Volume Of Extraction Solvent Research Articles

Ultrasound assisted solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry for determination of BADGE, BFDGE and their derivatives in packed vegetables

The problem of the presence of trace organic pollutants in food is of growing importance due to increasing awareness about their impact on newborns, infants and adults of reproductive age. Despite the fact that packaged food products offer many advantages, packaging can be a source of contamination for stored food. Thus, monitoring such pollution in food is of high importance. In this work, a novel methodology based on the solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry was applied for the determination of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives in packed vegetables. Several parameters of the extraction process were optimized, including the volume and type of extraction solvent as well as the sonication time. Due to advantages such as simplicity of use, short analysis time, and a reduction in the required amount solvent, the developed procedure can be considered green. In addition, the developed methodology was characterized by good validation parameters. Limit if quantitation (LOQ) was found to be in the range of 0.8 to 1.5 ng/g. The obtained recoveries varied from 78.3% to 111.2%. The repeatability of the extraction ranged between 0.6% and 5.8% (RSD). The proposed method was successfully applied to determine the presence of BADGE, BFDGE and their derivative compounds in the vegetable samples stored in different types of containers. The obtained data indicate that the majority of investigated samples were contaminated by chlorinated and hydroxyl derivatives of BADGE.

Trace analysis of rimantadine in human urine after dispersive liquid liquid microextraction followed by liquid chromatography-post column derivatization.

The first dispersive liquid liquid microextraction scheme followed by liquid chromatography-post column derivatization for the determination of the antiviral drug rimantadine in urine samples is demonstrated. The effect of the type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time, and centrifugation speed on the extraction efficiency were studied. Rimantadine and the internal standard (amantadine) were chromatographed using a reversed phase monolithic stationary phase with a mixture of equal volumes of methanol and phosphate buffer (pH=3) as mobile phase. On-line post-column derivatization of the analyte was performed using a "two-stream" manifold with o-phthalaldehyde and N-acetyl-cysteine at alkaline medium. Under the optimized extraction conditions, the enrichment factor of rimantadine was 58. The linear range was 5-100 µg/L with correlation coefficient r of 0.9984 while the limit of detection achieved was 0.5 µg/L. The within-day and between-day precision for the tested concentration levels were less than 14.3% and the mean recoveries obtained from the spiked samples were ranged between 87.5 and 113.9%. The main advantages of the proposed method are the simplicity of operation, rapidity, low cost, and low limit of detection of the analyte.

Ultrasonic‐assisted dispersive liquid–liquid microextraction based on a simple and green deep eutectic solvent for preconcentration of macrolides from swine urine samples

AbstractIn this study, a simple and green deep eutectic solvent based dispersive liquid‐liquid microextraction methodology had been proposed for the assessment of four macrolides in swine urine samples. Some important parameters including type and volume of extraction solvent and demulsifier solvent, sample pH, salt concentration affecting extraction efficiency were investigated. The quantitative recoveries were achieved at pH 9 and 20% (w/v) NaCl by using 0.3 mL of deep eutectic solvent consisting of choline chloride‐phenol (1:2, molar ratio) and 0.3 mL of tetrahydrofuran. Under optimal conditions, the linear ranges of four macrolides were 0.5–20.0 µg/L with correlation coefficient higher than 0.999. Limits of detection and quantification were in the ranges of 0.02–0.1 and 0.1–0.5 µg/L, respectively. The relative recoveries for macrolides in spiked swine urine samples ranged from 80 to 93% with relative standard deviations less than 6%.

Dispersive Liquid-Liquid Microextraction Method for the Simultaneous Determination of Four Isomers of Hexachlorocyclohexane and Six Pyrethroid Pesticides in Milk by Gas Chromatography Electron Capture Detector

In this study, a simple and rapid dispersive liquid-liquid microextraction method was established, and the residuals of four isomers of hexachlorocyclohexane and six kinds of pyrethroid pesticides in milk were simultaneously determined by gas chromatography electron capture detector (GC-ECD). The milk sample was first extracted with acetonitrile and cleaned with primary secondary amine (PSA). Then 0.5 mL of acetonitrile was mixed with 140 μL of cyclohexane and rapidly injected into 3 mL of pure water. After vortexing and centrifugation, the floating phase was removed with a 0.1-mL pipette into the GC-ECD. The type and volume of extraction solvent, volume of disperser solvent, volume of water, vortex time, and amount of salt were optimized. Under optimal extraction conditions, the ten pesticides showed a good linear relationship in a certain concentration range in milk matrix, and the correlation coefficients were greater than 0.99. The limits of detection ranged from 0.07 to 2 μg/kg, and the limits of quantitation ranged from 0.2 to 5 μg/kg. The average recovery rates were between 70.1% and 106.3%, and the relative standard deviations were less than 15.2%. This method can be used for the determination of hexachlorocyclohexane and pyrethroid pesticides in milk and for subsequent research.

