Beyond dispersive liquid–liquid microextraction

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<ul><li><p>Journal of Chromatography A, 1335 (2014) 214</p><p>Contents lists available at ScienceDirect</p><p>Journal of Chromatography A</p><p>jo ur nal ho me pag e: www.elsev ier .com/ locate /chroma</p><p>Review</p><p>Beyond dispersive liquidliquid microextraction</p><p>Mei-I. Lea Centro de Segb Department oc Department o</p><p>a r t i c l</p><p>Article history:Received 24 OReceived in reAccepted 10 FAvailable onlin</p><p>Keywords:Dispersive liquDispersion liquid-phase microextractionPreconcentrationSample preparation</p><p>tion, DLLME methods are separated in two categories: DLLME with low-density extraction solvent andDLLME with high-density extraction solvent. Besides these methods, many novel special devices for col-lecting low-density extraction solvent are also mentioned. In addition, various dispersion techniqueswith LPME, including manual shaking, air-assisted LPME (aspirating and injecting the extraction mix-ture by syringe), ultrasound-assisted emulsication, vortex-assisted emulsication, surfactant-assistedemulsication, and microwave-assisted emulsication are described. Besides the above methods, com-</p><p>Contents</p><p>1. Introd1.1. </p><p>1.2. </p><p>2. Devel2.1. </p><p> CorresponE-mail add</p><p>1 Tel.: +886 </p><p>http://dx.doi.o0021-9673/ binations of DLLME with other extraction techniques (solid-phase extraction, stir bar sorptive extraction,molecularly imprinted matrix solid-phase dispersion and supercritical uid extraction) are introduced.The combination of nanotechnique with DLLME is also introduced. Furthermore, this review illustratesthe application of DLLME or dispersion LPME methods to separate and preconcentrate various organicanalytes, inorganic analytes, and samples.</p><p> 2014 Elsevier B.V. All rights reserved.</p><p>uction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3DLLME with lower-density extraction solvent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1.1. DLLME based on solidication of oating organic droplet (DLLME-SFO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1.2. DLLME with special extraction devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.1.3. Low-density-solvent based solvent demulsication DLLME (LDS-SD-DLLME). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7DLLME with higher-density extraction solvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2.1. DLLME with low-toxicity solvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2.2. Auxiliary solvent to adjust the density of DLLME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.2.3. DLLME with automated online sequential injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7</p><p>opment of DLLME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Various techniques for assisting dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1.1. Manual shaking for assisting dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1.2. Air-assisted liquidliquid microextraction (AALLME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1.3. Ultrasound-assisted emulsication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8</p><p>ding author. Tel.: +886 3 572 1194; fax: +886 3 573 6979.resses: msfuh@mail.scu.edu.tw (M.-R. Fuh), sdhuang@mx.nthu.edu.tw (S.-D. Huang).2 2881 9471x6821; fax: +886 2 2881 1053.</p><p>rg/10.1016/j.chroma.2014.02.0212014 Elsevier B.V. All rights reserved.onga, Ming-Ren Fuhb,1, Shang-Da Huangc,</p><p>uranca Alimentar, Instituto para os Assuntos Cvicos e Municipais (IACM), Macau, Chinaf Chemistry, Soochow University, Taipei 11102, Taiwanf Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan</p><p> e i n f o</p><p>ctober 2013vised form 9 February 2014ebruary 2014e 15 February 2014</p><p>idliquid microextraction</p><p>a b s t r a c t</p><p>Dispersive liquidliquid microextraction (DLLME) and other dispersion liquid-phase microextraction(LPME) methods have been developed since the rst DLLME method was reported in 2006. DLLMEis simple, rapid, and affords high enrichment factor, this is due to the large contact surface area ofthe extraction solvent. DLLME is a method suitable for the extraction in many different water sam-ples, but it requires using chlorinated solvents. In recent years, interest in DLLME or dispersion LPMEhas been focused on the use of low-toxicity solvents and more conveniently practical procedures. Thisreview examines some of the most interesting developments in the past few years. In the rst sec-</p></li><li><p>M.-I. Leong et al. / J. Chromatogr. A 1335 (2014) 214 3</p><p>2.1.4. Surfactant-assisted emulsication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1.5. Vortex-assisted emulsication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.1.6. Microwave-assisted emulsication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10</p><p>2.2. Combination of techniques for extraction and analysis with DLLME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10. . . . . .