Efficient Motif Discovery in Protein Sequences Using a Branch and Bound Algorithm.

Identifying motifs within sets of protein sequences constitutes a pivotal challenge in proteomics, imparting insights into protein evolution, function prediction, and structural attributes. Motifs hold the potential to unveil crucial protein aspects like transcription factor binding sites and protein-protein interaction regions. However, prevailing techniques for identifying motif sequences in extensive protein collections often entail significant time investments. Furthermore, ensuring the accuracy of obtained results remains a persistent motif discovery challenge. This paper introduces an innovative approach-a branch and bound algorithm-for exact motif identification across diverse lengths. This algorithm exhibits superior performance in terms of reduced runtime and enhanced result accuracy, as compared to existing methods. To achieve this objective, the study constructs a comprehensive tree structure encompassing potential motif evolution pathways. Subsequently, the tree is pruned based on motif length and targeted similarity thresholds. The proposed algorithm efficiently identifies all potential motif subsequences, characterized by maximal similarity, within expansive protein sequence datasets. Experimental findings affirm the algorithm's efficacy, highlighting its superior performance in terms of runtime, motif count, and accuracy, in comparison to prevalent practical techniques.

Estimating the heritability of nitrogen and carbon isotopes in the tail hair of beef cattle.

BACKGROUND: The natural abundance of nitrogen (δ15N) and carbon (δ13C) isotopes in animal tissues are used to estimate an animal's efficiency in nitrogen utilization, and their feed conversion efficiency, especially in tropical grazing systems with prolonged protein restriction. It is postulated that selection for improving these two characteristics (δ15N and δ13C) would assist the optimisation of the adaptation in ever-changing environments, particularly in response to climate change. The aim of this study was to determine the heritability of δ15N and δ13C in the tail hair of tropically adapted beef cattle to validate their inclusion in genetic breeding programs. METHODS: In total, 492 steers from two breeds, Brahman (n = 268) and Droughtmaster (n = 224) were used in this study. These steers were managed in two mixed breed contemporary groups across two years (year of weaning): steers weaned in 2019 (n = 250) and 2020 (n = 242). Samples of tail switch hair representing hair segments grown during the dry season were collected and analysed for δ15N and δ13C with isotope-ratio mass spectrometry. Heritability and variance components were estimated in a univariate multibreed (and single breed) animal model in WOMBAT and ASReml using three generations of full pedigree. RESULTS: The estimated heritability of both traits was significantly different from 0, i.e. 0.43 ± 0.14 and 0.41 ± 0.15 for δ15N and δ13C, respectively. These traits had favourable moderate to high genetic and phenotypic correlations (- 0.78 ± 0.16 and - 0.40 ± 0.04, respectively). The study also provides informative single-breed results in spite of the limited sample size, with estimated heritability values of 0.37 ± 0.19 and 0.19 ± 0.17 for δ15N and δ13C in Brahman, and 0.36 ± 0.21 and 0.46 ± 0.22 for δ15N and δ13C in Droughtmaster, respectively. CONCLUSIONS: The findings of this study show, for the first time, that the natural abundances of both nitrogen and carbon isotopes in the tail hair in cattle may be moderately heritable. With further research and validation, tail hair isotopes can become a practical tool for the large-scale selection of more efficient cattle.

Metal-organic frameworks-derived layered double hydroxides: From controllable synthesis to various electrochemical energy storage/conversion applications.

Over the past years, metal-organic frameworks (MOF) have been directly used as electrodes or as a precursor for MOF-derived materials in energy storage and conversion systems. In the wide range of existing MOF derivatives, MOF-derived layered double hydroxides (LDHs) are determined to be promising materials due to their unique structure and features. However, MOF-derived LDHs (MDL) materials can suffer from insufficient intrinsic conductivity and agglomeration during formation. Various techniques and approaches were designed and applied to tackle these problems, such as using ternary LDHs, ion-doping, sulphurization, phosphorylation, selenization, direct growth, and conductive substrates. All the mentioned enhancement techniques aim to create the ideal electrode materials with maximum performance. In this review, we gathered and discussed the most recent progressive advances, different synthesis methodologies, unsolved challenges, applications, and electrochemical and electrocatalytic performance of MDL materials. We hope this work will be a reliable source for future progress and synthesis of these materials.

A Spatiotemporal Deep Neural Network Useful for Defect Identification and Reconstruction of Artworks Using Infrared Thermography.