Optimization of Air-assisted Liquid–liquid Microextraction by Box–behnken Design for Spectrophotometric Determination of Palladium in Water Samples

In this research, a fast, simple and highly efficient sample pretreatment technique based on air-assisted liquid–liquid microextraction (AALLME) followed by UV−Vis spectrophotometric detection has been applied for the preconcentration and determination of palladium in water samples. 1-(2-Pyridylazo)-2-naphthol (PAN) and chloroform were used as a chelating agent and extraction solvent, respectively. Parameters affecting AALLME, including pH of sample solution, concentration of PAN, volume of extraction solvent and number of extraction cycles were studied and optimized using Box–Behnken design. Under the optimum conditions, the calibration curve was linear in the concentration range of 5–700 ng/mL with the correlation coefficient (r2) of 0.996. Detection limit, enrichment factor, intra- and inter-day precision were 0.7 ng/mL, 193, 1.3 and 1.8%, respectively. Finally, the developed method was successfully applied for the determination of trace amounts of palladium in environmental water samples.

β-Cyclodextrin Assisted Liquid-Liquid Microextraction Based on Solidification of the Floating Organic Droplets Method for Determination of Neonicotinoid Residues.

An efficient and environment-friendly microextraction method, namely, β-cyclodextrin assisted liquid–liquid microextraction, based on solidification of the floating organic droplets method coupled with HPLC is investigated for the sensitive determination of trace neonicotinoid pesticide residues. In this method, β-cyclodextrin is used as a disperser solvent, while 1-octanol is selected as an extraction solvent. β-cyclodextrins was found to decrease interfacial tension and increase the contact area between the organic and water phases with the help of centrifugation. A cloudy solution was rapidly formed and then centrifuged to complete phase separation. Various key parameters influencing extraction efficiency were systematically investigated and optimized; they include salt addition, concentration of β-cyclodextrin, and volume of extraction solvent (1-octanol). Under optimum conditions, good linearity was obtained with coefficient for determination (R2) greater than 0.99. A low limit of detection, high enrichment factor, and good recovery (83 – 132) were achieved. This proves that the proposed method can be applied to determine trace neonicotinoid pesticide residues in natural surface water samples.

Simultaneous determination of drug active compound, hormones, pesticides, and endocrine disruptor compounds in wastewater samples by GC-MS with direct calibration and matrix matching strategies after preconcentration with dispersive liquid-liquid microextraction.

DLLME was coupled with GC-MS for the simultaneous determination of a drug active compound, hormones, pesticides, and endocrine disruptor compounds with high accuracy and reproducibility in this study. Extraction parameters that affect extraction output including types and volumes of dispersive and extraction solvents, and effect of salt addition were optimized to lower the detection limits for 12 compounds. Under the optimum conditions, LOD and LOQ values were found between 1.99-5.05 and 6.63-16.87 ng/mL, respectively. Spiked recovery tests were also applied to wastewater samples to check the applicability of the method. Matrix matching strategy was used to improve the overall recovery results of the analytes obtained for municipal wastewater. Two different municipal wastewater samples were used in the matrix matching studies. Percent recovery values calculated with the matrix matching experiments were between 85-114%. The results obtained indicated that the developed method could be applied for the determination of the analytes of interest with high accuracy and sensitivity.