</p><p> with. . . . . . . . . . . .</p><p>2.3. . . . . . . 3. DLLM . . . . . .</p><p>3.1. . . . . . . . . . . . .. . . . . . </p><p>3.2. . . . . . .4. Concl . . . . . . </p><p>Con . . . . . .Ackno . . . . . .Refer . . . . . . </p><p>1. Introdu</p><p>Liquidlextraction ooperationalporous holvent. The organic solsurface aretion times. Imicroextracmatic hydromethods emwater-misction solvendisperser sohigher thanin both wat5 mL of the with a conicvent) and 8is injected ing of watethe test tubextraction pcould be inMany convesolvents as510 mL of centrifugatinique incluenrichmenttion solventcarbon tetra</p><p>There arsion LPME mextraction) DLLME usincludes the (based on socedures, theproceduresanalysis [9]applicationceuticals, ot</p><p>e nepmeries: aterater d seviallyhich</p><p>adfar DLLMconc</p><p> andarizesion dever betn of</p><p> for Dds inendi</p><p> to o extion een om siliarymeths so2.2.1. Solid-phase extraction combined with DLLME . . . . . . . . . . . . . . . . . . 2.2.2. Stir bar sorptive extraction (SBSE) combined with DLLME . . . . . . 2.2.3. Molecularly imprinted matrix solid-phase dispersion combined2.2.4. Supercritical uid extraction (SFE) combined with DLLME . . . . . 2.2.5. Nanotechniques combined with DLLME . . . . . . . . . . . . . . . . . . . . . . . . . Other methods using low-toxicity solvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </p><p>E applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of DLLME for various analytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1. Organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2. Inorganic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of DLLME to various eld samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . </p><p>usion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ict of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . wledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </p><p>ences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </p><p>ction</p><p>iquid microextraction (LPME) is usually applied in thef environmental samples. LPME has several different</p><p> modes, such as those that use a drop of solvent [1,2],low ber-protected solvent [35], and disperser sol-rst two methods are simple and use lower volumes ofvent. However, they are limited by the small contacta of the drop or ber, which necessitates long extrac-n 2006, Rezaee et al. developed dispersive liquidliquidtion (DLLME) for preconcentration of polycyclic aro-carbons (PAHs) in water samples [6]. The rst DLLMEploy a mixture of a high-density extraction solvent, a</p><p>ible solvent, and a polar disperser solvent. The extrac-t must be able to extract analytes, is soluble in thelvent, insoluble in aqueous samples, and have density</p><p> that of water. The disperser solvent has to be solubleer and extraction solvent. In this method (Fig. 1(a)) [6],aqueous solution is placed in a screw-cap glass test tubeal bottom. A solution of 1 mL of acetone (disperser sol-</p><p> L of tetrachloroethylene (TCE, the extraction solvent)into the sample solution. A cloudy dispersion consist-r, disperser solvent, and extraction solvent is formed ine and is centrifuged. The dispersed ne droplets of thehase settle at the bottom of the conical test tube andjected into a gas chromatograph for further analysis.ntional DLLME typically use 20100 L of chlorinated</p><p> extraction solvent, 0.52 mL of disperser solvent, and</p><p>of thesdevelocategothan wthan wmarizebe initvent, w[12]. Dtion offor premetalssummdispervents, transfebinatiodevicemetho</p><p>Depbelongdensityextracthave bvent fran auxthese sampleaqueous sample. The total extraction time including theon time is generally 510 min. Advantages of this tech-de simplicity of operation, rapid extraction, and high</p><p> factors (EFs) [7,8]. However, the high-density extrac- used, which is typically chlorobenzene, chloroform, orchloride, is highly toxic.e many excellent recent reviews on DLLME or disper-ethods (methods that disperse extraction solvent for</p><p>[913]. Kocrov et al. summarized a lot of details aboutg organic solvents lighter than water methods, and con-uses of special devices, the low-density solvent usedlidication and solvent demulsication) in DLLME pro-</p><p> adjustment of extraction solvents mixture density and based on automation of DLLME by sequential injection. Zgoa-Grzeskowiak and Grzeskowiak described the</p><p> of DLLME to pre-concentration of metal ions, pharma-her organic compounds and many more modications</p><p>mated procanalytical m</p><p>1.1. DLLME</p><p>1.1.1. DLLM(DLLME-SFO</p><p>Liquidlorganic dro[14,15]. It istion of orgathat of DLLMbenets of does not inDLLME, it dglass tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 DLLME (MIMMSPDDLLME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11</p><p> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11</p><p> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12</p><p> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....</p></li></ul>