Magnetic solid-phase extraction (M-SPE) is a procedure based on the use of magnetic sorbents for the separation and preconcentration of different organic and inorganic analytes from large sample ...volumes. The magnetic sorbent is added to the sample solution and the target analyte is adsorbed onto the surface of the magnetic sorbent particles (M-SPs). Analyte-M-SPs are separated from the sample solution by applying an external magnetic field and, after elution with the appropriate solvent, the recovered analyte is analyzed. This approach has several advantages over traditional solid phase extraction as it avoids time-consuming and tedious on-column SPE procedures and it provides a rapid and simple analyte separation that avoids the need for centrifugation or filtration steps. As a consequence, in the past few years a great deal of research has been focused on M-SPE, including the development of new sorbents and novel automation strategies. In recent years, the use of magnetic carbon nanotubes (M-CNTs) as a sorption substrate in M-SPE has become an active area of research. These materials have exceptional mechanical, electrical, optical and magnetic properties and they also have an extremely large surface area and varied possibilities for functionalization. This review covers the synthesis of M-CNTs and the different approaches for the use of these compounds in M-SPE. The performance, general characteristics and applications of M-SPE based on magnetic carbon nanotubes for organic and inorganic analysis have been evaluated on the basis of more than 110 references. Finally, some important challenges with respect the use of magnetic carbon nanotubes in M-SPE are discussed.
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•Magnetic carbon nanotubes (M-CNTs) as a sorption substrate for SPE.•Synthesis of M-CNTs and approaches for their use in M-SPE.•M-CNTs as sample preparation substrates for organic and inorganic analysis.
•The use of solid phase extraction for speciation of inorganic Se is described.•Different SPE strategies and sorbents used for inorganic selenium speciation are discussed.•Analytical methods for ...speciation of inorganic Se in water samples are reviewed.
Selenium is an essential element for the normal cellular function of living organisms. However, selenium is toxic at concentrations of only three to five times higher than the essential concentration. The inorganic forms (mainly selenite and selenate) present in environmental water generally exhibit higher toxicity (up to 40 times) than organic forms. Therefore, the determination of low levels of different inorganic selenium species in water is an analytical challenge. Solid-phase extraction has been used as a separation and/or preconcentration technique prior to the determination of selenium species due to the need for accurate measurements for Se species in water at extremely low levels. The present paper provides a critical review of the published methods for inorganic selenium speciation in water samples using solid phase extraction as a preconcentration procedure. On the basis of more than 75 references, the different speciation strategies used for this task have been highlighted and classified. The solid-phase extraction sorbents and the performance and analytical characteristics of the developed methods for Se speciation are also discussed.
In the last decades, the extensive use of chromium in industrial activities has led to the discharge of different chromium species into the biosphere. The two stable chromium forms are Cr(III) and ...Cr(VI), which have dramatically different properties. While the first one is essential, the second is harmful and carcinogenic, even at very low concentration. Therefore, the appropriate analysis of chromium in environmental, biological, food and other kind of samples need a reliable separation and subsequent quantification of both Cr species. The present paper provides a critical review of chromium speciation methods in which solid phase extraction was employed as sample pretreatment using graphene and carbon nanotubes (and their diverse oxidized, functionalized and magnetic derivatives) as sorbents. The different published methods for the speciation of Cr(III), Cr(VI) or both species are described and classified on the basis of the separation strategy employed: (i) the selective retention of only one of the two species by the sorbent, (ii) the retention of a Cr-chelate formed by using a ligand selective for only one of the Cr-species, or (iii) the sorption of both Cr(III) and Cr(VI) species. In addition, the distinct applied SPE modes (on-column, dispersive or magnetic) and their automation possibilities, the analytical techniques utilized for measurement of the Cr-species after separation, as well as the analytical figures of merit of the methods developed up to date are evaluated. Finally, the expected future trends of solid phase extraction for Cr speciation based on carbon nanomaterials such as graphene, carbon nanotubes and their derivatives as sorbents are commented.
