The asymmetric mechanical response and corresponding statistical grain-scale slip/twinning activity for extruded Mg-(0~5 wt%)Y sheets during room-temperature uniaxial tension and compression along ...the extruded direction were investigated using slip trace analysis and EBSD-based misorientation analysis. The tension-compression asymmetry, in terms of yield strength, ultimate strength and uniform elongation, reduced with the addition of 0.5% Y to Mg. Increasing the Y concentration to 5% resulted in a reversed yield asymmetry (compressive yield strength > tensile yield strength). The non-basal slip activity increased (up to 31%) and the twinning activity decreased with increasing Y content, for both tension and compression. The Y-induced texture change did not significantly affect the pyramidal <c + a> slip, while it promoted basal slip and suppressed prismatic slip. The observed trends of the slip activity suggested that the critical resolved shear stress (CRSS) ratios of CRSSpyramidal <c+a>/CRSSbasal and CRSSpyramidal <c+a>/CRSSprismatic decreased with Y addition. The correlation between macroscopic asymmetric behavior and slip/twinning activity implied that the pronounced pyramidal <c + a> slip, together with the negligible twinning, were responsible for the reversed yield asymmetry. A higher activity of pyramidal <c + a> slip was observed when the slip plane underwent tension compared with that for compression.
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•RT T-C asymmetry of extruded Mg-(0-5)Y sheets was comprehensively and quantitatively investigated.•Statistical grain-scale slip/twinning activity was quantified and correlated to the macroscopic deformation behavior.•Non-basal slip increased, and twinning decreased with increasing Y alloying content.•Enhanced pyramidal slip was observed when the slip plane underwent tension.•The reversed asymmetry was rationalized by the pronounced pyramidal slip and negligible twinning.
Heavy metal ions in water resources present great threats to human health. Chromium (Cr), as the frequently used heavy metal in industrial processes and everyday life, requires a low-cost, fast and ...effective means to determine its concentration, especially in drinking water. Conventional colorimetric paper-based analytical devices (PADs), due to the limited sensitivity, are unable to quantify the most harmful heavy metal ions to the drinking water standard. In this work, we present a method of using a superhydrophobic (SH) paper to concentrate Cr6+ from solutions of very low concentration to obtain the precipitated Cr6+ salt particulates. A known volume of Cr6+-containing solution was concentrated to “a spot” on the SH paper through drying, so that trace amount of Cr6+ can be quantified via the application of a specifically-designed chemical-responsive adhesive tape (CAT) sensor, loaded with Cr6+- specific indicator, on to the concentrated Cr6+ spot. The detection limit of the SH-CAT method for Cr6+ is 0.05 mg/L, which is the permitted maximum concentration in drinking water and is significantly lower than that of conventional PADs. The interference and the accuracy studies also show the reliability of this method for measuring trace amounts of analytes.
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•Superhydrophobic (SH) paper concentrating trace amount of Cr6+ to “a spot”.•Chemical-responsive adhesive tape (CAT) sensor for dried Cr6+ salt quantification.•The CAT-SH method decreasing detection limit of Cr6+ to the drinking water standard.
In this work, the combination of dispersive micro solid-phase extraction (DµSPE) with laser-induced breakdown spectroscopy (LIBS) was evaluated for simultaneous preconcentration and detection of Zn, ...Cd, Mn, Ni, Cr and Pb in aqueous samples. Two adsorbent materials were tested in the microextraction step, namely graphene oxide and activated carbon. In both cases, the microextraction process consisted in the dispersion of a small quantity of adsorbent in the sample solution containing the analytes. However, while the use of activated carbon required a previous chelation of the metals, this step was avoided with the use of graphene oxide. After extraction, the analytes retained in the adsorbents were analysed by LIBS. Several experimental factors affecting the extraction of the metals (adsorbent amount, pH and extraction time) were optimized by means of the traditional univariate approach. Under optimum microextraction conditions, the analytical features of the proposed DµSPE-LIBS methods were assessed, leading to limits of detection below 100 µg kg−1 and 50 µg kg−1 with the use of activated carbon and graphene oxide, respectively, as adsorbents in the DµSPE process. Trueness evaluation of the most sensitive procedure was carried out by spike and recovery experiments in a real sample of tap water, leading to recovery values in the range 98–110%.
