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.     

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 (R²) 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%.     

Comparative study of hollow-fiber liquid-phase micro-extraction and an aqueous two-phase system for determination of phytohormones in soil

Two methods, hollow-fiber liquid-phase micro-extraction (HF-LPME) and an aqueous two-phase system (ATPS), have been systematically optimized and compared for extraction and determination of phytohormones in soil by high-performance liquid chromatography (HPLC). The effects on extraction of conditions including solvent type and volume, extraction time, temperature, and amount of salt were evaluated. It was shown that ATPS was superior to HF-LPME for determination of paclobutrazol and uniconazole under the optimum conditions. The limits of detection (LODs) of ATPS were 0.002 μg g(-1) for uniconazole and 0.01 μg g(-1) for paclobutrazol, whereas LODs of HF-LPME were 0.005 μg g(-1) and 0.03 μg g(-1), respectively. Relative standard deviations (RSDs, n=5) and recovery were in the range 1.7-5.3 % and 86-102 %, respectively, for ATPS and 6.7-7.9 % and 40-60 % for HF-LPME. In addition, the advantages of ATPS were shorter extraction time, suitable for simultaneous pretreatment of batches of samples, and higher extraction capacity. ATPS was therefore applied to the determination of paclobutrazol and uniconazole in real soil samples. Uniconazole was detected in all the samples analyzed whereas paclobutrazol was not found.     

中空纤维支载离子液体液液微萃取法检测环境水体中的三氯生

三氯生(5 Chloro-2-(2,4-dichlorophenoxy) phenol,TCS)是一种新型环境水体污染物,具有潜在的生态与健康风险,因此发展合适的分析方法来检测水环境中这类化合物极其必要.本研究以1-辛基-3-甲基咪唑六氟磷酸离子液体( [C8 MIM][PF6])为萃取剂,基于中空纤维的离子液体液液微萃取方法,结合HPLC/UV用于环境水样中TCS的分析测定;通过对各参数(萃取剂、供体相的体积、供体相pH值、离子强度、萃取时间等)的优化在最优条件下(样品相体积为50 mL,pH值2,盐浓度为0.2 mol/L,200 r/min振荡萃取8 h),获得了较高的富集倍数(907倍)、较低的检出限(0.05 μg/L,RSD=7.4％,n=6)和较好的线性范围(0.1～100 μg/L);以4种环境水样加标实验对方法的准确性进行评估,其回收率可达94.2％～108.5％(RSD=5.5％～8.0％,n=6);本方法可广泛应用于环境水体中痕量TCS的分析检测.     

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 (R²) ≥ 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.     

Microwave-assisted extraction combined with dispersive liquid-liquid microextraction as a new approach to determination of chlorophenols in soil and sediments

A new method was applied for extraction of five chlorophenols from soil and marine sediment samples. Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction followed by semi-automated in-syringe back-extraction technique was used as an extraction technique. Microwave-assisted extraction was performed by using 2.0 mL of alkaline water at pH 10.0. After extraction, the pH of extraction solution was adjusted at 6.0 and dispersive liquid-liquid microextraction procedure was done using 1.0 mL of acetone as a disperser solvent and 37.0 μL of chlorobenzene as extraction solvent. About 20.0 ± 0.5 μL sedimented phase was collected after centrifugation step. Then, chlorophenols were back extracted into 20 μL of alkaline water at pH 12.0 within the microsyringe. Finally, 20.0 μL of aqueous solution was injected into high performance liquid chromatography with ultra violet detection for analysis. The obtained recovery and preconcentration factors for the analytes were in the range of 68.0-82.0% and 25-30, respectively, with relative standard deviations ≤7.6%. The limits of the detection were found in the range of 0.0005-0.002 mg/kg. The method provides a simple and fast procedure for the extraction and determination of chlorophenols in soil and marine sediment samples.     

