A Granular Bed for Use in a Nanoparticle Respiratory Deposition Sampler

Aerosol Science and Technology

Mudunkotuwa

et al. 2016

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Porous polyurethane foam was evaluated to replace the eight nylon meshes used as a substrate to collect nanoparticles in the Nanoparticle Respiratory Deposition (NRD) sampler. Cylindrical (25-mm diameter by 40-mm deep) foam with 110 pores per inch was housed in a 25-mm-diameter conductive polypropylene cassette cowl compatible with the NRD sampler. Pristine foam and nylon meshes were evaluated for metals content via elemental analysis. The size-selective collection efficiency of the foam was evaluated using salt (NaCl) and metal fume aerosols in independent tests. Collection efficiencies were compared to the nanoparticulate matter (NPM) criterion and a semi-empirical model for foam. Changes in collection efficiency and pressure drop of the foam and nylon meshes were measured after loading with metal fume particles as measures of substrate performance. Substantially less titanium was found in the foam (0.173 μg sampler−1) compared to the nylon mesh (125 μg sampler−1), improving the detection capabilities of the NRD sampler for titanium dioxide particles. The foam collection efficiency was similar to that of the nylon meshes and the NPM criterion (R2 = 0.98, for NaCl), although the semi-empirical model underestimated the experimental efficiency (R2 = 0.38). The pressure drop across the foam was 8% that of the nylon meshes when pristine and changed minimally with metal fume loading (~ 19 mg). In contrast, the pores of the nylon meshes clogged after loading with ~ 1 mg metal fume. These results indicate that foam is a suitable substrate to collect metal (except for cadmium) nanoparticles in the NRD sampler.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Porous polyurethane foam for use as a particle collection substrate in a nanoparticle respiratory deposition sampler

Mines

Aerosol Science and Technology

Mudunkotuwa

et al. 2016

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“…Dry and particle-free air, controlled by a mass flow controller (MFC; MPC20, Porter Instrument, USA), was delivered to a spark discharge system equipped with stainless steel electrodes (303 alloy; 2EXC7, Grainger, USA) to generate stainless steel particles (Park et al, 2015). Highly charged, <10 nm sized, and chain-like aggregated particles containing Cr and Fe, were generated from the spark discharge system.…”

Section: Methodsmentioning

confidence: 99%

Rapid analysis of the size distribution of metal-containing aerosol

Aerosol Science and Technology

Mudunkotuwa

Crawford

et al. 2016

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Conventional methods to measure the metallic content of particles by size are time consuming and expensive, requiring collection of particles with a cascade impactor and subsequent metals analysis by inductively coupled plasma mass spectrometry (ICP-MS). In this work, we describe a rapid way to measure the size distribution of metal-containing particles from 10 nm to 20 μm, using a nano micro-orifice uniform-deposit impactor (nano-MOUDI) to size-selective and collect particles that are then analyzed with a field portable X-ray fluorescence (FP-XRF) to determine metal composition and concentration. The nano-MOUDI was used to sample a stainless-steel aerosol produced by a spark discharge system. The particle-laden substrates were then analyzed directly with FP-XRF and then with ICP-MS. Results from FP-XRF were linearly correlated with results from ICP-MS (R2 = 0.91 for Fe and R2 = 0.84 for Cr). Although the FP-XRF was unable to detect Fe particles at mass per substrate loadings less than 2.5 μg effectively, it produced results similar to those using the ICP-MS at a mass per substrate loading greater than 2.5 μg.

“…P imp (da) was calculated as (15) :

P_{italicimp (d a)} = 1 + \frac{\ln (d_{a} 10^{6})}{8.65} + 0.15, d_{a} \leq 133.3 n m

P_{italicimp (d a)} = 1 - 0.46 (1 + italicerf (\frac{\ln (\frac{d_{a} 10^{6}}{0.45})}{\sqrt{2} \ln (1.43)})) - 0.08, d_{a} > 133.3 n m

where d a is the aerodynamic diameter in meters. The d a was converted to the mobility diameter, d , using Equations 10 and 11 (16) :

d_{v} = d_{a} \sqrt{\frac{χ ρ_{italic0} C c_{(d_{a})}}{ρ_{p} C c_{(d_{v})}}}

d = d_{v} \frac{χ C c_{(d)}}{C c_{(d_{v})}}

where d v is the volumetric diameter, χ is the dynamic shape factor ( χ was assumed to be 1.08 for salt particles (16) ), ρ 0 was the unit density (1000 kg m −3 ) and ρ p was assumed to be 2200 kg m −3 for salt particles.…”

Section: Methodsmentioning

confidence: 99%

Nonwoven textile for use in a nanoparticle respiratory deposition sampler

Vosburgh

Journal of Occupational and Environmental Hygiene

Mines

et al. 2017

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The nanoparticle respiratory deposition (NRD) sampler is a personal sampler that combines a cyclone, impactor, and a nylon mesh diffusion stage to measure a worker’s exposure to nanoparticles. The concentration of titanium in the nylon mesh of the diffusion stage complicates the application of the NRD sampler for assessing exposures to titanium dioxide nanoparticles. This study evaluated commercially available nonwoven textiles for use as an alternative media in the diffusion stage of the NRD sampler. Three textiles were selected as containing little titanium from an initial screening of 11 textiles by field portable x-ray fluorescence (FPXRF). Further evaluation on these three textiles was conducted to determine the concentration of titanium and other metals by inductively coupled plasma – optical emission spectroscopy (ICP-OES), the number of layers required to achieve desired collection characteristics for use as the diffusion stage in the NRD sampler (i.e., the nanoparticulate matter, NPM, criterion), and the pressure drop associated with that number of layers. Only three (two composed of cotton fibers, C1 and C2; and one of viscose bamboo and cotton fibers, BC) of 11 textiles screened had titanium concentrations below the limit of detection the XRF device (0.15 μg/cm2). Multiple metals, including small amounts of titanium, were found in each of the three nonwoven textiles using ICP-OES. The number of 25-mm-diameter layers required to achieve the collection efficiency by size required for the NRD sampler was three for C1 (R2 = 0.95 with reference to the NPM criterion), two for C2 (R2 = 0.79), and three for BC (R2 = 0.87). All measured pressure drops were less than the theoretical and even the greatest pressure drop of 65.4 Pa indicated that a typical personal sampling pump could accommodate any of the three nonwoven textiles in the NRD sampler. The titanium concentration, collection efficiency, and measured pressure drops show there is a potential for nonwoven textiles to be used as the diffusion stage of the NRD sampler.