Microextraction Tech

Thermo-responsive molecularly imprinted monolith in extraction Molecularly imprinted polymers (MIPs) are widely employed sorbents due to their improved selectivity. They are synthesized in the presence of the analyte, which is called template, and therefore the polymeric network is constructed around the target leaving selective chemical cavities when it is washed away. After the bulk synthesis, the polymer is crashed and sieved to obtain a solid with a particle size as homogeneous as possible. In a recent article published in Analytical and Bioanalytical Chemistry, researchers from the Tianjin Medical University at China have proposed a smart MIP monolith for the extraction of ketoprofen from milk samples. Link to the post Simultaneous electromembrane extraction of acidic and basic drugs In most of the cases, microextraction techniques are applied to isolate and preconcentrate a target compound or a narrow group of them. The simultaneous extraction of a given sample into frac...

We recommend the following articles that deal with different aspects related to sample preparation. 1. Coumarins as turn on/off fluorescent probes for detection of residual acetone in cosmetics following headspace single-drop microextraction. This article presents an interesting application of HS-SDME for the indirect determination of acetone residues in cosmetics. The method takes advantage of the special characteristics of the native fluorescence of coumarins whose intensity depends, among other factors, on the chemical composition of the medium where they are dissolved. In fact, the fluorescence intensity of an ethanol/water solution of 7-diethylamino-4- methylcoumarin (MDAC) increases in the presence of acetone while the intensity of an ethanol/water solution of 7-hydroxy-4-methylcoumarin (4-MU) decreases when acetone is dissolved in that medium. These are the so-called turn-on and turn-off fluorescent effects. In short, the method comprises different steps. First of all, a de...

The article that we highlight today describes a new, simple, efficient and automated extraction technique for high throughput bioanalysis. It has been published in Analytical Chemistry under the title " Gas Pressure Assisted Microliquid–Liquid Extraction Coupled Online to Direct Infusion Mass Spectrometry: A New Automated Screening Platform for Bioanalysis" (1). It is interesting to note that we have described another article from the same research group in a previous post ( Three phase electroextraction ). According to the title, Gas Pressure Assisted Microliquid–Liquid Extraction (GPA-µLLE) is based on the thorough mixture of an aqueous biological sample (donor phase) and a organic solvent (acceptor phase) by means of a gas stream. However, the potential of this technique goes beyond this simple description for many reasons, among which the following are of note : The technique is developed in a multi-plate platform and therefore it can process a high number of s...

We recommend the following articles that deal with different aspects related to sample preparation. 1. Energy-dispersive X-ray spectrometry combined with directly suspended droplet microextraction for determination of dissolved silicate in surface water via silico molybdenum blue complex. Dr. Pytlakowska from the University of Silesia (Poland) faces up the determination of silicate in samples by energy-dispersive X-ray spectrometry, which is not especially sensitive for this determination due to the low energy of the Kα line of silicon. In order to overcome this limitation, a indirect method based on the use of molybdenum (a more intense emitter) as marker is proposed. For this purpose, silicate is transformed into silicomolybdenum blue which is finally isolated and preconcentrated by means of suspended droplet microextraction. After the extraction, the organic solvent is deposited over a polymeric membrane where molybdenum (whose concentration is related to the original silicate ...

The availability of easy to handle interfaces for the direct analysis of samples by mass spectrometry is highly desirable as it clearly simplifies the analytical measurement process. Moreover, the reduction of errors in the final result given can be highlighted as a great advantage. These interfaces must reduce the amount of interferents that can eventually reach the detector while providing a reproducible and quantitative response. Researchers from the University of Hong Kong developed a pipette-tip-ESI-MS technique for the direct analysis of solid samples. The interface coupled a pipette-tip with a syringe and a syringe pump (1). Now they have evolved this interface to the microextraction context by replacing the empty pipette tip by a new one filled with conventional reverse-phase C18 sorbent (2). In this way, after retention, the analytes are directly sprayed out for the ESI-MS analysis by applying a high voltage to the syringe needle (see the diagram in this picture free avai...

We recommend the following articles that deal with different aspects related with sample preparation. 1. Molecularly imprinted polymer dedicated to the extraction of glyphosate in natural waters . Glyphosate is a widely employed pesticide. Glyphosate determination is challenging due to its small size and high polarity. In this article, researchers from the University of Orleans at France have proposed a new molecularly imprinted polymer (MIP) that allows, thanks to electrostatic and polar interactions, the isolation of this analyte from natural waters. The MIP showed higher selective recognition toward the target analyte than the obtained with the non-imprinted polymer (NIP). Although the pH and ionic strength are critical variables on the analyte extraction, this method is a promising tool for the resolution of this complex analytical problem.  Link to the article 2. Water-contained surfactant-based vortex-assisted microextraction method combined with liquid chromatograph...

The determination of volatile compounds in gas samples is a challenging issue. Firstly, because it is difficult to collect large and representative samples and secondly due to the potential losses of the analyte by diffusion through the pores of the sample container. Moreover, the mandatory preconcentration step that must be implemented prior to the instrumental analysis must be carried out maintaining the sample homogeneity. From the Centers for Disease Control and Prevention in Atlanta, we can read a very interesting approach for the simultaneous determination of up to 22 volatile organic compounds (VOCs) present in cigarette smoke (1). In addition to their elegant approach to overcome the previously mentioned difficulties, they are able to quantify a broad range of smoke VOCs, usually measured by separated assays. It should also be noticed that all the samples (cigarette smokes) were generated following the ISO3308:2000 standard which assure the validity of the results in terms...

In most of the cases, microextraction techniques are applied to isolate and preconcentrate a target compound or a narrow group of them. The simultaneous extraction of a given sample into fractions of analytes with similar chemical characteristics is especially interesting in bioanalysis since biological samples contain plenty of compounds with biological effects that cover a wide range of polarities. Electromembrane extraction (EME) is an electro-driven technique where the analytes migrate between two aqueous phases, separated by a polymeric membrane where an organic solvent is immobilized in the form of a supported liquid membrane (SLM), due to the application of a voltage gradient at both sides of the SLM. EME, which is characterized by its efficacy and expeditiousness, is usually employed for the isolation of acidic or basic compounds from aqueous samples although some efforts have been developed in order to make possible the simultaneous extraction of both types of analytes (...

Molecularly imprinted polymers (MIPs) are widely employed sorbents due to their improved selectivity. They are synthesized in the presence of the analyte, which is called template, and therefore the polymeric network is constructed around the target leaving selective chemical cavities when it is washed away. After the bulk synthesis, the polymer is crashed and sieved to obtain a solid with a particle size as homogeneous as possible. In a recent article published in Analytical and Bioanalytical Chemistry, researchers from the Tianjin Medical University at China have proposed a smart MIP monolith for the extraction of ketoprofen from milk samples. In an old post entitled “ Smart molecularly imprinted hydrogels for protein recognition ”, we discussed the advantages of these materials that combine the selectivity enhancement of MIPs with the advantages of smart polymers. In short, a smart polymer is a porous polymeric network that may respond to external stimulus (mainly pH, ionic str...