Sensitive determination of amide herbicides in environmental water samples by a combination of solid‐phase extraction and dispersive liquid–liquid microextraction prior to GC–MS

In this paper, solid‐phase extraction (SPE) in combination with dispersive liquid–liquid microextraction (DLLME) has been developed as a sample pretreatment method with high enrichment factors for the sensitive determination of amide herbicides in water samples. In SPE–DLLME, amide herbicides were adsorbed quantitatively from a large volume of aqueous samples (100 mL) onto a multiwalled carbon nanotube adsorbent (100 mg). After elution of the target compounds from the adsorbent with acetone, the DLLME technique was performed on the resulting solution. Finally, the analytes in the extraction solvent were determined by gas chromatography–mass spectrometry. Some important extraction parameters, such as flow rate of sample, breakthrough volume, sample pH, type and volume of the elution solvent, as well as salt addition, were studied and optimized in detail. Under optimum conditions, high enrichment factors ranging from 6593 to 7873 were achieved in less than 10 min. There was linearity over the range of 0.01–10 μg/L with relative standard deviations of 2.6–8.7%. The limits of detection ranged from 0.002 to 0.006 μg/L. The proposed method was used for the analysis of water samples, and satisfactory results were achieved.     

Determination of cadmium and copper in water and food samples by dispersive liquid–liquid microextraction combined with UV–vis spectrophotometry

In this work, a new method based on dispersive liquid–liquid microextraction (DLLME) preconcentration using tetrachloromethane (CCl₄) as extraction solvent was proposed for the spectrophotometric determination of cadmium and copper in water and food samples. The influence factors relevant to DLLME, such as type and volume of extractant and disperser solvent, concentration of chelating reagents, pH, salt effect, were optimized. Under the optimal conditions, the limits of detection for cadmium and copper were 0.01 ng/L and 0.5 μg/L, with enhancement factors (EFs) of 3458 and 10, respectively. The tremendous contrast of EFs could come from the different maximum absorption wavelength caused by the different extraction acidity compared with some conventional works and the enhancement effect of acetone used as dilution solvent during the spectrophotometric determination. The proposed method was applied to the determination of water and food samples with satisfactory analytical results. The proposed method was simple, rapid, cost-efficient and sensitive, especially for the detection of cadmium.     

Use of an ionic liquid‐based surfactant as pseudostationary phase in the analysis of carbamates by micellar electrokinetic chromatography

The applicability of an ionic liquid‐based cationic surfactant 1‐dodecyl‐3‐methyl‐imidazolium tetrafluoroborate (C₁₂MImBF₄) as pseudostationary phase in MEKC has been evaluated for the analysis of 11 carbamate pesticides (promecarb, carbofuran, metolcarb, fenobucarb, aldicarb, propoxur, asulam, benomyl, carbendazim, ethiofencarb, isoprocarb) in juice samples. Under optimum conditions (separation buffer, 35 mM NaHCO₃ and 20 mM C₁₂MImBF₄, pH 9.0; capillary temperature 25°C; voltage –22 kV) the analysis was carried out in less than 12 min, using hydrodynamic injection (50 mbar for 7.5 s) and detection at 200 nm. For the extraction of these CRBs from juice samples, a dispersive liquid–liquid microextraction (DLLME) procedure has been proposed, by optimization of variables affecting the efficiency of the extraction. Following this treatment, sample throughput was approximately 12 samples per hour, obtaining a preconcentration factor of 20. Matrix‐matched calibration curves were established using tomato juice as representative matrix (from 5 to 250 μg/L for CBZ, BY, PX, CF, FEN, ETH, ISP, and 25–250 μg/L for ASL, ALD, PRC, MTL), obtaining quantification limits ranging from 1 to 18 μg/L and recoveries from 70 to 96%, with RSDs lower than 9%.     

