Recent advances in dispersive liquid-liquid microextraction for pesticide analysis

A critical review of pesticides in aquatic environment: Current trends, environmental impacts, and advances in analytical extraction techniques

Pesticides are applied in agricultural fields to manage pests and diseases that threaten crop health and productivity. However, their presence in natural water systems is a significant concern due to their persistent composition and complex molecular structures. Additionally, their toxic and recalcitrant nature poses potential risks, leading to chronic health effects in humans. Typically detected in trace concentrations, pesticides present analytical challenges owing to their intricate chemical structures and diverse physical properties. Recent research highlights notable advancements in conventional pesticide extraction methods, aiming to develop eco-friendly and cost-effective techniques with high enrichment and recovery rates. This review begins by exploring the latest trends and ongoing research related to the occurrence and extraction of pesticides from various aquatic environments. The study then discusses the innovative extraction techniques currently employed for pesticide removal. Among liquid-phase microextraction (LPME) techniques, methods such as ionic liquid-based extraction (IL-LPME), deep eutectic solvent-based extraction (DES-LPME), air-assisted extraction, solidification of a floating organic drop (SFO), and ultrasound-assisted LPME are gaining attention due to their ease of handling, operational simplicity, cost-effectiveness, and environmental sustainability. In the, solid-phase extraction (SPE) field, researchers have increasingly utilized approaches like magnetic solid-phase extraction (MSPE), green sorbents, metal-organic framework (MOF) based extraction, cartridge-based SPE, and carbon nanotube-based SPE as the most widely adopted methods. These methods are preferred for their benefits, including efficient separation, rapid analysis, and environmentally sustainable practices. The latter sections of this review present a detailed comparative analysis of these extraction methods, evaluating critical parameters such as operational time, cost, chemical and energy consumption, and analytical accuracy.

Development of a Dispersive Liquid-Liquid Microextraction Method for Quantification of Volatile Compounds in Wines Using Gas Chromatography-Mass Spectrometry

Background/Objectives: This study reports the development of a straightforward, efficient, and cost-effective dispersive liquid-liquid microextraction (DLLME) method for the gas chromatography-mass spectrometry (GC-MS) analysis of volatile compounds present in wine. Methods: Four critical parameters were optimised using a D-optimal design to maximise extraction outcomes of the targeted analytes from a 10 mL sample, while minimising interference from other compounds. The analytical characteristics of the method were assessed using 36 target compounds. Results: The method provided satisfactory linearity (correlation coefficients > 0.990), good repeatability for both for intra- and inter-day measurements (RSD < 10.3%), and suitable recoveries of target analytes from both model (83-110%) and real matrices (80-120%). The validated method was subsequently applied to analyse the aroma profile of 30 New Zealand Pinot noir (PN) wine samples. Conclusions: This study contributes to the advancement of analytical techniques available to both industry and researchers to explore the complex aroma profiles of wines.

An Efficient Fluorescent Chemosensing Probe for Total Determination and Speciation of Ultra-Trace Levels of Mercury (II) Species in Water

The current study reports a novel fluorescent chemosensor based on the tagging agent 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein (Rose Bengal, RB) for detection of trace levels of Hg2+in environmental water. The established probe has been based upon liquid-liquid extraction (LLE) of the developed ternary complex ion associate {[Hg (bpy)2]2+.[RB]2-} of Hg2+ -2,2- bipyridyl complex [Hg (bpy)2]2+ and RB at pH 9.0 onto chloroform and measuring the resulting fluorescence enhancement signal intensity at λex/em = 570/ (580-600) nm. The limits of detection (LOD) and quantification (LOQ) of for Hg2+ was calculated to be 6.06 and 20 nM with a linear dynamic range (LDR) of 0.02-20µM, respectively. The stability constant, stoichiometry, chemical equilibria, and the thermodynamic parameters (ΔH, ΔS, and ΔG) of the developed ion associate were evaluated and assigned. Student's t and F tests at 95% confidence were fruitfully used for validation of the proposed methodology for Hg2+ detection in water samples with the aid of inductively coupled plasma-optical emission spectrometry (ICP-OES). The established strategy was successfully applied for detection of trace levels of Hg2+ in water samples with acceptable results. The proposed probe was satisfactorily applied for total determination and speciation of Hg in various water samples. Integrating the functional chelating agent onto associate formation to improve the selectivity and sensing properties of the LLE combining sensing probe towards target analyte in water represent the main interest.

