Salting‐out assisted liquid–liquid extraction coupled to dispersive liquid–liquid microextraction for the determination of chlorophenols in wine by high‐performance liquid chromatography

A novel procedure of sample preparation combined with high‐performance liquid chromatography with diode array detection is introduced for the analysis of highly chlorinated phenols (trichlorophenols, tetrachlorophenols, and pentachlorophenol) in wine. The main features of the proposed method are (i) low‐toxicity diethyl carbonate as extraction solvent to selectively extract the analytes without matrix effect, (ii) the combination of salting‐out assisted liquid–liquid extraction and dispersive liquid–liquid microextraction to achieve an enrichment factor of 334–361, and (iii) the extract is analyzed by high‐performance liquid chromatography to avoid derivatization. Under the optimum conditions, correlation coefficients (r) were >0.997 for calibration curves in the range 1–80 ng/mL, detection limits and quantification limits ranged from 0.19 to 0.67 and 0.63 to 2.23 ng/mL, respectively, and relative standard deviation was <8%. The method was applied for the determination of chlorophenols in real wines, with recovery rates in the range 82–104%.     

Development of new extraction method based on liquid–liquid–liquid extraction followed by dispersive liquid–liquid microextraction for extraction of three tricyclic antidepressants in plasma samples

In the present study, a new extraction method based on a three–phase system, liquid–liquid–liquid extraction, followed by dispersive liquid–liquid microextraction has been developed and validated for the extraction and preconcentration of three commonly prescribed tricyclic antidepressant drugs – amitriptyline, imipramine, and clomipramine – in human plasma prior to their analysis by gas chromatography–flame ionization detection. The three phases were an aqueous phase (plasma), acetonitrile and n–hexane. The extraction mechanism was based on the different affinities of components of the biological sample (lipids, fatty acids, pharmaceuticals, inorganic ions, etc.) toward each of the phases. This provided high selectivity toward the analytes since most interferences were transferred into n–hexane. In this procedure, a homogeneous solution of the aqueous phase (plasma) and acetonitrile (water–soluble extraction solvent) was broken by adding sodium sulfate (as a phase separating agent) and the analytes were extracted into the fine droplets of the formed acetonitrile. Next, acetonitrile phase was mixed with 1,2–dibromoethane (as a preconcentration solvent at microliter level) and then the microextraction procedure mentioned above was performed for further enrichment of the analytes. Under the optimum extraction conditions, limits of detection and lower limits of quantification for the analytes were obtained in the ranges of 0.001–0.003 and 0.003–0.010 μg mL⁻¹, respectively. The obtained extraction recoveries were in the range of 79–98%. Intra– and inter–day precisions were < 7.5%. The validated method was successfully applied for determination of the selected drugs in human plasma samples obtained from the patients who received them.     

Trace analysis of some organophosphorus pesticides in rice samples using ultrasound‐assisted dispersive liquid–liquid microextraction and high‐performance liquid chromatography

An ultrasound‐assisted dispersive liquid–liquid microextraction based on solidification of a floating organic drop method followed by high‐performance liquid chromatography was developed for the extraction, preconcentration, and determination of trace amounts of organophosphorus pesticides in rice samples. Variables affecting the performance of both steps were thoroughly investigated. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, recoveries for rice sample are in the range of 58.0–66.0%. The calibration graphs are linear in the range of 4–800 μg/kg and, limits of detection and limits of quantification are in the range of 1.5–3 and 4.2–8.5 μg/kg, respectively. The relative standard deviation for 50.0 μg/kg of organophosphorus pesticides in rice sample are in the range of 4.4–5.1% (n = 5). The obtained results show that proposed method is a fast and simple method for the determination of pesticides in cereals.     

Application of dispersive liquid–liquid microextraction followed by HPLC–MS/MS for the trace determination of clotrimazole in environmental water samples

A method for the analysis of clotrimazole was developed with dispersive liquid–liquid microextraction for sample pre‐concentration and HPLC–MS/MS for analysis. A linear ion trap was used for the confirmation of clotrimazole identity in the samples. The developed method enables the analysis of clotrimazole in river water and sewage effluent from wastewater treatment plants with a LOQ of 0.7 ng/L. Environmental monitoring of clotrimazole was undertaken. Samples from river water and sewage effluents were analysed over a one‐year period. Clotrimazole was found in every tested sample with concentration range from 1 to 31 ng/L. The amount of clotrimazole in tested samples was highly dependent on sampling season. The highest results were obtained in summer and autumn.     