Promoted reaction microextraction for determining pesticide residues in environmental water samples using gas chromatography-mass spectrometry

A microextraction technique termed promoted reaction microextraction (PRME) based on a liquid-liquid microextraction was developed by applying a chemical reaction for promoting the extraction of the analytes into the extracting solvent. PRME is a very simple, rapid and high-performance method for extraction and pre-concentration of organic compounds from water samples. In PRME, different types of chemical reactions can be used. In the present work, an acid-base reaction that produces a gaseous product is employed. In this method, appropriate amounts of auxiliary solvent (methanol), acidic promotor (oxalic acid), and extraction solvent (chloroform) were added rapidly into a water sample containing a basic promotor (sodium bicarbonate). After adding the solution containing the acidic promoter to the water sample containing the basic promoter, the acid-base reaction started with high intensity. The reaction product consisted of salt, water, and carbon dioxide gas. The produced carbon dioxide generated bubbles in the reaction medium that promoted the extraction of the analytes into the extracting solvent. After centrifuging, the fine particles of the extraction solvent were sedimented in the bottom of the conical tube. The denes phase was analyzed by gas chromatography-mass spectrometry (GC/MS). Several parameters affecting the extraction of 17 target pesticides by PRME-GC/MS (i.e., a selection of extraction solvent, extraction solvent volume, selection of auxiliary solvent, basic promotor content, and acidic promotor content) were investigated. Under the optimum conditions, the calibration graph was linear in the range of 0.035–40.0 µgL−1 with the detection limit of 0.003–0.035 µgL−1 for pesticides. The relative standard deviations (RSDs) of the PRME-GC/MS method were in the ranges of 2.29–4.76% (n = 3 and c = 0.30 µgL−1).

Synthesis and characterization of deep eutectic solvents (five hydrophilic and three hydrophobic), and hydrophobic application for microextraction of environmental water samples.

Hydrophilic and hydrophobic deep eutectic solvents (DESs) as "green" solvents were applied in this study for the microextraction of environmental samples. A series of DESs (five hydrophilic and three hydrophobic) were synthesized and characterized by Fourier transform infrared spectroscopy. Physicochemical property parameters of eight DESs including water solubility, density, conductivity, and freezing point were assessed. Compared with the performance of five hydrophilic DESs in water phase, the three hydrophobic DESs were more suitable for application in dispersive liquid-liquid microextraction for the determination of sulfonamides in water sample. In dispersive liquid-liquid microextraction process, analytical parameters including type and volume of extraction solvent, extraction time, and pH of water sample were investigated. Under optimum conditions, 60μL of hydrophobic DESs was used for extraction for 2min in pH = 7.0 sample. The linear ranges were 0.05-5.0μg/mL for the four sulfonamides with the correlation coefficients in the range of 0.9991-0.9999. The limits of detection were in the range of 0.0005-0.0009μg/mL and the limits of quantification were in the range of 0.0019-0.0033μg/mL. The recoveries of the analytes of the proposed method for the spiked samples were 80.17-93.5%, with the relative standard deviation less than 6.31%. The results indicated that three hydrophobic DESs showed commendable performance for extraction of sulfonamides, and hydrophobic DES-based microextraction method was successfully applied for monitoring sulfonamides in water samples. Graphical abstract.

Combination of ultrasonic-assisted dispersive liquid phase micro-extraction with magnetic dispersive solid-phase extraction for the pre-concentration of trace amounts of atrazine in various water samples

ABSTRACT Herein, ultrasonic-assisted liquid phase micro-extraction in tandem with dispersive µ-solid-phase extraction was utilised for the determination of atrazine at µg L−1 concentration levels. Initially, a liquid phase micro-extraction based on dispersion of organic solvent was used for the rapid extraction of atrazine from aqueous solution followed by the extraction organic solvent effectively collected from the solution by using C-18-magnetic nanoparticles without any requirement to centrifugation step. After the elution of the extracted targets from the magnetic nanoparticles, atrazine concentration was monitored by high-performance liquid chromatography with Ultraviolet detector at µg L−1 level. The influencial parameters in the pre-concentration step were as follows: pH of solution, magnetic-based sorbent amount (mg) and 1-octanol volume (µL). Additionally, the selected data for the factors produced by the Box-Behnken design were: pH of sample: 9.0, sorbent amount: 22 mg and the extraction solvent volume: 36 µL. Relative standard deviations under the optimised conditions by the hybrid mentioned extraction method was determined to be <7% and the method detection limit for atrazine was calculated to be 0.3 µg L−1. Limit of quantification was calculated to be 0.8 µg/L for the studied analyte.

