•MEPS is a green sample preparation technique that has been widely used by several research groups.•This review provides an overview of recent applications of MEPS in different research areas.•Sorbent type, matrix and device in MEPS are presented.•Future directions, progress and potential developments of the MEPS technique are discussed. Microextraction by packed sorbent (MEPS) is a new miniaturized form of solid-phase extraction and it is a green sample pretreatment technology. MEPS has been widely accepted and used by several research groups online or offline as a sample preparation technique before instrument analysis. MEPS reduces the sample handling time and organic solvent consumption. MEPS is suitable for small sample volumes and can easily be connected with different chromatographic techniques without modification. The sorbent bed in MEPS is integrated into a liquid handling syringe that allows for low void volume sample manipulations either manually or in combination with laboratory robotics. MEPS is a simple, fast and robust sample preparation technique with several advantages, miniaturization, automation, fast operation course, on-line coupling with analytical instruments and low-cost operation with less solvent and low sample consumption. Sorbent type, device, and matrix are important factors in MEPS research and applications. The performance of MEPS has recently been illustrated by online with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry assays for pharmaceutical, environmental, and food analyses. This paper deals with MEPS device-optimized sorbent, sample matrix, and application. The progress and potential development of the technique are also discussed.
A very interesting possibility of coal combustion ashes reutilization is their use as adsorbent materials, that can also take advantage from proper beneficiation techniques. In this work, adsorption of cadmium from aqueous solutions was taken into consideration, with the emphasis on the intertwining among waste properties, beneficiation treatments, properties of the beneficiated materials and adsorption capacity. The characterization of three solid materials used as cadmium sorbents (as-received ash, ash sieved through a 25 μm-size sieve and demineralized ash) was carried out by chemical analysis, infrared spectroscopy, laser granulometry and mercury porosimetry. Cadmium adsorption thermodynamic and kinetic tests were conducted at room temperature, and test solutions were analyzed by atomic absorption spectrophotometry. Maximum specific adsorption capacities resulted in the range 0.5–4.3 mg g −1. Different existing models were critically considered to find out an interpretation of the controlling mechanism for adsorption kinetics. In particular, it was observed that for lower surface coverage the adsorption rate is governed by a linear driving force while, once surface coverage becomes significant, mechanisms such as the intraparticle micropore diffusion may come into play. Moreover, it was shown that both external fluid-to-particle mass transfer and macropore diffusion hardly affect the adsorption process, which was instead regulated by intraparticle micropore diffusion: characteristic times for this process ranged from 4.1 to 6.1 d, and were fully consistent with the experimentally observed equilibrium times. Results were discussed in terms of the relationship among properties of beneficiated materials and cadmium adsorption capacity. Results shed light on interesting correlations among solid properties, cadmium capture rate and maximum cadmium uptake.
Display omitted] ► Microextraction by packed sorbents (MEPS) is a new online sample preparation technique. ► MEPS is more greener than SPE and LLE and can be used for small sample volumes (10 μL). ► Extraction of drugs from whole blood samples is possible. ► This emerging technique has been used in a number of recent research works in pre-clinical, clinical and environmental analysis. This tutorial provides an overview on a new technique for sample preparation, microextraction by packed sorbent (MEPS). Not only the automation process by MEPS is the advantage but also the much smaller volumes of the samples, solvents and dead volumes in the system. Other significant advantages such as the speed and the simplicity of the sample preparation process are provided. In this tutorial the main concepts of MEPS will be elucidated. Different practical aspects in MEPS are addressed. The factors affecting MEPS performance will be discussed. The application of MEPS in clinical and pre-clinical studies for quantification of drugs and metabolites in blood, plasma and urine will be provided. A comparison between MEPS and other extraction techniques such as SPE, LLE, SPME and SBSE will be discussed.
•Microextraction by packed sorbent (MEPS) is a green method of sample preparation.•We describe the structure and format of microextraction by packed sorbent (MEPS).•Recent applications of microextraction by packed sorbent (MEPS), such as MEPS-MS/MS.•The advantages and the disadvantages of microextraction by packed sorbent (MEPS). Sample preparation is an important stage in separation and determination of components of interest from complex matrices. Sample preparation strongly influences the reliability and the accuracy of the analysis and the data quality. Recent trends in sample preparation include miniaturization, automation, high-throughput performance, on-line coupling with analytical instruments and low-cost operation using little or no solvent consumption. In the past decade, microextraction by packed sorbent (MEPS) was introduced as a simple, fast, on-line sample-preparation technique. Also, MEPS requires less sample and less solvent. This review gives an outline of the MEPS technique, including fields of application, common formats and sorbents, factors that affect performance, and the major advantages and limitations. Further, we offer and discuss our perspective on the future of MEPS.
