Development and Application of a Needle Trap Device for Time-Weighted Average Diffusive Sampling

Abstract

A simple, cost-effective analysis combining solventless extraction, thermal desorption, and determination of volatile organic compounds (VOCs) was developed and validated. A needle trap device (NTD) packed with the sorbent Carboxen1000 was used as a time-weighted average (TWA) diffusive sampler to collect target compounds by molecular diffusion and adsorption to the packed sorbent. This process can be described with derivations of Fick's first law of diffusion, which expresses the relation between the TWA concentrations to which the passive sampler is exposed and the mass of analytes adsorbed to the packed sorbent in the sampler. The effects of experimental factors such as temperature, pressure, humidity, and face velocity were taken into account in applying diffusive sampling under nonideal conditions. This study demonstrates that NTD is effective for air analysis of benzene, toluene, ethylbenzene, and o-xylene (BTEX), due to the good adsorption/desorption quality of Carboxen 1000 and to the special geometric shape of the needle with a small cross section avoiding the need for calibration. Storage tests showed good storage stability for BTEX. Verification of the theoretical model showed good agreement between theoretical and experimental sampling rates. Method validation done against NIOSH method 1501, SPME, and NTD active sampling revealed good agreement between those methods. Automated NTD sample introduction to a gas chromatograph facilitates the use of this technology for industrial hygiene applications.

Analytical challenges in breath analysis and its application to exposure monitoring

“…These devices allow direct thermal desorption inside a GC injector (equivalent to SPME) and have performed as well or better than SPME when both methods have been compared [108][109][110][111]. The small i.d.…”

Extraction of Gaseous VOCs Using Passive Needle Trap Samplers

“…Wang et al (2005) designed a NTS, packed with segmental layers of adsorbents, polydimethylsiloxane (PDMS), divinylbenzene (DVB) and Carboxen particles for extracting gaseous benzene, toluene, ethylene and o-xylene (BTEX); in addition, the individual detection limits ranged from 0.23 to 2.10 ng/L for BTEX. Gong et al (2008) packed a NTS with the sorbent Carboxen1000 as a TWA diffusive sampler to collect BTEX under different sampling conditions, i.e. air flowing speeds of 1.44-32.48 cm/min and relative humidity (RH) of 17-53%.…”

“…The relations of extracting VOCs mass and sampling flow rates were evaluated. Actually, the NTS has the potential to be used as a personal passive VOC sampler due to its small size for wearing by a worker for a long period, like a badgelike or penlike sampler (Pawliszyn, 2003;Gong et al, 2008). In order to assessing the feasibility of this self-designed DVB-NTS as a passive sampler for the working place, the long sampling periods of 4-12 hr was also examined.…”

“…In order to assessing the feasibility of this self-designed DVB-NTS as a passive sampler for the working place, the long sampling periods of 4-12 hr was also examined. The Carboxen/PDMS coated SPME fiber has been extensively adopted to sample gaseous BTEX due to its strong affinity to BTEX (Koziel and Novak, 2002;Larroque et al, 2006;Gong et al, 2008). Therefore, TEX (toluene, ethylene and o-xylene) was also simultaneously sampled using a 75 μm Carboxen/PDMS-SPME fiber for comparing in terms of extraction efficiency of NTS.…”

Identification of Coffee Fragrances Using Needle Trap Device-Gas Chromatograph/Mass Spectrometry (NTD-GC/MS)

“…A standalone heater needs to use to get thermal desorption and in many cases, the cryogenic refocusing should be used to attain sharp chromatogram. 10 Needle trap device (NTD) [11][12][13][14][15][16] introduced recently to overcome these disadvantages over the conventional sorbent tubing. The NTD is a miniaturized format of sorbent tubing but it takes the most advantages of SPME techniques described above.…”