Advances in ionic liquids and deep eutectic solvents-based liquid phase microextraction of metals for sample preparation in Environmental Analytical Chemistry

Liquid phase micro-extraction (LPME) of metals has showed its potential for sample preparation in environmental analysis. In particular, the incorporation of ionic liquids to LPME (IL-LPME) has gotten increasing interest due to their unique properties as organic salts liquid at room temperature. In the last years, IL-LPME of metals has evolved to more efficient and selective extraction methods thanks to the development of task specific ionic liquids, and deep eutectic solvents. ILs have been implemented in the main LPME modalities: SDME, DLLME and HFLPME, resulting in new versions of these techniques. In this review we have analyzed and discussed the latest developments done in IL-LPME of metals, their advantages and limitations, as well as the potential fields of future development. © 2021 The Author(s). Published by Elsevier B.V.This work has been supported by Spanish Ministry of Economy and Competitiveness through the research project PGC2018- 101894-B-I00. BHS also thanks the Spanish Ministry of Education, Culture and Sports for the pre-doctoral grant FPU15/03924 and the University of Cadiz for the post-doctoral grant 2019-011/PU/ AY.PUENTE/CD

Solvent bar micro-extraction with graphite atomic absorption spectrometry for the determination of silver in ocean water

Main drawbacks for silver determination in seawater are the effects of samples matrix and that Ag appears in the sub ng L−1. Available methods for sample preparation in Ag analysis are based on solid and liquid extraction using tedious process that increase the cost of analysis and the risk of sample contamination, producing important waste amounts. Solvent bar micro-extraction (SBME) allows the pre-concentration of Ag in a micro-volume of the ionic liquid Aliquat 336® in kerosene solution. For this reason, it is considered as a green alternative to standard methods. The method has been optimized using synthetic seawater samples, offering the highest response for samples at pH=2, using 5% Aliquat 336® dissolved in kerosene containing 5% dodecan-1-ol as acceptor solution and after 1 h stirring at 800 rpm. The method exhibited linearity up to 50 ng L−1, with a limit of detection of 0.09 ng L−1, covering the concentration range of interest for environmental studies. Finally, it was applied for determination of Ag in real seawater samples, and the results were compared with the reference method of liquid-liquid extraction with 1-pyrrolidine-dithiocarbamate and diethylammonium-diethyldithiocarbamate, showing the applicability of ionic liquid based SBME using Aliquat 336® for the simple monitoring of silver ultra-traces in seawater analysis

Ionic liquid solvent bar micro-extraction of CdCln(n-2)- species for ultra-trace Cd determination in seawater

Water analysis of trace metals has been benefited by recent studies on sample preparation by liquid micro-extraction. However, there are still limitations for its application to seawater, such as the need of additives to preserve the sample or the availability of chemical extractants for the selective extraction from highly saline samples. In this work, a three phase solvent bar micro-extraction (3SBME) system containing the ionic liquid trioctylmethylammonium chloride (Aliquat® 336) has been used for isolation and pre-concentration of Cd from seawater samples, due to its ability for ionic exchange of CdCln(n−2)-. The system was optimized to work at the natural pH of seawater, and conditions for application to real samples were 0.18 M Aliquat® 336 dissolved in kerosene with 0.25 M dodecan-1-ol as organic solution, 1.5 M HNO3 as acceptor solution, 60 min extraction time, and 800 rpm stirring speed in the sample. Loss of organic solution into the sample during extraction was evaluated and revealed its dependence on stirring rate and extraction time. Under optimum conditions samples containing Cd 0.09–0.90 nM were pre-concentrated 65 times. GF-AAS was used for metal quantification with a limit of detection of 0.04 nM. Accuracy was successfully evaluated measuring Cd in a seawater certified reference material BCR-403

Three phase solvent bar micro-extraction as an approach to silver ultra-traces speciation in estuarine water samples