Assessment of cultural heritage assets is now extremely important all around the world. Non-destructive inspection is essential for preserving the integrity of artworks while avoiding the loss of any precious materials that make them up. The use of Infrared Thermography is an interesting concept since surface and subsurface faults can be discovered by utilizing the 3D diffusion inside the object caused by external heat. The primary goal of this research is to detect defects in artworks, which is one of the most important tasks in the restoration of mural paintings. To this end, machine learning and deep learning techniques are effective tools that should be employed properly in accordance with the experiment's nature and the collected data. Considering both the temporal and spatial perspectives of step-heating thermography, a spatiotemporal deep neural network is developed for defect identification in a mock-up reproducing an artwork. The results are then compared with those of other conventional algorithms, demonstrating that the proposed approach outperforms the others.

Novel proton conducting core-shell PAMPS-PVBS@Fe2TiO5 nanoparticles as a reinforcement for SPEEK based membranes.

In this study, new nanocomposite membranes from sulfonated poly (ether ether ketone) (SPEEK) and proton-conducting Fe2TiO5 nanoparticles are prepared by the solution casting method. Sulfonated core-shell Fe2TiO5 nanoparticles are synthesized by redox polymerization. Therefore, 4-Vinyl benzene sulfonate (VBS) and 2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS) are grafted on the surface of nanoparticles through radical polymerization. The different amounts of hybrid nanoparticles (PAMPS@Fe2TiO5 and PVBS@Fe2TiO5) are incorporated into the SPEEK matrix. The results show higher proton conductivity for all prepared nanocomposites than that of the SPEEK membrane. Embedding the sulfonated Fe2TiO5 nanoparticles into the SPEEK membrane improves proton conductivity by creating the new proton conducting sites. Besides, the nanocomposite membranes showed improved mechanical and dimensional stability in comparison with that of the SPEEK membrane. Also, the membranes including 2 wt% of PAMPS@Fe2TiO5 and PVBS@Fe2TiO5 nanoparticles indicate the maximum power density of 247 mW cm-2 and 226 mW cm-2 at 80 °C, respectively, which is higher than that of for the pristine membrane. Our prepared membranes have the potential for application in polymer electrolyte fuel cells.

Extraction of antidepressant drugs in biological samples using alkanol-based nano structured supramolecular solvent microextraction followed by gas chromatography with mass spectrometric analysis.

In the present study, a supramolecular solvent was formed from reverse micelle aggregates of octanol. The proposed supramolecular solvent was used for rapid extraction of some antidepressants drugs including amitriptyline, imipramine, desipramine, maprotiline, sertraline, and doxepin from biological samples. Alkanol-based supramolecular solvents have a unique array of physicochemical properties, making them a very attractive alternative to replace organic solvents in analytical extractions. The parameters affecting the extraction of target analytes (i.e., the volume of tetrahydrofuran and octanol as the major components comprising the supramolecular solvent, chain length of alkanols, sample solution pH, salt addition, and ultrasonic time) were investigated and optimized by factor by factor optimization method. Under the optimum conditions, preconcentration factors of 470, 490, 460, 385, 370, and 430 were obtained for amitriptyline, doxepin, imipramine, desipramine, maprotiline, and sertraline, respectively. The linear ranges and coefficients of determination (R2 ) were obtained in the range of 0.01-100 µg/L and 0.9974-0.9991, respectively. Also the limits of detection (S/N = 3) of 0.003-0.03 µg/L, and precisions (n = 5) of 4.9-8.9% were calculated. Finally, the method was successfully applied for the extraction of antidepressant drugs in biological samples, and relative recoveries in the range of 91-102% were obtained.

Nanostructured gemini-based supramolecular solvent coupled with ultrasound-assisted back extraction as a preconcentration step before GC-MS.

Liquid-phase microextraction based on gemini-based supramolecular solvent was successfully applied as a preconcentration step before gas chromatography with mass spectrometry. To eliminate the interferences of gemini surfactant, the analytes were back-extracted into an immiscible organic solvent in the presence of ultrasonic sound waves. Three phthalate esters (di-n-butyl-, butylbenzyl-, bis(2-ethylhexyl)-, and di-n-octyl phthalatic esters) were used as target analytes. The effective parameters on extraction efficiency of the target analytes (i.e., the amount of surfactant and volume of propanol as major components making up the supramolecular solvent, ionic strength, hexane volume, and ultrasound time) were investigated and optimized by a one-variable-at-a-time method. Under the optimum conditions, the preconcentration factors of the analytes were in the range of 95-182. The linear dynamic range of 0.05-200.00 µg/L with a correlation of determination of (R2 ) ≥ 0.9935 was obtained. The proposed method had an excellent limit of detection (S/N = 3) of 0.01 for di-n-octyl and 0.02 µg/L for butylbenzyl- and di-n-butyl-phthalatic ester. Good relative recoveries in the range of 85.7-105.2% guaranteed the accuracy of the amount of phthalates distinguished in the nonspiked samples.