Vortex‐assisted extraction combined with dispersive liquid–liquid microextraction for the determination of polycyclic aromatic hydrocarbons in sediment by high performance liquid chromatography

A simple, rapid, and efficient method, vortex‐assisted extraction followed by dispersive liquid–liquid microextraction (DLLME) has been developed for the extraction of polycyclic aromatic hydrocarbons (PAHs) in sediment samples prior to analysis by high performance liquid chromatography fluorescence detection. Acetonitrile was used as collecting solvent for the extraction of PAHs from sediment by vortex‐assisted extraction. In DLLME, PAHs were rapidly transferred from acetonitrile to dichloromethane. Under the optimum conditions, the method yields a linear calibration curve in the concentration range from 10 to 2100 ng g^?1 for fluorene, anthracene, chrysene, benzo[k]fluoranthene, and benzo[a]pyrene, and 20 to 2100 ng g^?1 for other target analytes. Coefficients of determinations ranged from 0.9986 to 0.9994. The limits of detection, based on signal‐to‐noise ratio of three, ranged from 2.3 to 6.8 ng g^?1. Reproducibility and recoveries was assessed by extracting a series of six independent sediment samples, which were spiked with different concentration levels. Finally, the proposed method was successfully applied in analyses of real nature sediment samples. The proposed method extended and improved the application of DLLME to solid samples, which greatly shorten the extraction time and simplified the extraction process.     

In‐syringe‐assisted dispersive liquid–liquid microextraction coupled to gas chromatography with mass spectrometry for the determination of six phthalates in water samples

A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in‐syringe dispersive liquid–liquid microextraction, coupled as a front end to GC–MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly. The denser‐than‐water organic droplets released in the extraction step, were accumulated at the head of the syringe, where the sedimented fraction was transferred to a rotary micro‐volume injection valve where finally was introduced by an air stream into the injector of the GC through a stainless‐steel tubing used as interface. Factors affecting the microextraction efficiency were optimized using multivariate optimization. Figures of merit of the proposed method were evaluated under optimal conditions, achieving a detection limit in the range of 0.03–0.10 μg/L, while the RSD% value was below 5% (n = 5). A good linearity (0.9956 ≥ r² ≥ 0.9844) and a broad linear working range (0.5–120 μg/L) were obtained. The method exhibited enrichment factors and recoveries, ranging from 14.11–16.39 and 88–102%, respectively.     

Simultaneous determination of six synthetic phenolic antioxidants in edible oils using dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography with diode array detection

A simple, rapid, organic‐solvent‐ and sample‐saving pretreatment technique, called dispersive liquid–liquid microextraction, was developed for the determination of six synthetic phenolic antioxidants from edible oils before high‐performance liquid chromatography with diode array detection. The entire procedure was composed of a two‐step microextraction and a centrifugal process and could be finished in about 5 min, only consuming only 25 mg of sample and 1 mL of the organic solvent for each extraction. The influences of several important parameters on the microextraction efficiency were thoroughly investigated. Recovery assays for oil samples were spiked at three concentration levels, 50, 100 and 200 mg/kg, and provided recoveries in the 86.3–102.5% range with a relative standard deviation below 3.5%. The intra‐day and inter‐day precisions for the analysis were less than 3.8%. The proposed method was successfully applied for the determination of synthetic phenolic antioxidants in different oil samples, and satisfactory results were obtained. Thus, the developed method represents a viable alternative for the quality control of synthetic phenolic antioxidant concentrations in edible oils.     