Development and Characterization of a Sol-Gel-Functionalized Glass Carbon Electrode Probe for Sensing Ultra-Trace Amounts of NH3 and NH4+ in Water

This study centers on the development and characterization of an innovative electrochemical sensing probe composed of a sensing mesoporous functional sol-gel coating integrated onto a glassy carbon electrode (sol-gel/GCE) for the detection of NH3 and/or NH4+ in water. The main interest for integrating a functional sol-gel coating onto a GCE is to increase the selective and sensing properties of the GCE probe towards NH3 and/or NH4+ ions. The structure and surface morphology of the newly developed sol-gel/GCE probe were characterized employing scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared (FTIR), while the electrochemical sensing properties were evaluated by Berthelot's reaction, cyclic voltammetry (CV), and adsorptive square wave-anodic striping voltammetry (Ads SW-ASV). It is shown that the newly developed sol-gel coating is homogeneously deposited on the GCE with a sub-micron and uniform thickness close to 630 nm and a surface roughness of 25 nm. The sensing testing of the sol-gel/GCE probe showed limits of detection and limits of quantitation of 1.7 and 5.56 nM of NH4+, respectively, as well as a probe sensitivity of 5.74 × 10-1 μA/μM cm-2. The developed probe was fruitfully validated for the selective detection of NH3/NH4+ in fresh and sea water samples. Computed Student texp (0.45-1.25) and Fexp (1.69-1.78) (n = 5) tests were less than the theoretical ttab (2.78) and Ftab (6.39) at 95% probability.

Biological Monitoring of Glyphosate Exposure among Knapsack Sprayers in Khon Kaen, Thailand

Sprayers' exposure to glyphosate was analyzed through detection of its biomarker in spot urine biological monitoring, and the health risk was assessed using the biomatrix model. Urine samples were collected from 15 sprayers after spraying, and the glyphosate concentration was determined by using the DLLME-HPLC method with a UV detector. The calibration curve for glyphosate was linear in the range of 0.4-100 µg/L, while the limits of detection and quantification were 0.1 µg/L and 0.4 µg/L, respectively. The human health risk was estimated using the hazard quotient (HQ) and the biomatrix of risk assessment. The internal dose ranged from 0.0001 to 0.0021 mg/kg b.w./day. The non-cancer HQ showed no potential health risk concerns (HQ < 1). The biomatrix of health risk assessment, based on urinary glyphosate concentration, exhibited a strong correlation with the health risk matrix model. This correlation was determined by considering the likelihood of exposure, calculated from the quantity of glyphosate used and the usage of personal protective equipment (r = 0.854, p < 0.001). Although low risk was observed in sprayers, proper PPE use and the application of more knowledge are required. The simplified health risk assessment can be used for easy self-assessment of risk in preventive action regarding health risk awareness among sprayers.

Sensitive quantitation of ultra-trace toxic aconitines in complex matrices by perfusion nano-electrospray ionization mass spectrometry combined with gas-liquid microextraction

The accurate analysis of ultra-trace (e.g. <10-4 ng/mL) substances in complex matrices is a burdensome but vital problem in pharmaceutical analysis, with important implications for precise quality control of drugs, discovery of innovative medicines and elucidation of pharmacological mechanisms. Herein, an innovative constant-flow perfusion nano-electrospray ionization (PnESI) technique was developed firstly features significant quantitative advantages in high-sensitivity ambient MS analysis of complex matrix sample. More importantly, double-labeled addition enrichment quantitation strategies of gas-liquid microextraction (GLME) were proposed for the first time, allowing highly selective extraction and enrichment of specific target analytes in a green and ultra-efficient (>1000-fold) manner. Using complex processed Aconitum herbs as example, PnESI-MS directly enabled the qualitative and absolute quantitative analysis of the processed Aconitum extracts and characterized the target toxic diester alkaloids with high sensitivity, high stability, wide linearity range, and strong resistance to matrix interference. Further, GLME device was applied to obtain the highly specific enrichment of the target diester alkaloids more than 1000-fold, and accurate absolute quantitation of trace aconitine, mesaconitine, and hypaconitine in the extracts of Heishunpian, Zhichuanwu and Zhicaowu was accomplished (e.g., 0.098 pg/mL and 0.143 pg/mL), with the quantitation results well below the LODs of aconitines from any analytical instruments available. This study built a systematic strategy for accurate quantitation of ultra-trace substances in complex matrix sample and expected to provide a technological revolution in many fields of pharmaceutical research.

An accurate and sensitive determination of selected pesticides in mixed fruit juice samples using the combination of a simple and efficient microextraction method and GC-MS with a matrix matching calibration strategy

Pesticides have been used on several fruits, vegetables and cereals to control harmful organisms in order to increase the quality of products; however, these substances cause serious health effects. Therefore, an accurate and sensitive analytical method should be developed for the determination of pesticides to evaluate their toxicity. In this study, an efficient microextraction strategy was applied to preconcentrate eight different selected pesticides from mixed fruit juice samples prior to gas chromatography-mass spectrometry detection. All significant parameters such as spraying number, extraction solvent type, sample volume and mixing type/period belonging to the developed extraction method were elaborately optimized to get low detection limits. After the optimization studies, system analytical performance studies were carried out and limit of detection (LOD) values varied from 0.04 μg /kg-1 to 1.99 μg kg-1 (mass based) for the selected analytes. Under the optimum experimental conditions, spiking recovery experiments were performed in the mixed fruit juice samples to evaluate the applicability and accuracy of the proposed method. The recovery results were recorded in the range of 81.4-123.5% with acceptable standard deviations by applying a matrix matching calibration strategy. The proposed analytical method can be used for the qualitative and quantitative determination of selected pesticides in the mixed fruit juice samples and can also be applied to other fruit juice samples using a matrix matching calibration strategy.