A new generation of nano-structured supramolecular solvents based on propanol/gemini surfactant for liquid phase microextraction.

A new supramolecular solvent (SUPRAS) made up of aggregates of gemini surfactant was introduced. A microextraction method, based on the SUPRAS followed with high performance liquid chromatography-ultraviolet detection, was applied for the determination of parabens in cosmetics, beverages and water samples. A SUPRAS is a nano-structured liquid made up of surfactant aggregates synthesized through a self-assembly process. In the present work, a new gemini-based SUPRAS was introduced. Methyl paraben (MP), ethyl paraben (EP), and propyl paraben (PP) were extracted on the basis of π-cation and Van der Waals interactions into the SUPRAS. The parameter affecting the extraction of target analytes (i.e., the amount of surfactant and volume of propanol as major components comprising the supramolecular solvent, sample solution pH, salt addition, ultrasonic and centrifugation time) were investigated and optimized by one-variable-at-a-time method. Under the optimum conditions, the preconcentration factors of 98, 143 and 156 were obtained for MP, EP and PP, respectively. The linearity ranged from 0.5 to 0.7-200 µg L-1 with the correlation of determination of (R2) ≥ 0.9938. The gemini-based SUPRAS followed by HPLC-UV has been found to have excellent detection sensitivity with a limit of detection (LOD, S/N = 3) of 0.5 µg L-1 for EP and PP, and 0.7 µg L-1 for MP. Good recoveries over the range of 92.0-108.3% assured the accuracy of the amount of parabens distinguished in the non-spiked samples.

Determination of phthalate esters in drinking water and edible vegetable oil samples by headspace solid phase microextraction using graphene/polyvinylchloride nanocomposite coated fiber coupled to gas chromatography-flame ionization detector.

In the current study, a graphene/polyvinylchloride nanocomposite was successfully coated on a stainless steel substrate by a simple dip coating process and used as a novel headspace solid phase microextraction (HS-SPME) fiber for the extraction of phthalate esters (PEs) from drinking water and edible vegetable oil samples. The prepared SPME fibers exhibited high extractability for PEs (due to the dominant role of π-π stacking interactions and hydrophobic effects) yielding good sensitivity and precision when followed by a gas chromatograph with a flame ionization detector (GC-FID). The optimization strategy of the extraction process was carried out using the response surface method based on a central composite design. The developed method gave a low limit of detection (0.06-0.08µgL(-1)) and good linearity (0.2-100µgL(-1)) for the determination of the PEs under the optimized conditions (extraction temperature, 70±1°C; extraction time, 35min; salt concentration, 30% w/v; stirring rate, 900rpm; desorption temperature, 230°C; and desorption time, 4min) whereas the repeatability and fiber-to-fiber reproducibility were in the range 6.1-7.8% and 8.9-10.2%, respectively. Finally, the proposed method was successfully applied to the analysis of PEs in drinking water and edible oil samples with good recoveries (87-112%) and satisfactory precisions (RSDs<8.3%), indicating the absence of matrix effects in the proposed HS-SPME method.

Nano-structured gemini-based supramolecular solvent for the microextraction of cyhalothrin and fenvalerate.

A novel supramolecular solvent-based microextraction followed by high-performance liquid chromatography with ultraviolet detection method has been developed for the extraction and determination of two pyrethroid analytes, cyhalothrin and fenvalerate, in water and soil samples. The liquid-liquid-phase separation of surfactants has been used in analytical extraction. The surfactant-rich phase is a nano-structured liquid, recently named as a supramolecular solvent, generated from the amphiphiles. The alkyl carboxylic acid based supramolecular solvents were introduced before. Coacervates made up of gemini surfactant, consisting of two amphiphilic moieties, were first used as solvent. The effective parameters on extraction (i.e., type of organic solvent, the amount of surfactant and volume of tetrahydrofuran, sample solution pH, salt addition, ultrasonic and centrifugation time) were investigated and optimized. Under the optimum conditions, preconcentration factors of 110 and 145 were obtained for the analytes. The linearity was 0.5-200.0 µg/L with the correlation of determination of (R(2) ) ≥ 0.9984. The limit of detection of the method was (S/N = 3) 0.2 µg/L, and precisions in the range of 6.3-10.3% (RSDs, n = 5) were obtained. This method has been successfully applied to analyze real samples, and good recoveries in the range of 101.2-108.8% were obtained.

