An Automated Approach to In-Syringe Dispersive Liquid-Liquid Microextraction

Abstract

Dispersive liquid-liquid microextraction (DiLLME) is an extraction technique developed over the last decade, with practical applications in both qualitative and quantitative analysis. The technique typically involves addition of small volumes of organic solvent to an aqueous sample, under conditions which favor dispersion of the organic phase into very small droplets. This research project develops and demonstrates an automated in-syringe DiLLME technique. The hardware platform consists of a home-built syringe pump with a multi-position valve that selects different liquids to be mixed in the syringe, such as a sample, buffers, extraction and dispersive solvents, and internal standards. Extracted samples are dispensed into separate vials for analysis by chromatography or spectroscopy. Best performance for the hardware requires optimizing voltage, current, and stepping speed for the stepper motor in the syringe pump, giving consistent and accurate volume displacement by the syringe pump. Quantitative application will be demonstrated by generating a calibration curve based on a parallel dilution of a dye standard. Qualitative application will be demonstrated by performing a previously-developed DiLLME-GC/MS method on common polyaromatic hydrocarbons (PAHs).