Dispersive Liquid-liquid Microextraction Step Research Articles

Evaluation of distribution of emerging mycotoxins in human tissues: applications of dispersive liquid–liquid microextraction and liquid chromatography-mass spectrometry

In this work, a complete study of the distribution of emerging mycotoxins in the human body has been carried out. Specifically, the presence of enniatins (A, A1, B, B1) and beauvericin has been monitored in brain, lung, kidney, fat, liver, and heart samples. A unique methodology based on solid–liquid extraction (SLE) followed by dispersive liquid–liquid microextraction (DLLME) was proposed for the six different matrices. Mycotoxin isolation was performed by adding ultrapure water, acetonitrile, and sodium chloride to the tissue sample for SLE, while the DLLME step was performed using chloroform as extraction solvent. Subsequently, the analysis was carried out by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS). The proposed method allowed limits of quantification (LOQs) to be obtained in a range of 0.001–0.150 ng g−1, depending on the tissue and mycotoxin. The precision was investigated intraday and interday, not exceeding of 9.8% of relative standard deviation. In addition, trueness studies achieved 75 to 115% at a mycotoxin concentration of 25 ng g−1 and from 82 to 118% at 5 ng g−1. The application of this methodology to 26 forensic autopsies demonstrated the bioaccumulation of emerging mycotoxins in the human body since all mycotoxins were detected in tissues. Enniatin B (ENNB) showed a high occurrence, being detected in 100% of liver (7 ± 13 ng g−1) and fat samples (0.2 ± 0.8 ng g−1). The lung had a high incidence of all emerging mycotoxins at low concentrations, while ENNB, ENNB1, and ENNA1 were not quantifiable in heart samples. Co-occurrence of mycotoxins was also investigated, and statistical tests were applied to evaluate the distribution of these mycotoxins in the human body.Graphical

Application of in-situ formed polymer-based dispersive solid phase extraction in combination with solidification offloating organic droplet-based dispersive liquid-liquid microextraction for the extraction of neonicotinoid pesticides from milk samples.

An in-situ formed polymer-based dispersive solid phase extraction in combination with solidification offloating organic droplet-based dispersive liquid-liquid microextraction was developed for the extraction of neonicotinoid pesticides from milk samples. The extracted analytes were determined using high performance liquid chromatography-diode array detector. In this approach, after precipitating the proteins of milk using a zinc sulfate solution, the supernatant phase was transferred into another glass test tube and a homogenous solution of polyvinylpyrrolidone and a suitable water-miscible organic solvent was rapidly injected into it. By this step, the polymer particles were re-produced and the analytes were extracted onto the sorbent surface. In the following step, the analytes were eluted by an appropriate organic solvent to use in the following solidification of floating organic droplet based dispersive liquid-liquid microextraction step that was done to acquire the low limits of detection. Under the optimized conditions, satisfactory results consisting of low limits of detection (0.13-0.21 ng mL-1 ) and quantification (0.43-0.70 ng mL-1 ), high extraction recoveries (73-85%) and enrichment factors (365-425), and good repeatability (relative standard deviations equal or less than 5.1 and 5.9% for intra- and inter day precisions, respectively) were obtained. This article is protected by copyright. All rights reserved.

Development of homogeneous dispersive solid phase extraction using albumin as a green sorbent and its combination with dispersive liquid-liquid microextraction: application in extraction of pesticides from fruit juices.