Zinc oxide/polypyrrole nanocomposite as a novel solid phase microextraction coating for extraction of aliphatic hydrocarbons from water and soil samples.

In this work, ZnO/PPy nanocomposite coating was fabricated on stainless steel and evaluated as a novel headspace solid phase microextraction (HS-SPME) fiber coating for extraction of ultra-trace amounts of environmental pollutants; namely, aliphatic hydrocarbons in water and soil samples. The ZnO/PPy nanocomposite were prepared by a two-step process including the electrochemical deposition of PPy on the surface of stainless steel in the first step, and the synthesis of ZnO nanorods by hydrothermal process in the pores of PPy matrix in the second step. Porous structure together with ZnO nanorods with the average diameter of 70 nm were observed on the surface by using scanning electron microscopy (SEM). The effective parameters on HS-SPME of hydrocarbons (i.e., extraction temperature, extraction time, desorption temperature, desorption time, salt concentration, and stirring rate) were investigated and optimized by one-variable-at-a-time method. Under optimized conditions (extraction temperature, 65±1°C; extraction time, 15 min; desorption temperature, 250°C; desorption time, 3 min; salt concentration, 10% w/v; and stirring rate, 1200 rpm), the limits of detection (LODs) were found in the range of 0.08-0.5 µg L(-1), whereas the repeatability and fiber-to-fiber reproducibility were in the range 5.4-7.6% and 8.6-10.4%, respectively. Also, the accuracies obtained for the spiked n-alkanes were in the range of 85-108%; indicating the absence of matrix effects in the proposed HS-SPME method. The results obtained in this work suggest that ZnO/PPy can be promising coating materials for future applications of SPME and related sample preparation techniques.

Application of a nanostructured supramolecular solvent for the microextraction of diphenylamine and its mono-nitrated derivatives from unburned single-base propellants.

A supramolecular solvent made up of nano-sized inverted hexagonal aggregates of 1-octanol is proposed for the microextraction of diphenylamine and its mono-nitrated derivatives in unburned single-base propellants. The procedure included the extraction of sub-gram quantities (30 mg) of homogenized propellant with 1.5 mL of the supramolecular solvent. Several conditions affecting extraction efficiency, for example the concentrations of the major components of the supramolecular solvent (tetrahydrofuran and alkanol), alkanol type, solvent pH, and extraction time, were investigated and optimized. The main forces for the microextraction of analytes in the nanostructured supramolecular solvent include both dispersion and hydrogen bond interactions. This mixed-mode mechanism resulted in high extraction efficiencies reaching low method detection limits (0.005-0.012 mg/g) without the need for extract evaporation. Under the optimum conditions, recoveries in samples ranged between about 82.6 and 98.7%. Compared to the reference method, the proposed method is simple and rapid, delivering accurate and precise results, and can be applied for routine determination of diphenylamine and its derivatives in propellants. The precision of the method, expressed as relative standard deviation, was about 4.3-10.9%.

DFT study of ozone dissociation on BC3 graphene with Stone-Wales defects.

Ozone (O3) adsorption on pristine Stone-Wales (SW) defective BC3 graphene-like sheets was investigated using density functional calculations. It was found that O3 is weakly adsorbed on the pristine sheet. Two types of SW-defective sheets were studied, SW-CC and SW-BC, in which a defect is formed by rotating a C-C or B-N bond, respectively. O3 molecules were found to be more reactive on SW-BC defective sheets. It was predicted that O3 molecules are reduced to O2 molecules on SW-BC sheets, overcoming an energy barrier of 34.2 kcal/mol(-1) at the B3LYP level of theory and 27.2 kcal/mol(-1) at the BP98 level of theory. Therefore, SW-BC sheets could potentially be employed as a metal-free catalyst for O3 reduction. The HOMO-LUMO gap of a SW-BC sheet decreases from 2.16 to 1.21 eV after O3 dissociation on its surface in the most stable state.

A comparison between emulsification of reverse micelle-based supramolecular solvent and solidification of vesicle-based supramolecular solvent for the microextraction of triazines.

