Background: Determination of organic pollutants usually requires extraction of the pollutants from samples, using hazardous solvent. Solid phase micro-extraction (SPME) is a solvent-free equilibrium extraction method, in which, proper calibration can allow quantitative measurements of organic pollutants at a very good sensitivity without the use of any organic solvent. Because individual VOCs are generally present in urine only at trace levels, a sensitive and accurate determination technique is essential.Methods: This study describes the optimization of headspace solid phase micro-extraction (HS-SPME) followed by gas chromatography equipped with flame ionization detector (GC-FID) for xylene in spiked urine. Through this investigation, the parameters affecting the extraction and GC determination of xylene, including extraction time, temperature, desorption temperature, desorption time, salt addition, sample pH, sample volume and sample agitation were studied.Results: An optimized headspace extraction was carried out at 30°C for 6 min in presence of 0.2 gml-1 of NaCl in the sample solution. Desorption of the xylene was carried out for 60 sec. at 250°C. The optimized procedure was also validated with three different pools of spiked urine samples and showed a good reproducibility over six consecutive days as well as six within-day experiments. In this study, the accuracy, linearity, and detection limits were also determined.Conclusion: The HS-SPME-GC-FID technique provided a relatively simple, convenient, practical procedure, which can be successfully applied for determination of xylene in spiked urine when an occupational exposure monitoring is required.

Background: Aromatic organic solvents are extensively used in various industries. xylene is a colorless, transparent liquid, with the characteristic odor of the aromatic hydrocarbons family, which is widely used in industries. Adsorption is a conventional method of purifying polluted air containing volatile organic compounds (VOCs). Zeolite has many unique properties such as high capacity, molecular sieve characteristics, nonflammability, thermal stability, and strong acid sites. Moreover, it is reconstructed at low temperatures. Objectives: In this study, we investigated the effect of various parameters on the adsorption capacity of natural zeolite (clinoptilolite) for xylene adsorption. Materials and Methods: Physical and chemical properties of natural zeolites were tested by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and elemental analyses of natural zeolites were characterized by X-ray diffraction. xylene concentration was measured at various times through concentrations-measured valve before and after the adsorbent bed reactor by the direct reading of Phocheck (Ion Science Ltd, UK).Results: Experimental results showed that clinoptilolite is a potential sorbent for xylene in the range of ppm, and the breakthrough time would be reduced by increasing the concentration. The optimal temperature of xylene adsorption on natural zeolite was 35℃ and by increasing the temperature, the absorption efficiency of clinoptilolite was declined. The results showed that the breakthrough time and the exhaustion point time at the optimal conditions are 65 and 95 minutes, respectively. Adsorption capacity of clinoptilolite was obtained as 1.69 mg xylene/g zeolite. Conclusions: Experimental results showed that clinoptilolite is a potential sorbent for xylene in the range of ppm and the breakthrough time was reduced by increasing the concentration. Adsorption rate were increased by increasing concentration of xylene. Presence of xylene molecules in high concentration enhances their transfer and contact with adsorbent; as a result, by increasing gas concentration, breakthrough time in zeolite will be shorter.

Catalytic alkylation of toluene with methanol was carried out over Zr- Cr- and Co- pillared clay catalysts in a catalytic flow system operated under atmospheric pressure at a temperature range of 250-450oC. The pillared clay catalysts were prepared via sonication technique. Results indicated that the pillaring of montmorilonitic clay material with polyoxy-metalic cations (Zr- Cr- and Co-) improves the texture properties and thermal stability of the obtained catalysts. The Co-PILC catalyst is the most active and selective catalyst towards p-xylene formation, i.e. Co-PILC catalyst is a shape selective for p-xylene formation.