Mycotoxins in Vegetable Oils: A Review of Recent Developments, Current Challenges and Future Perspectives in Sample Preparation, Chromatographic Determination, and Analysis of Real Samples

Mycotoxins are toxic compounds that are formed as secondary metabolites by some fungal species that contaminate crops during pre- and postharvest stages. Exposure to mycotoxins can lead to adverse health effects in humans, such as carcinogenicity, mutagenicity, and teratogenicity. Hence, there is a need to develop analytical methods for their determination in vegetable oils that possess high sensitivity and selectivity. In the current review (116 references), the recent developments, current challenges, and perspectives in sample preparation techniques and chromatographic determination are summarized. It is impressive that current sample preparation techniques such as dispersive liquid-liquid microextraction (DLLME), quick, easy, cheap, rugged, and safe method (QuEChERS) and solid phase extraction (SPE) have exhibited high extraction recoveries and minimal matrix effects. However, a few studies have reported signal suppression or enhancement. Regarding chromatographic techniques, high sensitivity and selectivity have been reported by liquid chromatography coupled to fluorescence detection, tandem mass spectrometry, or high-resolution mass spectrometry. Furthermore, current challenges and perspectives in this field are tentatively proposed.

Traditional methods and biosensors for detecting disinfection by-products in water: A review

In recent years, pollution caused by disinfection by-products (DBPs) has become a global concern. Initially, there were fewer contaminants, and the mechanism of their generation was unclear; however, the number of contaminants has increased exponentially as a result of rapid industrialization and numerous economic activities (e.q., during the outbreak of COVID-19 a surge in the use of chlorinated disinfectants was observed). DBP toxicity results in various adverse health effects and organ failure in humans. In addition, it profoundly affects other forms of life, including animals, plants, and microorganisms. This review comprehensively discusses the pre-treatment methods of traditional and emerging DBPs and the technologies applied for their detection. Additionally, this paper provides a detailed discussion of the principles, applicability, and characteristics of traditional large-scale instrumentation methods (such as gas/liquid/ion chromatography coupled with mass spectrometry) for detecting DBPs based on their respective detection techniques. At the same time, the design, functionality, classification, and characteristics of rapid detection technologies (such as biosensors) are also detailed and analyzed.

An Eco-Friendly, Interference, and Solvent Free Surfactant-Assisted Dual-Wavelength β-CorrectionSpectrometric Method for Total Determination and Speciation of Cu2+ Ions in Water

Spectral interference through the presence of uninformative variables, excess reagents, and complications in the refinement of the analyte signal is common in the quest to identify complex species in real samples. Therefore, an economical green, facile, and sensitive strategy has been developed for Cu2+ detection using the anionic surfactant sodium dodecylsulphate- (SDS-) assisted dual-wavelength β-correction spectrophotometric strategy combined with the chromogenic reagent zincon (ZI). The low limits of detection (LOD) and quantification (LOQ) of Cu2+ using ordinary (single wavelength) spectrophotometry were 0.19 (3.02) and 0.63 (10.0) μgmL-1, and these values were improved to 0.08 (1.27) and 0.26 μgmL-1 (4.12 μM)) using β-correction (dual wavelength) spectrophotometry, respectively. The LOD and LOQ were improved from 0.08 (1.27) and 0.26 (4.12) μgmL-1 to 0.02 (0.32) and 0.08 μgmL-1 (1.27 μM) using SDS-assisted dual-β-correction spectrometry, respectively. Ringbom, s, and the corrected absorbance (Ac) versus Cu2+ concentration plots were linear over the concentration range 1.10-2.4 (17.4-38.1) and 0.50-2.40 μgmL-1 (7.94-38.1 μM), respectively. Sandell's sensitivity index of 3.0 × 10-3 μg/cm2 was achieved. The selectivity was further confirmed via monitoring the impact of common diverse ions and surfactants on the corrected absorbance. Total determination and Cu2+ speciation in water were favorably implemented and validated by ICP-OES at 95% (P=0.05). Satisfactory Cu2+ recoveries in tap (92.2-98.0%) and mineral (105-111.0%) water samples were achieved. The sensing system is simple, reliable, sensitive, and selective for Cu2+ detection.

