Optimization of QuEChERS procedure by hydrophobic magnetic nanocomposites for residual OCPs determination coupled with GC-MS

Resumen del póster presentado a la XX Conference EuroAnalysis, celebrada en Estambul (Turquía) del 1 al 5 de septiembre de 2019.Food safety and environmental protection issues have attracted significant international attention in the recent years. The detection of organochlorine pesticides (OCPs) in food products is of key importance for the health of the consumers. Pesticides are found in food at very low concentrations, the separation and pre-concentration of the target analytes has become one of the most critical steps in the sample preparation technology. The QuEChERS is a type of sample preparation method for screening of pesticides in completely food matrixes. This procedure involves initial extraction with acetonitrile followed by a solid phase extraction with amine-loaded adsorbents in combination with hydrophobic C18 and graphitized carbon black for cleaning-up. In this work the application of magnetite nanoparticles modified with hydrophobic non-ionic surfactant Triton X-100 motives as an excellent clean-up agent is proposed. Hydrophobic groups grafted to the surface of magnetite nanoparticles can effectively remove non-polar components from the food matrix (fat, pigment, etc.) and then the particles can easily be separated from the extract by external magnetic field avoiding additional steps of centrifugation or filtration. The sample preparation method based on QuEChERS implying the use of new magnetic nanocomposite has been applied for the monitoring of various OCPs in food products. Under the found optimal conditions such parameters as sensitivity, precision, recoveries have been evaluated for the target analytes by GC-MS method. The results have shown a good linearity (R2≥ 0.9916), satisfactory average recoveries reaching the values between 89 and 110%, RSD of 2-15 %, except those for the hexane extraction of strawberry, radish and watermelon samples. The OCPs have been detected in strawberry (α- HCH; lindane) and radish (α, β-HCH isomers) samples. The magnetic nanocomposites have provided the lower level of co-extracted interferences (including pigments) in the samples and have displayed a better clean-up performance than C18 or carbon adsorbents. Thus, the developed method demonstrates the improved purification and simultaneous recovery of various OCPs

Efficient adsorption of pharmaceutical drugs from aqueous solution using a mesoporous activated carbon

The removal of widely used pharmaceuticals by new granular mesoporous activated carbon materials prepared via a simple one-step pyrolysis process was studied. The series of mesoporous carbons (MC) were derived from sucrose/polystyrene using two mesoporous matrices: MCM-48 and SBA-15 sieves. Two different activation schemes were used to obtained samples: steam-pyrolysis at 900 °C, and chemical modification (with HNO3, H2O2 and their mixture) at 200 °C. The studied conditions of chemical oxidation led to significant structural alterations. Compared to the activated carbon treated by steam at 900 °C, the treatment via chemical oxidation increased the total volume of pores from 1.09 to 2.73 cm3 g−1. The total adsorption capacity towards tetracycline was found to be proportional to the mesoporous volume and the amount of surface O-containing groups. From the experimental adsorption isotherms, the maximum adsorption capacity was calculated 909.2 mg g−1 for tetracycline at pH 7. The kinetics of adsorption fits the pseudo-second order model perfectly. The adsorption data treated by both Langmuir and Freundlich models indicates that the adsorption was monomolecular. This research provides insight into the adsorption behavior of antibiotics on non-activated and activated mesoporous carbonous materials and facilitates their application to removal of pharmaceuticals from contaminated aqueous solutions. The potential adsorption mechanism of mesoporous carbons for the adsorption of antibiotics was proposed. The granular mesoporous carbon after oxidation by mixture of HNO3 and H2O2 with ration 1:1 exhibited much higher adsorptive activity and still showed relatively high adsorption stability even after five cycles, which were potentially suitable for easy separation and high efficiency.This study was supported by grants from EU FP-7-PEOPLE-2009-IRSES (№ 247603). The University of Oviedo is grateful for financial support from Spain’s Ministry for the Economy and Business - MINECO (MAT2016-78155-C2-1-R).Peer reviewe