A bifunctional catalyst for the sorbent-enhanced steam methane reforming (SE-SMR) reaction was derived from a hydrotalcite-based precursor synthesized via a coprecipitation technique. The material contained both the Ni reforming catalyst and the Ca-based CO2 sorbent and was characterized using X-ray diffraction, H2 chemisorption, N2 physisorption, transmission electron microscopy, and temperature-programmed reduction. Reduction of the calcined hydrotalcite converted the (Al:Ca:Mg:Ni)O x mixed oxide into nickel and CaO particles supported on an (Al:Mg)O x matrix with a surface area of 54 m2·g–1. The high CO2 absorption capacity and its stability with carbonation cycles was attributed to the high dispersion of CaO on the porous and thermally stable (Al:Mg)O x network, whereas for naturally occurring limestone, a rapid decay in the CO2 absorption capacity was observed. Under SE-SMR conditions, the recorded mole fraction of hydrogen in the effluent stream was 99 vol % (dry and without inert component); that is, thermodynamic equilibrium calculated to be 99 vol % (without inert component) was reached. The CO2 uptake of the bifunctional material averaged 0.074 g CO2/g sorbent over 10 cycles. After approximately seven cycles, the CO2 capture capacity stabilized, resulting in an average decay rate of only 0.3% per cycle over the last three cycles. The bifunctional material developed here produced a larger amount of high-purity H2 than limestone mixed with Ni–SiO2 or a Ca-free, nickel hydrotalcite-derived catalyst, making the new material an interesting candidate for the SE-SMR process.
This paper presents a review of the research on CO2 capture by lime-based looping cycles undertaken at CanmetENERGY's (Ottawa, Canada) research laboratories. This is a new and very promising technology that may help in mitigation of global warming and climate change caused primarily by the use of fossil fuels. The intensity of the anticipated changes urgently requires solutions such as more cost-effective technologies for CO2 capture. This new technology is based on the use of lime-based sorbents in a dual fluidized bed combustion (FBC) reactor which contains a carbonator-a unit for CO2 capture, and a calciner-a unit for CaO regeneration. However, even though natural materials are cheap and abundant and very good candidates as solid CO2 carriers, their performance in a practical system still shows significant limitations. These limitations include rapid loss of activity during the capture cycles, which is a result of sintering, attrition, and consequent elutriation from FBC reactors. Therefore, research on sorbent performance is critical and this paper reviews some of the promising ways to overcome these shortcomings. It is shown that reactivation by steam/water, thermal pre-treatment, and doping simultaneously with sorbent reforming and pelletization are promising potential solutions to reduce the loss of activity of these sorbents over multiple cycles of use.
This study firstly aimed to investigate the potential of simultaneous metal (loid) removal from metal (oid) solution through adsorption on iron-peat, where the sorbent was made from peat and Fe by-products. Up-flow columns filled with the prepared sorbent were used to treat water contaminated with As, Cu, Cr, and Zn. Peat effectively adsorbed Cr, Cu, and Zn, whereas approximately 50% of inlet As was detected in the eluent. Iron-sand was effective only for adsorbing As, but Cr, Cu, and Zn were poorly adsorbed. Only iron-peat showed the simultaneous removal of all tested metal (loid)s. Metal (loid) leaching from the spent sorbent at reducing conditions as means to assess the behaviour of the spent sorbent if landfilled was also evaluated. For this purpose, a standardised batch leaching test and leaching experiment at reducing conditions were conducted using the spent sorbent. It was found that oxidising conditions, which prevailed during the standardised batch leaching test, could have led to an underestimation of redox-sensitive As leaching. Substantially higher amounts of As were leached out from the spent sorbents at reducing atmosphere compared with oxidising one. Furthermore, reducing environment caused As(V) to be reduced into the more-toxic As (III).
The accumulation of harmful and persistent organic molecules in soils and sediment is a major environmental concern. Removal by physical means such as riverine, lacustrine, or marine dredging can be prohibitively difficult, expensive, and may not ultimately prove effective. An alternative is to locally change the geochemistry to stabilize and sequester the contaminants and render them biologically unavailable. Ghosh et al. report on pilot projects to determine whether activated carbon would be so useful. Their Feature concludes with what more needs to be done to minimize anthropogenic chemical blights in soil and sediments.