Time-Weighted Average Passive Sampling with a Solid-Phase Microextraction Device

Abstract

A modified Solid-Phase Microextraction (SPME) device has been used as a passive sampler to determine the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which the fiber is extended outside its needle housing, during TWA passive sampling, the fiber is retracted a known distance into its needle housing. The SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to a coated fiber as collection medium. This process has been shown to be described by Fick's first law of diffusion, whereby determination of the amounts of analytes accumulated over time enable measurement of the TWA concentration to which the sampler was exposed. A series of fibers, 100-microm poly(dimethylsiloxane), 65-microm poly(dimethylsiloxane)/divinylbenzene, and 75-microm Carboxen/poly(dimethylsiloxane), were tested for their "zero sink", face velocity, and response time behavior. Of the fibers tested, that coated with 75-microm Carboxen/poly(dimethylsiloxane) was found to be an excellent passive sampler for VOCs. TWA passive sampling with a SPME device was shown to be almost independent of face velocity and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length could be changed. It was found that environmental conditions, e.g., temperature, pressure, relative humidity, and ozone, have little or no effect on sampling. The 75-microm Carboxen/poly(dimethylsiloxane) fiber can retain VOCs for up to two weeks without significant loss. When the SPME device was tested in the field and the results were compared with those from National Institute of Occupational Health and Safety method 1501, good agreement was obtained.

Quantification of benzene, toluene, ethylbenzene and o-xylene in internal combustion engine exhaust with time-weighted average solid phase microextraction and gas chromatography mass spectrometry

“…SPME can be used for determination of TWA concentrations of VOCs in indoor air [18][19][20][21][22][24][25][26][27]29,30]. For this purpose, fiber coating is kept inside protecting needle for a known distance from the needle opening during a prescribed sampling period.…”

“…Decision to further investigate the contribution amount of BTEX by the stainless steel of a SPME assembly was driven by early observations of apparent significant, yet very reproducible BTEX mass extracted. Chen and Pawliszyn [18,19] recommended using deactivated SPME needle assemblies (i.e., prototypes that are not commercially available) in order to minimize adsorption of semi-VOCs onto stainless steel, to minimize variations and ensure constant uptake rate in TWA SPME mode. However, such deactivated needles are not available commercially and would be very challenging to assemble.…”

“…Still to date, relatively few attempts were made to bring SPME to the field [21][22][23]. The TWA SPME approach was used for quantification of toluene in indoor air [18,19], dodecane in indoor air [24], air monitoring of formaldehyde in indoor air [25][26][27], PAH in creek water [28], n-alkanes in indoor air [29], n-valeraldehyde in air [30], and chlorinated semi-VOCs in landfill gas [31].…”

Potential Roles of Essential Oils on Controlling Plant Pathogenic Bacteria Xanthomonas Species: A Review

“…Solid-phase micro extraction is a convenient and completely solvent-free technique in which a small fused silica fiber with a polymeric coating is used to extract analytes from sample matrices. These methods have been developed for a wide range of vapor-monitoring applications, and they can be regarded as passive and diffusive sampling methods (Batlle et al, 2001;Chen and Pawliszyn, 2003), thus avoiding the need for the air-sampling pumps or aspirators that are typically used in dynamic or active methods.…”

Échantillonnage rapide des BTEX dans l’air par SPME dans la ville de Nice et à l’aéroport Nice-Côte d’Azur

“…Des études sont en cours à l'École des Mines d'Alès pour déterminer l'importance de ce phénomène [11]. Cependant, pour la fibre que nous avons utilisée, il a été observé que les conditions environnementales avaient relativement peu d'importance sur l'échan-tillonnage des hydrocarbures [27][28].…”