Solid-phase extraction followed by dispersive liquid–liquid microextraction for the sensitive determination of selected fungicides in wine

A novel approach for the determination of seven fungicides (metalaxyl-M, penconazole, folpet, diniconazole, propiconazole, difenoconazole and azoxystrobin) in wine samples is presented. Analytes were extracted from the matrix and transferred to a small volume of a high density, water insoluble solvent using solid-phase extraction (SPE) followed by dispersive liquid–liquid microextraction (DLLME). Variables affecting the performance of both steps were thoroughly investigated (metalaxyl-M was not included in some optimisation studies) and their effects on the selectivity and efficiency of the whole sample preparation process are discussed. Under optimised conditions, 20 mL of wine were first concentrated using a reversed-phase sorbent and then target compounds were eluted with 1 mL of acetone. This extract was mixed with 0.1 mL of 1,1,1-trichloroethane (CH₃CCl₃) and the blend added to 10 mL of ultrapure water. After centrifugation, an aliquot (1–2 μL) of the settled organic phase was analyzed by gas chromatography (GC) with electron capture (ECD) and mass spectrometry (MS) detection. The method provided enrichment factors (EFs) around 200 times and an improved selectivity in comparison to use of SPE as single sample preparation technique. Moreover, the yield of the global process was similar for red and white wine samples and the achieved limits of quantification (LOQs) (from 30 to 120 ng L⁻¹ and from 40 to 250 ng L⁻¹, for GC–ECD and GC–MS, respectively) were low enough for the determination of target species in commercial wines. Among compounds considered in this work, metalaxyl-M and azoxystrobin were found in several wines at concentrations from 0.8 to 32 ng mL⁻¹.     

Low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction combined with gas chromatography-tandem mass spectrometry for the determination of carbamate pesticides in water samples

A simple and fast method of low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction (ST-DLLME) was developed for the highly sensitive determination of carbamate pesticides in the water samples by gas chromatography-tandem mass spectrometry (GC-MSMS). After dispersing, the obtained emulsion cleared into two phases quickly when an aliquot of acetonitrile was introduced as a chemical demulsifier into the aqueous bulk. Therefore, the developed procedure does not need centrifugation to achieve phase separation. It was convenient for the usage of low-density extraction solvents in DLLME. Under the optimized conditions, the limits of detection for all target carbamate pesticides were in range of 0.001–0.50 ng mL⁻¹ and the precisions were in the range of 2.3–6.8% (RSDs, 2 ng mL⁻¹, n = 5). The proposed method has been successfully applied to the analysis of real water samples and good spiked recoveries over the range of 94.5–104% were obtained.     

Solvent-based de-emulsification dispersive liquid–liquid microextraction combined with gas chromatography–mass spectrometry for determination of trace organochlorine pesticides in environmental water samples

In this work, we propose solvent-based de-emulsification dispersive liquid–liquid microextraction (SD-DLLME) as a simple, rapid and efficient sample pretreatment technique for the extraction and preconcentration of organochlorine pesticides (OCPs) from environmental water samples. Separation and analysis of fifteen OCPs was carried out by gas chromatography–mass spectrometry (GC/MS). Parameters affecting the extraction efficiency were systematically investigated. The detection limits were in the range of 2–50 ng L⁻¹ using selective ion monitoring (SIM). The precision of the proposed method, expressed as relative standard deviation, varied between 3.5 and 10.2% (n = 5). Results from the analysis of spiked environmental water samples at the low-ppb level met the acceptance criteria set by the EPA.     

Ultrasound-assisted dispersive liquid–liquid microextraction for the determination of six pyrethroids in river water

A simple ultrasound-assisted dispersive liquid–liquid microextraction method combined with liquid chromatography was developed for the preconcentration and determination of six pyrethroids in river water samples. The procedure was based on a ternary solvent system to formatting tiny droplets of extractant in sample solution by dissolving appropriate amounts of water-immiscible extractant (tetrachloromethane) in watermiscible dispersive solvent (acetone). Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvent, extraction time, ultrasonic time, and centrifuging time) were evaluated. Under the optimum condition, good linearity was obtained in a range of 0.00059–1.52 mg L⁻¹ for all analytes with the correlation coefficient (r²) > 0.999. Intra-assay and inter-assay precision evaluated as the relative standard deviation (RSD) were less than 3.4 and 8.9%. The recoveries of six pyrethroids at three spiked levels were in the range of 86.2–109.3% with RSD of less than 8.7%. The enrichment factors for the six pyrethroids were ranged from 767 to 1033 folds.     

