Multiresidue pesticides analysis in soils using modified QuEChERS with disposable pipette extraction and dispersive solid‐phase extraction

QuEChERS original method was modified into a new version for pesticides determination in soils. The QuEChERS method is based on liquid–liquid portioning with ACN and was followed by cleanup step using dispersive SPE and disposable pipette tips. Gas chromatographic separation with MS detection was carried out for pesticides quantification. The method was validated using recovery experiments for 36 multiclass pesticides. Mean reco‐veries of pesticides at each of the four spiking levels between 10–300 μg/kg of soil ranged from 70–120% for 26 pesticides with RSD values less than 15%. The method achieved low limit of detection less than 7.6 μg/kg. Matrix effects were observed for 13 pesticides. Matrix effects were compensated by using matrix‐matched calibration. The method was applied successfully using d‐SPE or DPX in the analysis of the pesticides in soils from organic farming and integrated pest management.     

Synthesis of a graphene‐based nanocomposite for the dispersive solid‐phase extraction of vancomycin from biological samples

The approach of this work was to study the capability of graphene‐based materials in the field of biological sample preparation. A polypyrrole/graphene composite was synthesized and characterized. The potential of the nanocomposite was investigated as a sorbent in dispersive solid‐phase extraction followed by high‐performance liquid chromatography with UV detection for vancomycin as a model drug. The effect of different parameters influencing extraction efficiency such as sample pH and sample volume, ionic strength, extraction time, type, and volume of desorption solvent and desorption time were investigated. A comparison study was also conducted between polypyrrole/graphene and some different novel and classic sorbents. Under optimized conditions, the calibration curve for vancomycin showed linearity in the range of 0.05–10 μg/mL. In addition, limits of detection, and quantification were 0.003 and 0.01 μg/mL, respectively. The intraday and interday relative standard deviations at a concentration of 0.05 μg/mL (n = 3) were 1.6 and 2.1%, respectively. Furthermore, the proposed method was successfully applied for the determination of vancomycin in plasma and urine samples. The relative recoveries indicated the feasibility of graphene‐based sorbents in biological sample analysis.     

Combination of dispersive solid‐phase extraction and salting‐out homogeneous liquid–liquid extraction for the determination of organophosphorus pesticides in cereal grains

A new analytical method for the determination of organophosphorus pesticides in cereal samples was developed by combining dispersive SPE (d‐SPE) and salting‐out homogeneous liquid–liquid extraction (SHLLE). The pesticides were first extracted from cereal grains with acetonitrile, followed by d‐SPE cleanup. A 2 mL aliquot of the extract was then added to a centrifuge tube containing 9.2 mL water and 3.3 g NaCl for SHLLE. Analysis of the extract was carried out by gas chromatography coupled with flame photometric detection. The d‐SPE procedure effectively provides the necessary cleanup of the extract while SHLLE is used as an efficient concentration technique. Experimental parameters influencing the extraction efficiency including amounts of added water and salt were investigated. Recovery studies were carried out at three fortification levels, yielding recoveries in the range of 57.7–98.1% with the RSD from 3.7 to 10.9%. The reported limits of determination obtained from this study were 1 μg/kg, which is better than the conventional methods. In the analysis of 40 wheat and corn samples taken from Beijing suburbs, only two wheat samples have chlorpyrifos residue over the limits of determination.     

Hypercrosslinked particles for the extraction of sweeteners using dispersive solid‐phase extraction from environmental samples

This work presents a new extraction material, namely, Q‐100, based on hypercrosslinked magnetic particles, which was tested in dispersive solid‐phase extraction for a group of sweeteners from environmental samples. The hypercrosslinked Q‐100 magnetic particles had the advantage of suitable pore size distribution and high surface area, and showed good retention behavior toward sweeteners. Different dispersive solid‐phase extraction parameters such as amount of magnetic particles or extraction time were optimized. Under optimum conditions, Q‐100 showed suitable apparent recovery, ranging in the case of river water sample from 21 to 88% for all the sweeteners, except for alitame (12%). The validated method based on dispersive solid‐phase extraction using Q‐100 followed by liquid chromatography with tandem mass spectrometry provided good linearity and limits of quantification between 0.01 and 0.1 μg/L. The method was applied to analyze samples from river water and effluent wastewater, and four sweeteners (acesulfame, saccharin, cyclamate, and sucralose) were found in both types of sample.     