In the current study, salt- and pH-induced homogeneous dispersive solid phase extraction was developed using albumin as a sorbent for the extraction of some pesticides (diazinon, diniconazole, haloxyfop-R-methyl, and hexaconazole) from fruit juice of orange, pomegranate, and barberry. The extracted analytes were more concentrated by dispersive liquid-liquid microextraction to obtain high enrichment factors and low detection limits prior to their determination by gas chromatography-mass spectrometry. In the extraction process, human serum albumin solution was added to the sample solution at the μL-level and a homogeneous solution was obtained. Then, albumin was precipitated into the solution by adding an inorganic salt and decreasing the solution pH. By doing so, the analytes were adsorbed by albumin effectively due to their high adsorption capacity and large surface area. Following this, the pesticides were eluted from the albumin sorbent using an elution solvent and used in a dispersive liquid-liquid microextraction step. Under the optimum extraction conditions, low limits of detection and quantification were achieved in the ranges of 0.02-0.04 and 0.07-0.13 ng mL-1, respectively. The calibration curves were linear in the range of 0.13-250 ng mL-1. Relative standard deviation as a criterion for precision and the method repeatability were in the ranges of 2.9-4.2% for intra- (n = 5, C = 5 or 50 ng mL-1) and 3.2-5.2% for inter-day (n = 5, 50 ng mL-1) precisions. The enrichment factors and extraction recoveries were in the ranges of 390-460 and 78-92%, respectively. Finally, the offered procedure was applied for the analysis of pesticide residues in some fruit juice samples.

Extraction of diazinon, haloxyfop-R-methyl, hexaconazole, diniconazole, and triticonazole in cheese samples using a ferrofluid based liquid phase extraction method prior to gas chromatography.

In the present study, a ternary phase solvent extraction combined with dispersive liquid-liquid microextraction was developed for the extraction of diazinon, haloxyfop-R-methyl, hexaconazole, diniconazole, and triticonazole from cheese samples. The extracted analytes were determined using gas chromatography. In this work, first, the analytes were extracted into an organic phase and then enriched using a dispersive liquid-liquid microextraction. Deep eutectic solvent-based ferrofluid was synthesized and used as an extraction solvent in the dispersive liquid-liquid microextraction step, which makes the method fast and green. After optimization of experimental conditions, under the best extraction conditions, limits of detection and quantification were found in the ranges of 0.18-0.39 and 0.6-1.3 ng g-1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 138-156 and 69-78%, respectively. In the end, the proposed method was successfully applied to assess the studied pesticides in cheese samples.

Development of a sensitive method for determining traces of prohibited acrylamide in cosmetic products based on dispersive liquid-liquid microextraction followed by liquid chromatography-ultraviolet detection

According to the European Regulation on cosmetic products, the presence of acrylamide in these consumer products is not allowed due to its mutagenic and potentially carcinogenic effects. Despite this ban, acrylamide might be present in those cosmetic products containing acrylamide-based polymers. However, there is no analytical method for its determination in this type of matrices. Based on this, the development of analytical methods for the determination of acrylamide in cosmetic products is required to guarantee consumer safety. In this work, an analytical method for determining traces of prohibited acrylamide in cosmetic products is presented for the first time. The method is based on dispersive liquid-liquid microextraction (DLLME), followed by liquid chromatography–ultraviolet (LC-UV) detection. A previous derivatization of acrylamide with 2-naphthalenethiol was performed to obtain a more lipophilic compound, and therefore, more extractable in the DLLME step, in addition to the bathochromic displacement of the measurement wavelength. The main variables involved in both derivatization and DLLME step were studied to provide the best enrichment factors. Under the optimized conditions, 6.5 mL of aqueous sample solution was cleaned-up from lipophilic matrix components by liquid-liquid extraction (LLE) using 3.5 mL of hexane. Then, 5 mL were taken and subjected to microwave derivatization with a mixture of 250 μL of 2-naphthalenethiol (0.5 mg mL−1) and 250 μL of di-sodium tetraborate (4 mg mL−1). Afterwards, it was subjected to DLLME by injecting a mixture of 250 µL of acetone (as disperser solvent) and 80 µL of chloroform (as extraction solvent). The extracts were evaporated to dryness, reconstituted in mobile phase and injected into the LC-UV system. The method was successfully validated showing good linearity (from 10 ng mL−1 to 20 µg mL−1), an enrichment factor of 103 ± 2, instrumental limits of detection and quantification of 3.0 and 9.8 ng mL−1, which, according to sample treatment, correspond to 0.7 and 2.4 µg kg−1 in the sample, respectively, and a good repeatability (RSD < 14%). Finally, the proposed analytical method was applied to the determination of acrylamide in commercial cosmetic samples of different nature with good relative recovery values (85 – 112%), which shows that the matrix effect is negligible. This method could help the cosmetic industry to control the cosmetic products containing potential acrylamide-releasing ingredients.

