PDMS Rod-SBSE System Coupled With Gas Chromatography For Determination Of PAHs In Aqueous Samples

SPME (Solid Phase Micro-extraction), which was introduced in1980s, is a solvent-free samplepretreatment technique that integrates sampling, extraction, concentration and sample introduction into asingle uninterrupted process. This process has important advantages over conventional extractiontechniques due to its ease of use, being rather rapid. Stir bar sorptive extraction (SBSE) is a novel samplepreparation technique based on the same principles as those of SPME. Because of simple operation, highersample capacity, good reproducibility and environmental friendly characteristics, SBSE has been popularlyapplied to enrich and determine volatile and semi-volatile organic compounds in environmental, food andbiological samples et al. In SBSE, the coating layer of extraction phase is the amount of PDMS is50-250times larger than SPME. This feature allowed the pre-concentration efficiency to be improved compared toSPME. The coating layer is vitally important to the extraction performance of the stir bar. Recently, thereare quit a few reports about novel coatings, but which were low heat resistance, short-lifetime andthin-coating layer. Those drawbacks limits the SBSE technology development and application largely.Therefore, it is important to develop new method to prepare high-temperature resistant, longer service lifeand thick-coating in further research.We have designed stainless steel molds by which one can fabricate stir bars with constant sizes ofPDMS (polydimethylsiloxane) using sol-gel method. A method for the analysis of trace polycyclic aromatichydrocarbons (PAHs) in aqueous samples has been established by PDMS rod aided SBSE. Thesulfurization processing of PDMS fiber was investigated and optimized. The preparation of thick-coatingbar great increases the loading capacity of PDMS coating. The homemade PDMS rod has a size of30mm×3mm o.d. with a volume of ca.200μL, stable in thermal desorption process. The coating can withstanddesorption temprature up to360°C and the life span of the stir bar was over200times at280°C, which hasadvantages than the commercial stir bar.The enriched PAHs by the PDMS rod were released in a homemade thermal desorption unit (TDU)coupled with gas chromatography. Experimental parameters for extraction of six PAHs were optimizedincluding extraction time, pH, ionic strength and temperature of solution. The procedure has goodrepeatability of0.84-4.02%and very low limits of detection of4.0-33ng/L.PAHs in rain and river water were analyzed by this method at optimized parameters. Through thestandard addition method (SAM), naphthalene, anthracene, fluoranthene and pyrene were detected,and had good recoveries of80.0%-100.3%.