Speciation analysis of mercury by dispersive solid‐phase extraction coupled with capillary electrophoresis

A pretreatment method of dispersive solid‐phase extraction (DSPE) along with back‐extraction followed by CE‐UV detector was developed for the determination of mercury species in water samples. Sulfhydryl‐functionalized SiO₂ microspheres (SiO₂−SH) were synthesized and used as DSPE adsorbents for selective extraction and enrichment of three organic mercury species namely ethylmercury (EtHg), methylmercury (MeHg), and phenylmercury (PhHg), along with L‐cysteine (L‐cys) containing hydrochloric acid as back‐extraction solvent. Several main extraction parameters were systematically investigated including sample pH, amount of adsorbent, extraction and back‐extraction time, volume of eluent, and concentration of hydrochloric acid. Under optimal conditions, good linearity was achieved with correlation coefficients over 0.9990, in the range of 4−200 μg/L for EtHg, and 2−200 μg/L for MeHg and PhHg. The LODs were obtained of 1.07, 0.34, and 0.24 μg/L for EtHg, MeHg, and PhHg, respectively, as well as the LOQs were 3.57, 1.13, and 0.79 μg/L, respectively, with enrichment factors ranging from 109 to 184. Recoveries were attained with tap and lake water samples in a range of 62.3−107.2%, with relative standard deviations of 3.5–10.1%. The results proved that the method of SiO₂−SH based DSPE coupled with CE‐UV was a simple, rapid, cost‐effective, and eco‐friendly alternative for the determination of mercury species in water samples.     

Efficient sample preparation method based on solvent‐assisted dispersive solid‐phase extraction for the trace detection of butachlor in urine and waste water samples

In this work, an efficient sample preparation method termed solvent‐assisted dispersive solid‐phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre‐concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent‐assisted dispersive solid‐phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples.     

Extraction of phenolic compounds from water samples by dispersive micro‐solid‐phase extraction

In this article, the use of magnetically separable sorbent polyaniline/silica‐coated nickel nanoparticles is evaluated under a dispersive micro‐solid‐phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica‐modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X‐ray powder diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box–Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02–100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10–23 and 33–77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%.     

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.     

Fabrication of a novel hydrophobic/ion‐exchange mixed‐mode adsorbent for the dispersive solid‐phase extraction of chlorophenols from environmental water samples

A novel mixed‐mode adsorbent was prepared by functionalizing silica with tris(2‐aminoethyl)amine and 3‐phenoxybenzaldehyde as the main mixed‐mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compounds, and the mixed hydrophobic and ion‐exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid‐phase extraction was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose, and extraction time were optimized. Under the optimal extraction conditions, the proposed dispersive solid‐phase extraction coupled with high‐performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22∽0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7∽109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples.     

Determination of haloacetic acids in water using layered double hydroxides as a sorbent in dispersive solid‐phase extraction followed by liquid chromatography with tandem mass spectrometry

In the present study, highly efficient and simple dispersive solid‐phase extraction procedure for the determination of haloacetic acids in water samples has been established. Three different types of layered double hydroxides were synthesized and used as a sorbent in dispersive solid‐phase extraction. Due to the interesting behavior of layered double hydroxides in an acidic medium (pH?4), the analyte elution step was not needed; the layered double hydroxides are simply dissolved in acid immediately after extraction to release the analytes which are then directly introduced into a liquid chromatography with tandem mass spectrometry system for analysis. Several dispersive solid‐phase extraction parameters were optimized to increase the extraction efficiency of haloacetic acids such as temperature, extraction time and pH. Under optimum conditions, good linearity was achieved over the concentration range of 0.05–100 μg/L with detection limits in the range of 0.006–0.05 μg/L. The relative standard deviations were 0.33–3.64% (n = 6). The proposed method was applied to different water samples collected from a drinking water plant to determine the concentrations of haloacetic acids.     

