Microextraction Tech

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...

Freeze concentration (FC) is a separation technique scarcely exploited for sample treatment in Analytical Chemistry although it has been successfully applied in the industrial field. For example, FC is used in the food industry to extract water avoiding losses of (semi)volatile and thermolabile compounds producing extracts enriched in the solutes of interest. FC is based on the fact that solutions (water plus solutes) have lower freezing points than pure water. Therefore, when a solution is cooled down at an appropriate temperature, ice crystals start to be formed excluding solutes which are concentrated in the remaining liquid phase. Prof. Logues´s research group at South Dakota State University (USA) have applied this principle in an innovative way to improve the extraction yield of stir bar sorptive extraction (SBSE). The overall extraction procedure is quite simple as it only requires cooling the vial that contains the sample while SBSE is performed. The cooling of the sample...

Optical monitoring of single drop microextraction Single drop microextraction, the first liquid phase microextraction technique, is a simple approach consisting of the extraction of the target analytes from the sample into a small drop of extractant. The characteristics of the drop, specially its chemical nature and mechanical stability, are key to guarantee the success of the extraction. The chemical composition defines the affinity towards the target analytes which are, in fact, extracted depending on their solubility. The mechanical stability of the drop during the extraction is critical since the drop detachment would ruin the extraction. (Read the post) Moving miniaturization a step forward Microextraction techniques have evolved from classical extraction procedures following three main trends, namely: miniaturization, simplification and automation, which have not received a similar attention in the last decades. In fact, simplification and miniaturization (in different d...

Carbon nanotubes sponges are three dimensional structures formed by the random self-assembly of these nanostructures during their synthesis. They are produced by the classical chemical vapor deposition method simply using special catalysts like ferrocene. The structure of an sponge can be observed in Figure 1A which shows a scanning electron micrograph of the bulk material. A closer view (Figure 1B) reveals how the nanostructures are interconnected(1). The sponges are characterized by a high superficial area (up to 100 m2/g), high porosity (derived from the 3D structure) and low density. From the chemical point of view they are superhydrophobic, property that has been exploited in some applications, such as the recovery of oil from water or the treatment of environmental waters. Figure 1. SEM micrographs of carbon nanotubes sponges at two magnifications. Reproduced from reference 1 Researchers from the Shandong Academy of Sciences and the Wuhan University of Technology have...

Microextraction techniques have evolved from classical extraction procedures following three main trends, namely: miniaturization, simplification and automation, which have not received a similar attention in the last decades. In fact, simplification and miniaturization (in different degrees) are almost inherent to the majority of the new approaches while automation is, in some cases, considered in a lesser extent. However, all these facets are capital, especially if we consider the new demands of analytical information. The modern analytical platforms will have to process a larger number of samples providing information even faster and cheaper. It seems obvious that in this scenario, the previous trends should go a step further. Microfluidic system can answer to these new demands. On the one hand, they allow the miniaturization of the analytical procedures reducing the requirements of sample and extractant volumes to the microliter range. On the other hand, these systems can be...

Single drop microextraction (SDME), the first liquid phase microextraction technique proposed, is a simple approach consisting of the extraction of the target analytes from the sample into a small drop of extractant. The characteristics of the drop, specially its chemical nature and mechanical stability, are key factors to guarantee the success of the extraction. Its chemical composition defines the affinity towards the target analytes which are, in fact, extracted depending on their solubility. The mechanical stability of the drop during the extraction is critical since the drop detachment would ruin the extraction. The drop volume and handling increase the probability of that detachment. Researchers from Ukraine and Slovak Republic have already published in Analytical Chemistry journal a nice contribution to SDME that overcomes this shortcoming(1). In this case, an optical probe is used as the drop holder in such a way that the continuous UV-Vis monitoring of the drop is achieve...

The implementation of microextraction techniques in process laboratories usually depends on their automation degree. In reality, the use of too manual procedures is not practical when a large number of samples must be processed. In addition, manual workflows are labor intensive and prone to errors. This situation can be further complicated when risky samples, pretty common in bioanalysis, are handled. The potential of electromembrane extraction (EME) has been highlighted several times in Microextraction Tech blog. Among other advantages, EME is a rapid process thanks to the migration of the target compounds from the sample to the acceptor phase (through an appropriate supported liquid membrane) under an electrical voltage gradient. No doubt, the automation of EME and its hyphenation to chromatographic techniques would have a high impact in the field. Researchers from the universities of Copenhagen and Oslo have reported this year two interesting articles in this context. Earli...

Selectivity is a main issue in any analytical process. Many strategies can be proposed to achieve the highest value of this basic analytical property. Among them, the use of selective sorbents can be highlighted. There are several alternatives that can be used to synthesize them, being the molecular imprinting one of the most reported. The so-called molecularly imprinted polymers (MIP) are usually employed to selectively isolate and preconcentrate target compounds from the sample matrix. Despite their potential, the synthetic process is complex and it requires the use of the target molecule to create the sterically and electrically recognition site on the polymeric network. It has two main inconveniences: a) the cost of the analyte which is used as template and b) the need for a complete elimination of the analyte to avoid memory effects. These negative aspects are relevant which MIP are intended to be used in a purification technique where the cost of the procedure exponentially incr...

