Review Developments in ultrasound-assisted microextraction techniques for isolation and preconcentration of organic analytes from aqueous samples Aleksandra Szreniawa-Sztajnert, Bo _ zena Zabiegała ⇑ , Jacek Namies´nik Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology (GUT), 11/12 Narutowicza Street, 80-233 Gdan´sk, Poland article info Article history: Available online 16 May 2013 Keywords: Aqueous sample Emulsification-dispersive liquid-liquid microextraction Emulsification microextraction Hollow-fiber liquid-phase microextraction Organic analyte Sample isolation Sample preconcentration Sample preparation Ultrasound-assisted microextraction Water analysis abstract The great potential of ultrasonic assistance in sample preparation, especially extraction, is being recog- nized. In this review, we discuss the applications of ultrasonic radiation in assisting microextraction. Topics covered include ultrasound-assisted emulsification microextraction, ultrasound-assisted-emulsi- fication-dispersive liquid-liquid microextraction, and ultrasound-assisted hollow-fiber liquid-phase microextraction with its modifications. We critically discuss the advantages and the limitations of each technique. Finally, we summarize recent practical applications. Published by Elsevier Ltd. Contents 1. Introduction .......................................................................................................... 45 2. Ultrasonic tools ....................................................................................................... 47 3. Ultrasound-assisted extraction ........................................................................................... 47 3.1. Emulsification ................................................................................................... 48 3.2. Solidification of floating organic droplet (using low-density extraction solvents) ............................................. 48 3.3. Surfactant-enhanced microextraction ................................................................................ 49 3.4. Dispersive liquid-liquid microextraction .............................................................................. 49 4. Future trends of ultrasonic assistance in water analysis ....................................................................... 52 5. Practical applications of ultrasound-assisted extraction techniques .............................................................. 52 6. Conclusions ........................................................................................................... 52 Acknowledgment ...................................................................................................... 52 References ........................................................................................................... 52 1. Introduction The oldest, most widely used, versatile isolation technique for a broad spectrum of organic substances from a liquid matrix is liquid extraction (LE) [1]. However, this method is time consuming, re- quires large amounts of a potentially toxic organic solvent, and has little potential for automation [2]. New trends in the development of analyte isolation and extrac- tion techniques from different types of matrices include a more 0165-9936/$ - see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.trac.2013.02.015 Abbreviations: BTEX, Benzene toluene ethyl benzene xylene; DIPAE, 2-(N,N- diisopropylamino)ethanol; DLLME, Dispersive liquid-liquid microextraction; EDEA, N-ethyldiethanolamine; HF-LPME, Hollow-fiber liquid-phase microextraction; LE, Liquid extraction; LLE, Liquid-liquid extraction; LPME, Liquid-phase microextrac- tion; MDEA, N-methyldiethanolamine; SFODME, Solidified floating organic drop microextraction; SPME, Solid-phase microextraction; TEA, Triethanolamine; UALE, Ultrasound-assisted liquid extraction; UASEME, Ultrasound-assisted surfactant- enhanced emulsification microextraction; US, Ultrasound; USAE, Ultrasound- assisted extraction; USA-DLLME, Ultrasound-assisted dispersive liquid-liquid microextraction; USAEME, Ultrasound-assisted emulsification microextraction; USA-HF-LPME, Ultrasound-assisted hollow-fiber liquid-phase microextraction; 3Q, 3-quinuclidinol. ⇑ Corresponding author. Tel.: +48 583471632. E-mail address: bozena.zabiegala@pg.gda.pl (B. Zabiegała). Trends in Analytical chemistry 49 (2013) 45–54 Contents lists available at SciVerse ScienceDirect Trends in Analytical chemistry journal homepage: www.elsevier.com/locate/trac