Trace determination of organophosphorus pesticides in environmental samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction

Dual-Functional Monomer MIPs and Their Comparison to Mono-Functional Monomer MIPs for SPE and as Sensors

A molecularly imprinted polymer (MIP) is a synthetic polymer that has characteristics such as natural receptors which are able to interact and bind to a specific molecule that is used as a template in the MIP polymerization process. MIPs have been widely developed because of the need for more selective, effective, and efficient methods for sample preparation, identification, isolation, and separation. The MIP compositions consist of a template, monomer, crosslinker, initiator, and porogenic solvent. Generally, MIPs are only synthesized using one type of monomer (mono-functional monomer); however, along with the development of MIPs, MIPs began to be synthesized using two types of monomers to improve the performance of MIPs. MIPs used for identification, separation, and molecular analysis have the most applications in solid-phase extraction (SPE) and as biochemical sensors. Until now, no review article has discussed the various studies carried out in recent years in relation to the synthesis of dual-functional monomer MIPs. This review is necessary, as an improvement in the performance of MIPs still needs to be explored, and a dual-functional monomer strategy is one way of overcoming the current performance limitations. In this review article, we discuss the techniques commonly used in the synthesis of dual-functional monomer MIPs, and the use of dual-functional monomer MIPs as sorbents in the MI-SPE method and as detection elements in biochemical sensors. The application of dual-functional monomer MIPs showed better selectivity and adsorption capacity in these areas when compared to mono-functional monomer MIPs. However, the combination of functional monomers must be selected properly, in order to achieve an effective synergistic effect and produce the ideal MIP characteristics. Therefore, studies regarding the synergistic effect of the MIP combination still need to be carried out to obtain MIPs with superior characteristics.

Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples

Developing effective and green methods for food analysis and separation has become an urgent issue regarding the ever-increasing concern of food quality and safety. Ionic liquids (ILs) are a new chemical medium and soft functional material developed under the framework of green chemistry and possess many unique properties, such as low melting points, low-to-negligible vapor pressures, excellent solubility, structural designability and high thermal stability. Combining ILs with extraction techniques not only takes advantage of ILs but also overcomes the disadvantages of traditional extraction methods. This subject has attracted intensive research efforts recently. Here, we present a brief review of the current research status and latest developments regarding the application of IL-assisted microextraction, including dispersive liquid–liquid microextraction (DLLME) and solid-phase microextraction (SPME), in food analysis and separation. The practical applications of ILs in determining toxic and harmful substances in food specimens with quite different natures are summarized and discussed. The critical function of ILs and the advantages of IL-based microextraction techniques over conventional extraction techniques are discussed in detail. Additionally, the recovery of ILs using different approaches is also presented to comply with green analytical chemistry requirements.

Surface-Active Ionic Liquid-Assisted Cloud Point Extraction for Pre-Concentration and Determination of Cobalt Ions in Pharmaceutical Preparations

: Herein we describe an efficient, simple, and precise micelle-mediated microextraction strategy based on the aggregation behavior of surface-active ionic liquids (SAILs) for the preconcentration and determination of cobalt ions in pharmaceutical preparations. Unlike the commonly used hydrophobic ionic liquids in IL-based microextraction methods, a water-soluble surface-active ionic liquid [1-hexadecyl 3-methylimidazolium chloride (C16MeImCl)] was used. A modified cloud point extraction (CPE) procedure based on the C16MeImCl-Triton X-114 mixed micellar system was proposed as an efficient extracting phase. A comparison of the analytical features of the extraction process with and without SAILs revealed the benefits of the proposed method. Advantages such as a wider linear range, lower detection limit, higher reproducibility, and improved extraction efficiency highlighted the proposed method over the conventional CPE method. These attractive specifications are due to the higher extraction efficiencies achieved in the presence of the SAIL and its favorable effects at the phase separation stage. Various parameters affecting the extraction efficiency were optimized by univariate and multivariate (Box-Behnken design) approaches. The calibration curve was obtained in the optimal experimental conditions with a linear range from 0.01 to 5.5 mg L-1 of cobalt ion concentration (R = 0.9992) and a detection limit of about 0.005 mg L-1. The RSD% for 10 replicate determinations of 1.0 mg L-1 Co was 0.9%. The proposed method was successfully applied to determine cobalt ions in vitamin B12 ampoules and tablets.

