Droplets-based microextraction assisted SPME for GC-MS analysis of polar compounds such as clopyralid in water
For the first time, we assessed the performance of liquid phase microextraction (LPME) with droplets of organic solvent that assists solid phase microextraction (SPME) with chemically bonded polydimethylsiloxane (PDMS) fiber for analysis by gas chromatography-mass spectrometry of trace amounts of polar compounds in water. Clopyralid was used as a target analyte. LPME with droplets was performed with dichloromethane and was compared with dispersive liquid–liquid microextraction (DLLME) by addition of acetone or methanol as disperser solvent to dichloromethane. The main factors potentially affecting the microextraction were optimized. The optimal volume of dichloromethane was 17 μL per mL of aqueous samples. The relative enrichment factor for LPME in the presence of dichloromethane droplets was 200 and decreased by addition of disperser solvent. Consequently, DLLME cannot be applied with this SPME fiber. A characteristic of the method is that LPME and SPME can be conducted simultaneously or in two steps in the same vial. The limit of detection and the limit of quantification were 0.02 μg L−1 and 0.07 μg L−1, respectively for 7 μm chemically bonded PDMS fiber and mass spectrometric detection was also carried out.