Silver ion inputs into the environment due to human activities have been increased in the last years because it has been used as a bactericide with application in medical, homecare and self-care products. In addition, it is toxic at low concentration for aquatic organisms. In estuarine waters, salinity and dissolved organic matter (DOM) regulate Ag+ concentration by the formation of complexes as AgCln(n-1)− and Ag-DOM. Difficulties of Ag+ analysis in estuaries are associated to its low concentration level and interferences of sample matrix. Liquid and solid phase extraction methods have been used for speciation of silver in waters; however, miniaturized methods that offer a better environmental profile are desirable. Hollow fiber liquid phase micro-extraction (HFLPME) allows obtaining higher pre-concentration factors with a reduction of waste generation. Notwithstanding, some operational improvements are needed to permit their use as a routine method that can be afforded using a configuration of three-phase solvent bar micro-extraction (3PSBME). In this work, tri-isobutylphosphine sulphide (TIBPS) has been used as an extractant for Ag+ pre-concentration in estuarine waters by 3PSBME. Under optimized conditions, Ag+ has been pre-concentrated 60 times and the method presents a limit of detection of 1.53 ng L−1. To evaluate which Ag species is transported by TIBPS, Cl− and DOM have been added to synthetic samples. As a result, a decrease in Ag pre-concentration efficiency after additions has been observed and quantified. Results showed that Ag+ is selectively transported by TIBPS from estuarine water samples after comparison of the results with those obtained by the reference method of liquid extraction with APDC/DDDC

Selective ionic liquid solvent bar micro-extraction for estimation of ultra-trace silver fractions in marine waters

Ag can be found in the ocean at the ultra-trace level, mainly as AgCln(n−1)− and complexed by dissolved organic matter (Ag-DOM). However, methods for studying Ag speciation in marine waters are limited by the lack of extractants capable to separate organic and inorganic silver species in natural conditions of seawater samples. In this work, a two-phase solvent bar micro-extraction method using the ionic liquid trihexyltetradecylphosphonium chloride (Cyphos® 101) was applied for selective micro-extraction of AgCln(n−1)− from organic silver in marine waters, working at seawater pH,. The application to real samples was performed under the following conditions: 2.5% Cyphos® 101 in kerosene solution with 10% dodecan-1-ol inside the fiber, and 30 min of sample extraction at a stirring rate of 800 rpm. The proposed SBME was successfully used for estimation of Ag fractions in waters from the Bay of Cádiz (South-west Spain) showing its applicability for a simple, fast and environmentally friendly speciation of silver in marine water samples. The method presented a linear response up to 500 ng L−1 and a detection limit of 0.4 ng L−1, using GF-AAS for instrumental determination

Multi-elemental ionic liquid-based solvent bar micro-extraction of priority and emerging trace metallic pollutants (Cd, Ag, Pd) in natural waters

Transition metals Cd, Pd and Ag are toxic even at very low concentration. Cd is considered a priority substance; while, Pd and Ag are emerging pollutants. Membrane technologies have been applied for their extraction; however, they require important amounts of reagents, time and energy. Additionally, effective reagents for metal extraction in saline natural waters are limited. In this case, hollow fiber liquid phase micro-extraction with a configuration of solvent bar (SBME) using the ionic liquid Cyphos® 101 as extractant is proposed. Optimized conditions for SBME of Cd, Ag and Pd were 50% Cyphos® 101 in the organic solution, extraction time 30 min and 800 rpm stirring rate. Leaching was in all cases lower than 0.1%. Metallic concentrations were measured by flame atomic absorption spectroscopy. The method was applied to the extraction of Ag, Cd and Pd in natural water samples. Except for waste water, Pd extraction was higher than 90% in all cases. Cd (≈100%) and Ag (93–95%) offered their best results for saline samples. Concluding, the proposed system is a low cost and green methodology that allows a simple and fast extraction of trace pollutants such as Ag, Cd and Pd in different natural waters, including highly saline samples

Ionic liquid based solvent micro-extraction of Ag and Cd from saline and hypersaline waters

Cadmium (Cd) and silver (Ag) are naturally occurring metals in saline natural waters, which may present toxic effects even at trace level. Membrane technology has been widely applied for their extraction, including hollow fiber supported liquid membranes. However, their application to saline waters is limited. In this work, a hollow fiber liquid micro-extraction system, with a configuration of 2 phase solvent bar micro-extraction (2SBME), using the ionic liquid N-methyl-N,N,N-trioctylammonium chloride (Aliquat® 336), dissolved in kerosene as extractant is proposed to overcome the limitations of existing HFLPME of Ag and Cd in saline waters. The use of an ionic liquid solution in the 2SBME leaded to higher stability of the organic solution in the fiber. The effect of chemical variables on the extraction was evaluated. Extraction of Cd and Ag with Aliquat® 336 was enhanced by Cl- in the sample, but it was independent of the concentration of organic matter. Extraction yield varied in the range 65-80% for Ag, and 45%-95% for Cd, depending on the salinity of samples. The highest extraction was obtained in seawater samples for 75% Aliquat® 336 dissolved in kerosene with 10% dodecan-1-ol, after 45 minutes, and 800 rpm stirring rate in the sample. Efficacy of the proposed system when applied to real samples was 88.10±4.14% for Cd, and 61.47±3.00% for Ag in seawater, and 92.73±5.37% for Cd and 64.23±2.85% for Ag in a hyper-saline lagoon (70 g L-1 NaCl). In conclusion, the proposed methodology allowed a miniaturization of Ag and Cd extraction in short times, requiring lower amount of reagents and solvents, less energy as well as reducing operational cost and wastes if compared with existing liquid membrane based methods

