Microextraction Tech

Solid phase extraction (SPE) is a consolidated technique in sample pretreatment thanks to its robustness, enrichment capacity and selectivity enhancement. The great variety of commercial sorbents covering a wide range of interaction mechanisms, as well as the development of novel materials makes SPE a very versatile technique. Despite its usefulness, classic SPE still presents some shortcomings such as the requirement of moderate to high sample volumes or the use of organic solvents in the milliliter range. These limitations have been faced up by different research groups and as a consequence of these efforts new techniques, for instance microextraction by packed sorbent or pipette tip extraction, have emerged. Pipette tip extraction is based on a simple but innovative idea which consists in placing the sorbent inside a pipette tip. This approach allows the handling of low sample volumes requiring also lower volumes of organic solvents in the elution step. The sorbent can be used...

The extraction of polar and/or metal traces from oily samples is an analytical challenging task due to the nature of the sample matrix. Casella et al. proposed, in 2010, the extraction induced by emulsion breaking technique which faced up this challenge with high success (1). This technique is based on the formation of a stable emulsion between the oily sample (diesel, oil etc.) and an aqueous phase that contains a surfactant. The surfactant promotes the emulsification of both phases favoring their contact and therefore, making easier the transference of the analytes from the non-polar to the polar phase. After the extraction, the emulsion should be broken, usually by centrifugation, in order to allow phase’s separation and the final analysis of the aqueous phase. In a recent article, accepted for publication in Talanta, the same authors have proposed a similar approach for the determination of Cu, Fe and Mn in used lubricating oils (2). This determination is quite important si...

Zinc oxide has been used as coating in solid phase microextraction (SPME) due to its good properties including thermal stability and affinity towards different analytes. In this sense, ZnO presents a high interaction with sulfur-containing molecules due to the strong coordination between Zn and S. However, this interaction is not completely exploited in SPME since pure ZnO coatings, prepared by sol-gel procedures, have a low surface area due to the enwrapping of ZnO nanoparticles (NPs) in the sol-gel network. In a recent article accepted for publication in Journal of Chromatography A, researchers from the Sun Ya-sen University at China have proposed a new approach to avoid this shortcoming. The proposal consists of the use of graphene as ZnO NPs support. The ZnO NPs are grown in the graphene (G) surface producing a composite which is final attached to a silica fiber by a sol-gel reaction in order to prepare the SPME coating. The whole synthetic procedure is described in detai...

On-site solid phase extraction is specially indicated for those analytes which present a limited stability in the sample matrix. The procedure consists of the extraction of the sample immediately after its sampling and the final storage of the sorbent , containing the target analytes , until the final analysis which is usually performed in a conventional lab. Moreover, on-site extraction presents additional advantages in environmental analysis such as the simplification of the sample storage and transportation processes as only the sorbent with the extracted analytes has to be stocked up. The potential of stir bar sorptive extraction (SBSE) for the extraction of organic pollutants, especially for the most hydrophobic ones, from water samples is clearly demonstrated in the scientific literature. However, the applicability of the SBSE in on-site extraction is limited as it usually requires a large size magnetic stirrer powered by alternating current. This limitation has been face...

The fabrication of liquid chromatographic columns with variable interaction chemistry (dual, sequential or gradient composition) is a challenge issue although it presents a high potential for separation and extraction purposes. The direct packing of the stationary phase in a column, the usual way for homogeneous phases, results unpractical when heterogeneous materials are used. Moreover, the final stationary phase´ characterization becomes difficult since it should be performed directly on the stationary phase holder. In this context, the easy in-situ synthesis of monolithic materials makes them a good alternative of choice compared to classic phases. The easy derivatization of the monoliths is also a crucial aspect. In a recent article, accepted for publication in Microchemical Journal, Currivan et al. have proposed an acrylate-based monolith with integrated gold nanoparticles for the successive extraction and separation of target proteins in the same column (1). The proposed ...

Polymeric frits are employed in solid phase extraction to confine the sorbent in the cartridge avoiding it losses during the extraction procedure and to filter the sample avoiding the clogging of the cartridge due to the potential particulate matter present in the sample. Taking advantage of their organic nature -they are usually built with polyethylene- polymeric frits can be used as active sorbent allowing the retention of non polar analytes. Moreover, polymeric frits have been recently proposed as support for the synthesis of monolithic material (1) or molecularly imprinted polymers (2) for extraction purposes. Stir frit microextraction In a recent article, accepted for publication in Journal of Chromatography A, researchers from the University of Cordoba at Spain have proposed the use of polyethylene frits in the so-called stir frit microextraction technique (3). The new technique combines the extraction capability of this polymeric material with the stirring element, an ...

Carbon nanotubes reinforced hollow fiber microextraction (HF-SLPM) was proposed for the first time by Es´haghi et al. in 2010 (1). The original technique consisted of a multi-phase system where the aqueous donor and acceptor phases were separated by a polymeric membrane with a dispersion of carbon nanotubes in 1-octanol immobilized in its pores. The pH gradient established at both sides of the reinforced hollow membrane allowed the extraction of the target analytes. Due to its multiphase nature,  HF-SLPM  involves a selectivity enhancement compared to traditional hollow fiber liquid phase microextraction. Diethylstilbestrol The direct immobilization of carbon nanotubes (CNTs) in the pores of a polypropylene hollow fiber have been recently proposed by researchers from the Chinese Academy of Sciences of Beijing at China (2), for the isolation and preconcentration of diethylstilbestrol from milk. Diethylstilbestrol is a steroid hormone used for animal growth and it pre...