Determination of anti‐malaria agent chloroquine using single drop liquid‐liquid‐liquid microextraction

A simple, sensitive, and inexpensive single drop liquid‐liquid‐liquid microextraction combined with isocratic RP‐HPLC and UV detection was developed for the determination of anti‐malaria drug, chloroquine. The target compound was extracted from alkaline aqueous sample solution (adjusted to 0.5 mol/L sodium hydroxide) through a thin layer of organic solvent membrane and back‐extracted to an acidic acceptor drop (adjusted to 0.02 mol/L phosphoric acid) suspended on the tip of a 25 μL HPLC syringe in the organic layer. This syringe was also used for direct injection after extraction. The linear range was 1–200 μg/L. The LOD and LOQ were 0.3 and 1.0 μg/L, respectively. Intra‐and inter‐day precisions were less than 2.0 and 2.3%, respectively. The real samples were successfully analyzed using the proposed method. The recoveries of spiked samples were more than 94.6%.     

Supramolecular-based dispersive liquid-liquid microextraction: a novel sample preparation technique utilizes coacervates and reverse micelles

The present study reports a novel sample enrichment method termed supramolecular-based dispersive liquid-liquid microextraction (SM-DLLME). The SM solvent selected was made up of reversed micelles of decanoic acid dispersed in tetrahydrofuran (THF)-water. THF plays double role, not only acts as a disperser solvent but also causes self-assembly of decanoic acid. The contaminant used as a model was Malachite Green (MG). It was a cationic dye and was preconcentrated without any derivatization or ion-pair formation reaction. In SM-DLLME, the most important advantages of DLLME technique and preconcentration strategy based on the coacervation and reverse micelles have come together. Moreover, in this method, disadvantages of DLLME such as extraction capability of only hydrophobic analytes and hiring toxic and hazardous organic solvents as the extraction solvent and disadvantages of coacervation-based extraction method such as tedious, labor-intensive and time-consuming stirring procedure have been avoided. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 5.00 mL of sample, the enhancement factor was 52, limit of detection (LOD) was 4 μg/L and relative standard deviations (RSDs) for 145 and 36 μg/L of MG in textile industry wastewater were 1.8 and 3.2%, respectively (n = 6).     

Determination of trace benzene derivatives in aqueous samples by ultrasonic enhanced hollow fiber liquid-phase microextraction prior to gas chromatography

A new method was developed for the determination of trace compounds in water samples using ultrasonic-enhanced hollow fiber liquid-phase microextraction (U-HF-LPME). The ultrasonic radiation, which produces mechanical vibration and ultrasonic cavitation, could be used for accelerating the diffusion mass transfer process. Thus, ultrasonic was introduced into the HF-LPME procedure to enhance the mass-transfer rate during the aqueous and extraction solvent phases. Experimental parameters such as the extraction solvent, the extraction time, the ultrasonic frequency and power, the extractant volume, and ionic strength of the sample were assessed and optimized. Under optimal conditions, HF-LPME was achieved within 10 min. The high enrichment factor in the range of 120-666 and a good relative recovery in the range of 97-103% were evaluated with the relative standard deviations (RSDs, n = 5) of 0.3-7.0%. The limit of detection was in the range of 0.8-3.0 μg/L. The method was applied to the analysis of groundwater, lake water, and seawater. The results showed that the method can determine trace benzene derivatives in real samples with RSD values of 1.1-4.2%. The results demonstrated that U-HF- LPME is a rapid, accurate, and effective sample preparation method, and could be successfully applied for the determination of trace compounds in analytical chemistry.     

分散液液微萃取-气相色谱/质谱法测定水中多环芳烃

用分散液液微萃取-气相色谱/质谱法测定水样中的16种多环芳烃(PAHs)。通过实验确定最佳萃取条件为:20μL四氯化碳作萃取剂,1.0 mL乙腈作分散剂,超声萃取1 min。在优化条件下,多环芳烃的富集倍数达到216～511,方法在0.05～50μg/L范围内呈良好的线性关系,相关系数(R2)在0.9873～0.9983之间,检出限为0.0020～0.14μg/L。相对标准偏差(RSD)在3.82%～12.45%(n=6)之间。该方法成功用于实际水样中痕量多环芳烃的测定。     

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 %).     

