherical carbonaceous particles constitute the main typology observed; the presence of vanadate has also been observed.

Characterization of sodium fire aerosols in the aerodynamic range by means of an inertial spectrometer

Characterization of sodium fire aerosols in the aerodynamic range by means of an inertial spectrometer

Characterization of the particulate emission by a large oil-fired power plant

Abstract The particulate matter in the stack effluents of an oil-fired power plant at different loads was collected and fractionated with an in-stack cascade impactor and a particle inertial spectrometer. The concentration, the size distribution and the particle density of the aerosols sampled have been determined. The elemental composition was measured as a function of particle size by means of proton induced x-ray emission (PIXE) and atomic absorption spectroscopy (AAS). The morphological characteristics (shape, surface feature) and the mineralogical compositions of single particles have been performed by scanning electron microscope (SEM), mineralogical microscope (MM) and X-ray diffractometer (XRD): spherical carbonaceous particles constitute the main typology observed; the presence of vanadate has also been observed.

Fibre collection and measurement with the inertial spectrometer

The inertial spectrometer separates aerosol particles according to their aerodynamic diameter and collects them on membrane or Nuclepore® filters. The instrument has been tested with asbestos and glass fibres and has shown a very good separation in terms of geometric and aerodynamic diameters. In addition, the throat design with converging walls produces a flow acceleration that aligns the fibres along the flow lines. The instrument is then suited to fibre characterization; furthermore the deposition surface can be selected for the desired optical or electron microscope observation and microanalysis.

An inertial spectrometer for aerosol particles

An inertial spectrometer is described which measures the size distribution of aerosols. It consists of a rectangular duct with a 90° bend through which clean air flows. A thin aerosol sheath is injected upstream of the bend and the overall flow is sucked downstream through a wall of the duct which is made of a membrane filter. The particles leave the original streamline by a distance which is a function of the aerodynamic size, while remaining airborne: the separation is magnified by projection to the filter which then contains the complete size information of the aerosol. An example of the characterization of polydisperse aerosols is given and possible applications of the spectrometer are discussed.