Dispersive liquid–liquid microextraction coupled with capillary electrophoresis for simultaneous determination of sulfonamides with the aid of experimental design

A novel method for the simultaneous determination of sulfonamides (SAs) in water samples has been developed by using dispersive liquid–liquid microextraction (DLLME) coupled with CE. Orthogonal and Box–Behnken designs were employed together to assist the optimization of DLLME parameters, including volumes of extraction and disperser solvents, ionic strength, extraction time, and centrifugation time and speed as variable factors. Under the optimum extraction and detection conditions, successful separation of the five SAs was achieved within 5 min, and excellent analytical performances were attained, such as good linear relationships (R>0.980) between peak area and concentration for each SA from 0.5 to 50 μg/mL, low limits of detection for the five SAs between 0.020 and 0.570 μg/mL and the intra‐day precisions of migration time below 0.80%. The method recoveries obtained at fortified 10 μg/mL for three water samples ranged from 53.6 to 94.0% with precisions of 1.23–5.60%. The proposed method proved highly sensitive and selective, rapid, convenient and cost‐effective, showing great potential for the simultaneous determination of SAs in water samples.     

Dispersive liquid–liquid microextraction combined with online preconcentration MEKC for the determination of some phenoxyacetic acids in drinking water

A fast and simple technique composed of dispersive liquid–liquid microextraction (DLLME) and online preconcentration MEKC with diode array detection was developed for the determination of four phenoxyacetic acids, 2,4,5‐trichlorophenoxyacetic acid, 2,4‐dichlorophenoxyacetic acid, 2,6‐dichlorophenoxyacetic acid, and 4‐chlorophenoxyacetic acid, in drinking water. The four phenoxyacetic acids were separated in reversed‐migration MEKC to the baseline. About 145‐fold increases in detection sensitivity were observed with online concentration strategy, compared with standard hydrodynamic injection (5 s at 25 mbar pressure). LODs ranged from 0.002 to 0.005 mg/L using only the online preconcentration procedures without any offline concentration of the extract. A DLLME procedure was used in combination with the proposed online preconcentration strategies, which achieved the determination of analytes at limits of quantification ranging from 0.2 to 0.5 μg/kg, which is far lower than the maximum residue limits established by China. The satisfactory recoveries obtained by DLMME spiked at two levels ranged from 67.2 to 99.4% with RSD <15%, making this proposed method suitable for the determination of phenoxyacetic acids in water samples.     

Ionic liquid-dispersive liquid-liquid microextraction for the simultaneous determination of pesticides and metabolites in soils using high-performance liquid chromatography and fluorescence detection

In this work, an ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) procedure was developed for the extraction of a group of pesticides (carbendazim/benomyl, thiabendazole, fuberidazole, carbaryl and triazophos) and some of their key metabolites in soils (2-aminobenzimidazole, metabolite of carbendazim and 1-naphthol, metabolite of carbaryl) from aqueous soil extracts, using high performance liquid chromatography (HPLC) with fluorescence detection (FD). Analytes were previously extracted from four soils with different physicochemical properties (forestal, ornamental, garden and lapilli soils) by ultrasound-assisted extraction (USE). The IL 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIm][PF(6)]) and methanol (MeOH) were used as extraction and dispersion solvent, respectively, for the DLLME procedure. Factors affecting IL-DLLME (sample pH, IL amount, volume of dispersion solvent and sodium chloride percentage) were optimized by means of an experimental design, obtaining the most favorable results when using 117.5 mg of IL and 418 μL of MeOH to extract the compounds from the aqueous soil extracts at pH 5.20 containing 30% (w/v) NaCl. Calibration of the USE-IL-DLLME-HPLC-FD method was carried out for every type of soil and accuracy and precision studies were developed at two levels of concentration, finding that no significant differences existed between real and spiked concentrations (Student's t test). LODs achieved were in the low ng/g range.     

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%.     