Determination of Two Antiepileptic Drugs in Urine by Homogenous Liquid-Liquid Extraction Performed in A Narrow Tube Combined with Dispersive Liquid-liquid Microextraction Followed by Gas Chromatography-flame Ionization Detection.

A simple and efficient homogenous liquid-liquid extraction method performed in a narrow tube combined with dispersive liquid-liquid microextraction method has been presented for the simultaneous determination of two antiepileptic drugs in urine followed by gas chromatography with flame ionization detection. In this method, a mixture of acetonitrile and urine sample (homogenous solution) is loaded into a column partially filled with solid sodium chloride. By passing the homogenous solution through the salt layer, acetonitrile is separated from the aqueous solution as the fine droplets and collected on top of the column as a separated phase. The obtained organic phase is removed and mixed with an extraction solvent, and then the resulting mixture is rapidly injected into an alkaline solution. Various experimental parameters affecting performance of the proposed method such as type and volume of extraction solvent, pH, and flow rate in homogenous liquid-liquid extraction step, and type and volume of extraction solvent and ionic strength in dispersive liquid-liquid microextraction step were investigated. The relative standard deviation of the proposed method was <8% (n = 6, C = 1 µg L-1 of each analyte). The limits of detection for phenobarbital and carbamazepine were 0.017 and 0.010 µg L-1 and the limits of quantification were 0.056 and 0.033 µg mL-1, respectively.

Magnetic Solid Phase Extraction Based on Modified Magnetite Nanoparticles Coupled with Dispersive Liquid–Liquid Microextraction as an Efficient Method for Simultaneous Extraction of Hydrophobic and Hydrophilic Drugs

In this work, surfactant-coated Fe3O4@decanoic acid nanoparticles was synthesized as a viable nanosorbent for coextraction of drugs with different polarities (hydrophobic, hydrophilic). To reach desirable enrichment factors, efficient clean-up and low limits of detection (LODs), the method was combined with dispersive liquid–liquid microextraction (DLLME). The coupling of these extraction methods with GC-FID detection was applied to simultaneous extraction and quantification of venlafaxine (VLF) as a hydrophilic model drug and desipramine (DESI) and clomipramine (CLO) as hydrophobic model drugs in urine samples. The effect of sample pH, nanosorbent amount, sorption time, surfactant concentration, eluent type, eluent volume, salt content, elution time in magnetic solid phase extraction step and extraction solvent and its volume along with sample pH in DLLME step were optimized. Under the selected conditions, linearity was achieved within the range of 5–5000 µg L−1. The LOD values were obtained in the range of 1.5–3.0 µg L−1 for DESI, 1.2–2.5 µg L−1 for VLF and 2.0–4.0 µg L−1 for CLO, respectively. The percent of extraction recoveries and relative standard deviations (n = 5) were in the range of 82.4–95.9 and 6.1 for DESI, 60.5–92.8 and 6.9 for VLF and 57.2–58.0 and 5.5 for CLO, respectively. Ultimately, the applicability of the new method was successfully confirmed by the extraction and quantification of DESI, VLF and CLO from human urine samples.