Elevated temperature-assisted surfactant-enhanced emulsification microextraction based on solidification of a floating organic drop for the determination of UV filters in water samples by high-performance liquid chromatography coupled to a diode array detector

A rapid and reliable procedure named as elevated temperature-assisted surfactant-enhanced emulsification microextraction based on solidification of floating organic drop was developed for determination of UV filters in environmental water samples followed by high-performance liquid chromatography with diode array detection analysis. In the present work, a mixture of extraction solvent (1-undecanol) and emulsifier (Tween 80) was injected rapidly into the sample solution heated at an elevated temperature. The preheated sample dispersed the extraction solvent into sample solution immediately on injection of the mixture. Various parameters influencing the extraction efficiency including type and volume of extraction solvent, type and concentration of surfactant, temperature of aqueous solution, extraction time and solution pH were investigated and optimized. Under the optimum conditions, low limits of detection (0.8–1.4 ng mL−1) and limits of quantification (2.7–4.0 ng mL−1) were obtained. The precision of this method was investigated at 10 ng mL−1, and the relative standard deviations ranged between 1.2 and 5.1% for intra-day and inter-days determinations. The proposed method was successfully applied to determine the UV filters in genuine water samples with relative recoveries ranged from 88.8 to 98.2%.

Vortex‐assisted Emulsification Microextraction for the Determination of Pyrethroids in Mushroom

In this research, a novel method—namely vortex‐assisted emulsification microextraction—was introduced for the determination of pyrethroids (flucythrinate, beta‐cypermethrin, and fenvalerate) in mushrooms (Agaricus bisporus, Lentinula edodes, Auricularia auricular, and Flammulina velutiper). A green solvent 1‐dodecanol was used as the extraction solvent. The low freezing point makes 1‐dodecanol easy to solidify and separate after retention in an ice bath. To avoid the use of dispersion solvents, vortex agitation was applied instead to increase the contact area between extraction solvent and samples. The type and volume of extraction solvent, time of extraction, and addition of sodium chloride were optimized. Under optimal conditions, linear responses were obtained within 1–100 μg/g (R2 ≥ 0.999). The extraction recovery was within 70.2–89.2% with relative standard deviations of less than 8.1%. This method was simple, fast, and environmentally friendly, and was successfully applied to extract and analyze pyrethroids in Agaricus bisporus, Lentinula edodes, Auricularia auricular, and Flammulina velutiper.

APPLICATION OF RESPONSE SURFACE MODELING FOR OPTIMIZATION AND DETERMINATION OF MALONDIALDIALDEHYDE BY VORTEX-ASSISTED DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AND GC-FID

An analytical method based on vortex-assisted dispersive liquid-liquid microextraction and gas chromatography-flame ionization detection is presented for the extraction and determination of malondialdehyde (MDA) in blood plasma of human. Various parameters affecting the extraction efficiency such as type and volume of extraction and dispersive solvents, vortex and centrifuge times, volume, ionic strength and pH of the sample solution were evaluated using, one-variable-at-a-time and response surface methodology. In order to optimize the MDA extraction and determination, seven factors in five- levels were used for design of experiments (DOE), slider optimum extraction condition, this method showed linear range of calibration curve between 10-1150 mu g L--(1). The detection limit of the proposed method was found to be 0.8 mu g L(-1 )with a relative standard deviation better than 5.5 (n=10) for blood serum samples. Enrichment factor was calculated to be 175 fold and the total analysis time including microextraction was about 13 min. The method was successfully applied for the analysis of MDA in blood plasma of human.

The experimental design approach to the optimization of a simple quick easy cheap effective rugged and safe method for the analysis of phytoestrogens in complex soy-based food.

The present paper deals with the multivariate optimization of an extraction-purification strategy for the determination of phytoestrogens (daidzein, genistein, coumestrol, formononetin, and biochanin A) in soy-based meat substitutes by high performance liquid chromatography with tandem mass spectrometry. For a reliable quantitation of these new concerning compounds in such a complex matrix, recovery and matrix effect must be carefully evaluated. Therefore, two sequential experimental designs were used to optimize the sample-pretreatment of soy-based burgers: the chosen technique was the quick, easy, cheap, effective, rugged and safe methodology, which does not require any particular facility or instrumentation. Thanks to the first screening design (Plackett-Burman), the significant factors influencing the studied responses were identified and further investigated through a response surface design (Box-Behnken). The optimal values of the variables (volume of extraction solvent mix/sample mass ratio and two clean-up sorbents) led to quantitative recoveries (97-104%) and low ion suppression (matrix effect 60-93%) for all analytes. This optimized method was characterized by low detection limits (0.2-1.5ng/g) and excellent intraday precision (RSD 2-4%). It was applied to the determination of the considered compounds in several soy-burgers from the Italian market, detecting low ng/g levels (up to 40ng/g) of coumestrol, formononetin, and biochanin A, and high concentrations (7.9-78µg/g) of genistein and daidzein.

Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry

A simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitating polychlorinated biphenyls (PCBs) in vegetable samples. Parameters affecting both the extraction yields and cleanup efficiency, including the type and volume of extraction solvent, extraction time, type and volume of cleanup sorbent, and cleanup time, were optimized. Matrix effects were evaluated, and matrix-matched calibration was recommended. Under the optimized conditions, carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), which exhibit excellent adsorption capabilities due to large surface area and unique structure, were employed as d-SPE sorbent to remove interfering substances, rather than the analytes, from vegetable samples. Satisfactory linear relationship was observed for all PCBs across a concentration range of 5–500 μg/kg with correlation coefficients no less than 0.9993. Four representative vegetables (cucumber, tomato, lettuce, and cabbage) were selected as matrices for method validation. Each matrix was spiked at concentrations of 5, 10, and 100 μg/kg to evaluate recoveries, which ranged from 84.5% to 116.5% with relative standard deviations (n=6) between 0.6% and 17.6%. The limits of detection and the limits of quantification ranged from 0.3 to 1.4 μg/kg and 0.8 to 4.5 μg/kg, respectively. Twelve real vegetable samples were analyzed using the proposed method. Three of the target PCBs were detected in one lettuce sample with the total concentration of 17.9 μg/kg.

Dispersive liquid–liquid microextraction coupled with graphite furnace atomic absorption spectrometry for determination of trace cobalt in environmental water samples

ABSTRACT A highly sensitive, simple and rapid method was developed for the determination of ultra-trace cobalt by dispersive liquid-liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GFAAS). The combination of DLLME and GFAAS methods is favourable for GFAAS is a well-established technique with excellent sensitivity, and is suitable for low volume of sample of the remained phase obtained after DLLME. For DLLME, a newly synthesised reagent 5-(5-Cyano-2-pyridylazo)-2,4-diaminotoluene (5-CN-PADAT) was used as a chelating agent, 1,2-dichloroethane (CH2ClCH2Cl) and acetonitrile (CH3CN) as extraction and dispersive solvent. Several variables potentially affecting the extraction efficiency and its subsequent determination, such as type and volume of extraction and disperser solvents, pH of test solution, extraction time, volume and concentration of the chelating agent and salt effect, were investigated and optimised. After phase separation, 10 µL of the sedimented phase containing enriched analytes was injected into GFAAS for the determination of cobalt. Under the optimised conditions, the analytical graph was linear in the range of 0.04 ~ 1.0 ng mL−1, and the limit of detection was 0.01 ng L−1 for cobalt. The relative standard deviation (RSD) for 10 replicate measurements of 0.2 ng L−1 of cobalt was 3.6%. Enrichment factor (EF) calculated as the ratio of the slopes of the calibration graphs obtained with and without DLLME was 96 for 5.0 mL sample solution. The method was successfully applied to the determination of trace cobalt in water samples with satisfactory results.

One‐step synthesized magnetic MIL‐101(Cr) for effective extraction of triazine herbicides from rice prior to determination by liquid chromatography‐tandem mass spectrometry

The magnetic metal-organic framework MIL-101(Cr) material-based solid-phase extraction method coupled with high-performance liquid chromatography and tandem mass spectrometry was applied to extract seven triazine herbicides in rices. Fe3 O4 /MIL-101(Cr) was synthesized using reduction-precipitation method, in which steps including pre-synthesis and modification of Fe3 O4 nanoparticles were by-passed. Various parameters including extraction solvent type and volume, ultrasonic extraction time, amount of Fe3 O4 /MIL-101(Cr) microspheres, adsorption time, desorption volume and time were investigated. Under optimal conditions, the proposed method had the limit of detection (S/N=3) and the limit of quantification (S/N=10) of 1.08-18.10 and 3.60-60.20 pg/g, respectively. Relative standard deviations calculated for all herbicides with concentrations of 2 and 20ng/g were in the range of 0.5 to 13% (n=3). In addition, at the two above-mentioned concentrations, the method achieved relative recoveries percentages of 79.3 to 116.7% when applied to determine the triazine herbicides in real samples spiked. This rapid, green, non-polluting, pre-concentrated extraction method was successfully developed and applied to analyze herbicides in rice samples.

