A Novel Extraction Procedure for Stir Bar Sorptive Extraction (SBSE): Sequential SBSE for Uniform Enrichment of Organic Pollutants in Water Samples

A novel stir bar sorptive extraction (SBSE) procedure termed sequential SBSE was developed. Compared to conventional SBSE, sequential SBSE provides more uniform enrichment over the entire polarity/volatility range for organic pollutants at ultra-trace levels in water. Sequential SBSE consists of a SBSE performed sequentially on a 5-mL sample fi rst without modifi er using one stir bar, then on the same sample after addition of 30 % NaCl using a second stir bar. The fi rst extraction with unmodifi ed sample is mainly targeting solutes with high Ko/w (log Ko/w > 4.0), the second extraction with modifi ed sample solution (containing 30 % NaCl) is targeting solutes with low and medium Ko/w (log Ko/w < 4.0). After extraction the two stir bars are placed in a single glass desorption liner and are simultaneously desorbed. The desorbed compounds were analyzed by thermal desorption and gas chromatography – mass spectrometry (TD – GC – MS). Recovery of model compounds consisting of 80 pesticides