On-line Extraction with Swollen PDMS Membranes for Its GC-MS and LC-MS with Cold EI Analysis

Ksenia Kladchenko, Chemistry, Tel Aviv University, Tel Aviv, Israel (kseniak@mail.tau.ac.il)
Svetlana Tsizin, Chemistry, Tel Aviv University, Tel Aviv, Israel
Aviv Amirav, Chemistry, Tel Aviv University, Tel Aviv, Israel

Swollen Membrane Extraction (SME) enables fast and efficient direct liquid-liquid like extraction with little or no sample preparation. SME is based on a polymer such as polydimethylsiloxane (PDMS) which comes in contact with a low polarity solvent (Hexane or Chloroform) which is sorbed inside it and makes it swollen. Consequently, the phase that comes in contact with the sample is a mixture of PDMS and the solvent, thereby enabling efficient liquid-liquid like extraction with minimal extracting volume for maximum enrichment factors at reduced extraction times. Thus, SME leads to a simple and fast extraction method 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 effectively 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 and the extraction selectivity can be controlled via the used in tube solvent.

For static extraction of Testosterone and Estradiol from various aqueous samples (water, saline and synthetic Urine), the use of Dichloromethane and Chloroform showed enrichment factors of up to 150 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.

Recently, an improved On-line monitoring device was coupled with an Electron Ionization LC-MS for continuous flow enrichment and extraction. This device has a kinetic advantage since it allows the use of thinner membranes and it enables semi-automation with less human interference in the extraction process. For swelled on-line extraction of Testosterone and Estradiol enrichment factors up to 210 were obtained, highest achieved so far.