A Gadolinium-Based Magnetic Ionic Liquid for Supramolecular Dispersive Liquid-Liquid Microextraction Followed by HPLC/UV for Determination of Favipiravir in Human Plasma

Favipiravir is a potential antiviral medication that has been recently licensed for COVID-19 treatment. In this work, a gadolinium based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid-liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50mg of the Gd-MIL and 150μL of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to FDA bioanalytical method validation guidelines. The coefficient of determination was found to be 0.9999, for a linear concentration range of 25 to 1.0 × 10⁵ ng/mL. The percent recovery (accuracy) varied from 99.83 to 104.2 %, with % RSD values (precision) ranging from 4.07 to 11.84 %. Total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was found simple, selective and sensitive for determination of favipiravir in real human plasma.

Ionic liquid and magnetic multiwalled carbon nanotubes for extraction of N-methylcarbamate pesticides from water samples prior their determination by capillary electrophoresis

A simple and rapid microextraction procedure is reported on the use of ionic liquid (IL) in combination with magnetic multiwalled carbon nanotubes (MMWCNTs). The procedure is based on temperature-controlled IL dispersive liquid phase microextraction (DLPME) and MMWCNTs, for selective preconcentration of N-methylcarbamate pesticides in water samples, followed by their hydrolysis in alkaline buffer, prior to being analyzed by capillary electrophoresis. The extraction procedure uses small volume of organic solvents, and there is no need for centrifugation. In the experimental approach the IL was quickly disrupted by an ultrasonic probe, heated with the temperature controlled at 90 °C and dispersed in water samples in a homogenous form. At this stage, N-methylcarbamate pesticides migrate into the IL. Then the solution was cooled and small amounts of MMWCNTs were dispersed into the sample solutions to adsorb the ionic liquid containing the analytes and phase separation was completed. The ionic liquid allowed the microextraction of the analytes and a small volume of dichloromethane (DCM) was used for elution. MMWCNTs favored the adsorption of the ionic liquid with the analytes and improved the final recovery with respect to the use of simple magnetic nanoparticles as a sorbent material. Under the optimum conditions, limit of quantifications (LOQ) were achieved in the 5.6-9.3 ng mL^-1 range, with recoveries between 85.0% and 102.4%.

Determination of arsenic species using functionalized ionic liquid by in situ dispersive liquid-liquid microextraction followed by atomic absorption spectrometry

Synthesis and application of a task-specific ionic liquids (TSILs) as extracting solvents or chelating agents in dispersive liquid-liquid micro-extraction (DLLME) was evaluated. The developed method was based on the use of an ammonium pyrrolidine dithiocarbamate (APDC) bonded ionic liquid for chelation with As(III), followed by conversion of the As(III) chelated TSIL to a hydrophobic ionic liquid using KPF₆ as an anion-exchange reagent. As(V) was reduced to As(III), using a 2/1 w/w blend of KI and Na₂S₂O₃ and then the total amount of As was measured through ETAAS analysis. Under optimal conditions, linear dynamic ranges of 0.2-15 ng mL^-1 and 0.2-20 ng mL^-1 were observed in the determination of As(III) and total As respectively. The relative standard deviations (RSD%, n = 5) for the determination of As(III) (10 ng mL^-1) was 3.2% and the limits of detection and quantitation were determined to be 0.01 ng mL^-1 and 0.0.034 ng mL^-1; respectively.

A gadolinium-based magnetic ionic liquid for dispersive liquid-liquid microextraction

A hydrophobic gadolinium-based magnetic ionic liquid (MIL) was investigated for the first time as an extraction solvent in dispersive liquid–liquid microextraction (DLLME). The tested MIL was composed of trihexyl(tetradecyl)phosphonium cations and paramagnetic gadolinium chloride anions. The prepared MIL showed low water miscibility, reasonable viscosity, markedly high magnetic susceptibility, adequate chemical stability, low UV background, and compatibility with reversed-phase HPLC solvents. These features resulted in a more efficient extraction than the corresponding iron or manganese analogues. Accordingly, the overall method sensitivity and reproducibility were improved, and the analysis time was reduced. The applicability of the proposed MIL was examined through the microextraction of four sartan antihypertensive drugs from aqueous samples followed by reversed-phase HPLC with UV detection at 240 nm. The DLLME procedures were optimized for disperser solvent type, MIL mass, disperser solvent volume, as well as acid, base, and salt addition. The limits of quantitation (LOQs) obtained with the analysis of 1.2-mL samples after DLLME and HPLC were 80, 30, 40, and 160 ng/mL for azilsartan medoxomil, irbesartan, telmisartan, and valsartan, respectively. Correlation coefficients were greater than 0.9988 and RSD values were in the range of 2.48–4.07%. Under the optimized microextraction conditions and using a 5-mL sample volume, enrichment factors were raised from about 40 for all sartans using a 1.2-mL sample to 175, 176, 169, and 103 for azilsartan medoxomil, irbesartan, valsartan, and telmisartan, respectively. The relative extraction recoveries for the studied sartans in river water varied from 82.5 to 101.48% at a spiked concentration of 0.5 μg/mL for telmisartan and irbesartan and 1 μg/mL for azilsartan medoxomil and valsartan.