A new method based on dispersive liquid-liquid microextraction for fat-soluble vitamin determination in serum by LC-MS/MS

A green and inexpensive pretreatment known as dispersive liquid-liquid microextraction (DLLME) was developed in this assay coupled with the LC-MS/MS method for routine analysis of fat soluble vitamins (FSVs). The technique was performed with methanol as the dispersive solvent and dichloromethane as the extraction solvent. The extraction phase containing FSVs was evaporated to dryness and reconstituted in a mixture of acetonitrile and water. The influence variables concerning the DLLME procedure were optimized. After that, the method was investigated for its applicability in LC-MS/MS analysis. As a result, the parameters were settled for the optimal conditions during the DLLME process. A cheap and lipid-free substance was found as an alternative to serum to eliminate the matrix effect while preparing the calibrators. The method validation indicated that it was suitable for determining FSVs in serum. Moreover, this method was applied successfully to determine serum samples, which was consistent with the literature. In summary, the DLLME method developed in this report was reliable and more cost-effective than the traditional LC-MS/MS method, and could be applied in the future.

Utilization of Waste Biomaterial as an Efficient and Eco-Friendly Adsorbent for Solid-Phase Extraction of Pantoprazole Contaminants in Wastewater

The objective of this analysis is to establish the potential of biodegradable agro-industrial waste materials as biosorbents in the solid-phase extraction (SPE) technique for sample preparation. In this regard, waste coffee husk (CH) powder was collected, washed, treated chemically, characterized, and applied as an SPE adsorbent to extract pantoprazole from the wastewater samples. Sample detection was accomplished using the UPLC-MS/MS system. The positive mode of electrospray ionization was exploited for the ionization of the sample, and quantification of the target analyte was performed by the multiple reaction monitoring modes. The precursor to product ion transition of 384.02→1380.05 and 384.02→200.05 was used as qualifiers and quantifiers, respectively. Optimization of the particle size, adsorbent dose, and contact time were evaluated to select the best combination of features. The efficiency and regeneration capability of the CH were compared with respect to a commercially available silica-based C18 SPE adsorbent, and it was found that CH possessed comparable (~50%) extraction, as well as regeneration capacity (~95%). The developed biosorbent was applied in a wastewater sample spiked with the target analyte and recovery studies were performed, which found a range of 93.0 to 102.0% with a %RSD of 3.72 to 12.7%. Thus, CH can be exploited as a ‘greener’ replacement for the commercially available adsorbents for the extraction/retention of active pharmaceutical ingredients present in water/wastewater samples.

Modified QuEChERS Method for Extracting Thiamethoxam and Imidacloprid from Stingless Bees: Development, Application, and Green Metrics

In the present study, a method for the determination of residues of the neonicotinoid insecticides thiamethoxam and imidacloprid in the stingless bee Melipona scutellaris Latreille (1811) was optimized through a factorial design, tested using green metrics, and then applied to exposed bees. It combines the extraction with a modified quick, easy, cheap, effective, rugged, and safe method and the determination by liquid chromatography-tandem mass spectrometry analysis. Different parameters such as the mass of the sample, dispersive sorbents, and elution solvents were assessed. Method validation parameters were checked and include sensitivity, specificity, and linearity. The limit of quantification of 0.0025 μg g^-1 was obtained for both insecticides, where accuracy was 94%-100% with satisfactory intraday and interday precisions (relative standard deviation <10%). The qualified method was applied to orally and topically exposed bee samples, and the results indicated that it is suitable for the determination and quantification of neonicotinoid pesticide residues in this species. Moreover, green analytical metrics like the National Environmental Methods Index, Eco Scale score, high-performance liquid chromatography with an environmental assessment tool (HPLC-EAT), waste generation, and amount of sample were compared with methods described in the literature involving neonicotinoid analysis in honeybees. As a result, the present study displayed the highest Eco Scale score and HPLC-EAT score and the second smallest amount of sample and waste generated. Thus, the method meets green analytical metrics more than other methods. In this sense, besides the application, the multicriteria decision analysis tool employed suggests that this is a good option as a green analytical method. Environ Toxicol Chem 2022;41:2365-2374. © 2022 SETAC.

Overview of Different Modes and Applications of Liquid Phase-Based Microextraction Techniques

Liquid phase-based microextraction techniques (LPµETs) have attracted great attention from the scientific community since their invention and implementation mainly due to their high efficiency, low solvent and sample amount, enhanced selectivity and precision, and good reproducibility for a wide range of analytes. This review explores the different possibilities and applications of LPμETs including dispersive liquid–liquid microextraction (DLLME) and single-drop microextraction (SDME), highlighting its two main approaches, direct immersion-SDME and headspace-SDME, hollow-fiber liquid-phase microextraction (HF-LPME) in its two- and three-phase device modes using the donor–acceptor interactions, and electro membrane extraction (EME). Currently, these LPμETs are used in very different areas of interest, from the environment to food and beverages, pharmaceutical, clinical, and forensic analysis. Several important potential applications of each technique will be reported, highlighting its advantages and drawbacks. Moreover, the use of alternative and efficient “green” extraction solvents including nanostructured supramolecular solvents (SUPRASs, deep eutectic solvents (DES), and ionic liquids (ILs)) will be discussed.