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•Carbon nanomaterials (graphene and CNTs) as sorbents in solid phase extraction.•Solid phase extraction strategies for Cr speciation with graphene and CNT as sorbents.•Last trends for Cr speciation with functionalized graphene and CNTs.
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► The use of CNTs as sorbent for metal species in solid phase extraction has been described. ► Physical and chemical strategies for functionalization of carbon nanotubes have been ...discussed. ► Published analytical methods concerning solid phase extraction and atomic spectrometric determination have been reviewed.
New materials have significant impact on the development of new methods and instrumentation for chemical analysis. From the discovery of carbon nanotubes in 1991, single and multi-walled carbon nanotubes – due to their high adsorption and desorption capacities – have been employed as sorption substrates in solid-phase extraction for the preconcentration of metal species from diverse matrices. Looking for successive improvements in sensitivity and selectivity, in the past few years, carbon nanotubes have been utilized as sorbents for solid phase extraction in three different ways: like as-grown, oxidized and functionalized nanotubes. In the present paper, an overview of the recent trends in the use of carbon nanotubes for solid phase extraction of metal species in environmental, biological and food samples is presented. The determination procedures involved the adsorption of metals on the nanotube surface, their quantitative desorption and subsequent measurement by means of atomic spectrometric techniques such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry/mass spectrometry, among others. Synthesis, purification and types of carbon nanotubes, as well as the diverse chemical and physical strategies for their functionalization are described. Based on 140 references, the performance and general properties of the applications of solid phase extraction based on carbon nanotubes for metal species atomic spectrometric determination are discussed.
Recent studies have indicated that the HCN-to-CO and HCO(+)-to-HCN ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to ...study the molecular gas properties in active galaxies and search for differences between AGN and SB environments, we observed the HCN,, HCO(+), and HCO(+) emission with the IRAM 30 m in the center of 12 nearby active galaxies which either exhibit nuclear SB and/or AGN signatures. Consistent with previous results, we find a significant difference of the HCN-to-HCN, HCN-to-HCN, HCO(+)-to-HCO(+), and HCO(+)-to-HCN intensity ratios between the sources dominated by an AGN and those with an additional or pure central SB: the HCN, HCO(+), and HCO(+)-to-HCN intensity ratios tend to be higher in the galaxies of our sample with a central SB as opposed to the pure AGN cases, which show rather low intensity ratios. Based on an LVG analysis of these data, i.e., assuming purely collisional excitation, the (average) molecular gas densities in the SB-dominated sources of our sample seem to be systematically higher than in the AGN sources. The LVG analysis seems to further support systematically higher HCN and/or lower HCO(+) abundances as well as similar or higher gas temperatures in AGNs compared to the SB sources of our sample. In addition, we find that the HCN-to-CO ratios decrease with increasing rotational number J for the AGNs while they stay mostly constant for the SB sources.
The Expanded Susceptibility to Smoking Index (ESSI) is based on the combination of susceptibility to smoking and curiosity about smoking. The ESSI can identify young people who are at risk of ...starting to smoke cigarettes and related products. The objective of this study was to analyse the ESSI results and to examine factors associated with ESSI scores in students between 12 and 16 years of age. Sociodemographic, social/environmental and personal variables were analysed, and the ESSI value was determined for non-smoking students recruited from three schools in western Spain. Regression models were used to examine the factors associated with smoking for the entire sample and the factors associated with ESSI scores in the non-smoking population. Of the 377 participants who were analysed, 20.4% were smokers. Among the non-smokers, 53.5% and 55.3% presented medium-high ESSI scores for cigarettes and e-cigarettes, respectively, and 39.8% presented medium-high ESSI scores for hookah use. A higher ESSI score was associated with greater exposure to people smoking in the home, having more friends who smoke, alcohol consumption, and a higher impulsivity scale score. These findings reinforce the importance of reducing peer pressure and suggest the important role of resolve under conditions of positive affect on reducing impulsivity. Approaches based on self-efficacy could be addressed in preventive programmes developed in educational settings.
