Mahdi Rahmani - Department of Chemistry, Faculty of Sciences, Arak Branch, Islamic Azad University, Arak, Iran
Ali Niazi - Department of Chemistry, Faculty of Sciences, Arak Branch, Islamic Azad University, Arak, Iran
Mahmoudreza Sohrabi - Department of Chemistry, Faculty of Sciences, Tehran Shomal branch, Islamic Azad University, Tehran

The goal of the present study is to find the optimal conditions of temperature and extraction time, VOC and NaClamount, and desorb time of extraction reaction that takes place in the vial while performing the HS-SPME procedurefor the determination by GC/MS of six analytes (benzene, toluene, ethyl benzene, ortho xylene, metha xylene and paraxylene) and the corresponding IS (MIBK) by fitting and analyzing a response surface for each one. The paper showsBox-behnken experimental design (BBD) as a useful technique to improve and optimize an extraction condition andembody the effect that some experimental factors exert on several analytical responses. A five-factor, three-level BBDwas used to optimizing. Forty six batches were prepared and evaluated for responses as dependent variables .In theoptimal experimental conditions (0.32 gr NaCl,2.67 microliter VOC, 40 ◦C extraction temperature, 15 min extractiontime and 60 second desorb time) determined by means of a HS-SPME–GC/MS system is carried out..

Box–Behnken; optimization; HS-SPME-GC ، MS; BTEX