固相萃取-离子交换色谱法测定浓缩苹果汁中残留的苯菌灵、多菌灵、噻菌灵

建立固相萃取-离子交换色谱法测定浓缩苹果汁中苯菌灵、多菌灵和噻菌灵的残留量。样品直接用水稀释后,于80 ℃下将苯菌灵完全转化为多菌灵,再经SCX固相萃取柱富集,采用LC-SCX离子交换色谱柱(25 cm×4.6 mm,5 μm)分离,二极管阵列检测器检测,以0.1 mol/L KH2PO4溶液(pH 2.5)-乙腈(体积比为70 ∶30)为流动相,在1.0 mL/min下等度洗脱,于282 nm波长下检测。在0.02～2.0 mg/L范围内,多菌灵和噻菌灵的峰面积与其浓度呈良好的线性关系,最低检出限均可达到0.004 mg/kg,回收率为94.2%～100.4%,相对标准偏差低于4.2%。该方法简便、快速、灵敏、准确,可用于浓缩苹果汁中苯菌灵、多菌灵和噻菌灵残留量的检测。     

Preconcentration of organochlorine pesticides in aqueous samples by dispersive liquid–liquid microextraction based on solidification of floating organic drop after SPE with multiwalled carbon nanotubes

SPE joined with dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME‐SFO) as a novel technique combined with GC with electron‐capture detection has been developed as a preconcentration technique for the determination of organochlorine pesticides (OCPs) in water samples. Aqueous samples were loaded onto multiwalled carbon nanotubes as sorbent. After the elution of the desired compounds from the sorbent by using acetone, the DLLME‐SFO technique was performed on the obtained solution. Variables affecting the performance of both steps such as sample solution flow rate, breakthrough volume, type and volume of the elution, type and volume of extraction solvent and salt addition were studied and optimized. The new method provided an ultra enrichment factor (8280–28221) for nine OCPs. The calibration curves were linear in the range of 0.5–1000 ng/L, and the LODs ranged from 0.1–0.39 ng/L. The RSD, for 0.01 μg/L of OCPs, was in the range of 1.39–13.50% (n = 7). The recoveries of method in water samples were 70–113%.     

Determination of estrogens in environmental water samples using 1,3‐dipentylimidazolium hexafluorophosphate ionic liquid as extraction solvent in dispersive liquid–liquid microextraction

In this work, the potential of a symmetric dialkyl‐substituted ionic liquid (IL), 1,3‐dipenthylimidazolium hexafluorophosphate ([PPIm][PF₆]), as extraction solvent in dispersive liquid–liquid microextraction (DLLME) has been studied for the analysis of a group of three natural (estriol, 17β‐estradiol, and 17α‐estradiol) and four synthetic (17α‐ethynylestradiol, diethylstibestrol, dienestrol, and hexestrol) estrogenic compounds as well as one mycotoxin with estrogenic activity (zearalenone) in different types of water samples (Milli‐Q, mineral, and wastewater). Separation, determination, and quantification were developed by HPLC‐DAD and a fluorescence detector (FD) connected in series. Factors influencing the IL‐DLLME procedure (sample pH, amount of IL, type and volume of disperser solvent, ionic strength, and assistance of vortex agitation) were investigated and optimized by means of a step‐by‐step approach. Once the optimum extraction conditions were established (10 mL of water at pH 8, 60 mg of [PPIm][PF₆], 500 μL of ACN as disperser solvent and vortex agitation for 1 min), the calibration curves of the whole method (IL‐DLLME‐HPLC‐DAD/FD) were obtained and precision and accuracy were evaluated. It was demonstrated that the developed methodology was repeatable, accurate, and selective with limits of detection in the 0.30–0.57 μg/L and 13.8–37.1 μg/L range for FD and DAD, respectively. Relative recovery values were higher than 85% for the different types of water samples and the Student's t test demonstrated that there were not significant differences between the added and the found concentration.     