Overarching issues on relevant pesticide transformation products in the aquatic environment: A review

The intensification of agricultural production during the last decades has forced the rapid increase in the use of pesticides that finally end up in the aquatic environment. Albeit well-documented, pesticides continue to raise researchers' attention, because of their potential adverse impacts on the environment and, inevitably, humans. Once entering the aquatic bodies, pesticides undergo biotic and abiotic processes, resulting in transformation products (TPs) that sometimes are even more toxic than the parent compounds. A substantial shift of the scientific interest in the TPs of pesticides has been observed since their environmental fate, occurrence and toxicity is still in its formative stage. In an ongoing effort to expand the existing knowledge on the topic, several interesting works have been performed mostly in European countries, such as France, Germany, Italy, Switzerland, Greece, and Spain that counts the highest number of relevant publications. Pesticide TPs have been also studied to a lesser extent in Asia, North and South America. To this end, the main objective of this review is to delineate the global occurrence, fate, toxicity as well as the analytical challenges related to pesticide TPs in surface, ground, and wastewaters, with the view to contribute to a better understanding of the environmental problems related with TPs formation. The concentration levels of the TPs, ranging from the low ng/L to high μg/L scale and distributed worldwide. Ultimately, an attempt to predict the acute and chronic toxicity of TPs has been carried out with the aid of an in-silico approach based on ECOSAR, revealing increased chronic toxicity for the majority of the identified TPs, despite the change they underwent, while a small portion of them presented serious acute toxicity values.

Current overview and perspectives in environmentally friendly microextractions of carbamates and dithiocarbamates

Carbamates and dithiocarbamates are two classes of pesticides widely employed in the agriculture practice to control and avoid pests and weeds, hence, the monitoring of the residue of those pesticides in different foodstuff samples is important. Thus, this review presents the classification, chemical structure, use, and toxicology of them. Moreover, it was shown the evolution of liquid- and solid-phase microextractions employed in the extraction of carbamates and dithiocarbamates in water and foodstuff samples. The classification, operation mode, and application of the microextractions of liquid-phase and solid-phase used in their extraction were discussed and related to the analytical parameters and guidelines of green analytical chemistry.

Development of a magnetic dispersive solid phase extraction method by employing folic acid magnetic nanoparticles as an effective, green, and reliable sorbent followed by dispersive liquid-liquid microextraction for the extraction and preconcentration of seven pesticides from fruit juices

Folic acid magnetic nanoparticles have been prepared and utilized as an effective and reliable sorbent in magnetic dispersive solid phase extraction combined with dispersive liquid-liquid microextraction for the extraction of seven pesticides from different juices before their determination by gas chromatography-flame ionization detector. The sorbent is prepared through ball milling process using a proper mixture of folic acid and magnetic iron oxide. Characterization of the sorbent was done with X-ray diffraction pattern, scanning electron microscopy, and vibrating sample magnetometry. In the current study, limits of detection were in the range 0.12-0.33 μg L^-1. Relative standard deviations at a concentration of 40 μg L^-1 of each analyte were in the ranges of 2.15-5.14% for intra-day (n = 6) and 3.78-6.91% for inter-day (n = 4) precisions. Extraction recoveries and enrichment factors were obtained in the ranges of 70-88 % and 566-708, respectively. The performance of the method was evaluated by determination the selected pesticides in different samples. Graphical Abstract.

A highly Sensitive Modified Glassy Carbon Electrode with Carboxylated Multi-walled Carbon Nanotubes/Nafion Nano composite for Efficient and Cheap Voltammetric Sensing of Dianabol Steroid in Biological Fluid