Two approaches based on emulsification of reverse micelle-based supramolecular solvent microextraction (ERM-SSME) and solidification of vesicle-based supramolecular solvent microextraction (SV-SSME) were compared for the extraction and preconcentration of four triazines (cyanazine, simazine, prometon and propazine) from water samples. Different ERM-SSME and SV-SSME parameters influencing the extraction efficiency were studied and optimized. The results showed that both extraction methods exhibited good linearity, precision, enrichment factor, and detection limit. Under optimal conditions, the limits of detection were 0.3 and 0.5µgL(-1) for ERM-SSME and SV-SSME, respectively. The enrichment factors were from 330 to 505 and 285 to 421 for ERM-SSME and SV-SSME, respectively. The applicability of the proposed methods was examined by analyzing triazines in water samples and good results were obtained.

Supramolecular solvent-based hollow fiber liquid phase microextraction of benzodiazepines.

A new, efficient, and environmental friendly hollow fiber liquid phase microextraction (HF-LPME) method based on supramolecular solvents was developed for extraction of five benzodiazepine drugs. The supramolecular solvent was produced from coacervation of decanoic acid aqueous vesicles in the presence of tetrabutylammonium (Bu4N(+)). In this work, benzodiazepines were extracted from aqueous samples into a supramolecular solvent impregnated in the wall pores and also filled inside the porous polypropylene hollow fiber membrane. The driving forces for the extraction were hydrophobic, hydrogen bonding, and π-cation interactions between the analytes and the vesicular aggregates. High-performance liquid chromatography with photodiode array detection (HPLC-DAD) was applied for separation and determination of the drugs. Several parameters affecting the extraction efficiency including pH, hollow fiber length, ionic strength, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, the preconcentration factors were obtained in the range of 112-198. Linearity of the method was determined to be in the range of 1.0-200.0 µg L(-1) for diazepam and 2.0-200.0 µg L(-1) for other analytes with coefficient of determination (R(2)) ranging from 0.9954 to 0.9993. The limits of detection for the target benzodiazepines were in the range of 0.5-0.7 µg L(-1). The method was successfully applied for extraction and determination of the drugs in water, fruit juice, plasma and urine samples and relative recoveries of the compounds studied were in the range of 90.0-98.8%.

Solid phase extraction as a cleanup step before microextraction of diclofenac and mefenamic acid using nanostructured solvent.

A new pretreatment method, solid-phase extraction combined with supramolecular solvents, was proposed for the first time for extraction of diclofenac (DIC) and mefenamic acid (MEF) from urine and water samples. Supramolecular solvent (SUPRAS) is a nano-structured liquid, generated from the amphiphiles through a sequential self-assembly process occurring on two scales, molecular and nano. SUPRAS tested were generated from solutions of reverse micelles of decanoic acid (DeA) in tetrahydrofuran (THF) by addition of water, which acted as the coacervating agent. In the present study, due to matrix effect, drugs were first extracted from the samples by SPE. The extracted analytes were then eluted from the sorbent with THF, and the eluate was subjected to SUPRAS formation (SUPRASF) process. Finally, the analytes in the SUPRAS were separated and determined by HPLC-UV. Several parameters affecting the SPE-SUPRASF process were investigated and optimized. The new method provides enrichment factors in the range of 431-489 for MEF and DIC, respectively. Calibration plots are linear in the range of 2-200 µg L(-1) for MEF and 1-200 µg L(-1) for DIC, with correlation of determination (r(2)) ranging from 0.996 to 0.999. The method was successfully applied for extraction and determination of analytes in urine and water samples and relative recoveries of the studied compounds were obtained in the range of 90.4-103.8%.

Polythiophene-coated Fe3O4 superparamagnetic nanocomposite: synthesis and application as a new sorbent for solid-phase extraction.

