Swollen PDMS Membranes for Easy Sampling and Compound Enrichment for its GC-MS and LC-MS Analysis

Ksenia Kladchenko, School of Chemistry, Tel Aviv University, Tel Aviv, Israel (kseniak@mail.tau.ac.il)
Aviv Amirav, School Of Chemistry, Tel Aviv University, Tel Aviv, Israel
Tal Alon, School Of Chemistry, Tel Aviv University, Tel Aviv, Israel

The Swollen Membrane Extraction (SME) technique method enables a fast and efficient direct liquid-liquid extraction with little or no sample preparation. SME is based on a polymer membrane such as polydimethylsiloxane (PDMS) which comes in contact with a low polarity solvent (Hexane or Chloroform) that is sorbed inside it. Consequently, the phase that comes in contact with the sample is a mixture of the PDMS and the solvent. This leads to efficient liquid-liquid-like extraction with minimal extracting volume for maximum enrichment factors and reduced extraction time. Furthermore, The SME technique allows a simple and fast extraction of analytes with exceptionally low detection limits from relatively large sample volumes. Since the membrane excels in rejecting polar compounds and salts it could be used for extraction from aqueous samples like contaminated water or biological fluids (Plasma, Urine). This approach allows shorter extraction periods while enabling the use of a simple GC syringe for sample introduction. It can also be adopted to on-line flowing liquids for LC-MS analysis.

SME experiments with hormones and pesticides in aqueous samples like water, saline and synthetic urine were performed using different low polarity aprotic extracting solvents. For Testosterone and Estradiol, the use of Dichloromethane and Chloroform showed enrichment factors of up to 200 for an extraction period of 20 min using standard GC-MS.

For organophosphate insecticide like Diazinone, Methidathion and Prochloraz in flower extracts, the use of Hexane as the extracting solvent showed enrichment factors up to 100 for the same extraction period.

An LC-MS coupled online sample monitoring device, utilizing the Swollen Membrane Extraction method, is currently under development.

Eventually, this method could have a significant impact in the fields of medical diagnostics, water quality monitoring and food safety.