Separation and preconcentration methods in trace species in environmental samples: from solid phase extraction to microextraction
Erciyes University, Faculty of Sciences, Department of Chemistry, 38039, Kayseri-Turkey
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The organic and inorganic trace species in our body are playing important roles. Their determinations in the environmental samples are critical due to this point. The sample preparation is one of the important steps prior to determination of inorganic and organic species at trace levels in environmental samples by instrumental techniques. Separation and enrichment step is one of the necessary sample preparation steps for this purpose, due to their lower levels than the detection limits of the detection system and the interferic effects of the matrix components of the samples [1-3]. Solvent extraction, coprecipitation, membrane filtration, electrodeposition and flotation are widely used separation-enrichment techniques for the traces analytes in high highly saline samples.
Nowadays solid phase extraction with new nanomaterials which has high adsorption capacity and chemically stable including carbon nanotubes, graphene, polymeric materials, nanocomposites, covalent organic frameworks and metal organic frameworks is also very popular for that purpose. These nanomaterials are syntheses and characterized in analytical chemistry labs. In the characterization FTIR, SEM, Raman, XAD and thermal techniques are used. These materials are generally filled a suitable glass column and adsorption-desorption process were performed on this column. Also, the magnetic solid phase extraction (MSPE) has been developed in recent years as a new sample preparation method. Instead of centrifugation and filtration the adsorbents in during solid phase experiments, the aqueous solution of magnetic particles that participate to analytes can be separated easily and quickly using the external magnetic field.
Microextraction with new generation solvents which are green solvents for our environments including deep eutectic solvents, ionic liquids and switchable solvents is also popular technique with different modifications for the separation and preconcentration of traces organic and inorganic species. Microextraction is considered as green because of the minimizing of consumption of harmful solvents. An important effort has been shifted to the development of liquid phase microextraction methods, mainly characterized for eliminating or minimizing the time consuming, tedious and multistage operations, consumption of potentially organic solvents, production of secondary laboratory waste, necessity of large and complex laboratory equipments, which commonly faced in conventional speciation and preconcentration methods. New generation of solvents of interest in green chemistry represent switchable solvents, deep eutectic solvents and ionic liquids. For example, ionic liquids have some good physical and chemical properties, such as negligible vapor pressure, non-flammability, good solubility for inorganic and organic compounds and good extractability for organic and inorganic species at trace levels in the environmental samples.
In the separation-preconcentration works, pH of the working media, amount of reagents, amout of adsorbents or type and volume of the extraction solvents, sample volume and matrix effects are the critical parameters for the quantitative recoveries of the analyte species. The optimizations of these parameters are performed by using model aqueous solutions. After optimization of the all analytical parameters, the accuracy is checked by the addition-recovery test and analyzing certificated materials. Lastly the method is applied to determination of the analyte contents of the real samples.
In the presented work, the usage of solid phase extraction and microextraction techniques for the separation-preconcentration of organic and inorganic species at trace levels in real samples will be discussed. Some applications of these techniques for environmental samples including natural water and food samples will be given.
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