Desirability function approach for the optimization of an in‐syringe ultrasound‐assisted emulsification‐microextraction method for the simultaneous determination of amlodipine and nifedipine in plasma samples

In the present study, an in‐syringe ultrasound‐assisted emulsification‐microextraction using a low‐density organic solvent was developed for simultaneous extraction and pre‐concentration of amlodipine besylate and nifedipine from plasma samples. The extracts were analyzed by high‐performance liquid chromatography with UV detection. Central composite design combined with desirability function was applied to find out the optimal experimental conditions providing the highest global extraction efficiency. The optimal conditions identified were volume of the extracting solvent 45 μL, ionic strength 18.95% w/v, sonication time 2.58 min, and centrifugation time 3 min. Under the optimal conditions, the proposed method was evaluated, and applied to the analysis of amlodipine besylate and nifedipine in plasma samples. The validation results of the method indicated a wide linear range (2–1200 ng/mL) with a good linearity (r² >0.9991) and low detection limits (0.17 ng/mL for amlodipine besylate and 0.15 ng/mL for nifedipine) with RSD less than 5.2% for both components, both in intra‐ and inter‐day precision studies. The applicability of the proposed in‐syringe ultrasound‐assisted emulsification‐microextraction coupled to high‐performance liquid chromatography with UV detection method was demonstrated by analyzing the drugs in spiked plasma samples.     

Deep eutectic solvent based homogeneous liquid–liquid extraction coupled with in‐syringe dispersive liquid–liquid microextraction performed in narrow tube; application in extraction and preconcentration of some herbicides from tea

A homogeneous liquid‐liquid extraction performed in narrow tube coupled to in–syringe‐dispersive liquid‐liquid microextraction based on deep eutectic solvent has been developed for the extraction of six herbicides from tea samples. In this method, sodium chloride as a separation agent is filled into the narrow tube and the tea sample is placed on top of the salt. Then a mixture of deionized water and deep eutectic solvent (water miscible) is passed through the tube. In this procedure, the deep eutectic solvent is realized as tiny droplets in contact with salt. By passing the droplets from the tea layer placed on the salt layer, the analytes are extracted into them. After collecting the solvent as separated layer, it is mixed with another deep eutectic solvent (choline chloride/butyric acid) and the mixture is dispersed into deionized water placed in a syringe. After adding acetonitrile to break up the cloudy state, the collected organic phase is injected into gas chromatography‐mass spectrometry. Under optimal conditions, limits of detection and quantification in the ranges of 2.6–8.4 and 9.7–29 ng/kg, respectively, were obtained. The extraction recoveries and enrichment factors in the ranges of 70–89% and 350–445 were obtained, respectively.     

Determination of acidic drugs in biological and environmental matrices by membrane‐based dual emulsification liquid‐phase microextraction followed by high‐performance liquid chromatography

A simple method is introduced providing a highly clean microextraction for the determination of some anti‐inflammatory drugs as the model analytes in human urine and environmental matrices. This method is based upon the implementation of two consecutive emulsification liquid‐phase microextractions, which are separated by a syringe filtration step. In this method, the organic extraction solvent (dihexyl ether) is dispersed into the aqueous sample solution (20 mL), and the resulting cloudy mixture is passed through a hydrophilic polytetrafluoroethylene syringe filter. By this action, the extraction phase containing the analytes and many interfering species that could be transferred into the organic phase is retained behind the hydrophilic membrane. The filter is then detached from the syringe and attached to another syringe containing an aqueous solution (pH 12.0, 150 μL), and by the in‐syringe dispersion of the organic phase into the aqueous phase, the analytes are selectively back‐extracted into the aqueous phase. The developed method is centrifuge‐free and very simple, and provides a high sample clean‐up in a few minutes. Under the optimized experimental conditions, the developed method provided a linearity in the range of 2.0–2000 ng/mL, a low limit of detection (0.5 ng/mL), and enrichment factors of 47–53.     

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%.     