Photophysics tunability through alteration of framework aperture (metal–organic framework (MOF) = variable; guest = constant) was probed for the first time in comparison with previously explored ...concepts (MOF = constant; guest = variable). In particular, analysis of the confinement effect on a photophysical response of integrated 5-(3-chlorobenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one (Cl-BI) chromophore allowed us to establish a photophysics–aperture relationship. To shed light on the observed correlation, the framework confined environment was replicated using a molecular cage, Pd6(TPT)4 (TPT = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine), thus allowing for utilization of crystallography, spectroscopy, and theoretical simulations to reveal the effect a confined space has on the chromophore’s molecular conformation (including disruption of strong hydrogen bonding and novel conformer formation) and any associated changes on a photophysical response. Furthermore, the chosen Cl-oHBI@Pd6(TPT)4 (Cl-oHBI = 5-(5-chloro-2-hydroxybenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one, chromophore) system was applied as a tool for targeted cargo delivery of a chromophore to the confined space of DNA, which resulted in promotion of chromophore–DNA interactions through a well-established intercalation mechanism. Moreover, the developed principles were applied toward utilizing a HBI-based chromophore as a fluorescent probe on the example of macrophage cells. For the first time, suppression of non-radiative decay pathways of a chromophore was tested by anchoring the chromophore to a framework metal node, portending a potential avenue to develop an alternative to natural biomarkers. Overall, these studies are among the first attempts to demonstrate the unrevealed potential of a confined scaffold environment for tailoring a material’s photophysical response.
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•Analytical techniques for characterization of CNTs: classification, description and examples.•Determination methods for CNTs in biological and environmental samples.•Future trends ...and perspectives for characterization and determination of CNTs.
In the present paper, a critical overview of the most commonly used techniques for the characterization and the determination of carbon nanotubes (CNTs) is given on the basis of 170 references (2000–2014). The analytical techniques used for CNT characterization (including microscopic and diffraction, spectroscopic, thermal and separation techniques) are classified, described, and illustrated with applied examples. Furthermore, the performance of sampling procedures as well as the available methods for the determination of CNTs in real biological and environmental samples are reviewed and discussed according to their analytical characteristics. In addition, future trends and perspectives in this field of work are critically presented.
Neutral lipids-involved in many cellular processes-are stored as lipid droplets (LD), those mainly cytosolic (cLD) along with a small nuclear population (nLD). nLD could be involved in nuclear-lipid ...homeostasis serving as an endonuclear buffering system that would provide or incorporate lipids and proteins involved in signalling pathways as transcription factors and as enzymes of lipid metabolism and nuclear processes. Our aim was to determine if nLD constituted a dynamic domain. Oleic-acid (OA) added to rat hepatocytes or HepG2 cells in culture produced cellular-phenotypic LD modifications: increases in TAG, CE, C, and PL content and in cLD and nLD numbers and sizes. LD increments were reversed on exclusion of OA and were prevented by inhibition of acyl-CoA synthetase (with Triacsin C) and thus lipid biosynthesis. Under all conditions, nLD corresponded to a small population (2-10%) of total cellular LD. The anabolism triggered by OA, involving morphologic and size changes within the cLD and nLD populations, was reversed by a net balance of catabolism, upon eliminating OA. These catabolic processes included lipolysis and the mobilization of hydrolyzed FA from the LD to cytosolic-oxidation sites. These results would imply that nLD are actively involved in nuclear processes that include lipids. In conclusion, nLD are a dynamic nuclear domain since they are modified by OA through a reversible mechanism in combination with cLD; this process involves acyl-CoA-synthetase activity; ongoing TAG, CE, and PL biosynthesis. Thus, liver nLD and cLD are both dynamic cellular organelles.
Let enzymes work: H2 was produced from xylose and water in one reactor containing 13 enzymes (red). By using a novel polyphosphate xylulokinase (XK), xylose was converted into H2 and CO2 with ...approaching 100 % of the theoretical yield. The findings suggest that cell‐free biosystems could produce H2 from biomass xylose at low cost. Xu5P=xylulose 5‐phosphate, G6P=glucose 6‐phosphate.
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