Simultaneous Determination of Trace Amounts of Cobalt and Nickel in Water and Food Samples Using a Combination of Partial Least Squares Method and Dispersive Liquid–Liquid Microextraction Based on Ionic Liquid

A new, sensitive, and simple combined method including ionic liquid (IL)-based dispersive liquid–liquid microextraction and partial least squares method (PLS) was developed for simultaneous preconcentration and determination of cobalt and nickel in water and food samples. In this work, a small amount of an IL 1-hexyl-3-methylimmidazolium bis (trifluormethylsulfonyl)imid ([Hmim][Tf₂N]) as an extraction solvent was dissolved in ethanol as a disperser solvent and then the binary solution was rapidly injected by a syringe into the water sample containing Co²⁺ and Ni²⁺, which were complexed by 1-(2-pyridylazo)-2-naphthol. After preconcentration, the absorbance of the extracted ions was measured in the wavelength range of 200–700 nm. The partial least squares method was then applied for simultaneous determination of each individual ion. The parameters controlling the behavior of the system were investigated and optimum conditions were selected. Eleven binary mixtures of cobalt and nickel were selected as the calibration set. The calibration models were validated with four synthetic mixtures containing the metal ions in different proportions, which were randomly designed. The best calibration model was obtained by using PLS-1 regression. Calibration graphs were linear in the range of 2.0–20.0 and 2.0–15.0 ng mL^?1 with a limit of detection of 0.65 and 0.32 ng mL^?1 for cobalt and nickel, respectively. The root mean square errors of prediction for cobalt and nickel were 0.4032 and 0.2980, respectively. Satisfactory results were reported for simultaneous determination of trace levels of cobalt and nickel in water, food, and geological certified reference material samples.     

Preconcentration and Trace Determination of Chromium Using Modified Ionic Liquid Cold-Induced Aggregation Dispersive Liquid–Liquid Microextraction: Application to Different Water and Food Samples

An efficient microextraction procedure based on modified ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (M-IL-CIA-DLLME) was developed for trace determination of chromium in water and food samples by flame atomic absorption spectrometry (FAAS), and it was used for speciation of Cr(III) and Cr(VI) in water samples by using Na₂SO₃ as the reducing agent. A mixture of water-immiscible 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF₆]) ionic liquid (IL) (microextraction solvent) and ethanol (disperser solvent) were directly injected into a heated aqueous solution containing bis(2-methoxy benzaldehyde) ethylene diimine as a Schiff’s base ligand (chelating agent), hexafluorophosphate (NaPF₆; as a common ion) and Cr(III). Afterwards, the solution was placed in an ice-water bath and a cloudy solution was formed due to a considerable decrease of IL solubility. After centrifuging, the sedimented phase containing enriched analyte was determined by FAAS. Under the optimum conditions, the calibration graph was linear over the range of 2–50 μg?L^?1 with limit of detection of 0.7 μg?L^?1. The accuracy of the present methodology was tested by recovery experiments and by analyzing a certified reference material. Relative standard deviation (RSD %) was 2.7 % for Cr(III). The proposed method was successfully applied for trace determination of chromium in water and food samples.     

Determination of Cobalt in Food and Water Samples by Ultrasound-assisted Surfactant-enhanced Emulsification Microextraction and Graphite Furnace Atomic Absorption Spectrometry

A novel method based on ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) has been developed for the preconcentration of cobalt prior to its determination by graphite furnace atomic absorption spectrometry. In the UASEME technique, chloroform was used as the extraction solvent, sodium dodecyl sulfate was adopted as emulsifier, and ultrasound was applied to assist emulsification. There is no need of using organic dispersive solvent which is typically required in conventional dispersive liquid–liquid microextraction method. Several parameters that affect the extraction efficiency, such as the kind and volume of the extraction solvent, the type and concentration of the surfactant, pH of sample solution, concentration of the chelating agent, and extraction time and temperature were investigated and optimized. Under the optimal conditions, the linearity of calibration curve was in the range of 0.1–5 ng mL^?1 with a correlation coefficient (R ²) of 0.9992. An enrichment factor of 58 was achieved with a sample volume of 5.0 mL. The detection limit of this method for Co was 15.6 ng L^?1, and the relative standard deviation (RSD) was 4.3 % at 1.0 ng mL^?1 concentration level of Co. The accuracy of the developed method was evaluated by analysis of the certified reference materials GBW07605 tea leaf and GBW10015 spinach. The method was successfully applied to determine trace cobalt in food and water samples with satisfactory results.     

Headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry for the determination of haloanisoles in sparkling (cava and cider) and non-sparkling (wine) alcoholic beverages

A highly sensitive analytical method was developed to determine 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA) and 2,3,4,5,6-pentachloroanisole (PCA) in sparkling alcoholic beverages. The method was based on the use of headspace solid-phase microextraction (HS-SPME) using a polydimethylsiloxane (PDMS) fibre. It was coupled to gas chromatography-triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) for the detection and quantification of the target haloanisoles. The method was fully automated and no sample preparation was needed. The method was validated for alcoholic beverages. The influence of CO₂ on the extraction efficiency was also evaluated for the studied sparkling drinks (cava and cider). All the calibration curves showed good linearity (R² > 0.98) within the tested range (1–50 ng l^?1). Recoveries were evaluated at three different levels (1, 5 and 50 ng l^?1) and were always between 71% and 119%. Precision was expressed as relative standard deviation (RSD), and was evaluated as intra- and inter-day precisions, with values ≤ 22% in both cases. Limits of quantitation (LOQs) were ≤ 0.91 ng l^?1, which are below the sensory threshold levels for such compounds in humans. The validated method was applied to commercial samples, 10 cavas and 10 ciders, but it was also used for the analysis of nine red wines and four white wines, demonstrating the further applicability of the proposed method to non-sparkling beverages. TCA was detected in most samples at up to 0.45 ng l^?1.     

A Miniaturized Preconcentration Method Based on Dispersive Liquid–Liquid Microextraction for the Spectrophotometric Determination of Aziridine in Food Simulants

In this work a simple, rapid and sensitive method using dispersive liquid–liquid microextraction (DLLME) combined with UV–Vis spectrophotometry has been developed for the preconcentration and determination of trace amounts of aziridine in food simulants. The method is based on derivatization of aziridine with Folin's reagent (1,2-naphthoquione-4-sulphonic acid) and extraction of color product using DLLME technique. Some important parameters, such as reaction conditions, and type and volume of extraction solvent and disperser solvent were studied and optimized. Under optimum conditions, a linear calibration curve in the range of 2.0–350 ng mL^?1 of aziridine was obtained. Detection limit based on 3S_b was 1.0 ng mL^?1, and the relative standard deviation for 50 ng mL^?1 of aziridine was 2.49c (n?=?7). The proposed method was applied for the determination of aziridine in food simulants.     

Validation of a lateral flow test (MRLAFMQ) for the detection of aflatoxin M1 at 50 ng l−1 in raw commingled milk

Aflatoxin M₁ contamination in dairy products is a risk when feedstuff contaminated with aflatoxin B₁ produced by moulds is consumed by milk-producing animals. Milk can be screened for aflatoxin M₁ at the European Union maximum limit of 50 ng l^?1 by a lateral flow test, the MRLAFMQ (Aflatoxin M1) Test. The method takes 15 min with no milk dilution or a sample preparation step. The lateral flow assay was validated at the Technology and Food Science Unit of the Institute for Agricultural and Fisheries Research (ILVO-T&V) according to European Union guidelines using fortified raw milk samples. A detection capability of 50 ng l^?1 was demonstrated with a false negative rate lower than 2% at 50 ng l^?1 and a false positive rate of less than 0.3%. Quantitative readings had a mean bias of +2 to 6 ng l^?1 at 50 ng l^?1 with a standard deviation of 5–8 ng l^?1. Based on the validation results, the test could be considered appropriate for milk screening prior to milk unload at dairies.     

Ionic Liquid-Based Surfactant Extraction Coupled with Magnetic Dispersive μ-Solid Phase Extraction for the Determination of Phthalate Esters in Packaging Milk Samples by HPLC

A highly selective sample cleanup procedure combining ionic liquid-based surfactant extraction (ILSE) and magnetic dispersive μ-solid phase extraction (MD-μ-SPE) was triumphantly developed for the synchronously extraction of four phthalate acid esters (PAEs) in packaging milk samples prior to high-performance liquid chromatography coupled with photodiode array detector (HPLC-DAD). In this ionic liquid (IL)-based surfactant method, 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈MIM] [PF₆]) was used as extraction solvent, anionic surfactant sodium linear alkylbenzene sulfonate (LAS) was used as auxiliary extraction solvent, and then sodium chloride (NaCl) was mixed to drive phase separation. The synthesized hydrophobic diatomaceous earth-supported Fe₃O₄ magnetic nanoparticles (DSMNPs) were applied as an efficient adsorbent to retrieve the analyte-containing IL and LAS. Under the optimal extraction situations, good linearity of the approach was obtained in the concentration range from 10 to 1000 ng/mL for target analytes, and the preconcentration process was rapidly accomplished in 5 min. The limits of detection (LODs) based on a signal-to-noise ratio (S/N = 3) were ranged from 1.42 to 3.57 ng/mL with the relative standard deviations (RSDs) over the range of 1.84–3.56% (n = 5). The above-mentioned method was applied to the trace analysis of four PAEs including benzyl butyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-n-butyl phthalate (DBP), and di-n-octyl phthalate (DNOP) in packaging milk samples, and recoveries were between 89.8 and 99.7%.     