A Fast and Easy QuEChERS-DLLME Method Combined with GC-MS for Ethion and Bifenthrin Residues Determination and Study of Their Dissipation Dynamics in Palm Dates

New fast and efficient analytical method based on QuEChERS followed by dispersive liquid-liquid microextraction (DLLME) was developed for extraction and pre-concentration of residues of ethion and bifenthrin insecticide/acaricides in palm date matrix. GC-MS was used for quantification of the pesticides. The developed method was validated according to the European regulations’ requirements. Method accuracy was 102.2% and 96.1% with a precision of 8.4% and 4.3% (intra-day) and 7.9 and 5.1% (inter-day) for ethion and bifenthrin, respectively. The validated QuEChERS and QuEChERS-DLLME methods were compared. Applying DLLME for preconcentration of pesticides lowered the limit of quantification nearly 20 times. By adding the DLLME step using chlorobenzene as extractant, the method achieved better sensitivity and enrichment factor. Matrix effects were evaluated. Developed methods were utilized in analysis of real samples originated from field trial and markets. For field trial, pre-harvest interval (PHI) and dissipation kinetics were investigated. QuEChERS-DLLME method detected ethion in all market samples and bifenthrin in two of them.

Simultaneous determination of five Alternaria toxins in cereals using QuEChERS-based methodology.

Two analytical approaches, including ultra-high performance liquid chromatograph linked with photo-diode array/fluorescence detector, and ultra-high performance liquid chromatography-tandem mass spectrometry, have been proposed for simultaneous determination of five Alternaria toxins in cereals, which both based on QuEChERS strategy. After QuEChERS extraction and salting out, the collected supernatant was subjected to an extra dispersive liquid-liquid microextraction step prior to quantitative analysis. Response surface methodology based on central composite design was employed to optimize the micro-extraction conditions. During photo-diode array/fluorescence detector method validation, satisfactory analytical characteristics, in terms of selectivity, recovery (72.7%-109.1%), precision (inter-day RSDs <9.6%), sensitivity (limits of quantification ranged from 2.1μgkg-1 to 120.0μgkg-1) and linearity (R2 all higher than 0.9984), were achieved. Mass spectrometry method was employed as a certified method for accuracy. The two methodologies were successfully applied to 71 samples including three different matrices and the quantitative results were compared. As the result of non-parametric test shown, the established two analytical approach exhibited comparable quantitative accuracy to each other.

Determination of synthetic phosphodiesterase-5 inhibitors by LC-MS2 in waters and human urine submitted to dispersive liquid-liquid microextraction

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS2) with a triple quadrupole is proposed for determining the synthetic phosphodiesterase-5 inhibitors, sildenafil, tadalafil and vardenafil, and the active metabolite N-desmethyl sildenafil. The method was successfully applied to the analysis of waters of different origins and human urine samples. Dispersive liquid-liquid microextraction (DLLME) was applied in the classical way for water analysis, whereas a previous extraction into an organic solvent was necessary for urine samples, the acetonitrile extract being used as dispersant solvent in the DLLME step. The analytes were determined by LC-ESI-MS2 in the multiple reaction monitoring mode. Detection limits were in the 5–50 and 15–250ngL−1 ranges for water and urine samples, respectively. The repeatability was calculated using the relative standard deviation, obtaining values of between 3.6% and 10.1%. The enrichment factors were between 75 and 81. Accuracy of the procedure was calculated through recovery assays and average recoveries ± SD (n = 48) of 93.6 ± 3.5 and 91.1 ± 3.5 were obtained for water and urine samples, respectively. None of the samples analyzed contained the target compounds, at least above the corresponding detection limits.

Glyoxal and methylglyoxal as urinary markers of diabetes. Determination using a dispersive liquid–liquid microextraction procedure combined with gas chromatography–mass spectrometry