Magnetic solid‐phase extraction or dispersive liquid–liquid microextraction for pyrethroid determination in environmental samples

The determination of 15 pyrethroids in soil and water samples was carried out by gas chromatography with mass spectrometry. Compounds were extracted from the soil samples (4 g) using solid–liquid extraction and then salting‐out assisted liquid–liquid extraction. The acetonitrile phase obtained (0.8 mL) was used as a dispersant solvent, to which 75 μL of chloroform was added as an extractant solvent, submitting the mixture to dispersive liquid–liquid microextraction. For the analysis of water samples (40 mL), magnetic solid‐phase extraction was performed using nanocomposites of magnetic nanoparticles and multiwalled carbon nanotubes as sorbent material (10 mg). The mixture was shaken for 45 min at room temperature before separation with a magnet and desorption with 3 mL of acetone using ultrasounds for 5 min. The solvent was evaporated and reconstituted with 100 μL acetonitrile before injection. Matrix‐matched calibration is recommended for quantification of soil samples, while water samples can be quantified by standards calibration. The limits of detection were in the range of 0.03–0.5 ng/g (soil) and 0.09–0.24 ng/mL (water), depending on the analyte. The analyzed environmental samples did not contain the studied pyrethroids, at least above the corresponding limits of detection.     

In situ derivatization and hollow‐fiber liquid‐phase microextraction to determine sulfonamides in water using UHPLC with fluorescence detection

A sensitive method for determining sulfonamides in water was developed and validated through in situ derivatization and hollow‐fiber liquid‐phase microextraction with ultra‐high performance liquid chromatography and fluorescence detection. The target sulfonamides were sulfadiazine, sulfacetamide, sulfamerazine, sulfamethazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethoxazole, and sulfisoxazole. Following in situ derivatization with fluorescamine, three‐phase hollow‐fiber liquid‐phase microextraction with an S 6/2 polypropylene hollow‐fiber membrane was applied automatically using a multipurpose autosampler. Experimental parameters including derivatization time, choice of organic phase, pH of donor and acceptor phase, stirring rate, extraction temperature and time were optimized. Under optimized conditions, the target sulfonamides achieved excellent linearity with correlation coefficients of 0.9924–0.9994 within the concentration range of 0.05–5 μg/L. The limits of detection of the eight sulfonamides were 3.1–11.2 ng/L, and the limits of quantification were 10.3–37.3 ng/L. Enrichment factors of 0.1 and 5 μg/L sulfonamides spiked in lake water were 14–60, and recoveries were 56–113% with relative standard derivations of 3–19%. Applied with the developed method, sulfamerazine and sulfamethoxazole were measurable in both influent and effluent water of the three sewage treatment plants in Guangzhou, China. The developed method was sensitive and provided an alternative method for simultaneously enriching and quantifying multiple sulfonamides in environmental water.     

Preconcentration and determination of 2‐mercaptobenzimidazole by dispersive liquid–liquid microextraction and experimental design

A method was developed to determine 2‐mercaptobenzimidazole in water and urine samples using dispersive liquid–liquid microextraction technique coupled with ultraviolet–visible spectrophotometry. It was essential to peruse the effect of all parameters that can likely influence the performance of extraction. The influence of parameters, such as dispersive and extraction solvent volume and sample volume, on dispersive liquid–liquid microextraction was studied. The optimization was carried out by the central composite design method. The central composite design optimization method resulted in 1.10 mL dispersive solvent, 138.46 μL extraction solvent, and 4.46 mL sample volume. Under the optimal terms, the calibration curve was linear over the range of 0.003–0.18 and 0.007–0.18 μg/mL in water and urine samples, respectively. The limit of detection and quantification of the proposed approach for 2‐mercaptobenzimidazole were 0.013 and 0.044 μg/mL in water samples and 0.016 and 0.052 μg/mL in urine samples, respectively. The method was successfully applied to determination of 2‐mercaptobenzimidazole in urine and water samples.     