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•DµSPE-LIBS, using graphene oxide as sorbent, has been evaluated for the first time.•Several metals in liquid samples has been detected at µg Kg−1 level by LIBS.•Metal chelation step has been avoided with the use of graphene oxide.•Graphene oxide provides superior analytical capabilities than activated carbon.
•Application of graphene (G) and graphene oxide (GO) in analytical chemistry.•Adsorption capacity of G and GO towards organic compounds and metal ions.•Application of G and GO in SPE, magnetic-SPE ...and SPME.
In the past three years, we have seen intense interest grow in graphene (G) and graphene oxide (GO) as new sorbents in analytical chemistry. This article focuses on the adsorptive properties of G and GO and their application in preconcentrating organic compounds and trace-metal ions, including trace analysis of water, food, biological and environmental samples using chromatography and spectroscopy techniques. Some methods of modification or chemical functionalization of G and GO are also discussed. The article shows that G, GO and their derivatives or composites can be very attractive as sorbents due to their adsorption capacities being much higher than those of any of the currently reported sorbents.
Plant hormones are a variety of trace endogenous compounds, playing vital role in plant growth, development and quick response to biotic and abiotic stresses. Precise plant hormone analysis ...contributes to a better understanding of the regulating network of plant hormone signaling, however, due to the instability and ultra-trace amounts of plant hormones, it is important to select an appropriate pre-treatment method to enrich the intended analytes from the complex plant matrices. Herein, recent advanced sample preparation methods for endogenous plant hormone analysis in the past five years are reviewed and summarized according to different extraction modes. Besides, the emerging chemical labelling approaches that enable to improve the sensitivity are also introduced. In the end, the future trends of plant hormone analysis are taken into discussion. We believe the perspective may serve as guidance for the research of plant hormones in the analytical, environmental and botanical fields.
•Recent advanced sample preparation methods for endogenous plant hormone analysis are reviewed and summarized.•The emerging chemical labelling approaches that enable to improve the sensitivity are also introduced.•Future outlook of plant hormone analysis are taken into discussion.
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The ultra-sensitive, efficient, and recyclable trace analysis of UO22+ ions in water using a surface enhanced Raman scattering (SERS)-based microfluidic biosensor was reported. And ...this biosensor has a certain application prospect in the field of nuclear emergency scenario.
•A portable and ultrasensitive, recyclable SERS-microfluidic biosensor was firstly reported for trace UO22+ ions detection.•The novel designed UO22+-specific response DNAzyme bioprobe greatly improved the detection efficiency.•Highly ordered ZnO-Ag arrays as rigid SERS substrates in microfluidic device ensured ultrasensitivity and reproducibility.
Sensitive, fast and reliable detection of UO22+ ions is of great significance in nuclear industry and environment protection, due to the serious threats of UO22+ ions to human health. However, such suitable sensor is still rare. Herein, an ultrasensitive and recyclable SERS-microfluidic biosensor with specific UO22+ response has been developed. Aptamer-modified ZnO-Ag hybrids arrays was firstly designed and utilized as highly functional sensor by colloidal crystals templating method. The relationship between aptamers (different types, length and reaction time) and UO22+ ions was fully screened to improve the detection efficiency. In the absence of UO22+, Rhodamine B (RhB)-labeled double-stranded DNA formed a rigid structure, and weak Raman signals were detected. After pumping the UO22+ solution into microdevice, DNAzyme-cleavage reaction was triggered. And RhB-modified 5′-single DNA strand (cleavage production) dropped down to the surface of SERS substrates, leading to strong Raman signals. After signal amplification, the detection limit of UO22+ achieved as low as 7.2 × 10−13 M, which is nearly five orders below the EPA-defined maximum contaminant level. More importantly, the specially designed microfluidic device could be reused and refreshed by supplementation of substrate strands DNA for three times. A further application to determine UO22+ ions in natural real systems such as tap water and river water was also complied with good recoveries and RSDs. This SERS-based microfluidic sensor shows great potential for in-the-field sensing platforms, due to its ultra-sensitivity, high efficiency, and portability.