Glyoxal (GO) and methylglyoxal (MGO) are α-oxoaldehydes that can be used as urinary diabetes markers. In this study, their levels were measured using a sample preparation procedure based on salting-out assisted liquid–liquid extraction (SALLE) and dispersive liquid–liquid microextraction (DLLME) combined with gas chromatography-mass spectrometry (GC–MS). The effect of the derivatization reaction with 2,3-diaminonaphthalene, the addition of acetonitrile and sodium chloride to urine, and the DLLME step using the acetonitrile extract as dispersant solvent and carbon tetrachloride as extractant solvent were carefully optimized. Quantification was performed by the internal standard method, using 5-bromo-2-chloroanisole. The intraday and interday precisions were lower than 6%. Limits of detection were 0.12 and 0.06ngmL−1, and enrichment factors 140 and 130 for GO and MGO, respectively. The concentrations of these α-oxoaldehydes in urine were between 0.9 and 35.8ngg−1 levels (creatinine adjusted). A statistical comparison of the analyte contents of urine samples from non-diabetic and diabetic patients pointed to significant differences (P=0.046, 24 subjects investigated), particularly regarding MGO, which was higher in diabetic patients. The novelty of this study compared with previous procedures lies in the treatment of the urine sample by SALLE based on the addition of acetonitrile and sodium chloride to the urine. The DLLME procedure is performed with a sedimented drop of the extractant solvent, without a surfactant reagent, and using acetonitrile as dispersant solvent. Separation of the analytes was performed using GC–MS detection, being the analytes unequivocal identified. The proposed procedure is the first microextraction method applied to the analysis of urine samples from diabetic and non-diabetic patients that allows a clear differentiation between both groups using a simple analysis.

Magnetic Solid-Phase Extraction Combined with Dispersive Liquid-Liquid Microextraction Followed by HPLC for Determination of Four Aromatic Amines Released from Azo Dyes in Paper Samples

A novel extraction technique combining dispersive liquid-liquid microextraction (DLLME) with magnetic solid-phase extraction (MSPE) is presented for pre-concentration of four primary aromatic amines (PAAs) released from azo dyes in paper samples prior to high performance liquid chromatography (HPLC). n-Octanol was used as the extractant and hydrophobic oleic acid modified Fe3O4 nanoparticles (Fe3O4@OA NPs) as an efficient adsorbent was applied to retrieve the PAAs-containing n-octanol in the DLLME step. Because of the rapid mass transfer associated with the DLLME and MSPE steps, fast extraction could be achieved. The main parameters affecting the efficiency of MSPE-DLLME procedure of PAAs were investigated and optimized. Under optimum conditions, the recoveries ranged from 79.6 to 88.5% and the limits of detection (LODs) were in the range of 0.21-1.16 ng mL-1 (S / N = 3). The intra-day precision (relative standard deviation (RSD)) was below 7.8% and inter-day RSD was less than 11%.

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.

Ultrasound-Assisted Extraction Followed by Solid-Phase Extraction Followed by Dispersive Liquid–Liquid Microextraction for the Sensitive Determination of Diazinon and Chlorpyrifos in Rice

Selectivity of solid-phase extraction (SPE) was combined with the concentration power of dispersive liquid–liquid microextraction (DLLME) to obtain a sensitive, low solvent consumption method for high-performance liquid chromatography determination of diazinon and chlorpyrifos in rice. In this method, rice samples were extracted by ultrasound-assisted extraction followed by SPE. Then, the SPE eluent was used as a disperser solvent in the next dispersive liquid-liquid microextraction step for further purification and enrichment of diazinon and chlorpyrifos. Under the optimal conditions, the linear range was from 5.0 to 250 μg kg−1 for diazinon and from 2.5 to 250 μg kg−1 for chlorpyrifos. Limits of detection of diazinon and chlorpyrifos were 1.5 and 0.7 μg kg−1, respectively. Limits of quantitation of diazinon and chlorpyrifos were 5.5 and 3.0 μg kg−1, respectively. The precisions and recoveries also were investigated by spiking 10 μg kg−1 concentration in rice. The recoveries obtained were over 90 % with relative standard deviation (RSD%) below 9.0 %. The new approach was utilized to successfully detect trace amounts of diazinon and chlorpyrifos in different Iranian rice samples.