The extraordinary prerequisite for the analysis of an anabolic steroid, namely dianabol (DB), has inspired towards the development of a cost-effective and high-performance sensing probe. Thus, a simple and robust electrochemical sensor (c-MWCNTs-Nafion®lGCE) for dianabol (DB), a widely used steroid, was developed using a glassy carbon electrode (GCE) modified with functionalized carboxylated multi-walled carbon nanotubes (c-MWCNT) and Nafion®. At pH 7 - 8, differential pulse-cathodic stripping voltammetry (DP-CSV) displayed two cathodic peaks at -0.85 and -1.35 V that varied linearly over a wide range (9.0 × 10-9 (2.7 μg L-1) - 9.0 × 10-6 (2.7 × 103 μg L-1) mol L-1) and 2.9 × 10-6 (8.7 × 102 μg L-1) - 8.0 × 10-5 (2.4 × 104 μg L-1) mol L-1) of DB concentrations, respectively. The low limits of detection and quantification at peak I (-0.85 V) were 2.7 × 10-9 (8.1 × 10-1 ng mL-1) and 9.0 × 10-9 (2.7 ng mL-1) mol L-1, respectively. The repeatability and reproducibility displayed relative standard deviations lower than 5%. The method was applied for DB analysis in human urine and subsequently compared with the standard HPLC method. Interference of common metabolites in biological fluids samples to DB sensing was insignificant. This method has distinctive advantages e.g. precise, short analytical time, sensitive, economical, reproducible and miniaturized sample preparation for DB analysis in biological samples of human origin.

Preparation of environmental samples for chemical speciation of metal/metalloids: A review of extraction techniques

Chemical speciation is a relevant topic in environmental chemistry since the (eco)toxicity, bio (geo)chemical cycles, and mobility of a given element depend on its chemical forms (oxidation state, organic ligands, etc.). Maintaining the chemical stability of the species and avoiding equilibrium disruptions during the sample treatment is one of the biggest challenges in chemical speciation, especially in environmental matrices where the level of concomitants/interferents is normally high. To achieve this task, strategies based on chemical properties of the species can be carried out and pre-concentration techniques are often needed due to the low concentration ranges of many species (μg L^-1 - ng L^-1). Due to the significance of the topic and the lack of reviews dealing with sample preparation of metal (loid)s (usually, sample preparation reviews focus on the total metal content), this work is presented. This review gives an up-to-date overview of the most common sample preparation techniques for environmental samples (water, soil, and sediments), with a focus on speciation of metal/metalloids and determination by spectrometric techniques. Description of the methods is given, and the most recent applications (last 10 years) are presented.

Determination of pyridaphenthion in soybean sprout samples by gas chromatography mass spectrometry with matrix matching calibration strategy after metal sieve linked double syringe based liquid-phase microextraction

A novel analytical strategy for the trace determination of pyridaphenthion pesticide was developed in this study. Gas chromatography-mass spectrometry (GC-MS) was used for the accurate, feasible and precise determination of this analyte. Liquid phase microextraction (LPME) was performed with a metal sieve linked double syringe (MSLDS) system, which eliminated the need for a disperser solvent. In order to increase extraction efficiency for the analyte, all variable parameters were optimized and the system analytical performance of the proposed method was determined. Limit of detection and quantification (LOD and LOQ) values of pyridaphenthion were found to be 0.8 and 2.7 µg L-1, respectively. Compared to GC-MS system's analytical performance, the developed method provided approximately 273-folds improvement in the detection limit of the analyte. Applicability/accuracy of the developed analytical strategy was checked by recovery experiments carried out with soybean sprouts, and the results obtained were satisfactory.

Centrifuge-free dispersive liquid-liquid microextraction coupled with thin-film microextraction for the preconcentration of molinate in real samples by ion mobility spectrometry

A tandem microextraction method, centrifuge free dispersive liquid-liquid microextraction and thin-film microextraction (DLLME-TFME), was used for analyzing molinate in environmental samples by ion mobility spectrometry (IMS). Considering the IMS as a competitive detection system, coupling these two popular sample preparation methods reduces the effect of solvent interference and improves the sensitivity of the technique. Trichloromethane and methanol were used as the extraction, and dispersive solvents for the DLLME method and electrospun polyacrylonitrile/copper-benzene-1,4-dicarboxylic acid fibers were used as a sorbent in the TFME method. Some effective experimental variables influencing the extraction efficiency of an analyte such as type and volume of dispersive and extraction solvents, solution pH, ionic strength, sonication time, and extraction time were studied. The linear dynamic range of 0.5-50 μg L^-1 and the limit of detection of 0.1 μg L^-1 were obtained under optimized conditions. The relative standard deviations for intra-and inter-day analysis were calculated less than 10%. The present method was used for the determination of molinate in different real samples such as agricultural wastewater, well water, river water, and apple, and the recovery was obtained between 82% and 113%, for the spiked samples.

