In this article, dispersive liquid-liquid microextraction (DLLME), based on the use of so-called switchable polarity dispersive solvent (SPDS) for microextraction, is presented for the first time. The new extraction technique makes use of a mixture of extraction solvent (dichloromethane) and the SPDS (acrylic acid). This mixture is injected into the aqueous sample solution, which was previously fortified with the alkaline agent (NaOH). The SPDS is dissolved in aqueous phase and a cloudy solution consisting of fine droplets of extraction solvent fully dispersed in the aqueous phase is observed. Simultaneously, as a consequence of the fast neutralization reaction, the SPDS investigated is converted into water-soluble salt and phase separation is achieved because the SPDS switches its polarity. Conversion of the SPDS excludes the negative influence of the conventional dispersive solvents used in DLLME on the solubility of target analytes in aqueous phase and, as a result, increases the DLLME efficiency. The proposed extraction technique was automated based on a flow system and coupled with high performance liquid chromatography system with fluorescence detection (HPLC-FLD) and demonstrated by the determination of ofloxacin (OFLX) in chicken meat samples. This analytical task was used as a proof-of-concept example. The automated method includes on-line ultrasound assisted solid-liquid extraction of OFLX from chicken meat samples followed by DLLME using SPDS, solvent exchange and the determination by HPLC-FLD. Under the optimal conditions, the detector response for OFLX was linear in concentration range of 6·10-9 - 5·10-7 mol L-1. The limit of detection, calculated from a blank test based on 3σ, was 2·10-9 mol L-1.
Keywords: Acrylic acid; Dispersive liquid-liquid microextraction; HPLC-FLD; Ofloxacin; Stepwise injection analysis; Switchable polarity dispersive solvent.
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