Recent Application of Deep Eutectic Solvents as Green Solvent in Dispersive Liquid-Liquid Microextraction of Trace Level Chemical Contaminants in Food and Water

As growing concerns on green, cost-effective, and time-saving chemistry analysis methods, deep eutectic solvents (DESs) are considered to be promising green alternatives to conventional solvents in dispersive liquid-liquid microextraction (DLLME) of trace level chemical contaminants in food and water, due to their biodegradability, low cost, and simple preparation. In the past few years, numerous innovative researches have focused on preconcentration of trace level chemical contaminants using DESs as extractant. In this context, this review aims to summarize the updated state-of-the-art effort dedicated to preconcentration of trace level chemical contaminants in food and water sample using DESs as extractants in DLLME. Furthermore, the major impact factors affecting the preconcentration efficiency and process mechanisms are thoroughly analyzed and discussed. Finally, prospects and challenges in application of DESs as solvents in DLLME to enrich trace level chemical contaminants are extensively elucidated and critically reviewed.

Green Approaches to Sample Preparation Based on Extraction Techniques

Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require that the consumption of hazardous organic solvents and energy be minimized or even eliminated in the analytical process. While no sample preparation is clearly the most environmentally friendly approach, complete elimination of this step is not always practical. In such cases, the extraction techniques which use low amounts of solvents or no solvents are considered ideal alternatives. This paper presents an overview of green extraction procedures and sample preparation methodologies, briefly introduces their theoretical principles, and describes the recent developments in food, pharmaceutical, environmental and bioanalytical chemistry applications.

Fabrication of Pt-Pd@ITO grown heterogeneous nanocatalyst as efficient remediator for toxic methyl parathion in aqueous media

In this study, nano-sized ITO supported Pt-Pd bimetallic catalyst was synthesized for the degradation of methyl parathion pesticide, a common extremely toxic contaminant in aqueous solution. On the characterization with different techniques, a beautiful scenario of honeycomb architecture composed of ultra-small nanoneedles or fine hairs was found. Average size of nanocatalyst also confirmed which was in the range of 3-5 nm. High percent degradation (94%) was obtained in 30 s using 1.5 × 10^- 1 mg of synthesized nanocatalyst, 0.5 mM NaBH₄, and 110 W microwave radiations power. Recyclability of nanocatalyst was efficient till 4th cycle observed during study of reusability. The supported Pt-Pd bimetallic nanocatalyst on ITO displayed many advantages over conventional methods for degradation of methyl parathion pesticide, such as high percent degradation, short reaction time, small amount of nanocatalyst, and multitime reusability. Graphical abstract Schematic illustration of reaction for degradation of methyl parathion.

In Situ Formation of Ionic Liquid by Metathesis Reaction for the Rapid Removal of Bisphenol A from Aqueous Solutions

In this work we present a rapid and easy method to remove the totality of bisphenol A from aqueous solutions using ionic liquid (IL). Dispersive liquid–liquid microextraction is employed. The IL 1-octyl-3-methylimidazolium bis((trifluoromethane)sulfonyl)imide ([C8C1im] [NTf2]) is formed in situ because of the mixture of 1-octyl-3-methylimidazolium chloride ([C8C1im]Cl) and lithium bis(trifluoromethanesulfonyl)imide (Li[NTf2]) aqueous solutions. A cloud of microdroplets of IL formed by the dispersion generated through the precursors metathesis reaction allows the rapid and total extraction of bisphenol A (BPA). After centrifugation, the formed IL phase is deposited at the bottom of the flask and the total amount of BPA is extracted in the sedimented phase. The volume of IL is very low, in the order of microliters, which enables us to remove all the BPA from the solution. The technique studied is highly efficient, cost-effective, and presents less environmental impact than other extraction techniques, thus becoming an outstanding alternative to the most commonly used methods. BPA concentration is determined by high performance liquid chromatography by injecting the IL phase directly. An extraction kinetic model for the kinetic profile has been tested for this method, which allows to infer the ideal experimental conditions to execute the extraction method.

