Microextraction Tech

Recently a novel dual substrate for both SERS and PS-MS based on the deposition of silver nanoflowers (AgNFs) onto a paper-based analytical device (PAD) has been developed. Although the obtention of the substrate requires several steps, it is possible to synthesize a bunch of them at the same time. Figure 1 illustrates the different stages involved in the synthesis process of the so-called ny-AgNF PADs (further details are included in the full article). To obtain the silver nanoflowers, an already described protocol was followed, which is based on a simple reaction involving silver nitrate and ascorbic acid as the reducing agent (Figure 1, steps 4-7). Furthermore, previous modification of the paper was needed to anchor the nanoflowers to its surface (Figure 1, steps 1-3, and 8). First, a coating of nylon-6 was needed to assure the surface availability of the analytes in Surface-enhanced Raman spectroscopy ( SERS). Next, a surface of metallic silver was acquired by the deposition of ...

In 2014 a new method for the synthesis of magnetic nanoparticles (MNPs)-nylon 6 composite was proposed. This method is simple and quick since only one step is needed. It is based on a solvent changeover, taking advantage of the different solubility of nylon 6 in formic acid and water. In Figure 1, it can be observed how this synthesis is carried out. The solution of MNPs and nylon-6 in formic acid is added to a beaker with water using a plastic syringe, inducing the precipitation of the polymer around the MNPs. To collect the composite after the synthesis, a magnet is used. Figure 1. Scheme of the synthesis When MNPs are combined with a polymer, the resulting composite has the properties of both materials, combining the high extraction capabilities of the polymer and the magnetic behaviour due to the nanoparticles. Moreover, another advantage of using polymers is their wide versatility since they can be tailored-synthesized and different functional groups can be added, to reac...

The usefulness of molecularly imprinted polymers is unquestionable. They have been extensively used for the selective extraction of different families of compounds in a wide variety of samples. The main problem associated to these sorbents is the impossibility to ensure that a high percentage of the recognition sites are available for analyte interaction as they can be embebed into the polymeric structure. These attractive solids have not been excluded from the nanometric approach. In this sense, a synergic combination of the selectivity of the imprinting process and nanometric dimension is achieved. The easiest way to obtain nanoMips is by using a conventional nanoparticle (NP) as the core whose surface is covered by the polymeric phase with recognition sites. Usually, magnetic NPs are the preferred option because they also implements a clear simplification of the extraction process as they are isolated by means of an external magnet. However, their preparation can be a little be...

The combination of highly efficient sorbent with commercially available extraction devices is the best way to consolidate microextraction techniques in routine laboratories. The potential of nanoparticles in this context is undeniable. In this regard, our colleagues of the Sharif University of Technology (Tehran, Iran) have evaluated the potential of a novel nanocomposite for microextraction in packed syringe (1). The new sorbent is based on silver nanoparticles/polyaniline (Ag NPs/PANI) and it was prepared by using interfacial polymerization. The procedure is rather simple and it is performed in an aqueous/organic biphasic system being the Ag NPs/PANI nanocomposite formed in the interface. The evolution of the reaction can be easily followed by the color change of the mixture which starts with a free color at the interface which becomes darker in the organic phase and eventually stop changing, indicating the reaction completion. After 24 h of ageing, the composite can be separate...

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...