Ultra‐fast liquid chromatography with tandem mass spectrometry determination of ochratoxin A in traditional Chinese medicines based on vortex‐assisted solid–liquid microextraction and aptamer‐affinity column clean‐up

A rapid, selective, and sensitive ultra‐fast liquid chromatography with tandem mass spectrometry method was developed for the determination of ochratoxin A in traditional Chinese medicines based on vortex‐assisted solid–liquid microextraction and aptamer‐affinity column clean‐up. Through optimizing the sample pretreatment procedures and chromatographic conditions, good linearity (r² ≥ 0.9993), low limit of detection (0.5–0.8 μg/kg), and satisfactory recovery (83.54–94.44%) expressed the good reliability and applicability of the established method in various traditional Chinese medicines. Moreover, the aptamer‐affinity column, prepared in‐house, showed an excellent feasibility owing to its specific identification of ochratoxin A in various kinds of selected traditional Chinese medicines. The maximum adsorption amount and applicability value were 188.96 ± 10.56 ng and 72.3%, respectively. The matrix effects were effectively eliminated, especially for m/z 404.2→358.0 of ochratoxin A. The application of the developed method for screening the natural contamination levels of ochratoxin A in 25 random traditional Chinese medicines on the market in China indicated that only eight samples were contaminated with low levels below the legal limit (5.0 μg/kg) set by the European Union. This study provided a preferred choice for the rapid and accurate monitoring of ochratoxin A in complex matrices.     

Trace determination of five triazole fungicide residues in traditional Chinese medicine samples by dispersive solid‐phase extraction combined with ultrasound‐assisted dispersive liquid–liquid microextraction and UHPLC–MS/MS

A novel and reliable method for determination of five triazole fungicide residues (triadimenol, tebuconazole, diniconazole, flutriafol, and hexaconazol) in traditional Chinese medicine samples was developed using dispersive solid‐phase extraction combined with ultrasound‐assisted dispersive liquid–liquid microextraction before ultra‐high performance liquid chromatography with tandem mass spectrometry. The clean up of the extract was conducted using dispersive solid‐phase extraction by directly adding sorbents into the extraction solution, followed by shaking and centrifugation. After that, a mixture of 400 μL trichloromethane (extraction solvent) and 0.5 mL of the above supernatant was injected rapidly into water for the dispersive liquid–liquid microextraction procedure. The factors affecting the extraction efficiency were optimized. Under the optimum conditions, the calibration curves showed good linearity in the range of 2.0–400 (tebuconazole, diniconazole, and hexaconazole) and 4.0–800 ng/g (triadimenol and flutriafol) with the regression coefficients higher than 0.9958. The limit of detection and limit of quantification for the present method were 0.5–1.1 and 1.8–4.0 ng/g, respectively. The recoveries of the target analytes ranged from 80.2 to 103.2%. The proposed method has been successfully applied to the analysis of five triazole fungicides in traditional Chinese medicine samples, and satisfactory results were obtained.     

Aptamer‐modified magnetic metal‐organic framework MIL‐101 for highly efficient and selective enrichment of ochratoxin A

A facile and efficient strategy is developed to modify aptamers on the surface of the magnetic metal‐organic framework MIL‐101 for the rapid magnetic solid‐phase extraction of ochratoxin A. To the best of our knowledge, this is the first attempt to create a robust aptamer‐modified magnetic MIL‐101 with covalent bonding for the magnetic separation and enrichment of ochratoxin A. The saturated adsorption of ochratoxin A by aptamer‐modified magnetic MIL‐101 was 7.9 times greater than that by magnetic metal‐organic framework MIL‐101 due to the former's high selective recognition as well as good stability. It could be used for extraction more than 12 times with no significant changes in the extraction efficiency. An aptamer‐modified magnetic MIL‐101‐based method of magnetic solid‐phase extraction combined with ultra high performance liquid chromatography with tandem mass spectrometry was developed for the determination of trace ochratoxin A with limit of detection of 0.067 ng/L. Ochratoxin A of 4.53–13.7 ng/kg was determined in corn and peanut samples. The recoveries were in the range 82.8–108% with a relative standard deviation (n = 5) of 4.5–6.5%. These results show that aptamer‐modified magnetic MIL‐101 exhibits selective and effective enrichment performance and have excellent potential for the analysis of ultra‐trace targets from complex matrices.     