Ion-Pair-Based Air-Assisted Liquid–Liquid Microextraction for the Extraction and Preconcentration of Phthalic Acids from Aqueous Samples

In the present study, a rapid, simple, and highly efficient sample preparation method based on ion-pair air-assisted liquid–liquid microextraction using a low-density extraction solvent followed by high performance liquid chromatography–diode array detection has been developed for the extraction, preconcentration, and determination of three phthalic acids (phthalic acid, iso-phthalic acid, and terephthalic acid) in aqueous samples. In this method, a mixture of tri-butyl amine (as an ion-pair reagent) and toluene (as an extraction solvent) is transferred into an aqueous sample solution. Fine organic solvent droplets are formed by aspirating and dispersing of the mixture via syringe needle. After that, the formed ion-pairs are extracted into toluene, and after centrifuging, the obtained collected phase is transferred into a microtube and is evaporated to dryness under a stream of nitrogen at room temperature. The residue is re-dissolved in mobile phase and injected into the separation system for analysis. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.09–0.24 and 0.29–0.78 ng mL^?1, respectively. Extraction recoveries and enrichment factors were from 88 to 98 % and 443 to 491, respectively. Relative standard deviations for the extraction of 5 ng mL^?1 of each analyte were less than 8.4 % for intra-day (n?=?6) and inter-days (n?=?5) precisions. Finally, different aqueous samples were successfully analyzed using the proposed method, and the target analytes were determined in some of them at ng mL^?1 level.     

Simple and fast spectrophotometric determination of low levels of thiabendazole residues in fruit and vegetables after pre-concentration with ionic liquid phase microextraction

There is a great importance of monitoring thiabendazole (TBZ) residues in fruits and vegetables to ensure food safety. Therefore, a new ionic liquid (IL) phase microextraction method using IL, 1-butyl-3-methylimidazoliumhexafluorophosphate [C₄mim][PF₆], as extracting solvent is proposed for simple and fast determination of low levels of TBZ in fruits and vegetables by spectrophotometry. The method is based on selective complex formation of TBZ with Cu(II) ions in presence of PF₆^– as counter ion at pH 5.5, and then microextraction of the complex into the fine micro-drops of IL phase. After optimisation of variables affecting microextraction efficiency, the analytical parameters of the method were determined by calibration curves. The method exhibits a linear relationship (0.3–280 μg L^?1), low detection limit (0.1 μg L^?1), good intra- and inter-day precision (2.4–4.5% as RSD_r%, 2.1–5.6% as RSD_R%), good recovery (≥95.1–98.2%) and high sensitivity enhancement factor (150) by solvent-based calibration curve. It allows a detection limit of 0.24 μg L^?1 and a range of 0.8–250 μg L^?1 by the matrix-matched calibration curve. After validation, the method was successfully applied to the determination of TBZ residues with method quantification limits in fruit and vegetables of 2.0 and 2.5 µg kg^?1 with and without adding polyvinylpyrrolidone (PVP-15) solution. Recoveries range from 85.5% to 98.2% after spiking (10, 50 and 100 µg kg^?1, n: 3).     

A rapid shaking-based ionic liquid dispersive liquid phase microextraction for the simultaneous determination of six synthetic food colourants in soft drinks,sugar- and gelatin-based confectionery by high-performance liquid chromatography

A novel and simple rapid shaking-based method of ionic liquid dispersive liquid phase microextraction for the determination of six synthetic food colourants (Tartrazine, Amaranth, Sunset Yellow, Allura Red, Ponceau 4R, and Erythrosine) in soft drinks, sugar- and gelatin-based confectionery was established. High-performance liquid chromatography coupled with an ultraviolet detector was used for the determinations. The extraction procedure did not require a dispersive solvent, heat, ultrasonication, or additional chemical reagents. 1-Octyl-3-methylimidazolium tetrafluoroborate ([C₈MIM][BF₄]) was dispersed in an aqueous sample solution as fine droplets by manual shaking, enabling the easier migration of analytes into the ionic liquid phase. Factors such as the [C₈MIM][BF₄] volume, sample pH, extraction time, and centrifugation time were investigated. Under the optimum experimental conditions, the proposed method showed excellent detection sensitivity with limits of detection (signal-to-noise ratio = 3) within 0.015–0.32 ng/mL. The method was also successfully used in analysing real food samples. Good spiked recoveries from 95.8%–104.5% were obtained.     

