Automated liquid-liquid extraction of organic compounds from aqueous samples using a multifunction autosampler syringe

Liquid-liquid extraction is one of the most widely used and simplest sample preparation techniques. However, consumption of large volumes of organic solvent and manual handling are two major drawbacks of this technique. A multifunction autosampler syringe is introduced which permits automated liquid-liquid extraction in an enclosed operating environment, with low consumption of organic solvents. The device described herein features a micromixer function in addition to common autosampler syringe features like accurate and precise aspirating and dispensing. To test the functionality of the micromixer syringe, manual extraction of caffeine from a tea infusion and semi-automated extraction of dichloroethane from water were carried out. Excellent recoveries of caffeine from a tea infusion (89% recovery with 1.3% RSD) and dichloroethane from water (107% recovery with 10% RSD) were obtained. Two automated workflows were tested using the micromixer syringe mounted in a laboratory autosampler. Standalone automated micro liquid-liquid extraction was performed for sample preparation of selected polychlorinated biphenyl (PCB) congeners prior to comprehensive two-dimensional gas chromatography – electron capture detection analysis. Extraction of PCBs using the described approach used substantially less solvent than a validated solid-phase extraction approach whilst delivering equivalent results for samples with high-level PCBs. Finally, fully automated extraction and GC-MS analysis of polynuclear aromatic hydrocarbons (PAHs) from water samples was performed. Mean recoveries of extraction for PCB and PAH analysis were > 70% using 4 min automated liquid-liquid extractions.