Rapid determination of ultra-trace amounts of acrylamide contaminant in water samples using dispersive liquid–liquid microextraction coupled to gas chromatography-electron capture detector

The objective of the present study was to develop and validate a rapid, highly sensitive, and reliable extraction method to determine acrylamide in water samples. The method was based on the derivatisation of the acrylamide in the presence of KBr, HBr and saturated Br₂ solution into 2,3-dibromopropionamide and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–electron capture detection (GC–ECD) of the analyte. Different parameters that affect the DLLME process such as types and volumes of disperser solvent, ionic strength of aqueous solution and extraction time were investigated and optimised. Under optimal conditions, excellent linearity was obtained between concentration of acrylamide and the response of ECD with correlation of determination (R²) of 0.9999. The precision of the method, which was determined by calculating the relative standard deviations (RSD) of the at least three replicate measurements, was 3.6%. The method presented in this study is sensitive enough for the determination of acrylamide in different water samples with the limit of detection (LOD) value of 1?ng?L^?1. The mean percentage recoveries exceeded 91% for all of spiking levels in the real water samples. The results obtained from DLLME method are validated by EPA method 8032A.     

Selective extraction of emerging contaminants from water samples by dispersive liquid-liquid microextraction using functionalized ionic liquids

Functionalized ionic liquids containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion were used as extraction solvents in dispersive liquid-liquid microextraction (DLLME) for the extraction of 14 emerging contaminants from water samples. The extraction efficiencies and selectivities were compared to those of an in situ IL DLLME method which uses an in situ metathesis reaction to exchange 1-butyl-3-methylimidazolium chloride (BMIM-Cl) to 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMIM-NTf(2)). Compounds containing tertiary amine functionality were extracted with high selectivity and sensitivity by the 1-(6-amino-hexyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (HNH(2)MPL-FAP) IL compared to other FAP-based ILs and the BMIM-NTf(2) IL. On the other hand, polar or acidic compounds without amine groups exhibited higher enrichment factors using the BMIM-NTf(2) IL. The detection limits for the studied analytes varied from 0.1 to 55.1 μg/L using the traditional IL DLLME method with the HNH(2)MPL-FAP IL as extraction solvent, and from 0.1 to 55.8 μg/L using in situ IL DLLME method with BMIM-Cl+LiNTf(2) as extraction solvent. A 93-fold decrease in the detection limit of caffeine was observed when using the HNH(2)MPL-FAP IL compared to that obtained using in situ IL DLLME method. Real water samples including tap water and creek water were analyzed with both IL DLLME methods and yielded recoveries ranging from 91% to 110%.     

Macrocyclic polyamine‐functionalized silica as a solid‐phase extraction material coupled with ionic liquid dispersive liquid–liquid extraction for the enrichment of polycyclic aromatic hydrocarbons

In this study, silica modified with a 30‐membered macrocyclic polyamine was synthesized and first used as an adsorbent material in SPE. The SPE was further combined with ionic liquid (IL) dispersive liquid–liquid microextraction (DLLME). Five polycyclic aromatic hydrocarbons were employed as model analytes to evaluate the extraction procedure and were determined by HPLC combined with UV/Vis detection. Acetone was used as the elution solvent in SPE as well as the dispersive solvent in DLLME. The enrichment of analytes was achieved using the 1,3‐dibutylimidazolium bis[(trifluoromethyl)sulfonyl]imide IL/acetone/water system. Experimental conditions for the overall macrocycle‐SPE–IL‐DLLME method, such as the amount of adsorbent, sample solution volume, sample solution pH, type of elution solvent as well as addition of salt, were studied and optimized. The developed method could be successfully applied to the analysis of four real water samples. The macrocyclic polyamine offered higher extraction efficiency for analytes compared with commercially available C₁₈ cartridge, and the developed method provided higher enrichment factors (2768–5409) for model analytes compared with the single DLLME. Good linearity with the correlation coefficients ranging from 0.9983 to 0.9999 and LODs as low as 0.002 μg/L were obtained in the proposed method.     