Accelerated solvent extraction combined with dispersive liquid–liquid microextraction before gas chromatography with mass spectrometry for the sensitive determination of phenols in soil samples

A method combining accelerated solvent extraction with dispersive liquid–liquid microextraction was developed for the first time as a sample pretreatment for the rapid analysis of phenols (including phenol, m‐cresol, 2,4‐dichlorophenol, and 2,4,6‐trichlorophenol) in soil samples. In the accelerated solvent extraction procedure, water was used as an extraction solvent, and phenols were extracted from soil samples into water. The dispersive liquid–liquid microextraction technique was then performed on the obtained aqueous solution. Important accelerated solvent extraction and dispersive liquid–liquid microextraction parameters were investigated and optimized. Under optimized conditions, the new method provided wide linearity (6.1–3080 ng/g), low limits of detection (0.06–1.83 ng/g), and excellent reproducibility (<10%) for phenols. Four real soil samples were analyzed by the proposed method to assess its applicability. Experimental results showed that the soil samples were free of our target compounds, and average recoveries were in the range of 87.9–110%. These findings indicate that accelerated solvent extraction with dispersive liquid–liquid microextraction as a sample pretreatment procedure coupled with gas chromatography and mass spectrometry is an excellent method for the rapid analysis of trace levels of phenols in environmental soil samples.     

Solid‐phase extraction combined with dispersive liquid–liquid microextraction for the determination of pyrethroid pesticides in wheat and maize samples

A rapid, selective and sensitive sample preparation method based on solid‐phase extraction combined with the dispersive liquid–liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid‐phase extraction and dispersive liquid–liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid‐phase extraction and dispersive liquid–liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.     

Determination of aromatic amines from textiles using dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction procedure coupled with GC‐MS is described for preconcentration and determination of banned aromatic amines from textile samples. Experimental conditions affecting the microextraction procedure were optimized. A mixture of 30 μL chlorobenzene (extraction solvent) and 800 μL ACN (disperser solvent), 5 min extraction time, and 5 mL aqueous sample volume were chosen for the best extraction efficiency by the proposed procedure. Satisfactory linearity (with correlation coefficients >0.9962) and repeatability (<9.78%) were obtained for all 20 aromatic amines; detection limits attained were much lower than the standardized liquid–liquid method. The proposed method has advantages of being quicker and easier to operate, and lower consumption of organic solvent.     

Dispersive solid‐phase extraction followed by vortex‐assisted dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge

A novel dispersive solid‐phase extraction combined with vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high‐performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean‐up of the extract was conducted by dispersive solid‐phase extraction using activated carbon as the sorbent. The vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1‐undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2–500 ng/g with correlation coefficients (r) of 0.9993–0.9999. The limits of detection were in the range of 0.08–0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography for the forensic determination of methamphetamine in human urine

Determination of methamphetamine in forensic laboratories is a major issue due to its health and social harm. In this work, a simple, sensitive, and environmentally friendly method based on ionic liquid dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography was established for the analysis of methamphetamine in human urine. 1‐Octyl‐3‐methylimidazolium hexafluorophosphate with the help of disperser solvent methanol was selected as the microextraction solvent in this process. Various parameters affecting the extraction efficiency of methamphetamine were investigated systemically, including extraction solvent and its volume, disperser solvent and its volume, sample pH, extraction temperature, and centrifugal time. Under the optimized conditions, a good linearity was obtained in the concentration range of 10–1000 ng/mL with determination coefficient >0.99. The limit of detection calculated at a signal‐to‐noise ratio of 3 was 1.7 ng/mL and the relative standard deviations for six replicate experiments at three different concentration levels of 100, 500, and 1000 ng/mL were 6.4, 4.5, and 4.7%, respectively. Meanwhile, up to 220‐fold enrichment factor of methamphetamine and acceptable extraction recovery (>80.0%) could be achieved. Furthermore, this method has been successfully employed for the sensitive detection of a urine sample from a suspected drug abuser.     

Coupling of homogeneous liquid–liquid extraction and dispersive liquid–liquid microextraction for the extraction and preconcentration of polycyclic aromatic hydrocarbons from aqueous samples followed by GC with flame ionization detection

In the present study, a simple and rapid method for the extraction and preconcentration of some polycyclic aromatic hydrocarbons in water samples has been developed. In this method, two sample preparation methods were combined to obtain high extraction recoveries and enrichment factors for sensitive analysis of the selected analytes. In the first stage of the method, a homogeneous solution containing an aqueous solution and cyclohexyl amine is broken by the addition of a salt. After centrifugation, the upper collected phase containing the extracted analytes is subjected to the following dispersive liquid–liquid microextraction method. Rapid injection of the mixture of cyclohexyl amine resulted from the first stage and 1,1,2‐trichloroethane (as an extraction solvent) into an acetic acid solution is led to form a cloudy solution. After centrifuging, the fine droplets of the extraction solvent are settled down in the bottom of the test tube, and an aliquot of it is analyzed by gas chromatography. Under the optimum extraction conditions, enrichment factors and limits of detection for the studied analytes were obtained in the ranges of 616–752 and 0.08–0.20 μg/L, respectively. The simplicity, high extraction efficiency, short sample preparation time, low cost, and safety demonstrated the efficiency of this method relative to other approaches.     