Development of an analytical procedure for the determination of polybrominated diphenyl ethers in environmental water samples by GC–ICP-MS

Polybrominated diphenyl ethers (PBDEs) are flame retardants, which due to their widespread use are frequently present as pollutants in the environment. In the EU Water Framework Directive (WFD) six PBDE congeners (BDE 28, BDE47, BDE 99, BDE 100, BDE 153 and BDE 154) are listed as priority substances. The uncertainty of the analytical method used for their determination in water samples at environmental quality standard (EQS) level (0.5 ng L⁻¹ for the ΣPBDEs) should be equal or less than 50% and the limit of quantification (LOQ) for ΣPBDEs below 0.15 ng L⁻¹. To meet these requirements, an analytical procedure for the determination of these six PBDEs in environmental water samples by gas chromatography–inductively coupled plasma mass spectrometry (GC–ICP-MS) was developed. The acidification of water samples to pH 2 maintained the stability of PBDEs for at least 20 days. The use of Tris–citrate buffer enabled efficient desorption of PBDEs from suspended particulate matter (SPM) and humic acids (HA), and their further quantitative solvent extraction into 2 mL of iso-octane. When 300 mL of water sample was used for analysis and the organic phase concentrated to 25 μL, the expanded uncertainty for determination of PBDEs at EQS level was found to be around 40% (a coverage factor for a confidence level of 95%, k = 2), and the LOQ for the ΣPBDEs 0.109 ng L⁻¹. Finally, to demonstrate the applicability of the newly developed GC–ICP-MS procedure, PBDEs were determined in river and sea water samples.     

Dispersive liquid–liquid–liquid microextraction combined with liquid chromatography for the determination of chlorophenoxy acid herbicides in aqueous samples

A novel sample preparation method “Dispersive liquid–liquid–liquid microextraction” (DLLLME) was developed in this study. DLLLME was combined with liquid chromatography system to determine chlorophenoxy acid herbicide in aqueous samples. DLLLME is a rapid and environmentally friendly sample pretreatment method. In this study, 25 μL of 1,1,2,2-tetrachloroethane was added to the sample solution and the targeted analytes were extracted from the donor phase by manually shaking for 90 s. The organic phase was separated from the donor phase by centrifugation and was transferred into an insert. Acceptor phase was added to this insert. The analytes were then back-extracted into the acceptor phase by mixing the organic and acceptor phases by pumping those two solutions with a syringe plunger. After centrifugation, the organic phase was settled and removed with a microsyringe. The acceptor phase was injected into the UPLC system by auto sampler. Fine droplets were formed by shaking and pumping with the syringe plunger in DLLLME. The large interfacial area provided good extraction efficiency and shortened the extraction time needed. Conventional LLLME requires an extraction time of 40–60 min; an extraction time of approximately 2 min is sufficient with DLLLME. The DLLLME technique shows good linearity (r² ≥ 0.999), good repeatability (RSD: 4.0–12.2% for tap water; 5.7–8.5% for river water) and high sensitivity (LODs: 0.10–0.60 μg/L for tap water; 0.11–0.95 μg/L for river water).     

Ultrasound-assisted dispersive liquid–liquid microextraction combined with high-performance liquid chromatography-fluorescence detection for sensitive determination of biogenic amines in rice wine samples

Ultrasound-assisted dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography-fluorescence detection was used for the extraction and determination of three biogenic amines including octopamine, tyramine and phenethylamine in rice wine samples. Fluorescence probe 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester was applied for derivatization of biogenic amines. Acetonitrile and 1-octanol were used as disperser solvent and extraction solvent, respectively. Extraction conditions including the type of extraction solvent, the volume of extraction solvent, ultrasonication time and centrifuging time were optimized. After extraction and centrifuging, analyte was injected rapidly into high-performance liquid chromatography and then detected with fluorescence. The calibration graph of the proposed method was linear in the range of 5–500 μg mL⁻¹ (octopamine and tyramine) and 0.025–2.5 μg mL⁻¹ (phenethylamine). The relative standard deviations were 2.4–3.2% (n = 6) and the limits of detection were in the range of 0.02–5 ng mL⁻¹. The method was applied to analyze the rice wine samples and spiked recoveries in the range of 95.42–104.56% were obtained. The results showed that ultrasound-assisted dispersive liquid–liquid microextraction was a very simple, rapid, sensitive and efficient analytical method for the determination of trace amount of biogenic amines.     