Dispersive liquid-liquid microextraction using a low transition temperature mixture and liquid chromatography-mass spectrometry analysis of pesticides in urine samples

Biomonitoring is a potent tool to control the health risk of people occupationally and non-occupationally exposed. The latest trend in bioanalytical chemistry is to develop quick, cheap, easy, safe and reliable green analytical procedures to analyse a large number of chemicals in easily accessible biomatrices such as urine. In this paper, a new dispersive liquid-liquid microextraction (DLLME) procedure, conceived to treat urine samples and based on the use of a low transition temperature mixture (LTTM), was developed and validated to analyse twenty pesticides commonly used in farm practises. The LTTM was composed of choline chloride and sesamol in molar ratio 1:3 (ChCl:Ses 1:3); its characterization via differential scanning calorimetry identified it as an LTTM and not as a deep eutectic solvent due to the occurrence of a glass transition at -71 °C. The prepared mixture was used as the extraction solvent in the DLLME procedure, while ethyl acetate as the dispersing solvent. The salting out effect (50 mg mL^-1 of NaCl in a diluted urine sample) improved the separation phase and the analyte transfer to the extractant. Due to the high ionic strength and despite the density of ChCl:Ses 1:3 (1.25 g mL^-1), the LTTM layer floated on the top of the sample solution after centrifugation. All extracts were analysed by high-performance liquid chromatography coupled to mass spectrometry. After optimization and validation of the whole method, lower limits of quantitation were in the range of 0.02 - 0.76 µg  L^-1. Extraction recoveries spanned from 50 to 101 % depending on the spike level and analytes. Precision and accuracy ranges were 3-18% and 5-20%, respectively. The extraction procedure was also compared with other methods, showing to be advantageous for rapidity, simplicity, efficiency, and low cost. Finally, urine samples from ten volunteers were effectively analysed using the developed method.

A miniaturized spray-assisted fine-droplet-formation-based liquid-phase microextraction method for the simultaneous determination of fenpiclonil, nitrofen and fenoxaprop-ethyl as pesticides in soil samples

RATIONALE

Pesticides are a group of micropollutants that persist for a long time in the environment and pose threats to life. Much effort has been devoted to developing pre-concentration methods capable of producing samples suitable for the detection of pesticides. However, better methods are still required to detect these compounds when they are present in trace concentrations in soils.

METHOD

Spray-assisted fine-droplet-formation-based liquid-phase microextraction was used to prepare soil samples containing three different pesticides, fenpiclonil, nitrofen and fenoxaprop-ethyl, for subsequent analysis by gas chromatography/mass spectrometry (GC/MS). A spraying apparatus was used for the dispersion of the extraction solvent into the sample/standard solution to improve the extraction efficiency. Optimization studies were performed to lower the detection limits of these analytes and the results obtained by the application of the newly developed system were compared with those obtained using the conventional GC/MS method.

RESULTS

A calibration curve over the range 5.0-100 μg L^-1 was obtained under the optimal conditions. The limits of detection and quantification were 1.56-1.80 μg L^-1 and 5.21-5.98 μg L^-1 , respectively. The enhancements in detection ability over the conventional method for the three tested pesticides were 188.01, 176.96 and 517.14 for fenpiclonil, nitrofen and fenoxaprop-ethyl, respectively Recovery studies performed in soil samples were satisfactory reflecting accurate applicability of the developed method.

CONCLUSIONS

The developed microextraction method is a time-saving and simple version of the traditional dispersive liquid-liquid microextraction method that also reduces the use of dispersive solvents.

Proposal of a new, fast, cheap, and easy method using DLLME for extraction and preconcentration of diazepam and its transformation products generated by a solar photo-Fenton process

This work evaluated the formation of transformation products (TPs) during the degradation of diazepam (DZP) by a solar photo-Fenton process. Six TPs were identified, three of them for the first time. After elucidation of the TPs, a new, cheap, fast, and easy method was employed to extract and preconcentrate DZP and its TPs, using dispersive liquid-liquid microextraction (DLLME). The method was optimized using factorial and Doehlert designs, with the best results obtained using acetonitrile as disperser solvent and chloroform as extraction solvent, with volumes of 1000 and 650 µL, respectively. When DZP degradation was performed in ultrapure water, the extraction/preconcentration of DZP and its TPs by DLLME was very similar to the results obtained using a traditional SPE method. However, when hospital wastewater was used as the matrix, more limited extraction efficiency was obtained using DLLME, compared to SPE. Meanwhile, all the TPs extracted by SPE were also extracted by the DLLME technique. Furthermore, DLLME was much less expensive than SPE, besides being faster, easier, and requiring only small amounts of organic solvents. This work reports a new and very important tool for the extraction and preconcentration of TPs formed during degradation using techniques such as advanced oxidation processes (AOPs), since without this step it would not be possible to identify all the TPs formed in some complex wastewater matrices.

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.