Liquid chromatographic determination of benomyl in water samples after dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method combined with solvolysis reaction for extraction of the carbamate fungicide benomyl as carbendazim from water samples is described. The method is based on the extraction of benomyl from acidified sample solution and its conversion into carbendazim via solvolysis reaction with DMF as organic solvent. The proposed DLLME method was followed by HPLC with fluorimetric detection for determination of benomyl. The proposed method has good linearity (0.998) with wide linear dynamic range (0.01–25 mg/L) and low detection limit (0.0033 mg/L), making it suitable for benomyl determination in water samples.     

Optimization of an accelerated solvent extraction dispersive liquid–liquid microextraction method for the separation and determination of essential oil from Ligusticum chuanxiong Hort by gas chromatography with mass spectrometry

In this study, an accelerated solvent extraction dispersive liquid–liquid microextraction coupled with gas chromatography and mass spectrometry was established and employed for the extraction, concentration and analysis of essential oil constituents from Ligusticum chuanxiong Hort. Response surface methodology was performed to optimize the key parameters in accelerated solvent extraction on the extraction efficiency, and key parameters in dispersive liquid–liquid microextraction were discussed as well. Two representative constituents in Ligusticum chuanxiong Hort, (Z)‐ligustilide and n‐butylphthalide, were quantitatively analyzed. It was shown that the qualitative result of the accelerated solvent extraction dispersive liquid–liquid microextraction approach was in good agreement with that of hydro‐distillation, whereas the proposed approach took far less extraction time (30 min), consumed less plant material (usually <1 g, 0.01 g for this study) and solvent (<20 mL) than the conventional system. To sum up, the proposed method could be recommended as a new approach in the extraction and analysis of essential oil.     

Dispersive liquid–liquid microextraction of five chlorophenols in water samples followed by determination using capillary electrophoresis

Dispersive liquid–liquid microextraction (DLLME) coupled with CE was developed for simultaneous determination of five types of chlorophenols (CPs), namely 2‐chlorophenol (2‐CP), 4‐chlorophenol (4‐CP), 2,4‐dichlorophenol (2,4‐DCP), 2,6‐dichlorophenol (2,6‐DCP), and 2,4,6‐trichlorophenol (2,4,6‐TCP) in water samples. Several parameters affecting DLLME and CE conditions were systematically investigated. Under the optimized DLLME‐CE conditions, the five CPs were separated completely within 7.5 min and good enrichment factors were obtained of 40, 193, 102, 15, and 107 for 4‐CP, 2,4,6‐TCP, 2,4‐DCP, 2‐CP, and 2,6‐DCP, respectively. Good linearity was attained in the range of 1–200 μg/L for 2,4,6‐TCP, 2,4‐DCP, 2−300 μg/L for 4‐CP and 2‐CP, and 1−300 μg/L for 2,6‐DCP, with correlation coefficients (r) over 0.99. The LOD (S/N = 3) and the LOQ (S/N = 10) were 0.31−0.75 μg/L and 1.01−2.43 μg/L, respectively. Recoveries ranging from 60.85 to 112.36% were obtained with tap, lake, and river water spiked at three concentration levels and the RSDs (for n = 3) were 1.31–11.38%. With the characteristics of simplicity, cost‐saving, and environmental friendliness, the developed DLLME‐CE method proved to be potentially applicable for the rapid, sensitive, and simultaneous determination of trace CPs in complicated water samples.     