State-of-the-art on the technique of dispersive liquid-liquid microextraction

Dispersive liquid-liquid microextraction is a new sample pretreatment technology based on traditional liquid liquid extraction. In this paper, the application of low-toxicity extractants such as low-density extractants, auxiliary extractants, stripping agents and ionic liquids in this technology and the extraction modes such as solvent de-emulsification, suspension extractant curing, auxiliary extraction, back extraction, and ionic liquid-dispersion liquid microextraction, are summarized. In addition, the synergism of this technique with other sample preparation techniques, such as liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, dispersive solid phase extraction, matrix solid-phase dispersion extraction, supercritical fluid extraction and ultrasound-assisted dispersive liquid-liquid microextraction is discussed.

Rational design of an ionic liquid dispersive liquid–liquid micro-extraction method for the detection of organophosphorus pesticides

In this study, a functionalized ionic liquid (IL), [MimCH₂COOCH₃][NTf₂] was rationally designed and explored as an extraction solvent in dispersive liquid–liquid microextraction (DLLME) combined with ultra-high performance liquid chromatography (UHPLC) for the sensitive determination of organophosphorus pesticides (OPs).

An Ionic Liquid-based Microextraction Method for Ultra-High Preconcentration of Paraquat Traces in Water Samples Prior to HPLC Determination

An ionic liquid (IL)-based microextraction method was developed for the preconcentration of paraquat traces in water samples prior to HPLC determination. On the basis of the relationship between the aqueous solubility and the extractability of known ILs, 1-ethyl-3-methylimidazolium bis(nonafluorobutanesulfonyl)amide ([EMIm][NNf₂]) was selected as the extractant for paraquat. The distribution ratio of paraquat dication in the [EMIm][NNf₂]/water biphasic system was theoretically estimated to be nearly 10⁸ at its maximum level, indicating that [EMIm][NNf₂] was suitable for the ultra-high preconcentration (a maximum of 10⁶-fold concentration) of paraquat with a quantitative recovery (more than 99%). The extraction procedure could be performed easily and quickly following the in situ solvent formation microextraction technique, and the paraquat traces in the IL phase could be determined by hydrophilic interaction chromatography with good detection limits and linearity ranges (0.16 and 1 - 50 ng mL^-1 for paraquat, respectively). The combined method was successfully applied to four real environmental water samples spiked with paraquat and its analog, diquat at 5.0 ng mL^-1.

Effects of soil acidification on the toxicity of organophosphorus pesticide on Eisenia fetida and its mechanism

Organophosphorus pesticides (OPs) have been widely used to control agricultural insects. Soil acidification is a major problem in soil of intensive agricultural systems, especially in red soil with a low pH buffer capacity. However, the effects of soil acidification on the toxicity of pesticides are still unclear. In the present study, the toxicity of three OPs on E. fetida was determined at individual (14-day lethal test) and biochemical levels (antioxidative defence enzymes) by using acidified soils (pH = 5.5, 4.3 and 3.1). The results showed that the toxicity of tested OPs was slightly increased with the decrease of soil pH. To interpret the phenomena, an optimum Quantitative Structure Activity Relationship (QSAR) model was developed based on the toxicity mechanism and the partial least squares regression (PLS) method. The model indicated bioavailability and toxicodynamics are key factors of soil acidification affecting the toxicity of the OPs. Further results revealed the bioavailability of the OPs was strongly related to their hydrolysis and biodegradation character, whereas the effects of soil acidification on toxicodynamics were mainly caused by the interaction between the acetylcholinesterase (AchE) and the OPs. Results will increase understanding of the effects of soil acidification on the toxicity of pesticides and its mechanism.

Recent Advances in Applications of Ionic Liquids in Miniaturized Microextraction Techniques

Green sample preparation is one of the most challenging aspects in green analytical chemistry. In this framework, miniaturized microextraction techniques have been developed and are widely performed due to their numerous positive features such as simplicity, limited need for organic solvents, instrumentation of low cost and short time of extraction. Also, ionic liquids (ILs) have unequivocally a “green” character, which they owe to their unique properties including the re-usage, the high reaction efficiency and selectivity in room temperature, the ability to dissolve both organic and inorganic compounds, and thermal stability. In the present review, the recent advances in the application of ionic liquids in miniaturized liquid and solid phase extraction techniques as extractants, intermediate solvents, mediators and desorption solvents are discussed, quoting the advantages and drawbacks of each individual technique. Some of the most important sample preparation techniques covered include solid-phase microextraction (SPME), dispersive liquid-liquid microextraction (DLLME), single-drop microextraction (SDME), stir bar sorptive extraction (SBSE), and stir cake sorptive extraction (SCSE).