Temperature‐controlled liquid–liquid microextraction combined with high‐performance liquid chromatography for the simultaneous determination of diazinon and fenitrothion in water and fruit juice samples

A simple, environmentally benign, and rapid method based on temperature‐controlled liquid–liquid microextraction using a deep eutectic solvent was developed for the simultaneous extraction/preconcentration of diazinon and fenitrothion. The method involved the addition of deep eutectic solvent to the aqueous sample followed by heating the mixture in a 75°C water bath until the solvent was completely dissolved in the aqueous phase. Then, the resultant solution was cooled in an ice bath and a cloudy solution was formed. Afterward, the mixture was centrifuged and the enriched deep eutectic solvent phase was analyzed by high‐performance liquid chromatography with ultraviolet detection for quantification of the analytes. The factors affecting the extraction efficiency were optimized. Under the optimized extraction conditions, the limits of detection for diazinon and fenitrothion were 0.3 and 0.15 μg/L, respectively. The calibration curves for diazinon and fenitrothion exhibited linearity in the concentration range of 1–100 and 0.5–100 μg/L, respectively. The relative standard deviations for five replicate measurements at 10.0 μg/L level of analytes were less than 2.8 and 4.5% for intra‐ and interday assays, respectively. The developed method was successfully applied to the determination of diazinon and fenitrothion in water and fruit juice samples.     

Switchable‐hydrophilicity solvent liquid‐liquid microextraction versus dispersive liquid‐liquid microextraction prior to HPLC‐UV for the determination and isolation of piperine from Piper nigrum L

Switchable‐hydrophilicity solvent liquid‐liquid microextraction and dispersive liquid‐liquid microextraction were compared for the extraction of piperine from Piper nigrum L. prior to its analysis by using high‐performance liquid chromatography with UV detection. Under optimum conditions, limits of detection and quantitation were found as 0.2–0.6 and 0.7–2.0 μg/mg with the two methods, respectively. Calibration graphs showed good linearity with coefficients of determination (R²) higher than 0.9962 and percentage relative standard deviations lower than 6.8%. Both methods were efficiently used for the extraction of piperine from black and white pepper samples from different origins and percentage relative recoveries ranged between 90.0 and 106.0%. The results showed that switchable‐hydrophilicity solvent liquid‐liquid microextraction is a better alternative to dispersive liquid‐liquid microextraction for the routine analysis of piperine in food samples. A novel scaled‐up dispersive liquid‐liquid microextraction method was also proposed for the isolation of piperine providing a yield of 102.9 ± 4.9% and purity higher than 98.0% as revealed by NMR spectroscopy.     

Microfunnel‐filter‐based emulsification microextraction followed by gas chromatography for simple determination of organophosphorus pesticides in environmental water samples

A simple and fast method named microfunnel‐filter‐based emulsification microextraction is introduced for an efficient determination of some organophosphorus pesticides including diazinon, malathion, and chlorpyrifos in the environmental samples including the river, sea, and well water. This method is based upon the dispersion of a low‐toxicity organic solvent (dihexyl ether), as the extractant, in a high volume of an aqueous sample solution (45 mL). It is implemented without a centrifugation step, and using a syringe filter and a micro‐funnel, the phase separation and transfer of the enriched analytes to the gas chromatograph are simply achieved. By filtration of the extractant phase, a suitable sample clean‐up is obtained, and the total extraction time is just a few minutes. The factors influencing the extraction efficiency are optimized, and under the optimal conditions, the proposed method provides a good linearity (in the range of 15–1500 ng/mL (R² > 0.996). A high enrichment factor is obtained (in the range of 306–342), and the method provides low limits of detection and quantification (in the ranges of 4–8 and 15–25 ng/mL, respectively).     