A liquid micro-extraction based one-step method for the chemical fractionation of copper in seawater

In this work, the reagent Cyanex® 272 has been incorporated in a three-phase solvent bar micro-extraction system to selectively separate the inorganic and organic fractions of copper in seawater. Optimized conditions for micro-extraction of Cu fractions were 0.2 M Cyanex® 272 in the organic solution contained into the fiber pores, 0.5 M HCl as acceptor solution within the fiber, stirring rate of 500 rpm, and 60 min time of extraction, providing an enrichment factor of 51.6 ± 2.3. Experimental results for selective extraction of organic and inorganic Cu showed a good correlation with theoretical data for Cu speciation, and the relationship between enrichment factor and dissolved organic carbon (DOC) concentration in the samples was used to predict total Cu concentration. Instrumental determination of Cu presented a linear response within the range 0.1–20 µg L−1, obtaining a limit of detection of 0.03 µg L−1. Finally, the method was successfully applied to the study of Cu fractions in real seawater samples collected from the Bay of Cádiz (Spain). © 2022 The AuthorsThe authors want to acknowledge the Spanish Ministry of Science and Innovation for the financial support of the project PGC2018-101894-B-I00 the FPU grant FPU15/03924 , and the ERASMUS + program for the grant received by Ibstissem Belbachir, which allowed her research stay at the University of Cádiz

A Critical Study of the Effect of Polymeric Fibers on the Performance of Supported Liquid Membranes in Sample Microextraction for Metals Analysis

Popularity of hollow fiber-supported liquid membranes (HF-SLM) for liquid-phase microextraction (HF-LPME) has increased in the last decades. In particular, HF-SLM are applied for sample treatment in the determination and speciation of metals. Up to the date, optimization of preconcentration systems has been focused on chemical conditions. However, criteria about fiber selection are not reflected in published works. HFs differ in pore size, porosity, wall thickness, etc., which can affect efficiency and/or selectivity of chemical systems in extraction of metals. In this work, Ag+ transport using tri-isobutylphosphine sulfide (TIBPS) has been used as a model to evaluate differences in metal transport due to the properties of three different fibers. Accurel PP 50/280 fibers, with a higher effective surface and smaller wall thickness, showed the highest efficiency for metal transport. Accurel PP Q3/2 exhibited intermediate efficiency but easier handling and, finally, Accurel PP S6/2 fibers, with a higher wall thickness, offered poorer efficiency but the highest stability and capability for metal speciation. Summarizing, selection of the polymeric support of HF-SLM is a key factor in their applicability of LPME for metals in natural waters

Deficiency of Parkinson’s Related Protein DJ-1 Alters Cdk5 Signalling and Induces Neuronal Death by Aberrant Cell Cycle Re-entry

DJ-1 is a multifunctional protein involved in Parkinson disease (PD) that can act as antioxidant, molecular chaperone, protease, glyoxalase, and transcriptional regulator. However, the exact mechanism by which DJ-1 dysfunction contributes to development of Parkinson’s disease remains elusive. Here, using a comparative proteomic analysis between wild-type cortical neurons and neurons lacking DJ-1 (data available via ProteomeXchange, identifier PXD029351), we show that this protein is involved in cell cycle checkpoints disruption. We detect increased amount of p-tau and α-synuclein proteins, altered phosphoinositide-3-kinase/protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) signalling pathways, and deregulation of cyclin-dependent kinase 5 (Cdk5). Cdk5 is normally involved in dendritic growth, axon formation, and the establishment of synapses, but can also contribute to cell cycle progression in pathological conditions. In addition, we observed a decrease in proteasomal activity, probably due to tau phosphorylation that can also lead to activation of mitogenic signalling pathways. Taken together, our findings indicate, for the first time, that aborted cell cycle re-entry could be at the onset of DJ-1-associated PD. Therefore, new approaches targeting cell cycle re-entry can be envisaged to improve current therapeutic strategies