Use of volatile organic solvents in headspace liquid‐phase microextraction by direct cooling of the organic drop using a simple cooling capsule

A low‐cost and simple cooling‐assisted headspace liquid‐phase microextraction device for the extraction and determination of 2,6,6‐trimethyl‐1,3 cyclohexadiene‐1‐carboxaldehyde (safranal) in Saffron samples, using volatile organic solvents, was fabricated and evaluated. The main part of the cooling‐assisted headspace liquid‐phase microextraction system was a cooling capsule, with a Teflon microcup to hold the extracting organic solvent, which is able to directly cool down the extraction phase while the sample matrix is simultaneously heated. Different experimental factors such as type of organic extraction solvent, sample temperature, extraction solvent temperature, and extraction time were optimized. The optimal conditions were obtained as: extraction solvent, methanol (10 μL); extraction temperature, 60°C; extraction solvent temperature, 0°C; and extraction time, 20 min. Good linearity of the calibration curve (R² = 0.995) was obtained in the concentration range of 0.01–50.0 μg/mL. The limit of detection was 0.001 μg/mL. The relative standard deviation for 1.0 μg/mL of safranal was 10.7% (n = 6). The proposed cooling‐assisted headspace liquid‐phase microextraction device was coupled (off‐line) to high‐performance liquid chromatography and used for the determination of safranal in Saffron samples. Reasonable agreement was observed between the results of the cooling‐assisted headspace liquid‐phase microextraction high‐performance liquid chromatography method and those obtained by a validated ultrasound‐assisted solvent extraction procedure.     

Determination of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction with high‐performance liquid chromatography

A novel method has been developed for the analysis of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction combined with HPLC and fluorescence detection. Maize samples were extracted with methanol/water (80:20, v/v) and the extraction solution was then used as the dispersive solvent in the microextraction procedure. The analyte was rapidly transmitted to a small volume of ionic liquid and was determined by HPLC. Various parameters affecting the recovery of the mycotoxin were investigated, such as the type and volume of the extraction solvent, the type and volume of the dispersive solvent, the pH of the aqueous phase, the salt addition, and the time of vortex and centrifugation. Under the optimal experimental conditions, a good linearity of the analyte was obtained in the range of 1.0–1000.0 μg/L with the correlation coefficient of 0.9998. The limit of detection (S/N = 3) and quantification (S/N = 10) were 0.3 and 1.0 μg/kg, and the mean recoveries ranged from 83.5 to 94.9%, with a relative standard deviation less than 5.0%. The proposed method was demonstrated to be simple, cheap, quick, and highly selective and was successfully applied to the determination of zearalenone in maize products.     

液相色谱串联质谱测定纺织品中的四溴双酚A

采用固相萃取/超快速液相色谱-串联质谱技术(SPE/UFLC-MS/MS)建立了纺织品中四溴双酚A的测定方法。样品经甲醇超声提取,C_(18)-SPE净化后分析,在串联质谱电喷雾(ESI)离子多反应监测(MRM)模式下检测,以保留时间以及特征离子对进行定性、定量分析。实验结果表明,四溴双酚A在1.0~100.0μg/L范围内呈良好的线性关系。称样量为1.0 g时,方法的定量下限为1.0μg/kg。平均回收率为80.9%~95.3%,相对标准偏差(RSDs)为2.3%~5.9%。所建方法快速、准确、灵敏,可用于纺织中四溴双酚A的分析测定。     

Comparison of hollow fiber liquid phase microextraction and dispersive liquid-liquid microextraction for the determination of organosulfur pesticides in environmental and beverage samples by gas chromatography with flame photometric detection