Vortex-Assisted Liquid–Liquid Microextraction Combined with HPLC for the Simultaneous Determination of Five Phthalate Esters in Liquor Samples

A vortex-assisted liquid–liquid microextraction (VALLME) method using hexanoic acid as extractant followed by high-performance liquid chromatography–diode array detection was developed for the extraction and determination of five phthalate esters (PAEs) including bis-methylglycol ester (DMEP), benzyl butyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-n-butyl phthalate (DBP), and di-n-octyl phthalate (DNOP) from liquor samples. In this method, hexanoic acid was employed as extraction solvent, because its density is lower than water. And vortex mixing was utilized as a mild emulsification procedure to reduce emulsification time and improve the effect of extraction. Under the studied conditions, five phthalate esters were successfully separated within 20 min and the limits of detection were 2.3 ng mL^?1 for DMEP, 1.1 ng mL^?1 for BBP, 1.9 ng mL^?1 for DCHP, 1.2 ng mL^?1 for DBP, and 1.5 ng mL^?1 for DNOP, respectively. Recoveries of the PAEs spiked into liquor samples were ranged from 89 to 93 %. The precisions of the proposed method were varied from 1.6 to 2.6 % (RSD). The VALLME method has been proved to have the potential to be applied to the preconcentration of the target analytes. Moreover, the method is simple, high sensitivity, consumes much less solvent than traditional methods and environmental friendly.     

Ionic Liquid-Based Dispersive Liquid–Liquid Microextraction Following High-Performance Liquid Chromatography for the Determination of Fungicides in Fruit Juices

This paper described an ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) combined with high-performance liquid chromatography (HPLC) method to determine fungicides in fruit juices. In this method, 1-hexyl-3-methyli-midazolium hexafluorophosphate (HMIMPF₆) was used as extraction solvent, which dispersed into the fruit juices under vigorously shaking with the vortex. The effects of experimental parameters, such as extraction solvent volume, disperser solvent and its volume, vortex time, centrifugation time, sample pH, on the extraction efficiency were investigated. Under the optimum conditions, the linear correlation coefficients ranged from 0.9902 to 0.9979 for concentration levels of 0.02–2 mg l^?1, the extraction recoveries were ranged 66.2–92.9 % except pyrimethanil (39.5–44.6 %), The relative standard deviations (RSDs; n?=?6) ranged from 2.2 % to 11.6 %, and the limits of detection (LODs) for the fungicides were between 3.1 and 10.2 μg l^?1. Two real samples including apple and grape juices, spiked at two concentration levels were analyzed and yielded recoveries ranging from 71.3–93.1 % and 65.4–87.7 %, respectively.     

Simultaneous Determination of Seven Polycyclic Aromatic Hydrocarbons in Coffee Samples Using Effective Microwave-Assisted Extraction and Microextraction Method Followed by Gas Chromatography-Mass Spectrometry and Method Optimization Using Central Composite Design

In this research, for the first attempt, we successfully determined seven polycyclic aromatic hydrocarbons (PAHs) in various coffee samples using microwave-assisted extraction and dispersive liquid-liquid microextraction (MAE-DLLME) coupled with gas chromatography-mass spectrometry (GC-MS). The effects of most important variables in microextraction step were investigated and optimized using response surface methodology (RSM) based on central composite design. The calibration curves were linear in the range of 1–200 ng g^?1, with a correlation coefficient (R ²) higher than 0.989. Limits of detection were obtained between 0.1 and 0.3 ng g^?1. The relative standard deviations (RSD%) for seven repeated analysis were less than 8% for all PAH compounds at a concentration of 10 ng g^?1. Relative recoveries were obtained 88.1–101.3%. The satisfactory results obtained by the proposed method and the comparison of these results with previous methods demonstrated that the MAE-DLLME-GC-MS is an accurate, rapid, and reliable sample-pretreatment method with low consumption of the organic solvent.     