Determination of nine volatile N‐nitrosamines in tobacco and smokeless tobacco products by dispersive solid‐phase extraction with gas chromatography and tandem mass spectrometry

A method was developed for the determination of nine volatile N‐nitrosamines in tobacco and smokeless tobacco products. The targets are N‐nitrosodimethylamine, N‐nitrosopyrrolidine, N‐nitrosopiperidine, N‐nitrosomorpholine, N‐nitrosoethylmethylamine, N‐nitrosodiethylamine, N‐nitrosodipropylamine, N‐nitrosobuylmethylmine, and N‐nitrosodibutylamine. The samples were treated by dispersive solid‐phase extraction using 1 g of primary secondary amine and 0.5 g of carbon and then analyzed by gas chromatography with tandem mass spectrometry with an electron impact ion source. The recoveries for the targets ranged from 84 to 118%, with <16% relative standard deviations at three spiking levels of 0.5, 1.25, and 2.5 ng/g. The limits of detection ranged from 0.03 to 0.15 ng/g. With the use of the proposed method, we detected the presence of six nitrosamines in the range of 0.4–30.7 ng/g. The study demonstrated that the method could be used as a rapid, convenient, and high‐throughput method for N‐nitrosamines analysis in tobacco matrix.     

Effervescence‐assisted dispersive solid‐phase extraction using ionic‐liquid‐modified magnetic β‐cyclodextrin/attapulgite coupled with high‐performance liquid chromatography for fungicide detection in honey and juice

In this study, a simple effervescence‐assisted dispersive solid‐phase extraction method was developed to detect fungicides in honey and juice. Most significantly, an innovative ionic‐liquid‐modified magnetic β‐cyclodextrin/attapulgite sorbent was used because its large specific surface area enhanced the extraction capacity and also led to facile separation. A one‐factor‐at‐a‐time approach and orthogonal design were employed to optimize the experimental parameters. Under the optimized conditions, the entire extraction procedure was completed within 3 min. In addition, the calibration curves exhibited good linearity, and high enrichment factors were achieved for pure water and honey samples. For the honey samples, the extraction efficiencies for the target fungicides ranged from 77.0 to 94.3% with relative standard deviations of 2.3–5.44%. The detection and quantitation limits were in the ranges of 0.07–0.38 and 0.23–1.27 μg/L, respectively. Finally, the developed technique was successfully applied to real samples, and satisfactory results were achieved. This analytical technique is cost‐effective, environmentally friendly, and time‐saving.     

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.     

Quantitative analysis of N‐acylphosphatidylethanolamine molecular species in rat brain using solid‐phase extraction combined with reversed‐phase chromatography and tandem mass spectrometry

A novel method for the sensitive and selective identification and quantification of N‐acylphosphatidylethanolamine molecular species was developed. Samples were prepared using a combination of liquid–liquid and solid‐phase extraction, and intact N‐acylphosphatidylethanolamine species were determined by reversed‐phase high‐performance liquid chromatography coupled to positive electrospray tandem mass spectrometry. As a result of their biological functions as precursors for N‐acylethanolamines and as signaling molecules, tissue concentrations of N‐acylphosphatidylethanolamines are very low, and their analysis is additionally hindered by the vast excess of other sample components. Our sample preparation methods are able to selectively separate the analytes of interest from any expected biological interferences. Finally, the highest selectivity is achieved by coupling chromatographic separation and two N‐acyl chain specific selected reaction monitoring scans per analyte, enabling identification of both the N‐acyl chain and the phosphatidylethanolamine moiety. The validated method is suitable for the reliable quantification of N‐acylphosphatidylethanolamine species from rat brain with a lower limit of quantification of 10 pmol/g and a linear range up to 2300 pmol/g. In total, 41 N‐acylphosphatidylethanolamine molecular species with six different N‐acyl chains, amounting to a total concentration of 3 nmol/g, were quantified.     

Humic acid functionalized hyperbranched polytriazine based dispersive solid‐phase extraction for acaricides determination in tea matrix

Hyperbranched polytriazine functionalized with humic acid was prepared and developed as new sorbents for dispersive solid‐phase extraction of three acaricides (clofentezine, fenpyroximate, and pyridaben) in tea samples combined with high‐performance liquid chromatography detection. The sorbents were characterized by scanning electron microscopy, energy dispersive spectroscopy, Zeta‐potential, and Fourier transform infrared spectroscopy. The extraction parameters (extraction time, ionic strength, desorption conditions) were optimized. The adsorption mechanism was evaluated utilizing Fourier transform infrared spectra. Under optimum conditions, satisfactory analytical performances were achieved, which included high precision (1.33–9.62%), low limits of detection (0.19–3.54 µg/L), and wide linear range (2.5–500 µg/L) for the analysis of the acaricides. Moreover, the proposed method proved highly effective for the determination of acaricides in tea samples, with the relative recoveries in the range of 65.20–108.13% and relative standard deviations < 9.87%. The method has great application potential for the detection of acaricides in tea samples.     