Two methods based on hollow fiber liquid phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME), have been critically compared for the analysis of organosulfur pesticides (OSPs) in environmental and beverage samples by gas chromatography-flame photometric detection (GC-FPD). Experimental conditions including extraction solvent, solvent volume, extraction time, temperature and ionic strength have been investigated for both HF-LPME and DLLME. Under the optimal conditions, the limits of detection for the six target OSPs (malathion, chlorpyrifos, buprofezin, triazophos, carbosulfan and pyridaben) obtained by HF-LPME-GC-FPD and DLLME-GC-FPD were ranged from 1.16 microg/L to 48.48 microg/L and 0.21 microg/L to 3.05 microg/L, respectively. The relative standard deviations (RSDs, n=5) were in the range of 3.4-8.0% and 8.5-13.7%with the enrichment factors (EFs) of 27-530 and 176-946 folds for HF-LPME-GC-FPD and DLLME-GC-FPD, respectively. Both methods were found to be simple, fast, efficient, and inexpensive. Compared with HF-LPME, the advantages of DLLME technique were less extraction time, suitable for batches of samples pretreatment simultaneously, a higher extraction capacity when analyzing simple samples such as water samples. While for the analysis of complicated matrix samples such as soil and beverage samples, HF-LPME was demonstrated to be more robust and more suitable. Both methods were applied to the analysis of six OSPs in different waters, soil and beverage samples, and no target OSPs was found in these samples. For analysis of the spiked samples, the recovery of 81.7-114.4% with RSDs of 0.6-9.6% were obtained for HF-LPME, and the recovery of 78.5-117.2% with RSDs of 0.6-11.9% were obtained for DLLME.     

中空纤维膜液相微萃取-超高效液相色谱测定蒙药毛勒日-达布斯-4汤中两种生物碱

建立了将中空纤维膜液相微萃取（HF-LPME）技术与超高效液相色谱（UPLC）技术联用检测蒙药毛勒日-达布斯-4汤中2种生物碱（胡椒碱和荜茇宁）的分析方法。通过考察该HF-LPME方法的影响参数，优化了萃取实验条件。HF-LPME优化条件如下：空隙率大于50%的偏氟乙烯中空纤维膜，萃取溶剂为正辛醇，氯化钠质量浓度为10 g/L，室温振荡，振荡速度为173 r/min，萃取时间为128 min。结果表明：该HF-LPME-UPLC方法对胡椒碱和荜菝宁的检出限（LOD）分别为2.2和2.5 μg/L，相对标准偏差不大于7.8%（n=5）。胡椒碱和荜菝宁分别在100~8500 和8.3~5000 μg/L范围内具有良好的线性关系，胡椒碱和荜茇宁的富集倍数分别为59和65。该方法简便、快速、准确、环保，适用于蒙药中胡椒碱和荜菝宁含量的测定。     

A hydrophobic deep eutectic solvent‐based vortex‐assisted dispersive liquid–liquid microextraction combined with HPLC for the determination of nitrite in water and biological samples

In recent years, hydrophobic deep eutectic solvents as new generation of green solvents have attracted wide attention in liquid microextraction technique. In this article, four hydrophobic deep eutectic solvents composed of trioctylmethylammonium chloride and oleic acid were designed and prepared firstly. Combined with high‐performance liquid chromatography, these deep eutectic solvents were used as an extraction solvent in vortex‐assisted dispersive liquid–liquid microextraction for the selective enrichment and indirect determination of trace nitrite from real water and biological samples. This method is based on the diazotization‐coupling reaction of nitrite with p‐nitroaniline and diphenylamine in acidic water, and then the nitrite is quantified indirectly by measuring the obtained azo compounds. Some factors influencing the extraction efficiency, including the reaction and extraction conditions, were investigated. Under the optimized conditions, the method has a linear range of 1–300 μg/L with a correlation coefficient of 0.9924, limit of detection of 0.2 μg/L, limit of quantitation of 1 μg/L, intraday and interday relative standard deviations of 4.0 and 6.0%. This method was successfully applied in determination of nitrite from three environmental water and two biological samples with the recovery in the range of 90.5–115.2%. In addition, these results were well agreement with those obtained by the conventional Griess method.     