Rapid extraction of copper ions in water, tea, milk and apple juice by solvent-terminated dispersive liquid–liquid microextraction using p-sulfonatocalix (4) arene: optimization by artificial neural networks coupled bat inspired algorithm and response surface methodology

A bat inspired algorithm with the aid of artificial neural networks (ANN-BA) has been used for the first time in chemistry and food sciences to optimize solvent-terminated dispersive liquid-liquid microextraction (ST-DLLME) as a green, fast and low cost technique for determination of Cu2+ ions in water and food samples using p-sulfonatocalix (4) arene as a complexing reagent. For this purpose, the influence of four important factors four factors which was influenced on the extraction efficiency such as salt addition, solution pH and disperser and extraction solvent volumes were investigated. Central composite design (CCD) as a comparative technique was employed for optimization of ST-DLLME efficiency. The ANN-BA optimization technique was regarded as a superior model due to its higher value of extraction efficiency (about 7.21%) compared to CCD method. Under ANN-BA optimal conditions, the limit of quantitation (S/N = 10), limit of detection (S/N = 3) and linear range were 0.35, 0.12 and 0.35-1000µgL-1, respectively. In these circumstances, the percentage recoveries for drinking tea, apple juice, milk, bottled drinking water, river and well water spiked with 0.05, 0.1 and 0.2mg L-1 of Cu2+ ions were in the acceptable range (91.4-107.1%). In comparison to other methods, the developed ST-DLLME method showed the lowest solvent and sample consumption, shortest value of extraction time, most suitable determination and detection limits and linear range with simple and low cost apparatus. Additionally, the use of bat inspired algorithm as a powerful metaheuristic algorithm with the aid of artificial networks is another advantage of the present work.

Rapid determination of antibiotic residues in cereals by liquid chromatography triple mass spectrometry.

Antibiotics may be present in agricultural soils through the application of organic amendments as fertilizers or by irrigation of fields with recycled water. As a result of these agricultural practices, antibiotics in soil can lead to their uptake by plants, entering in this way the food chain. Studies on the levels of antibiotics in cereal samples are scarce in the available literature. In this work, an analytical method was developed for the determination of 19 antibiotics (fluoroquinolones, sulfonamides, tetracyclines, and lincosamides) in four types of cereal grains (wheat, barley, rice, and oat). Ultrasound-assisted matrix solid-phase dispersion was selected as extraction technique with recoveries of target analytes ranging from 73 to 127% for the four cereals analyzed. Limits of quantification obtained ranged from 0.8 to 5.8ngg-1. Compared with methods described for the analysis of antibiotics in cereals, the developed method uses a lower volume of extraction solvent and very good recoveries were obtained for all compounds. The validated method was applied to the analysis of different types of cereals samples, harvested from agricultural fields or purchased from local supermarkets. The analysis of the five cereal samples grown in fields with 3years of consecutive organic amendments revealed that none of the nineteen antibiotics selected were found in any sample. Eleven commercial samples of cereals of different types and presentations were analyzed and enrofloxacin was detected in one rice sample; the presence of enrofloxacin in cereals or its incorporation into crops from soil or water not previously reported. Graphical abstract.

Packed hybrids of gold nanoparticles and halloysite nanotubes for dispersive solid phase extraction of triazine herbicides, and their subsequent determination by HPLC.

Halloysite nanotubes (HNTs) were functionalized with gold nanoparticles. The morphology and structures of this composite were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, and surface area and pore-size analyses. The material was employed, in conjunction with a syringe pump and an organic filter head, to the enrichment of five triazines (atrazine, desmetryn, prometorn, tebumeton, ametryn) in spiked rice samples. Several parameters that may affect the extraction efficiencies, including type and volume of extraction solvent, amount of sorbent, times of ultrasonic extraction and adsorption, volume and flow rate of elution solvent, were optimized. Following elution with acetonitrile, the herbicides were quantified by using HPLC. Under the optimum conditions, the LODs of the method, when applied to spiked rice samples, are the range from 0.06 to 1.32ngg-1 (LODs = 3SD/k). The relative intra-day and inter-day recoveries ranged from 80.6 to 106.5% and 80.4-107.3%, respectively, and relative standard deviations ranged from 0.8 to 8.7% and 3.6-9.6%, respectively. Graphical abstract Packed hybrids of gold nanoparticles and halloysite nanotubes (Au/HNTs) were prepared and applied tothedispersive solid-phase extraction by packed sorbent of five triazine herbicides from rice.