Determination of fipronil and bixafen pesticides residues using gas chromatography mass spectroscopy with matrix matching calibration strategy after binary dispersive liquid-liquid microextraction

The objective of this study was to determine bixafen and fipronil residues in domestic and industrial wastewater, soil and mint samples by binary dispersive liquid-liquid microextraction method (BDLLME) prior to gas chromatography-mass spectrometry (GC-MS). Extraction efficiency for the selected analytes was improved by optimizing the parameters such as solvent type, ratio and volume, dispersive solvent type/volume, mixing type and duration to increase overall analytical performance. Under the optimum chromatographic and extraction conditions, limits of detection values for bixafen and fipronil were determined as 7.3 and 6.1 µg L^-1, respectively. Spiking experiments were performed for domestic and industrial wastewater, soil and mint samples to evaluate applicability and accuracy of the proposed method. Recovery results for the samples were calculated in the range of 89.4%-112.6% via matrix matching calibration strategy. It was determined that the detection power of GC-MS system was improved 7.8 times for bixafen and 119 times for fipronil over LOD comparisons of conventional GC-MS and B-DLLME-GC-MS systems.

Miniaturized QuEChERS method for determination of 97 pesticide residues in wine by ultra-high performance liquid chromatography coupled with tandem mass spectrometry

A miniaturized sample preparation method was developed and validated for the multiresidue determination of 97 pesticides in wine samples. The proposed extraction procedure is based on the QuEChERS acetate method with dispersive solid phase extraction (d-SPE) for the clean-up step. Ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) was used for determination. The extraction and clean-up steps were evaluated to obtain the best conditions for the selected pesticides. Miniaturization of the sample preparation step provided a reduction in the consumption of samples and chemicals. The method limit of quantification was between 10 and 20 μg L-1. Trueness results, obtained by recovery assays at the spike levels 10, 20, 50 and 100 μg L-1, ranged from 70 to 120% with precision in terms of relative standard deviations (RSD) ≤ 20%. The method was successfully applied for the analysis of wine samples and different pesticides were found at concentrations from 14 to 55 μg L-1.

Landing microextraction sediment phase onto surface enhanced Raman scattering to enhance sensitivity and selectivity for chromium speciation in food and environmental samples

The current study explores the first full mode liquid microextraction technique coupled with surface-enhanced Raman spectroscopy (SERS), and has been successfully applied for chromium speciation in food and environmental matrices. Herein, chromium as chlorochromate anion [CrO3Cl]- and the cationic rhodamine 6G [RG]+ dye has been extracted in organic phase as a complex ion associate [RG+.CrO3Cl-.nS]org at pH ≤ 1.0. Afterwards, the extracted phase was deposited on the surface of the nano-flower shaped silver nanoparticles substrate and the SERS response was monitored against the reagent blank at 1505 cm-1. Substrate characterizations, reaction mechanism assignment, stoichiometry, speciation, analytical applications, selectivity and validation were performed. The analytical procedure exhibits a detection limit of 0.03 µg L-1 under the optimized experimental conditions. The accuracy of the proposed strategy was validated by inductively coupled plasma optical emission spectrometry method using student's t- and F tests at 95% confidence.

Biogenic Amines Formation Mechanism and Determination Strategies: Future Challenges and Limitations

The evolution in foodstuff-monitoring processes has increased the number of studies on biogenic amines (BAs), in recent years. This trend with future perspective needs to be assembled to address the associated health risks. Thus, this study aims to cover three main aspects of BAs: (i) occurrence, physiology, and toxicological effects, most probable formation mechanisms and factors controlling their growth; (ii) recent advances, strategies for determination, preconcentration steps, model technique, and nature of the matrix; and (iii) milestone, limitations with existing methodologies, future trends, and detailed expected developments for clinical use and on-site ultra-trace determination. The core of the ongoing review will discuss recent trends in pre-concentration toward miniaturization, automation, and possible coupling with electrochemical techniques, surface-enhanced Raman scattering, spectrofluorimetry, and lateral flow protocols to be exploited for the development of rapid, facile, and sensitive on-site determination strategies for BAs.

Green pre-concentration techniques during pesticide analysis in food samples

The ever-increasing demand for determining pesticides at low concentration levels in different food matrices requires a preliminary step of pre-concentration which is considered a crucial stage. Recently, the parameter of "greenness" during sample pre-concentration of pesticides in food matrices is as important as selectivity in order to avoid using harmful organic solvents during sample preparation. Developing new green pre-concentration techniques is one of the key subjects. Thus, to reduce the impact on the environment during trace analysis of pesticides in food matrices, new developments in pre-concentration have gone in three separate directions: the search for more environmentally friendly solvents, miniaturization and development of solvent-free pre-concentration techniques. Eco-friendly solvents such as supercritical fluids, ionic liquids and natural deep eutectic solvents have been developed for use as extraction solvents during pre-concentration of pesticides in food matrices. Also, miniaturized pre-concentration techniques such as QuEChERS, dispersive liquid-liquid micro-extraction and hollow-fiber liquid-phase micro-extraction have been used during trace analysis of pesticides in food samples as well as solvent-free techniques such as solid-phase micro-extraction and stir bar sorptive extraction. All these developments which are aimed at ensuring that pesticide pre-concentration in different food matrices is green are critically reviewed in this paper.