悬浮固化-分散液液微萃取-液相色谱-串联质谱测定纺织废水中磷系阻燃剂

建立了悬浮固化-分散液液微萃取结合液相色谱-串联质谱测定纺织废水中5种痕量磷系阻燃剂的方法。通过对萃取过程中萃取剂、分散剂的种类与体积、盐浓度、溶液pH值等对萃取效率的影响因素优化,确立了最佳萃取条件。采用了密度小于水的十一烷醇（400 μL）为萃取剂,甲醇（300 μL）为分散剂,控制溶液pH值在6~9之间,NaCl添加量为2 g,萃取时间为涡旋2 min。在优化的萃取条件下,该方法在2~100 μg/L均有良好的线性关系,相关系数大于0.995,除二（2,3-二溴丙基）磷酸酯（BIS）的检出限为5 μg/L外,三（2-氯乙基）磷酸酯（TCEP）、三（1,3-二氯-异丙基）磷酸酯（TDCP）、三（1-氮丙啶基）氧化膦（TEPA）和三（2,3-二溴丙基）磷酸酯（TRIS）的检出限均为2 μg/L。后整理、染色和印花等实际废水样品加标试验表明,方法的平均回收率为71.6%~114.5%,RSD为2.7%~11.2%（n=6）。对11个样品进行检测,其中3个废水样品检出TCEP与TDCP化合物,含量为2.6~3.4 μg/L。本方法简单,快速,灵敏度好且环保绿色,能够对纺织废水中的5种痕量磷系阻燃剂进行准确的定性与定量检测。     

Tandem use of solid-phase extraction and dispersive liquid-liquid microextraction for the determination of mononitrotoluenes in aquatic environment

Solid‐phase extraction (SPE) in tandem with dispersive liquid–liquid microextraction (DLLME) has been developed for the determination of mononitrotoluenes (MNTs) in several aquatic samples using gas chromatography‐flame ionization (GC‐FID) detection system. In the hyphenated SPE‐DLLME, initially MNTs were extracted from a large volume of aqueous samples (100 mL) into a 500‐mg octadecyl silane (C₁₈) sorbent. After the elution of analytes from the sorbent with acetonitrile, the obtained solution was put under the DLLME procedure, so that the extra preconcentration factors could be achieved. The parameters influencing the extraction efficiency such as breakthrough volume, type and volume of the elution solvent (disperser solvent) and extracting solvent, as well as the salt addition, were studied and optimized. The calibration curves were linear in the range of 0.5–500 μg/L and the limit of detection for all analytes was found to be 0.2 μg/L. The relative standard deviations (for 0.75 μg/L of MNTs) without internal standard varied from 2.0 to 6.4% (n=5). The relative recoveries of the well, river and sea water samples, spiked at the concentration level of 0.75 μg/L of the analytes, were in the range of 85–118%.     

Preconcentration and determination of methyl methacrylate by dispersive liquid–liquid microextraction

This article describes the preconcentration of methyl methacrylate in produced water by the dispersive liquid–liquid microextraction using extraction solvents lighter than water followed by gas chromatography. In the present experiments, 0.4 mL dispersive solvent (ethanol) containing 15.0 μL extraction solvent (toluene) was rapidly injected into the samples and followed by centrifuging and direct injection into the gas chromatograph equipped with flame ionization detector. The parameters affecting the extraction efficiency were evaluated and optimized including toluene (as extraction solvent), ethanol (as dispersive solvent), 15 μL and 0.4 mL (as the volume of extraction and dispersive solvents, respectively), pH 7, 20% ionic strength, and extraction's temperature and time of 20°C and 10 min, respectively. Under the optimum conditions, the figures of merits were determined to be LOD = 10 μg/L, dynamic range = 20–180 μg/L, RSD = 11% (n = 6). The maximum recovery under the optimized condition was determined to be 79.4%.