Detection of Organophosphorus Pesticides in Wheat by Ionic Liquid-Based Dispersive Liquid-Liquid Microextraction Combined with HPLC

Food safety issues closely related to human health have always received widespread attention from the world society. As a basic food source, wheat is the fundamental support of human survival; therefore, the detection of pesticide residues in wheat is very necessary. In this work, the ultrasonic-assisted ionic liquid-dispersive liquid-liquid microextraction (DLLME) method was firstly proposed, and the extraction and analysis of three organophosphorus pesticides were carried out by combining high-performance liquid chromatography (HPLC). The extraction efficiencies of three ionic liquids with bis(trifluoromethylsulfonyl)imide (Tf₂N) anion were compared by extracting organophosphorus in wheat samples. It was found that the use of 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM][Tf₂N]) had both high enrichment efficiency and appropriate extraction recovery. Finally, the method was used for the determination of three wheat samples, and the recoveries of them were 74.8-112.5%, 71.8-104.5%, and 83.8-115.5%, respectively. The results show that the method proposed is simple, fast, and efficient, which can be applied to the extraction of organic matters in wheat samples.

Development of supramolecular solvent based microextraction prior to high performance liquid chromatography for simultaneous determination of phenols in environmental water

SUPRAS based microextraction for phenols.

Faster dispersive liquid-liquid microextraction methods using magnetic ionic liquids as solvents

Three hydrophobic magnetic ionic liquids (MILs) containing the tetrachloromanganate(II) (MnCl4(2-)) anion, namely, aliquat tetrachloromanganate(II) ([Aliquat(+)]2[MnCl4(2-)]), methyltrioctylammonium [MnCl4(2-)] ([N1,8,8,8(+)]2[MnCl4(2-)]), and trihexyltetradecylphosphonium [MnCl4(2-)] ([P6,6,6,14(+)]2[MnCl4(2-)]) were employed as extraction solvents in DLLME coupled to high-performance liquid chromatography (HPLC) employing UV detection. The MILs were developed with the features of magnetic susceptibility to permit rapid retrieval of the extraction solvent, hydrophobicity to allow for phase separation from water, and mobile phase compatibility with reversed phase HPLC. Additionally, the MILs were customized to minimize hydrolysis of the anionic component in aqueous media as well as reduce absorbance when subjected to HPLC. The three MILs were applied for the extraction of pharmaceutical drugs, phenolics, insecticides, and polycyclic aromatic hydrocarbons. The disperser solvent type, disperser solvent volume, mass of MIL, extraction time, the pH of the sample solution, and salt concentration were studied in order to achieve optimal extraction efficiency for each MIL. The [P6,6,6,14(+)]2[MnCl4(2-)] MIL exhibited the best extraction efficiencies for most of the target analytes compared to the other MILs. Good linearity was obtained using this MIL with correlation coefficients (R) varying from 0.997 to 0.999. The limits of detection (LODs) of all analytes ranged from 0.25 to 1.00μgL(-1). The relative recovery was studied in lake water and river water. The relative recovery in lake water varied from 53.8% to 114.7% at a spiked concentration of 20μgL(-1) (5μgL(-1) for phenanthrene) and from 52.1% to 106.7% at 150μgL(-1) (37.5μgL(-1) for phenanthrene). In river water, the relative recovery varied from 44.6% to 110.7% at a spiked concentration of 20μgL(-1) (5μgL(-1) for phenanthrene) and 42.9% to 83.6% at 150μgL(-1) (37.5μgL(-1) for phenanthrene).

Application of hollow fiber liquid phase microextraction and dispersive liquid–liquid microextraction techniques in analytical toxicology

The recent developments in hollow fiber liquid phase microextraction and dispersive liquid –liquid microextraction are reviewed. Applications of these newly emerging developments in extraction and preconcentration of a vast category of compounds including heavy metals, pesticides, pharmaceuticals and abused drugs in complex matrices (environmental and biological matrices) are reviewed and discussed. The new developments in these techniques including the use of solvents lighter than water, ionic liquids and supramolecular solvents are also considered. Applications of these new solvents reduce the use of toxic solvents and eliminate the centrifugation step, which reduces the extraction time.