Molecularly imprinted polymer on a SiO2‐coated graphene oxide surface for the fast and selective dispersive solid‐phase extraction of Carbamazepine from biological samples

A surface carbamazepine‐imprinted polymer was grafted and synthesized on the SiO₂/graphene oxide surface. Firstly SiO₂ was coated on synthesized graphene oxide sheet using the sol–gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO₂/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross‐linker and porogen, respectively. Nonimprinted polymer was also prepared for comparison. The properties of the molecularly imprinted polymer were characterized using field‐emission scanning electron microscopy and Fourier‐transform infrared spectroscopy. The surface molecularly imprinted polymer was utilized as an adsorbent of dispersive solid‐phase extraction for separation and preconcentration of carbamazepine. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the nonimprinted polymer was examined in absence and presence of competitive drugs. The carbamazepine calibration curve showed linearity in the ranges 0.5–500 μg/L. The limits of detection and quantification under the optimized conditions were 0.1 and 0.3 μg/L, respectively. The within‐day and between‐day relative standard deviations (n = 3) were 3.6 and 4.3%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 85%.     

Multiresidue analytical method of pesticides in peanut oil using low-temperature cleanup and dispersive solid phase extraction by GC-MS

A method for the determination of 33 pesticides in peanut oil by GC-MS was described. Two extraction procedures based on (i) low-temperature extraction and (ii) liquid-liquid extraction were tested for the optimization of the method. The mixture of anhydrous MgSO(4) with primary secondary amine (PSA) or with PSA and C(18) was performed as sorbents in dispersive SPE. Low temperature along with PSA and C(18) cleanup gave the best results. Pesticides were identified and quantified by GC-MS in SIM mode. The correlation coefficients, R(2), in the linear range tests were better than 0.990. The average recoveries for most pesticides (spiked at 0.02, 0.05, 0.2, and 1 mg/kg) ranged from 70 to 110%, the RSD was below 20% in most instances, and LODs varied from 0.5 to 8 mug/kg.     

Application of a dispersive solid‐phase extraction method using an amino‐based silica‐coated nanomagnetic sorbent for the trace quantification of chlorophenoxyacetic acids in water samples

Herein, an amino‐based silica‐coated nanomagnetic sorbent was applied for the effective extraction of two chlorophenoxyacetic acids (2‐methyl‐4‐chlorophenoxyacetic acid and 2,4‐dichlorophenoxyacetic acid) from various water samples. The sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy, X‐ray diffraction, and Fourier‐transform infrared spectroscopy. The analytes were extracted by the sorbent mainly through ionic interactions. Once the extraction of analytes was completed, they were desorbed from the sorbent and detected by high‐performance liquid chromatography with ultraviolet detection. A number of factors affecting the extraction and desorption of the analytes were investigated in detail and the optimum conditions were established. Under the optimum conditions, the calibration curves were linear over the concentration range of 1–250, and based on a signal‐to‐noise ratio of 3, the method detection limits were determined to be 0.5 μg/L for both analytes. Additionally, a preconcentration factor of 314 was achieved for the analytes. The average relative recoveries obtained from the fortified water samples varied in the range of 91–108% with relative standard deviations of 2.9–8.3%. Finally, the method was determined to be robust and effective for environmental water analysis.     

Computational design and fabrication of core–shell magnetic molecularly imprinted polymer for dispersive micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the determination of rhodamine 6G

A novel core–shell magnetic nano‐adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro‐solid‐phase extraction followed by determination of rhodamine 6G using high‐performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m‐aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA₉ (3⁴) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid‐base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano‐adsorbent was successfully applied to dispersive micro‐solid‐phase extraction coupled to high‐performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0–99.1, 89.5–92.7, and 86.9–105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%.