Determination of strobilurin fungicides in cotton seed by combination of acetonitrile extraction and dispersive liquid−liquid microextraction coupled with gas chromatography

The simultaneous determination of four strobilurin fungicides (picoxystrobin, kresoxim‐methyl, trifloxystrobin, and azoxystrobin) in cotton seed by combining acetonitrile extraction and dispersive liquid?liquid microextraction was developed prior to GC with electron capture detection. Several factors, including the type and volume of the extraction and dispersive solvents, extraction condition and time, and salt addition, were optimized. The analytes were extracted with acetonitrile from cotton seed and the clean‐up was carried out by primary secondary amine. Afterwards, 60 μL of n‐hexane/toluene (1:1, v/v) with a lower density than water was mixed with 1 mL of the acetonitrile extract, then the mixture was injected into 7 mL of distilled water. A 0.1 mL pipette was used to collect a few microliters of n‐hexane/toluene from the top of the aqueous solution. The enrichment factors of the analytes ranged from 36 to 67. The LODs were in the range of 0.1 × 10^?3?2 × 10^?3 mg/kg. The relative recoveries varied from 87.7 to 95.2% with RSDs of 4.1?8.5% for the four fungicides. The good performance of the method, compared with the conventional pretreatments, has demonstrated it is suitable for determining low concentrations of strobilurin fungicide residues in cotton seed.     

Simultaneous dispersive liquid–liquid microextraction based on a low‐density solvent and derivatization followed by gas chromatography for the simultaneous determination of chloroanisoles and the precursor 2,4,6‐trichlorophenol in water samples

Chloroanisoles, particularly 2,4,6‐trichloroanisole, are commonly identified as major taste and odor compounds in water. In the present study, a simple and efficient method was established for the simultaneous determination of chloroanisoles and the precursor 2,4,6‐trichlorophenol in water by using low‐density‐solvent‐based simultaneous dispersive liquid–liquid microextraction and derivatization followed by gas chromatography with electron capture detection. 2,4‐Dichloroanisole, 2,6‐dichloroanisole, 2,4,6‐trichloroanisole, 2,3,4‐trichloroanisole, and 2,3,6‐trichloroanisole were the chloroanisoles evaluated. Several important parameters of the extraction‐derivatization procedures, including the types and volumes of extraction solvent and disperser solvent, concentrations of derivatization agent and base, salt addition, extraction‐derivatization time, and temperature were optimized. Under the optimized conditions (80 μL of isooctane as extraction solvent, 500 μL of methanol as disperser solvent, 60 μL of acetic anhydride as derivatization agent, 0.75% of Na₂CO₃ addition w/v, extraction‐derivatization temperature of 25°C, without salt addition), a good linearity of the calibration curve was observed by the square of correlation coefficients (R²) ranging from 0.9936 to 0.9992. Repeatability and reproducibility of the method were < 4.5% and <7.3%, respectively. Recovery rates ranged from 85.2 to 101.4%, and limits of detection ranged from 3.0 to 8.7 ng/L. The proposed method was applied successfully for the determination of chloroanisoles and 2,4,6‐trichlorophenol in water samples.     

Ultrasound‐assisted dispersive liquid–liquid microextraction coupled with capillary gas chromatography for simultaneous analysis of nine pyrethroids in domestic wastewaters

A simple and rapid ultrasound‐assisted dispersive liquid–liquid microextraction method coupled with GC‐flame ionization detection was developed for simultaneous determination of nine pyrethroids in domestic wastewater samples. An ultrasound‐assisted process was applied to accelerate the formation of the fine cloudy solution using small volume of disperser solvent, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters affecting the extraction efficiency were investigated, including the type and volume of extraction solvent and disperser solvent, extraction and ultrasonic time. Good linearity was obtained for all analytes in the range of 0.8–100 μg/L with the correlation coefficient (r²)≥0.998. The recoveries at three spiking levels ranged from 75.3 to 101.2% with the RSD less than 8.7% (n=5). Under the optimum condition, the enrichment factors for the nine pyrethroids ranged from 728‐ to 1725‐fold. This method offered a good alternative for routine analysis due to its simplicity and reliability.     

Determination of three antidepressants in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction (TA‐DLLME) followed by gas chromatography–flame ionization detection (GC‐FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2‐tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC‐FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r² > 0.993), enrichment factors (820–1070), limits of detection (2–4 ng mL^?1) and quantification (8–12 ng mL^?1), and relative standard deviations (3–6%) for both intraday and interday precisions (concentration = 50 ng mL^?1) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine. Copyright © 2014 John Wiley & Sons, Ltd.