Hollow Fiber Liquid Phase Microextraction Method Combined with High-Performance Liquid Chromatography for Simultaneous Separation and Determination of Ultra-Trace Amounts of Naproxen and Nabumetone in Cow Milk,Water, and Biological Samples

A simple and highly sensitive method based on hollow fiber liquid phase microextraction combined with high-performance liquid chromatography and fluorescence detection has been developed for simultaneous separation, preconcentration, and determination of naproxen and nabumetone from water, wastewater, milk, and biological samples. Parameters affecting the microextraction efficiency were evaluated and optimized. Under optimum conditions (extractant (14 μL of 1-undecanol), sample pH (3.0), extraction time (20 min), stirring rate (600 rpm), temperature (45 °C), potassium chloride concentration (4.0 %) and sample volume (9 mL)), the limits of detection based on (S/N?=?3) were 1.3 ng L^?1 for naproxen and 2.9 ng L^?1 for nabumetone. The intra- and inter-assay relative standard deviations for naproxen and nabumetone were in the ranges of 3.2–6.1 % and 6.5–9.5 %, respectively. The calibration curves were linear in concentration ranges of 4.0–300.0 ng L^?1 and 9.0–300.0 ng L^?1 for naproxen and nabumetone, respectively, with good coefficient of determination (r ²?>?0.999). The method was successfully applied to the determination of naproxen and nabumetone in cow milk, water, wastewater, human plasma, and urine samples.     

Speciation Analysis of Mn(II)/Mn(VII) in Tea Samples Using Flame Atomic Absorption Spectrometry After Room Temperature Ionic Liquid-Based Dispersive Liquid–Liquid Microextraction

A simple and rapid method based on dispersive liquid–liquid microextraction with room temperature ionic liquid 1,3-dibutylimidazolium hexafluorophosophate ([BBIM][PF₆]) coupled to flame atomic absorption spectrometry was developed for the speciation of Mn(II)/Mn(VII) in tea samples. The main factors affecting dispersive liquid–liquid microextraction were investigated in detail. Mn(II) and total manganese [Mn(II)+Mn(VII)] were quantitatively extracted after adjusting aqueous sample solution to pH 10.0 and 7.0, respectively. Mn(VII) was calculated by subtraction of Mn(II) from total manganese. Under the optimized conditions, the limits of detection (3σ) for Mn(II) and Mn(VII) were 0.26 and 1.86 ng/mL, and their relative standard deviations were 2.6 and 4.8 % (n?=?7, c?=?25.00 ng/mL). The proposed method was validated by the determination of Mn(II) and Mn(VII) in the certified reference material [GBW(E)08513] of tea sample and different local tea samples with satisfactory results.     

Graphene Reinforced Hollow Fiber Liquid-Phase Microextraction Combined with HPLC for the Determination of Bisphenol A and 4-Tert-Butylphenol in Bottled Juice

A new analytical method by graphene-reinforced hollow fiber liquid-phase microextraction combined with high-performance liquid chromatography fluorescence detection was developed for the determination of bisphenol A and 4-tert-butylphenol in bottled juices. Several important experimental parameters were studied to get optimal extraction conditions for the analytes. Under the optimized conditions, the method showed a good performance having a linear response in the range from 0.05 to 10.0 ng mL^?1 with the correlation coefficients (r) of 0.9965–0.9994 and limits of detection of 0.01 ng mL^?1. The relative standard deviations were in the range from 6.4 to 7.2 % at the spiked concentration of 1.0 ng mL^?1. The method combines the high-adsorption capacity of graphene and the excellent clean-up performance of hollow fiber liquid-phase microextraction and has been successfully applied to the analysis of the analytes in bottled juice samples.     

Ionic liquid-modified countercurrent chromatographic isolation of high-purity delphinidin-3-rutinoside from eggplant peel

Delphinidin-3-rutinoside, a high-value of anthocyanin, was isolated and purified by ionic liquid (IL)-modified countercurrent chromatography (CCC) from waste peel of eggplant (Solanum melongena), one of the most common vegetables consumed all around the world. Different conventional CCC and IL-CCC solvent systems were evaluated in respect of partition coefficient (K), separation factor (α), and stationary phase retention factor (S_f) to separate polar target and other components. Basic solvent system, kind of ILs, and amount of ILs were systematically optimized by totally K-targeted strategy, which drastically reduced the experimental effort. Finally, a novel CCC two-phase solvent system (methyl tert-butyl ether–butanol–acetonitrile–1% trifluoroacetic acid water–1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]) [2:4:1:5:0.2; v/v/v/v/v]) was successfully established and applied. The baseline separation of target fraction was obtained in one cycle process. The purity of delphinidin-3-rutinoside was over 99%. Moreover, the distribution behavior of different kinds of ILs in biphasic solvent system and the removal method of ILs were explored. The results showed that hydrophobic IL significantly improved the partition of polar anthocyanin in organic solvent system, thereby the separation resolution and stationary phase retention through introducing intermolecular forces. This IL-modified CCC strategy may be applied for the separation of other anthocyanins from variety of natural food resources and waste.     

