Microextraction Tech

We highlight today an article that describes the combination of laser desorption and solid phase microextraction (SPME) for the analysis of solid samples. The article has been published in Rapid Communications in Mass Spectrometry under the title " Laser desorption sample transfer for gas chromatography/mass spectrometry" (1) . It is not necessary to describe the potential of SPME since it is a well established technique in almost every analytical laboratory. Despite its potential, SPME is the focus of an intense research and its direct combination with mass spectrometry (MS) or its in-vivo applications are strongly remarkable. Our colleagues, from the Louisiana State University, have proposed an innovative approach that allows the isolation of target compounds from solid samples followed by their preconcentration in a conventional SPME fiber. The manifold proposed is quite simple. First of all, the sample (solid or liquid) is deposited in a metal target. A laser radiati...

Nucleic acids have several practical applications in Analytical Sciences as they can be used as biorecognition molecules (e.g. aptamer) in the design of sensors and even extraction phases. However, this post deals with those methods that are aimed to determining nucleic acids in samples of different origin (usually biosamples). Among these applications, we can highlight paternity tests, the study of genetic diseases, the identification of the virus or bacteria behind an infection or the certification of the origin of a meat in a processed food. Whatever the application is. the extraction of nucleic acids of the system under study is the initial (and usually) critical step. The conventional extraction procedure, which is based on the use of silica particles as extractant, involves several steps like extraction or clean-up that makes the process tedious, especially if we consider that the particles should be separated from the sample or washing solutions by centrifugation. The use o...

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 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. Although there are some commercially available phases, the development of novel ones as well as the design of formats different than the conventional particle-packed column one are attractive research lines. In this context, the use of polymer mats synthesized by electro-spinning allows the fabrication of extraction disks that have special properties like high surface to volume ratio. In addition, they permit the continuous flow of the sample through the extractant phase increasing the sample throughput. Polypyrrole (PPy) coated nylon fibers have been recently proposed as sorbent for the extraction of azo dyes, which are compound...

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. The toxicological application is, in itself, interesting but the tools used in this research makes it attractive to "microextracters". This study has come up several challenges related to cell culture studies. First of all, in this field the sample volume is usually limited so miniaturized instrumental techniques are required. In addition, the inherent nature of biosamples (complex matrices and low target concentrations) further complicate the situation. Our colleagues have on-line comb...

Using pomelo peel for the synthesis of monolithic ordered mesoporous silica Monolithic ordered mesoporous silicas are highly attractive as sorbents in extraction techniques due to their physicochemical characteristics. To be really effective, there must be a balance between their macroporous and mesoporous structure. Macropores enhance the extraction kinetics allowing an easier diffusion of the target compounds from the bulk samples to the active surface of the material. Mesoporous defines the active surface of the material.... Link to the post Dynamic electromembrane extraction The potential of electromembrane extraction (EME) is beyond any doubt [1]. As you well know, it is based on the electromigration of the target charged analyte from the donor phase (the sample) to the aqueous acceptor phase through a polymeric membrane that physically separates both phases. The extraction is rapid and it provides high enrichment factors...... Link to the post Bubble-in- drop single ...

We recommend the following articles that deal with different aspects related with sample preparation. 1. Application of graphitic sorbent for on-line microextraction of drugs in human plasma samples . Graphitic carbon has a great potential as sorbent since it may develop different interaction chemistries with target compounds. Commercial graphitic carbons like graphitized carbon black or porous graphitic carbon presents some disadvantages including a lack of mechanical stability or a high retention (almost irreversible) of some analytes. These shortcomings are faced in this article where a new carbon material is presented. The new material is based on the deposition of a graphitic carbon layer over an inert substrate like alumina. This combination increases the mechanical strength which is key for chromatographic uses. The material has been packed in a lab made microextraction in packed sorbent (MEPS) device and it has been applied for the extraction of ropivacaine and lidocaine f...

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. Researchers from Italy and Israel have chemically evaluated the original manuscript of the novel with the intention of identifying potential drugs consumed by Mikhail Bulgakov to fight the nephrosis [1]. For this purpose, they have proposed a solid phase enrichment protocol using cation exchange (SCX) and hydrophobic (C8) beads of different particle sizes. In this proposal, wet beads are deposited on the manuscript surface and thanks to the different sizes (SCX have larger sizes than C8) a complete covering of the document with the particles is achieved. The targets are extracted by a mixed-mode mechanism and after the extraction, the final extracts are analyzed by GC/MS. Morphine T...

The intentional incorporation of air bubbles to solvent drops enhances the extraction efficiency in single drop microextraction (SDME). The reason behind this experimental fact is simple: the air bubble increases the surface to volume ratio of the drop. In other words, the same organic solvent volume presents a larger surface and therefore a better extraction kinetics. This idea, which was firstly proposed by Williams et al. in 2011, [1] has been recently revisited by the same research group proposing mixed solvents as extractant. Mixed solvents can present even better extraction properties, due to special combination of physicochemical characteristics, than the individual solvents used in that mixture. In fact, our colleagues confirmed both aspects in a recent article published in Talanta [2]: According to the results, the enrichment factors obtained for the bubble in drop SDME (BID-SDME) are higher (ca. 1.5 times) than that obtained with the conventional SDME. The use of ...