In the present work, a novel type of superparamagnetic nanosorbent, polythiophene-coated Fe3O4 nanoparticles (Fe3O4@PTh NPs), have been successfully synthesized. The synthesized NPs were characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized Fe3O4@PTh NPs were applied as an efficient sorbent for extraction and preconcentration of several typical plasticizer compounds (di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and dioctyl adipate (DOA)) from environmental water samples. Separation of Fe3O4@PTh NPs from the aqueous solution was simply achieved by applying external magnetic field. Separation and determination of the extracted plasticizers was performed by gas chromatography-flame ionization detection (GC-FID). Several variables affecting the extraction efficiency of the analytes i.e., amount of NPs sorbent, salt concentration, extraction time, and desorption conditions were investigated and optimized. The best working conditions were as follows: amount of sorbent, 100 mg; NaCl concentration, 30% (w/v); sample volume, 45 mL; extraction time, 10 min; and 100 µL of ethyl acetate for desorption of the analytes within 2 min. Under optimized conditions, preconcentration factors for DBP, DEHP, and DOA were obtained as 86, 194, and 213, respectively. The calibration curves were linear (R(2)>0.998) in the concentration range of 0.4-100 µg L(-1) for both DEHP and DOA and 0.7-100 µg L(-1) for DBP. The limits of detection (LODs) were obtained in the range of 0.2-0.4 µg L(-1). The intra-day relative standard deviations (RSDs%) based on four replicates were obtained in the range of 4.0-12.3%. The proposed procedure was applied to analysis of water samples including river water, bottled mineral water, and boiling water exposed to polyethylene container (after cooling) and recoveries between 85 and 99% and RSDs lower than 12.8% were obtained.

Ultrasound-assisted liquid-phase microextraction based on a nanostructured supramolecular solvent.

Novel ultrasonically enhanced supramolecular solvent microextraction (USESSM) then high-performance liquid chromatography with ultraviolet detection have been used for extraction and determination of phthalates in water and cosmetics. Coacervates consisting of decanoic acid-based nano-structured aggregates, specifically reverse micelles, have been used the first time as solvents for ultrasound-assisted emulsification microextraction (USAEME). Sonication accelerated mass transfer of the target analytes into the nano-structured solvent from the aqueous sample, thus reducing extraction time. Several conditions affecting extraction efficiency, for example the concentrations of major components of the supramolecular solvent (tetrahydrofuran and decanoic acid), sample solution pH, salt addition, and ultrasonication time, were investigated and optimized. Under the optimum conditions, preconcentration of the analytes ranged from 176 to 412-fold and the linear range was 0.5-100 µg L(-1), with correlation coefficients (R(2)) ≥ 0.9984. The detection sensitivity of the method was excellent, with limits of detection (LOD, S/N = 3) in the range 0.10-0.70 µg L(-1) and precision in the range 4.1-11.7 % (RSD, n = 5). This method was successfully used for analysis of phthalates in water and cosmetics, with good recovery of spiked phthalates (91.0-108.5 %).

Surfactant roles in modern sample preparation techniques: a review.

The pressure to decrease organic solvent usage in laboratories is increasing. Thus miniaturization and improvement of sample handling using alternatives is a challenge that has been discussed by several researchers. From this perspective, surfactant-based sample preparations were an educated choice. Since the introduction of cloud point extraction by Watanabe, considerable studies have been focused on the chemical properties of surfactants in the extraction methods. The unique properties of surfactants make them flexible agents for different miniaturized sample preparation techniques based on solid- or liquid-phase extraction. As a result, the use of surfactants with different roles in sample-preparation methodologies (such as surfactant as an emulsifier, surfactant rich phase as an extraction medium, ion pair-based extraction, hemimicelle/admicelle extraction, surfactant-coated magnetic nanoparticle, solid-phase microextraction with micellar desorption) is an important contribution to minimizing the problems arising from preliminary operations, which are the weakest step in analytical measurement. This paper reviews the literature dealing with the application of surfactant-based sample preparations to the separation and the preconcentration of organic and inorganic species.

Reverse micelle-mediated dispersive liquid-liquid microextraction of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid.

A supramolecular solvent consisting of reverse micelles of decanoic acid, dispersed in a continuous phase of tetrahydrofuran:water, was proposed as an efficient microextraction technique for extraction of selected chlorophenoxy acid herbicides from water samples prior to high-performance liquid chromatography UV determination. The disperser solvent (1.0 mL tetrahydrofuran) containing 20 mg decanoic acid was rapidly injected into 10.0 mL of water sample. After centrifugation, the reverse micelle-rich phase (25 ± 0.5 µL) was floated at top of the home-designed centrifuge tube. The solvent was collected and 20 µL of it was injected into high-performance liquid chromatography for analysis. The results showed that the in situ solvent formation and extraction process can be completed in a few seconds. Under the optimal conditions, limits of detection of the method for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid were in the range of 0.5-0.8 µg L(-1) and the repeatability of the proposed method, expressed as relative standard deviation, varied in the range of 2.5-3.2%. Linearity was found to be in the range of 1-200 µg L(-1) and the preconcentration factors were between 148 and 157. The mean percentage recoveries exceeded 92.0% for all the spiking levels in real water samples.