Combination of dispersive liquid–liquid microextraction and solid–phase microextraction: An efficient hyphenated sample preparation method

Two well-known microextraction methods, dispersive liquid–liquid microextraction (DLLME) and solid–phase microextraction (SPME), were combined, resulting in as an encouraging method. The method, named DLLME–SPME, was performed based on total vaporization technique. For the DLLME step, 1,1,2,2-tetrachloroethane and acetonitrile were used as extraction and disperser solvents, respectively. Halloysite nanotubes–titanium dioxide was used as the fiber coating in the SPME step. The method was applied for the extraction of diazinon and parathion (as the test compounds) in environmental water samples and fruit juices, and gas chromatography–corona discharge ion mobility spectrometry was used as the determination apparatus. Desorption temperature and time, extraction temperature and time, and the volume of the extracting solvent in the DLLME step were optimized as the effective parameters on the extraction efficiency. The relative standard deviations (RSDs) of intra-day were found to be 4–7% and 6–8% for diazinon and parathion, respectively. Also, the RSDs of inter-day were 7–9% and 8–10% for diazinon and parathion, respectively. The limits of quantification and detection were obtained to be 0.015 and 0.005μgL−1 for diazinon, and 0.020 and 0.007μgL−1 for parathion. A good linearity range (r2˃0.993) was obtained in the range of 0.015–3.000 and 0.020–3.000μgL−1 for diazinon and parathion, respectively. The high enrichment factors were obtained as 3150 and 2965 for diazinon and parathion, respectively. This method showed high sensitivity with good recovery values (between 87 and 99%) for the extraction of target analytes in the real samples. Overall, the results revealed that the developed DLLME–SPME method had better extraction efficiency than DLLME and SPME alone.

Application of ionic‐liquid‐supported magnetic dispersive solid‐phase microextraction for the determination of acaricides in fruit juice samples

In this study, ionic liquid (IL) supported magnetic dispersive solid-phase microextraction was developed and a systematic investigation was conducted on imidazolium ILs for their extraction performance. This nano-based pretreatment procedure was then applied for the determination of acaricides in fruit juice samples for the first time. A feature of this technique is that the commonly laborious chemical modification of magnetic nanoparticles (MNPs) was skillfully circumvented. Because of the combination of ILs, dispersive liquid-liquid microextraction, and dispersive MNP solid-phase microextraction, the extraction efficiency can be significantly improved using commercial MNPs. Parameters of the extraction method were investigated by one-factor-at-a-time approach. The optimal experimental conditions were as follows: emulsification for 2 min by sonication with the addition of 50 μL [C6MIM][NTf2] in the dispersive liquid-liquid microextraction step and vortexing for 90 s after adding 40 mg spherical barium ferrite nanoparticles (20 nm). The desorption time was 2 min. Good linearity (0.5-500 ng/mL) and detection limits within the range of 0.05-0.53 ng/mL were achieved. The application of the proposed method was demonstrated by the analysis of real fruit juice samples, in which recoveries between 85.1 and 99.6% were obtained.

Ionic liquid-linked dual magnetic microextraction of lead(II) from environmental samples prior to its micro-sampling flame atomic absorption spectrometric determination

A novel and rapid microextraction approach termed as ionic liquid-linked dual magnetic microextraction (IL-DMME), was developed for the atomic absorption spectrometric determination of lead. The developed method based on a combination of dispersive liquid–liquid microextraction (DLLME) and dispersive micro solid-phase extraction (D-μ-SPE). In the first DLLME step, 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6], was selected to extract the lead-pyrrolidine-dithiocarbamate (Pb-PDC) complex from sample solution by the assistance of vortex agitator. After the first step, fifty milligrams of Fe3O4 magnetic nanoparticles (MNPs) were added to extraction of the ionic liquid and Pb-PDC complex in aqueous solution. The effective factors in proposed IL-DMME procedure, including volume of 1-butyl-3-methylimidazolium hexafluorophosphate, amount of Fe3O4 magnetic nanoparticles, vortex time, amount of ammonium pyrrolidinedithiocarbamate, sample volume and matrix effect were optimized in details. Under the optimal conditions, the method present has low detection limit (0.57μgL−1), high preconcentration factor (160) and good repeatability (<7.5%, n=10). The accuracy of the developed method was evaluated by the analysis of the certified reference materials and addition-recovery tests. The method was successfully applied to the determination of lead in water, plant and hair samples.