Solid-phase microextraction of benzimidazole fungicides in environmental liquid samples and HPLC–fluorescence determination

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) with fluorescence detection was optimized for extraction and determination of four benzimidazole fungicides (benomyl, carbendazim, thiabendazole, and fuberidazole) in water. We studied extraction and desorption conditions, for example fiber type, extraction time, ionic strength, extraction temperature, and desorption time to achieve the maximum efficiency in the extraction. Results indicate that SPME using a Carboxen–polydimethylsiloxane 75 μm (CAR–PDMS) fiber is suitable for extraction of these types of compound. Final analysis of benzimidazole fungicides was performed by HPLC with fluorescence detection. Recoveries ranged from 80.6 to 119.6 with RSDs below 9% and limits of detection between 0.03 and 1.30 ng mL⁻¹ for the different analytes. The optimized procedure was applied successfully to the determination of benzimidazole fungicides mixtures in environmental water samples (sea, sewage, and ground water).     

Pressurized Liquid Extraction Combined with Dispersive Liquid‐liquid Micro‐extraction as an Efficient Sample Preparation Method for Determination of Volatile Components in Tobacco

The pressurized liquid extraction (PLE) followed by dispersive liquid–liquid micro‐extraction (DLLME) has been developed for extraction of volatile components in tobacco. 35 volatile components were detected by gas chromatography mass spectrometry (GC‐MS). Methanol–methyl tert‐butyl ether (MTBE) (8:2, v/v) was selected as PLE extraction solvent. The optimized DLLME procedure, 3 mL of pure water and 1.0 mL tobacco extract solution, 40 μL of chloroform as extraction solvent, 0.5 mL of acetonitrile as disperser solvent, was validated. Under the optimum conditions, the enrichment factors were in the range of 96‐159. The limits of detection were between 0.14 and 0.33 μg/kg. The repeatability of the proposed method, expressed as relative standard deviation, varied between 4.3 and 7.5% (n = 6). The recoveries of the analytes evaluated by fortification of tobacco samples were in the range of 84.7‐96.4%. Compared with the conventional sample preparation method for determination of volatile components in tobacco, the proposed method was quick and easy to operate, and had high‐enrichment factors and low consumption of organic solvent.     

Ionic liquid-based dispersive liquid–liquid microextraction for the separation and preconcentration of lead in water samples prior to FAAS determination without chelating agent

In the present study, an environment-friendly sample preparation method termed ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry has been developed for the determination of Pb(II) ion in water samples prior to flame atomic absorption spectrometry determination. In this method, ionic liquid was used as an extraction solvent instead of the organic solvent used in the conventional dispersive liquid–liquid microextraction (DLLME) assay, and there is no need for a chelating agent. Several variables that may affect extraction efficiencies, including pH, the volume of ionic liquid, the type and volume of disperser solvent, salt addition, and the time for centrifugation and extraction were studied and optimised. Under the optimised conditions, the calibration curve exhibited linearity over the range of 20.0–1000.0 μg L^?1. The enrichment factor and the limit of detection based on 3S_b/m were 35.0 and 5.9 μg L^?1, respectively. Seven replicate determination of a solution containing of 100.0 μg L^?1 Pb(II) ions gave a relative standard deviation of ±2.1%. Finally, the feasibility of the proposed method for Pb(II) determination was assessed by the analysis of certi?ed reference material and various water samples and the satisfactory results were obtained.     

Dispersion‐solidification liquid–liquid microextraction for volatile aromatic hydrocarbons determination: Comparison with liquid phase microextraction based on the solidification of a floating drop

