In the work presented here, highly sensitive determination of around 100 contaminants in surface water in the concentration range from low doubledigit to low triple-digit pg/L was performed. Priority compounds from the EU water framework directive (EU-WFD) as well as substances from other legislation were included. A sequential stir bar sorptive extraction (SBSE) approach employing the GERSTEL Twister was used for analyte enrichment from 100 mL water samples. The Twister was thermally desorbed, compounds were separated via GC and detected by tandem mass spectrometry (MS/MS) utilizing an Agilent 7010 MS.

The analysis method was comprehensively validated and requirements of the EU-WFD for inland surface water were fulfi lled. Repeat analyses of water samples spiked at concentrations close to the Limits of Quantification (LOQ) of the respective analytes demonstrated relative standard deviations between 1 and 15 % with an average of 6.9 %. Trueness was mainly between 90 and 110 %. The correct quantitation of particle-adsorbed compounds like PAHs was examined and confirmed using certifi ed reference sediment.

Cypermethrin, heptachlor and heptachlorepoxide were the only compounds for which the required LOQs could not be reached. To date there is no technique known to the authors that reaches the required LOQs of 0.06 pg/L for heptachlor and heptachlorepoxide. The developed analysis method was successfully applied to real world water samples.

Twister® / Stir Bar Sorptive Extraction (SBSE)

The GERSTEL Twister® enables efficient extraction of organic compounds from aqueous matrices based on Stir Bar Sorptive Extraction (SBSE). SBSE is a solvent-free extraction technique, which is significantly faster than most conventional extraction techniques. SBSE is up to 1000x more sensitive than SPME since the stir bar has significantly more sorbent volume and since it can extract, and concentrate analytes from, a much larger sample volume due to the efficient stirring.