Current trends in sample preparation focus on the miniaturization of the process resulting in what is known as microextraction techniques. Among them stir bar sorptive dispersive microextraction ...(SBSDME) is one of the most recent techniques. It was presented a few years ago as a hybrid microextraction technique that combines the principles of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE). This novel technique introduces, into the sample solution, a bar-shaped magnet coated with a magnetic (nano)material, which is maintained on the surface by magnetism. Once stirring starts, the competitive action between magnetism and rotational force is exploited. At low rotational speed the (nano)material is retained on the magnet reminding SBSE, whereas at high sufficiently rotational speed the rotational force surpasses magnetism so that the magnetic (nano)material is dispersed into the sample solution as in DSPE. Upon halting rotation, the magnetic field prevails again and attracts the magnetic (nano)material containing the analytes back on the surface of the stirring bar. Finally, the extracted analytes are chemically or thermally desorbed before their measurement with the appropriate analytical instrument. When compared separately to SBSE and DSPE procedures, SBSDME affords, in a single approach, advantages such as lower extraction times than SBSE and easier extraction and post-extraction treatment than DSPE. The main purpose of this tutorial review is to describe the fundamentals and the experimental variables involved in this technique, as well as to compile and critically discuss the published papers concerning analytical methods based on the use of the SBSDME approach, analyzing its evolution and future prospects.
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•Fundamentals of stir bar sorptive dispersive microextraction (SBSDME) are described.•Advantages and benefits compared to other microextraction approaches are discussed.•Special emphasis on the experimental variables involved in the technique is done.•An overview of the published SBSDME-based methods is presented.•This tutorial may be used as guide for the development of SBSDME-based methods.
•A novel self-designed foam fractionation device was assembled and built.•High enrichment ratios of 138.2 and 85.5 were achieved for MPD and OPD, respectively.•The mechanisms of key processes during ...foam fractionation were thoroughly discussed.•The method provided new insights for the detection of trace organic compounds.
In this study, a foam fractionation technique was developed for the separation and enrichment of the trace m-phenylenediamine (MPD) and o-phenylenediamine (OPD) in solution. Firstly, a self-designed foam fractionation device was assembled and built, followed by a comprehensive characterization on gas types, foam fractionation column parameters, and porous sieve plate material used in the apparatus. Subsequently, the most crucial parameters for the separation and enrichment, such as surfactant species, solution pH, electrolyte categories, and gas flow rate, were identified and optimized. The mechanisms of key processes during foam fractionation under the influence of these parameters were thoroughly discussed. Other influencing factors, such as surfactant concentration, foam collection time, and solution volume in the fractionation column, were optimized using response surface methodology (RSM). Under these optimal conditions, maximal enrichment ratios of 138.2 and 85.5 were achieved for MPD and OPD, respectively. Finally, foam fractionation coupled with high-performance liquid chromatography (HPLC) was employed to detect MPD and OPD in the solution. The results demonstrated limits of detection (LOD) of 1.5 × 10−2 μg/L and 1.5 μg/L for MPD and OPD, with relative standard deviation (RSD) values of 4.1 % and 3.9 %. When testing various actual samples, the recoveries were in the range from 92.0 % or greater in all cases. The method exhibited advantages of high sensitivity, precision, and accuracy, attributed to the high enrichment efficiency of foam fractionation. In conclusion, the foam fractionation method established in this study offers simplicity in apparatus, operational convenience, environmental friendliness (minimized use of organic solvents), and high enrichment efficiency. It proves valuable for the quantitative analysis of trace amounts of MPD and OPD in solution, presenting a novel approach for the detection of trace organic compounds in solutions.
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