Electrospun fibres (EFs) have a great potential in microextraction techniques thanks to their advantageous characteristics. They are versatile as a relatively large number of different polymers, with different interaction chemistries, can be used as precursors. In addition, the use of mixtures of polymers as well as the introduction of nanoparticles in the fibrous network have extended the applicability and have improved their performance. Although EFs can be obtained in several formats (e.g as solid phase microextraction coatings), they can be easily fabricated as a mat of ordered or random fibers. These membranes present a high surface to volume ratio which is key for a rapid extraction kinetics. In some cases, EFs membranes can be used as filters where the sample flows through the polymeric network while the analytes are retained. In other cases, the membrane can be immersed into the sample and the analytes are transferred from the bulk solution to the sample thanks to the sample a...

Despite the importance of solid-liquid extraction in the analysis of solid materials, this technique has been scarcely discussed in this blog. This post aims to be an inflection point in this trend and we have selected a very interesting article for this purpose. The article has been published in Analytical Chemistry by our colleagues from Valencia (Spain) under the appealing title " Hard cap espresso machines in Analytical Chemistry. What else ?". In this study, the authors proposed the use of espresso machines and their hard caps as extractors for the isolation of polycyclic aromatic hydrocarbons from soil samples. The idea is simple and clever and it involves the introduction of the soil into commercial caps and its extraction, as a conventional coffee cap, in the espresso machine with slight modifications. To make the extraction feasible, an acetonitrile/water mixture, instead of pure water, is used as extractant. The extraction pressure, which depends on the ...

Miniaturization of classical extraction procedures, which was the origin of microextraction techniques, has reduced the consumption/requirement of extractant solvents in the liquid-based formats from the mL to the m L range. The use of lower droplets, at the nL or even pL levels, opens a door to process special systems characterized by their small sizes or low availability. In a previous post, we discussed the potential of liquid extraction surface analysis (LESA) [1,2]. This technique is so powerful to analyze surfaces as it integrates the liquid extraction of the solid samples with the on-line mass spectrometric (MS) analysis of the extracts. LESA works with nL droplets allowing the superficial analysis of tissues or bacteria colonies. One question arises in this context. Is it possible to use this technology to analyze single cells? For the theoretical point of view, that approach is possible. However, a recent study published in Nature points up that using nL droplets to ext...

Carbon nanoparticles and specifically carbon nanotubes can be considered as an inflection point in the development of microextraction techniques on account of their excellent sorbent properties. This fact permits the reduction of the dimensions of the extraction step while maintaining or even improving the preconcentration of the target compounds on the nanosorbent. Since then, different metallic and silica-based nanoparticles have been successfully evaluated in this context. In the last two-three years, a new nanosorbent has revolutionized again microextraction techniques. Graphene (G) and its oxide (GO) present a unique planar structure which makes them different from other nanoparticles and even from allotropic forms of carbon, which confers them with outstanding electrical, mechanical and structural properties. Carbon-based nanomaterials have been extensively used for the isolation and preconcentration of organic compounds usually of aromatic nature thanks to the possibility of re...

The study of historical documents: morphine in Bulgakov´s famous manuscript Mikhail Bulgakov was a recognized writer born in Kiev in 1891. His famous novel, The master and Margarita, criticizes the soviet society and the literature establishment. He wrote the novel by the end of his life. In these days, Bulgakov was suffering nephrosis that caused his death in 1940. (read more) Magnetic solid phase extraction coupled to ambient ionization mass spectrometry Direct coupling of microextraction techniques and ambient ionization mass spectrometry opens a door to rapid, selective and sensitive analyses that are quite attractive in the bioanalytical field. The use of nanoparticles (NPs) in this combination may be problematic since they are not fully compatible with MS although they have a great potential as sorbent in microextraction techniques. (read more) Magnetomotive ionic liquids The potential of ionic liquids (ILs) in the microextraction context is beyond any doubt. IL...

Magnetic SPME in micro-fluidics, speciation of Hg in cells Mercury is a well known toxicant with different exposure sources. Although its use on medical products is banned in many countries, other sources like environmental pollution or contaminated food still exist. Professor Bin Hu and co-workers have been recently researched how Hg species are distributed and even modified in cell cultures [1]. In their own words, this type of research is of paramount importance in order to fully understand the toxicity but also the cell protection mechanisms.  (post) Polypyrrole coated nylon fibers for disk-based solid phase extraction The extraction of polar compounds from aqueous matrices is not a easy process due to the high solubility of these compounds into the sample that weakens the interactions with the extractant. Polymeric phases, comprising different monomer in their structure that may establish polar interactions and even ionic, have been widely used to solve this problem. ...