The potential of electromembrane extraction (EME) is beyond any doubt [1]. As you well know, it is based on the electromigration of the target charged analyte from the donor phase (the sample) to the aqueous acceptor phase through a polymeric membrane that physically separates both phases. The extraction is rapid and it provides high enrichment factors. In its conventional format, EME is developed in static mode. What would happen if the sample and even the acceptor phase are dynamically introduced in the extraction device? This question has been recently answered in an article published in Journal of Chromatography A [2]. Our colleagues have designed an extraction device where the sample and the acceptor phase can flow dynamically thanks to a peristaltic and a syringe pump, respectively. This configuration permits to process a larger sample volume (increasing the enrichment factor) without modifying the diffusion distance sample/acceptor phase. In fact, the flow of the sample...

Monolithic ordered mesoporous silicas are highly attractive as sorbents in extraction techniques due to their physicochemical characteristics. To be really effective, there must be a balance between their macroporous and mesoporous structure. Macropores enhance the extraction kinetics allowing an easier diffusion of the target compounds from the bulk samples to the active surface of the material. Mesoporous defines the active surface of the material (directly related to the extraction capacity) and they are usually related to the selectivity of the material through a shape/size restriction mechanism. This balance is not easy to achieve and some research groups are investigating in new synthesis procedures. Prof. Yu-Qi Feng and coworkers have recently proposed a new alternative in RSC Advances journal using a natural product, pomelo peel, as precursor [1]. The potential of the new material as well as the natural origin of one of the precursor (green chemistry) are highly remarkable...

Information about drug distribution after intake in a certain tissue is of relevance as it provides useful information for the development of novel medicines. Conventional homogenization methods are not applicable in this context as they provide a qualitative information about the drug present in the analyzed samples. However, data about the spatial distribution and the ability of the drug to cross the cellular barrier is usually missing. To overcome this drawback, Swales and coworkers have studied the drug distribution in brain tissue using liquid extraction surface analysis combined to mass spectrometry (LESA-MS). LESA-MS is a surface sampling technique that combines liquid extraction from the surface of tissue sections with mass spectrometry. The authors use mass spectrometric imaging (MSI) to build an image of xenobiotic and endogenous compound distribution to asses drug brain barrier penetration. LESA-MSI was useful to obtain the map distribution of poorly penetrative compoun...

The analysis of ancient documents, pictures, archeological pieces and related added-value samples is a challenging issue for any analytical chemist. The unique character of the samples and the priceless values of most of them require the sampling of a very small quantity to obtain as much information as possible. Undoubtedly, the direct analysis or the use of non destructive analytical techniques must be the first option for the researchers. But not the only one!! Our loved microextraction techniques could play a relevant role in this scientific field as they are able to maximize the amount of information obtained from a very low sample amount. Recently, The Analyst journal has published a research carried out by our colleagues from the University of North Texas dealing with the potential of direct analyte-probed nanoextraction (DAPNe) coupled to different instrumental techniques for the determination of the authenticity of documents (1). The ink used for writing the manuscript is...

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. In fact, these NPs may be blown during the ionization step causing the entering of this material in the spectrometer. Prof. Yu-Qi Feng and coworkers have recently proposed the use of magnetic NPs (MNPs) for this arrangement avoiding the previously mentioned shortcoming. The extraction protocol follows the typical workflow of a dispersive solid phase extraction (DSPE). In short, the MNPs are dispersed into the sample to favor the interaction/isolation of the analytes. Afterwards, they are cleaned-up with an appropriate solvent and finally recovered in a special capillary for instrumental analysis. T...

Design and fabricate your own extraction devices in a cheap and rapid way. This is the main conclusion that we can infer after reading an article recently accepted for publication in Analytical Chemistry. This dream has come true by our colleagues form the National Tsing-Hua University at Taiwan (1). They have designed a solid phase extraction device which has been finally fabricated in acrylate using a 3D printer. The fabrication time (approximately 38 min) and the cost of each unit (US$ 1.5) are really motivating. The extraction device consists of a microfluidic channel where cuboids of defined dimensions are printed on surface to increase the superficial area and thus the extraction kinetics. The device presents a high permeability, it allows the use of high sample flow rates (essential to pass larger sample volumes allowing high preconcentration factors) and it is easy to regenerate. In addition, it can be easily adapted to flow systems as it can work with low-pressure pumping...

Membranes can be used for different purposes in Analytical Chemistry. In the extraction context, they permit the development of several liquid-liquid extraction techniques such as dialysis, osmosis, among others. Also, they can provide an additional enhancement of the selectivity by the direct selection of the pore size. They are also commercialized in different formats (planar, tubular) and polarities in such a way that they can be applied to almost any analyte-sample binomial. In liquid phase microextraction, membranes have been used under the 2 phases and 3 phases formats depending on the number, nature and role played by the different liquid phases involved. In order to favor the kinetic of the whole process the continuous agitation of the system is recommended to accelerate the diffusive transport of the target compounds in both the donor and acceptor phases reducing the thickness of the diffusion layer near the membrane. Prof. Dr March and Prof. Dr. Cerdá have recently pro...

The potential of ionic liquids (ILs) in the microextraction context is beyond any doubt. ILs, especially those that are liquid at room temperature (RTILs), present a negligible vapour pressure (attractive in HS-SDME), tuneable solubility in water (interesting in in-situ solvent formation technique) and they may be tailored to extract target analytes by the proper selection of the forming ions. RTIL have been extensively used in DLLME for these reasons, its recovery after extraction, being usually developed by centrifugation thanks to their higher density than water. However, this centrifugation step is time-consuming and several alternatives like in-syringe DLLME have been proposed to avoid it. Magnetic materials present a clear advantage over other materials in dispersive procedures as they can be recovered from the bulk solution using an external magnet. The combination of magnetic materials/ionic liquids has been studied from different approaches. For example, ILs can be used t...