Determination of abamectin in citrus fruits using SPE combined with dispersive liquid–liquid microextraction and HPLC–UV detection

A new pretreatment method, SPE combined with dispersive liquid-liquid microextraction, was proposed for the determination of abamectin in citrus fruit samples for the first time. In this method, fruit samples were extracted by ultrasound-assisted extraction followed by SPE. Then, the SPE was used as a disperser solvent in the next dispersive liquid-liquid microextraction step for further purification and enrichment of abamectin. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. Good linearity of abamectin was obtained from 0.005 to 10.0 mg/kg for B1a and from 0.05 to 10.0 mg/kg for B1b with correlation coefficient (r(2)) of 0.998 for B1a and 0.991 for B1b, respectively. The LODs were 0.001 and 0.008 mg/kg (S/N = 3) for B1a and B1b, respectively. The relative recoveries at three spiked levels were ranged from 87 to 96% with the RSD less than 11% (n = 3). The method has been successfully applied to the determination of abamectin in citrus fruit samples.

Ionic liquid-linked dual magnetic microextraction: A novel and facile procedure for the determination of pyrethroids in honey samples

A novel and facile microextraction technique, termed as ionic liquid-linked dual magnetic microextraction (IL-DMME), was developed for the determination of pyrethroids in honey samples. The distinct advantage of the proposed method is that high recoveries can be readily achieved through the combination of dispersive liquid-liquid microextraction (DLLME) and dispersive microsolid-phase extraction (D-μ-SPE) with the aid of synthetic ionic liquid and non-modified magnetic nanoparticles (MNPs), respectively. In the first DLLME step, [C6MIM]NTf2 was used to extract the pyrethroids without the addition of any toxic dispersive solvent. In the following D-μ-SPE steps, non-modified MNPs were added to retrieve the ionic liquid. The effect of different variables on the extraction efficiency was studied simultaneously using the response surface methodology. The Plackett-Burman design was first employed to screen for the variables that significantly affected the extraction efficiency. Central composite design (CCD) was then introduced to optimize the significant factors using a polynomial fit. The optimal experimental conditions obtained from this statistical evaluation included: ionic liquid volume, 75 μL; S-BaFe quantity, 60 mg; sonication time, 4 min; vortex time, 100 s; desorption time, 150 s; and no addition of salt. Under the optimal conditions, good linearity in the range of 0.5 μg L(-1)-500 μg L(-1), repeatability (RSD 1.1-3.8%), low LODs (0.03-0.05 μg L(-1)) and good recovery (86.7-98.2%) were obtained. Finally, the developed method was evaluated for the extraction and determination of four pyrethroids in real honey samples.

Mixed-mode solid-phase extraction followed by dispersive liquid–liquid microextraction for the sensitive determination of ethylphenols in red wines

Selectivity of mixed-mode solid-phase extraction (SPE) was combined with the concentration power of dispersive liquid–liquid microextraction (DLLME) to obtain a sensitive, low solvent consumption method for gas chromatography-mass spectrometry determination of ethylphenol off-flavours (4-ethylphenol, EP; 4-ethylguaicol, EG and 4-ethylcathecol, EC) in complex red wine samples. Under optimized conditions, limits of quantification (LOQs) between 0.3 and 0.8ngmL−1 were obtained using just 5mL of wine and 0.06mL of 1,1,1-trichloroethane (TCE) as extractant in the DLLME step. Analytes were acetylated after SPE and previously to DLLME concentration to enhance the performance of their GC–MS determination. The overall extraction efficiency of the method was unaffected by the particular characteristics of each wine; thus, accurate results (relative recoveries from 89 to 109% for samples spiked at concentrations from 20 to 1000ngmL−1) were obtained using matrix-matched standards, without requiring the use of the time consuming standard addition quantification methodology. The applicability of the method was demonstrated with the analysis of different red wines. Analytes concentrations varied from 6 to 2265ngmL−1 (EP), 0.8 to 251ngmL−1 (EG) and non-detected to 158ngmL−1 (EC).