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).     

Ionic liquid based dispersive liquid–liquid microextraction for the extraction of pesticides from bananas

This paper describes a dispersive liquid–liquid microextraction (DLLME) procedure using room temperature ionic liquids (RTILs) coupled to high-performance liquid chromatography with diode array detection capable of quantifying trace amounts of eight pesticides (i.e. thiophanate-methyl, carbofuran, carbaryl, tebuconazole, iprodione, oxyfluorfen, hexythiazox and fenazaquin) in bananas. Fruit samples were first homogenized and extracted (1 g) with acetonitrile and after suitable evaporation and reconstitution of the extract in 10 mL of water, a DLLME procedure using 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) as extraction solvent was used. Experimental conditions affecting the DLLME procedure (sample pH, sodium chloride percentage, ionic liquid amount and volume of disperser solvent) were optimized by means of an experimental design. In order to determine the presence of a matrix effect, calibration curves for standards and fortified banana extracts (matrix matched calibration) were studied. Mean recovery values of the extraction of the pesticides from banana samples were in the range of 69–97% (except for thiophanate-methyl and carbofuran, which were 53–63%) with a relative standard deviation lower than 8.7% in all cases. Limits of detection achieved (0.320–4.66 μg/kg) were below the harmonized maximum residue limits established by the European Union (EU). The proposed method, was also applied to the analysis of this group of pesticides in nine banana samples taken from the local markets of the Canary Islands (Spain). To the best of our knowledge, this is the first application of RTILs as extraction solvents for DLLME of pesticides from samples different than water.     

Determination of carbohydrates in tobacco by pressurized liquid extraction combined with a novel ultrasound-assisted dispersive liquid–liquid microextraction method

A novel derivatization-ultrasonic assisted-dispersive liquid–liquid microextraction (UA-DLLME) method for the simultaneous determination of 11 main carbohydrates in tobacco has been developed. The combined method involves pressurized liquid extraction (PLE), derivatization, and UA-DLLME, followed by the analysis of the main carbohydrates with a gas chromatography-flame ionization detector (GC-FID). First, the PLE conditions were optimized using a univariate approach. Then, the derivatization methods were properly compared and optimized. The aldononitrile acetate method combined with the O-methoxyoxime-trimethylsilyl method was used for derivatization. Finally, the critical variables affecting the UA-DLLME extraction efficiency were searched using fractional factorial design (FFD) and further optimized using Doehlert design (DD) of the response surface methodology. The optimum conditions were found to be 44 μL for CHCl₃, 2.3 mL for H₂O, 11% w/v for NaCl, 5 min for the extraction time and 5 min for the centrifugation time. Under the optimized experimental conditions, the detection limit of the method (LODs) and linear correlation coefficient were found to be in the range of 0.06–0.90 μg mL⁻¹ and 0.9987–0.9999. The proposed method was successfully employed to analyze three flue-cured tobacco cultivars, among which the main carbohydrate concentrations were found to be very different.     

A microwave-assisted extraction method combined with magnetic ionic liquid-based dispersive liquid–liquid microextraction for the extraction of chloramine–T from fish samples prior to its determination by high-performance liquid chromatography

In the present work, a combination of microwave-assisted extraction with magnetic ionic liquid–based dispersive liquid–liquid microextraction was developed for the extraction of chloramine–T from fish samples. In this method, the sample was mixed with a hydrochloric acid solution and exposed to microwave irradiations. By doing so, chloramine–T was converted to p–toluenesulfonamide and extracted from the sample into an aqueous phase. Then, a mixture of acetonitrile (as a dispersive solvent) and magnetic ionic liquid (as an extraction solvent) was rapidly injected into the obtained solution. In the following, the magnetic solvent droplets including the extracted analytes were isolated from the aqueous solution in the presence of an external magnetic field and after diluting with acetonitrile injected into high-performance liquid chromatography equipped with a diode array detector. Under the optimum extraction conditions, high extraction recovery (78%), low limits of detection (7.2 ng/g) and quantification (23.9 ng/g), good repeatability (relative standard deviations ≤5.8 and 6.8% for intra– and inter-day precisions, respectively), and wide linear range (23.9–1000 ng/g) were obtained. Finally, various fish samples marketed in Tabriz city (East Azarbaijan, Iran) were analyzed with the suggested method.     

Ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction followed high-performance liquid chromatography for the determination of ultraviolet filters in environmental water samples

In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (IL-USA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for the extraction and preconcentration of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from three different water matrices. The procedure was based on a ternary solvent system containing tiny droplets of ionic liquid (IL) in the sample solution formed by dissolving an appropriate amount of the IL extraction solvent 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) in a small amount of water-miscible dispersive solvent (methanol). An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvents, ionic strength, pH and extraction time) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 354–464, and good repeatability of the extractions (RSDs below 6.3%, n = 5). The limits of detection were in the range of 0.2–5.0 ng mL⁻¹, depending on the analytes. The linearities were between 1 and 500 ng mL⁻¹ for BP, 5 and 500 ng mL⁻¹ for BP-3 and HMS and 10 and 500 ng mL⁻¹ for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in river, swimming pool and tap water samples and acceptable relative recoveries over the range of 71.0–118.0% were obtained.     

Riboflavin as a green sorbent in dispersive micro-solid-phase extraction of several pesticides from fruit juices combined with dispersive liquid–liquid microextraction

A vortex-assisted dispersive micro-solid-phase extraction procedure using a new and green sorbent was developed as a simple, fast, and efficient sample preparation method for the extracting five pesticides in several fruit juice samples. In this study, for the first time, riboflavin was used as an efficient sorbent. A few milligrams of riboflavin was directly added into the aqueous solution containing the analytes to adsorb them. After adsorption the analytes, they were desorbed and more concentrated by a dispersive liquid–liquid microextraction procedure. The influence of several effective parameters such as amount of riboflavin, pH, vortex time, eluent nature and volume, and extraction solvent type and volume on the extraction efficiency was investigated. In optimal conditions, linear ranges of the calibration curves were broad. The limits of detection and quantification were attained in the ranges of 0.56–1.5  and 1.9–0.52 ng mL⁻¹, respectively. The proposed method demonstrated to be suitable for concurrent extraction of the studied pesticides in various fruit juice samples with high enrichment factors (320–360) and precision (relative standard deviation ≤7.8% for intra- [n = 6] and interday [n = 4] precisions at a concentration of 25 ng mL⁻¹ of each pesticide).     

Determination of polybrominated diphenyl ethers in river water by combination of liquid–liquid extraction and gas chromatography–mass spectrometry

In this work,a reliable and sensitive method for detecting polybrominated diphenyl ethers(PBDEs) has been developed by the combination of liquid–liquid extraction and gas chromatography–mass spectrometry.PBDEs were extracted from a large volume of water by liquid–liquid extraction and purified by silica gel chromatography.In order to reduce the deviation,dibromobiphenyl was exploited as the internal standard to minimize differences among the injections.The quantification was performed using an external standard.Good linear correlation coefficients(0.991) and a wide linearity range(1.0–500.0 ng/L) indicated the steadiness of the proposed method.Moreover,the satisfactory recovery(75%)suggested that successful determination of PBDEs in river water had been achieved.Furthermore,the deduction behavior of PBDEs in river water could be inferred according to the results.     

Dispersive solid-phase extraction followed by dispersive liquid–liquid microextraction for the determination of some sulfonylurea herbicides in soil by high-performance liquid chromatography