Two microextraction techniques – liquid phase microextraction based on solidification of a floating organic drop (LPME‐SFO) and dispersive liquid–liquid microextraction combined with a solidification of a floating organic drop (DLLME‐SFO) – are explored for benzene, toluene, ethylbenzene and o‐xylene sampling and preconcentration. The investigation covers the effects of extraction solvent type, extraction and disperser solvents' volume, and the extraction time. For both techniques 1‐undecanol containing n‐heptane as internal standard was used as an extracting solvent. For DLLME‐SFO acetone was used as a disperser solvent. The calibration curves for both techniques and for all the analytes were linear up to 10 μg/mL, correlation coefficients were in the range 0.997–0.998, enrichment factors were from 87 for benzene to 290 for o‐xylene, detection limits were from 0.31 and 0.35 μg/L for benzene to 0.15 and 0.10 μg/L for o‐xylene for LPME‐SFO and DLLME‐SFO, respectively. Repeatabilities of the results were acceptable with RSDs up to 12%. Being comparable with LPME‐SFO in the analytical characteristics, DLLME‐SFO is superior to LPME‐SFO in the extraction time. A possibility to apply the proposed techniques for volatile aromatic hydrocarbons determination in tap water and snow was demonstrated.     

Primary secondary amine as a sorbent material in dispersive solid‐phase extraction clean‐up for the determination of indicator polychlorinated biphenyls in environmental water samples by gas chromatography with electron capture detection

A simple, rapid, and novel method has been developed and validated for determination of seven indicator polychlorinated biphenyls in water samples by gas chromatography with electron capture detection. 1 L of water samples containing 30 g of anhydrous sodium sulfate was first liquid–liquid extracted with an automated Jipad‐6XB vertical oscillator using n‐hexane/dichloromethane (1:1, v/v). The concentrated extract was cleaned up by dispersive solid‐phase extraction with 100 mg of primary secondary amine as sorbent material. The linearity of this method ranged from 1.25 to 100 μg/L, with regression coefficients ranging between 0.9994 and 0.9999. The limits of detection were in the ng/L level, ranging between 0.2 and 0.3 ng/L. The recoveries of seven spiked polychlorinated biphenyls with external calibration method at different concentration levels in tap water, lake water, and sea water were in the ranges of 85–112, 76–116, and 72–108%, respectively, and with relative standard deviations of 3.3–4.5, 3.4–5.6, and 3.1–4.8% (n =  5), respectively. The performance of the proposed method was compared with traditional liquid–liquid extraction and solid‐phase extraction clean‐up methods, and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of polychlorinated biphenyls in different water samples.     

Determination of As(III) using developed dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

The method relies on selective complexation of As(III) with a suitable chelating agent followed by dispersive liquid–liquid microextraction (DLLME) method. Flame atomic absorption spectrometry (FAAS) equipped with microsample introduction system was utilised for determination of As(III). 1-Undecanol and acetone were used as extraction solvent and disperser solvent respectively. Some effective parameters on complex formation and extraction have been optimised. Under the optimum conditions, the enrichment factor of 108 for As(III) was obtained from 9.8?mL of water samples. The calibration graph was linear in the range of 2–15?µg?L^?1 with detection limits of 0.60?µg?L^?1 for As(III). The relative standard deviation (R.S.D.) for ten replicate measurements of 5.00?µ?gL^?1 of As(III) was 6.2%. Operation simplicity and high enrichment factors are the main advantages of DLLME for the determination of As(III) without necessity for hydride generation in water samples.     

Determination of some carbamate pesticides in watermelon and tomato samples by dispersive liquid–liquid microextraction combined with high performance liquid chromatography

A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in watermelon and tomato samples was developed by dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography-diode array detection (HPLC-DAD). Some experimental parameters that influence the extraction efficiency were studied and optimised to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 10 to 1000?ng?g^?1 for all the five carbamate pesticides, with the correlation coefficients (r) varying from 0.9982 to 0.9992. Good enrichment factors were achieved ranging between 80 and 177, depending on the compound. The limits of detection (LODs) (S/N?=?3) were ranged from 0.5 to 1.5?ng?g^?1. The method has been successfully applied to the analysis of the pesticide residues in watermelon and tomato samples. The recoveries of the method fell in the range between 76.2% to 94.5% with RSDs less than 9.6%, indicating the feasibility of the DLLME method for the determination of the five carbamate pesticides in watermelon and tomato samples.