Application of dispersive liquid–liquid microextraction for the preconcentration of eight parabens in real samples and their determination by high‐performance liquid chromatography

A simple and sensitive method for the simultaneous determination of eight parabens in human plasma and urine samples was developed. The samples were preconcentrated using dispersive liquid–liquid microextraction based on the solidification of floating organic drops and determined by high‐performance liquid chromatography with ultraviolet detection. The influence of variables affecting the extraction efficiency was investigated and optimized using Placket–Burman design and Box–Behnken design. The optimized values were: 58 μL of 1‐decanol (as extraction solvent), 0.65 mL methanol (as disperser solvent), 1.5% w/v NaCl in 5.0 mL of sample solution, pH 10.6, and 4.0 min centrifugation at 4000 rpm. The extract was injected into the high‐performance liquid chromatography system for analysis. Under the optimum conditions, the linear ranges for eight parabens in plasma and urine were 1.0–1000 ng/mL, with correlation coefficients above 0.994. The limit of detection was 0.2–0.4 and 0.1–0.4 ng/mL for plasma and urine samples, respectively. Relative recoveries were between 80.3 and 110.7%, while relative standard deviations were less than 5.4%. Finally, the method was applied to analyze the parabens in 98 patients of primary breast cancer. Results showed that parabens existed widely, at least one paraben detected in 96.9% (95/98) of plasma samples and 98.0% (96/98) of urine samples.     

Effervescence‐assisted dispersive liquid–liquid microextraction using a solid effervescent agent as a novel dispersion technique for the analysis of fungicides in apple juice

A novel effervescence‐assisted dispersive liquid–liquid microextraction method has been developed for the determination of four fungicides in apple juice samples. In this method, a solid effervescent agent is added into samples to assist the dispersion of extraction solvent. The effervescent agent is environmentally friendly and only produces an increase in the ionic strength and a negligible variation in the pH value of the aqueous sample, which does not interfere with the extraction of the analytes. The parameters affecting the extraction efficiency were investigated including the composition of effervescent agent, effervescent agent amount, formulation of effervescent agent, adding mode of effervescent agent, type and volume of extraction solvent, and pH. Under optimized conditions, the method showed a good linearity within the range of 0.05–2 mg/L for pyrimethanil, fludioxonil, and cyprodinil, and 0.1–4 mg/L for kresoxim‐methyl, with the correlation coefficients >0.998. The limits of detection for the method ranged between 0.005 and 0.01 mg/L. The recoveries of the target fungicides in apple juice samples were in the range of 72.4–110.8% with the relative standard deviations ranging from 1.2 to 6.8%.     

Pipette vial dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice

A simple, sensitive, and efficient method of using a pipette vial to perform dispersive liquid–liquid microextraction based on the solidification of floating organic droplets was coupled with high‐performance liquid chromatography (HPLC) and a diode array detector for the preconcentration and analysis of four benzoylurea insecticides in fruit juice. In this method, 1‐dodecanol was used as an extractant, and a snipped pipette was used as an experimental vial to simplify the procedure of collecting and separating solidified extractant. The experimental parameters were optimized using a Plackett–Burman design and one‐factor‐at‐a‐time method. Under the optimal conditions in the water model, the limits of detection for analytes varied from 0.03 to 0.28 μg/L, and the enrichment factors ranged from 147 to 206. Linearity was achieved for diflubenzuron and flufenoxuron in a range of 0.5–500 μg/L, for hexaflumuron in a range of 1–500 μg/L, and for triflumuron in a range of 5–500 μg/L. The correlation coefficients for the analytes ranged from 0.9986 to 0.9994 with recoveries of 91.4–110.9%. Finally, the developed technique was successfully applied to fruit juice samples with acceptable results. The relative standard deviations of the analytes at two spiking levels (50 and 200 μg/L) varied between 0.2 and 4.5%.     

Determination of four acidic nonsteroidal anti‐inflammatory drugs in wastewater samples by dispersive liquid–liquid microextraction based on solidification of floating organic droplet and high‐performance liquid chromatography

A simple, environmentally friendly, and sensitive dispersive liquid–liquid microextraction based on solidification of floating organic droplet for the extraction of four acidic nonsteroidal anti‐inflammatory drugs (ketoprofen, naproxen, ibuprofen, and diclofenac) from wastewater samples subsequent by high‐performance liquid chromatography analysis was developed. The influence of extraction parameters such as pH, the effect of solution ionic strength, type of extraction solvent, disperser solvent, and extraction solvent volume were studied. High enrichment factors (283–302) were obtained through the developed method. The method provides good linearity (r > 0.999) in a concentration range of 1–100 μg/L, good intra‐ and inter‐day precision (relative standard deviation < 7%) and low limits of quantification. The relative recoveries of the selected compounds were situated over 80% both in synthetic and real water samples. The developed method has been successfully applied for the analysis of the selected compounds in wastewater samples.     