Dispersive solid-phase extraction (DSPE) combined with dispersive liquid–liquid microextraction (DLLME) has been developed as a new approach for the extraction of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in soil prior to high-performance liquid chromatography with diode array detection (HPLC-DAD). In the DSPE-DLLME, sulfonylurea herbicides were first extracted from soil sample into acetone–0.15 mol L⁻¹ NaHCO₃ (2:8, v/v). The clean-up of the extract by DSPE was carried out by directly adding C₁₈ sorbent into the extract solution, followed by shaking and filtration. After the pH of the filtrate was adjusted to 2.0 with 2 mol L⁻¹ HCl, 60.0 μL chlorobenzene (as extraction solvent) was added into 5.0 mL of it for DLLME procedure (the acetone contained in the solution also acted as dispersive solvent). Under the optimum conditions, the enrichment factors for the compounds were in the range between 102 and 216. The linearity of the method was in the range from 5.0 to 200 ng g⁻¹ with the correlation coefficients (r) ranging from 0.9967 to 0.9987. The method detection limits were 0.5–1.2 ng g⁻¹. The relative standard deviations varied from 5.2% to 7.2% (n = 5). The relative recoveries of the four sulfonylurea herbicides from soil samples at spiking levels of 6.0, 20.0 and 60.0 ng g⁻¹ were in the range between 76.3% and 92.5%. The proposed method has been successfully applied to the analysis of the four target sulfonylurea herbicides in soil samples, and a satisfactory result was obtained.     

Matrix solid-phase dispersion coupled with magnetic ionic liquid dispersive liquid–liquid microextraction for the determination of triazine herbicides in oilseeds

A novel method was developed for the determination of six triazine herbicides from oilseeds by matrix solid-phase dispersion combined with magnetic ionic liquid dispersive liquid–liquid microextraction (MSPD-MIL-DLLME), followed by ultrafast liquid chromatography with ultraviolet detection (UFLC-UV). The MIL, 1-butyl-3-methylimidazolium tetrachloroferrate ([C₄mim][FeCl₄]), was used as the microextraction solvent to simplify the extraction procedure by magnetic separation. The effects of several important experimental parameters, including type of dispersant, ratio of sample to dispersant, type and volume of collected elution solvent, type and volume of MIL, were investigated. Using the present method, UFLC-UV gave the limits of detection (LODs) of 1.20–2.72 ng g⁻¹ and the limits of quantification (LOQs) of 3.99–9.06 ng g⁻¹ for triazine herbicides. The recoveries were ranged from 82.9 to 113.7% and the relative standard deviations (RSDs) were equal or lower than 7.7%. The present method is easy-to-use and effective for extraction of triazine herbicides from oilseeds and shows the potentials of practical applications in the treatment of the fatty solid samples.     

Application of dispersive liquid–liquid microextraction and reversed phase-high performance liquid chromatography for the determination of two fungicides in environmental water samples

Dispersive liquid–liquid microextraction (DLLME) has been developed for the extraction and preconcentration of diethofencarb (DF) and pyrimethanil (PM) in environmental water. In the method, a suitable mixture of extraction solvent (50 µL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) are injected into the aqueous samples (5.00 mL) and the cloudy solution is observed. After centrifugation, the enriched analytes in the sediment phase were determined by HPLC-VWD. Different influencing factors, such as the kind and volume of extraction and dispersive solvent, extraction time and salt effect were investigated. Under the optimum conditions, the enrichment factors for DF and PM were both 108 and the limit of detection were 0.021 ng mL^?1 and 0.015 ng mL^?1, respectively. The linear ranges were 0.08–400 ng mL^?1 for DF and 0.04–200 ng mL^?1 for PM. The relative standard deviation (RSDs) were both almost at 6.0% (n = 6). The relative recoveries from samples of environmental water were from the range of 87.0 to 107.2%. Compared with other methods, DLLME is a very simple, rapid, sensitive (low limit of detection) and economical (only 5 mL volume of sample) method.     

Hollow fiber-based liquid–liquid–liquid microextraction combined with electrospray ionization-ion mobility spectrometry for the determination of pentazocine in biological samples

A new method based on liquid–liquid–liquid microextraction combined with electrospray ionization-ion mobility spectrometry (LLLME-ESI-IMS) was used for the determination of pentazocine in urine and plasma samples. Experimental parameters which control the performance of LLLME, such as selection of composition of donor and acceptor phase, type of organic solvent, ionic strength of the sample, extraction temperature and extraction time were studied. The limit of detection and relative standard deviation of the method were 2 ng/mL and 5.3%, respectively. The linear calibration ranged from 10 to 500 ng/mL with r² = 0.998. Pentazocine was successfully determined in urine and plasma samples without any significant matrix effect.