Arroz

Spectrochimica Acta Part B 64 (2009) 1–15

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Spectrochimica Acta Part B
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s a b

Review

Miniaturized preconcentration methods based on liquid–liquid extraction and their application in inorganic ultratrace analysis and speciation: A review
Francisco Pena-Pereira, IselaLavilla, Carlos Bendicho ⁎
Departamento de Química Analítica y Alimentaria, Area de Química Analítica, Facultad de Química, Universidad de Vigo, Campus As Lagoas-Marcosende s/n, 36310 Vigo, Spain

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Liquid–liquid extraction (LLE) is widely used as a pre-treatment technique for separation and preconcentration of both organic and inorganic analytes fromaqueous samples. Nevertheless, it has several drawbacks, such as emulsion formation or the use of large volumes of solvents, which makes LLE expensive and labour intensive. Therefore, miniaturization of conventional liquid–liquid extraction is needed. The search for alternatives to the conventional LLE using negligible volumes of extractant and the minimum number of steps has driven the developmentof three new miniaturized methodologies, i.e. single-drop microextraction (SDME), hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid–liquid microextraction (DLLME). The aim of this paper is to provide an overview of these novel preconcentration approaches and their potential use in analytical labs involved in inorganic (ultra)trace analysis and speciation. Relevantapplications to the determination of metal ions, metalloids, organometals and non-metals are included. © 2008 Elsevier B.V. All rights reserved.

Article history: Received 27 May 2008 Accepted 24 October 2008 Available online 6 November 2008 Keywords: Miniaturization Sample preparation Liquid-liquid microextraction Ultratrace elemental analysis Speciation

Contents 1. 2. Introduction . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . Miniaturization of conventional liquid–liquid extraction . . . . . . . . . 2.1. Single-drop microextraction (SDME) . . . . . . . . . . . . . . . 2.1.1. Direct single-drop microextraction (Direct-SDME) . . . . . 2.1.2. Headspace single-drop microextraction (HS-SDME) . . . . 2.1.3. Liquid–liquid–liquid microextraction (LLLME) . . . . . . . 2.1.4.Continuous-flow microextraction (CFME) . . . . . . . . . 2.2. Hollow fibre liquid-phase microextraction (HF-LPME) . . . . . . . 2.3. Dispersive liquid–liquid microextraction (DLLME) . . . . . . . . . 3. Extractant phases . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Organic solvents . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Ionic liquids (ILs) . . . . . . . . . . . . . . . . . . . . . . .. 3.3. Aqueous drops . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1. Noble metal-containing aqueous drops . . . . . . . . . . 3.3.2. Acidic and alkaline aqueous drops . . . . . . . . . . . . 4. Application of SDME, HF-LPME and DLLME to ultratrace inorganic analysis 4.1. Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Metalloids . . . . . . . . . . . . . . . . . . . .. . . . . . . 4.3. Organometals . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Non-metals . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Related microextraction techniques . . . . . . . . . . . . . . . . . . . 5.1. Solid phase microextraction (SPME) . . . . . . . . . . . . . . . 5.2. Stir bar sorptive extraction (SBSE) . . . . . . . . . . . . . . . . 6. Conclusions . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....