Preparation of metal‐organic framework UiO‐66‐incorporated polymer monolith for the extraction of trace levels of fungicides in environmental water and soil samples

A zirconium terephthalate metal‐organic framework‐incorporated poly(N‐vinylcarbazole‐co‐divinylbenzene) monolith was fabricated in a capillary by a thermal polymerization method. The optimized monolith had a homogeneous structure, good permeability, and stability. The monolith could be used for the effective enrichment of fungicides through π‐π interactions, electrostatic forces, and hydrogen bonds. The potential factors that affect the extraction efficiency, including ionic strength, solution pH, sample volume, and eluent volume, were investigated in detail. The monolith‐based in‐tube solid‐phase microextraction coupled with ultra‐high‐performance liquid chromatography and high‐resolution Orbitrap mass spectrometry was performed for the analysis of five fungicides (pyrimethanil, tebuconazole, hexaconazole, diniconazole, and flutriafol) in environmental samples. Under the optimized conditions, the linear ranges were 0.005–5 ng/mL for pyrimethanil, 0.01–5 ng/mL for flutriafol, and 0.05–5 ng/mL for other fungicides, respectively, with coefficients of determination ≥0.9911. The limits of detection were 1.34–14.8 ng/L. The columns showed good repeatability (relative standard deviations ≤9.3%, n = 5) and desirable column‐to‐column reproducibility (relative standard deviations 5.3–9.4%, n = 5). The proposed method was successfully applied for the simultaneous detection of five fungicides in water and soil samples, with recoveries of 90.4–97.5 and 84.0–95.3%, respectively.     

Dispersive liquid‐liquid microextraction coupled with pressure‐assisted electrokinetic injection for simultaneous enrichment of seven phenolic compounds in water samples followed by determination using capillary electrophoresis

Offline dispersive liquid‐liquid microextraction combined with online pressure‐assisted electrokinetic injection was developed to simultaneously enrich seven phenolic compounds in water samples, followed by determination using capillary electrophoresis, namely phenol, 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2,4‐dichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol. Several parameters affecting separation performance of capillary electrophoresis and the enrichment efficiency of pressure‐assisted electrokinetic injection and dispersive liquid‐liquid microextraction were systematically investigated. Under the optimal conditions, seven phenolic compounds were completely separated within 14 min and good enrichment factors were obtained of 61, 236, 3705, 3288, 920, 86, and 1807 for phenol, 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2,4‐dichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol, respectively. Good linearity was attained in the range of 0.1–200 μg/L for 2,4‐dichlorophenol, 0.5–200 μg/L for 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol, as well as 1–200 μg/L for phenol, with correlation coefficients (r) over 0.9905. The limits of detection and quantification ranging from 0.03–0.28 and 0.07–0.94 μg/L were attained. This two step enrichment method was potentially applicable for the rapid and simultaneous determination of phenolic compounds in water samples.     

Sol–gel/nanoclay composite as a sorbent for microextraction in packed syringe combined with corona discharge ionization ion mobility spectrometry for the determination of diazinon in water samples

In this work, the microextraction in packed syringe technique combined with corona discharge ion mobility spectrometry was used for determining diazinon in water samples. A new porous composite of nanoclay and polysiloxane was prepared using a sol–gel process. An amount of 2.0 mg of the sorbent was packed in a 250 μL syringe and used for extraction. A volume of 2 mL of the sample was passed through the sorbent bed, and the entrapped analyte was eluted by 25 μL of methanol. Important parameters influencing the extraction performance were investigated. Under optimum experimental conditions, the detection limit for diazinon was 0.07 ng/mL. The intra‐ and inter‐day relative standard deviations were 5.0 and 12.3%, respectively. The calibration curve was linear in the concentration range from 0.2 to 20.0 ng/mL (r² = 0.999). The applicability of the method was demonstrated by analyzing spiked real water samples and the spiking recoveries were in the range of 95 to 106%.