Ionic Liquid-Based Vortex-Assisted Liquid–Liquid Microextraction for Simultaneous Determination of Neonicotinoid Insecticides in Fruit Juice Samples

A simple, rapid, and effective method was developed for preconcentration of neonicotinoid insecticides including clothianidin, imidacloprid, acetamiprid, and thiacloprid in fruit juice samples. Room-temperature ionic liquids [C₄MIM][PF₆] can be used as green extractant phases in vortex-assisted liquid–liquid microextraction (VALLME), being compatible with high-performance liquid chromatographic systems. The effect of extraction parameters, including the addition of salt, volume of (C₄MIM)(PF₆), vortex time, and centrifugation time is identified as the key parameters of the method. Under the selected conditions, the high enrichment factors of 100 could be achieved with the limit of detection in the range of 0.25–0.30 ng mL^?1 and with the relative standard deviations of lower than 2.68 and 5.38 % for retention time and peak area, respectively. The proposed method was applied to the analysis of fruit juice samples, and the recoveries of the analytes ranged from 95 to 108 % and relative standard deviations were lower than 7 %. The developed method proposes advantages in reduction of the exposure danger to toxic organic solvents used in the conventional liquid–liquid extraction, simplicity of the extraction processes, rapidity, and sensitivity improvement.     

Dispersive Liquid–Liquid Microextraction Followed by Magnetic Solid-Phase Extraction for Determination of Four Parabens in Beverage Samples by Ultra-performance Liquid Chromatography Tandem Mass Spectrometry

In this study, a two-step extraction technique was developed for extraction and preconcentration of parabens from beverage samples using ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) and magnetic solid-phase extraction (MSPE). In this IL-DLLME followed by MSPE method, ionic liquid (IL, 1-octyl-3-methylimidazolium hexafluorophosphate) formed hydrophobic microdroplets in beverage samples as an extractant of parabens; after the IL-DLLME process was completed, graphene modified Fe₃O₄ nanoparticles (Fe₃O₄@G) were placed to adsorb and isolate IL from the sample solution. After the supernatant was carefully moved, acetonitrile was added to elute the IL containing parabens from Fe₃O₄@G. The experimental variables affecting the extraction procedure have been systematically studied. Under optimal conditions, the detection limits were less than 1.53 ng/mL and the linear detection ranges were 2–500 ng/mL (R ² ≥ 0.998) for these analytes. The recoveries for spiked samples were 58.8–89.2% and satisfactory precision (RSD ≤ 4.8%) were obtained.     

Vortex-Assisted Ionic Liquid Dispersive Liquid-Liquid Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Triazole Fungicides in Fruit Juices

A rapid, efficient, and environmentally friendly method using vortex-assisted ionic liquid dispersive liquid-liquid microextraction (VA-IL-DLLME) prior to high-performance liquid chromatography coupled with photodiode array detection (HPLC-PDA) has been developed for the determination of six triazole fungicides (triazolone, triadimenol, epoxiconazole, flusilazole, tebuconazole, and diniconazole) in various fruit juices. 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and acetonitrile were used as extraction and dispersive solvents, respectively. A single factor experiment was selected to obtain the significant variables from the several related parameters that could affect the extraction efficiencies, such as the volume of IL and acetonitrile, extraction time, centrifugation time, and salt addition. Under the optimum conditions, an excellent linearity with correlation coefficients higher than 0.997 was obtained. Enrichment factors and average recoveries in three concentration levels ranged from 51 to 72, and 71.0 to 104.5 %, respectively, and the relative standard deviations (RSDs) from 1.4 to 11.8 %. The limits of detection (LODs) (S/N?=?3) for the six triazole fungicides were between 0.4 and 6.7 μg L^?1. The proposed method was successfully applied for the determination of trace amounts of triazole fungicides in various fruit juices including peach, apple, and orange juices.