Novel Active Personal Nanoparticle Sampler for the Exposure Assessment of Nanoparticles in Workplaces

Abstract

A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 μm and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 μm in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 ± 0.22 μm and 101.4 ± 0.1 nm, respectively. The d(pa50) at the loaded micro-Al(2)O(3) mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO(2) mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.

Design and Testing of the NCTU Micro-Orifice Cascade Impactor (NMCI) for the Measurement of Nanoparticle Size Distributions

“…(Stk 50 ) 1/2 is seen to deviate from the theoretical value of Marple and Liu (1974), 0.477 and that of Radar and Marple (1985), 0.49. This finding is consistent with that found by Tsai et al (2012). In addition, the minimum S/W ratio of the 9th-10th stages corresponds to a higher (Stk 50 ) 1/2 than that of the 8th stage, because the pressure drop across the former is larger than the latter.…”

“…Equation (11) was further validated by the experimental data of the micro-orifice impactor with smooth nozzle shape in Tsai et al (2012) with the porosity of 0.9% and the Re of 385. The d pa50 value estimated by Equation (11) is 120 nm which is close to the design value of 100 nm.…”

“…These problems include particle bounce from the collection surface, overloading of collected particles on the impaction plate, and interstage loss (Marple and Olson 2011). Oil-coated substrates (Reischl and John 1978;Turner and Hering 1987;Pak et al 1992;Peters et al 2001;Gulijk et al 2003;Liu et al 2011;Tsai et al 2012), porous substrates (Huang et al , 2005, and specially designed substrates (Tsai and Cheng 1995;Chang et al 1999) were used as impaction substrates to reduce solid particle bounce. For uncoated substrates used as a collection surface to avoid interference with chemical analysis from coating materials, conditioning the relative humidity of the incoming aerosols of the MOUDI was suggested to ensure that the measurement of mass distributions is not influenced by particle bounce (Vasiliou et al 1999;Chen et al 2011).…”

“…For uncoated substrates used as a collection surface to avoid interference with chemical analysis from coating materials, conditioning the relative humidity of the incoming aerosols of the MOUDI was suggested to ensure that the measurement of mass distributions is not influenced by particle bounce (Vasiliou et al 1999;Chen et al 2011). To increase the particle loading capacity on impaction substrates, many efforts have been made using oil-soaked Teflon filters (Turner and Hering 1987;Tsai et al 2012), rotating substrates Tsai et al 2012), and specially designed impaction plates (Tsai and Cheng 1995).…”

“…The theoretical d pa50 were also found to be lower than the experimental values. Tsai et al (2012) and Liu et al (2013) found that the cutoff characteristics of the micro-orifice impactors are very sensitive to the S/W ratios for d pa50 100 nm. The results of these studies are limited to the variation of S/W ratio with the corresponding cutoff characteristics.…”