Extraction and determination of monocyclic aromatic hydrocarbons (BTEX) in urban air with solid phase nano-extraction

The BTEX are volatile monoaromatic hydrocarbons that comprise one of the most ubiquitous and hazardous groups of ambient air pollutants of concern [1] The objective of this research was to develop a simple, low-budget, and accurate method by solid phase nano-extraction (SPNE) for quantification of BTEX in ambient air based on SPNE -GC–FID. The electrospinning technique was successfully used to create nano-fiber of the polydimethylsiloxane/polyacrylonitrile as a synthesis SPNE coating. Standard 20 mL head-space vials were used for field air sampling and calibration. SPNE experimental conditions, such as extraction time, extraction temperature, desorption time, desorption temperature, were optimized using one-at-time. The optimum conditions were extraction time 40 min, extraction temperature 25ºC desorption time 5 min and desorption temperature 250 ºC. Under these conditions, calibration curve in the two range for benzene and toluene 20-1000 µg/m3 and ethylbenzene and xylene 5-1000 µg/m3 were linear with R2= 0.998, 0.997, 0.998 and 0.998, respectively. The repeatability at two concentration levels (50 and 400 µg/m3) was calculated. Relative standard deviations were 10-12%, 9.1-10.7% and 9.3-11.9% for inter-day, intra-day and fiber-to-fiber, respectively. The limit of detection and limit of quantification were found 0.3-2.8 and 1-9.6 µg/m3. The relative recoveries were obtained from 91-105%. Air samples were collected from the bus station and analyzed by the mentioned method. The mean concentration of ethylbenzene and xylene in the air samples were 6 and 8 µg/m3, respectively.