Sunflower biomass power plant by-products: Properties and its potential for water purification of organic pollutants

The present study explores possibility of using sunflower seed husk agricultural biowastes from industrial pyrolysis power plant as a feedstock for preparation of activated carbon (AC). Sunflower biomass by-products contain up to 70 % of carbon with residual seed husk components, have low specific surface area (less than 21 m2 g−1) and smaller number of oxygen-containing groups in comparison with wood-based biochars. The main process parameters of AC preparation, namely a type of an activation agent (organic solvent, HNO3, NaOH), temperature and duration of the carbonization step, were optimized in respect to adsorption efficiency. We found that simple pre-treatment of sunflower biomass with tetrahydrofuran easily converts it into biochar precursor having large number of carbonyl and hydroxyl groups. Further thermal and chemical activation of the biochar precursor results in formation of AC products with specific surface area in the range from 625 to 980 m2 g−1 and from 1000 to 1755 m2 g−1, respectively. Methylene blue (MB) was used as a test molecule for characterization of adsorption properties of the obtained AC. Kinetics studies showed that MB adsorption on AC is fast and follows pseudo-second-order model. MB adsorption on biochar and AC is well described by Langmuir isotherm, assuming monolayer formation of MB on the surface of adsorbents via chemical interactions. Adsorption capacity of AC towards MB achieved by nitric acid activation is higher (379.0 mg g−1) than capacity of benchmark commercial activated carbon from Norit. The study opens up possibilities for the development of by-product-based adsorbents via the straightforward, eco-friendly approach, with specific focus on the economic effect achieved with these materials.The University of Oviedo is grateful for financial support from Spain’s Ministry for the Economy and Business - MINECO (MAT2016-78155-C2-1-R).Peer reviewe

Application of hydrophobic magnetic nanoparticles as cleanup adsorbents for pesticide residue analysis in fruit, vegetable, and various soil samples

A cleanup procedure based on hydrophobic magnetic nanoparticles for QuEChERS extraction followed by GC-MS method for the simultaneous determination of 16 organochlorine pesticides was developed. The type and amount of cleanup adsorbents (C18/GCB/Fe3O4/Fe3O4@Triton), the volume and polarity of the extraction solvent were optimized. The method was validated according to SANTE/11813/2017 and ICH/2005/Q2/R1 guidelines. Spiked-sample recoveries of 84–108% with RSD below 8% were obtained for all the tested pesticides in strawberry. Quantification was carried out using matrix-matched calibration plots, which displayed good linearity (R2 > 0.99), the limits of quantification being less than the maximum residue limits (MRL) for food. The elaborated procedure with satisfactory results was applied in to determine the pesticides in fruit, vegetable (strawberries, avocadoes, watermelons, radishes, and flesh kiwis) and soil (agricultural, urban and lab-made) samples. The most frequently founded pesticide residues were 4,4′-DDE, 4,4′-DDD, lindane, and 4,4′-DDT, which in all cases were found to be below MRL. The highest concentration of 4,4′-DDT was founded in agricultural and lab-made soils.This research was supported by the Research Program - MINECO (MAT2016-78155-C2-1-R). The authors are grateful to the Ministry for the Economy and Business (Spain) for this financial support.Peer reviewe

Advanced core-shell EDTA-functionalized magnetite nanoparticles for rapid and efficient magnetic solid phase extraction of heavy metals from water samples prior to the multi-element determination by ICP-OES

A method for preconcentration and simultaneous determination of trace heavy metals in water media by core-shell superparamagnetic nanoparticles with the immobilized derivative of ethylenediaminetriacetic acid (referred to as MNPs/SiO2-EDTA) is proposed. The specific layer-by-layer covering of magnetite endowed the new material with essentially increased chemical stability of MNPs including acidic media and improved the affinity toward traces of toxic metal ions. The initial and modified materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, elemental analysis, and vibrating sample magnetometry. The obtained particles were nanodimensional with a 7–12-nm magnetic core and a 4–6-nm silica shell. The MNPs/SiO2-EDTA quantitatively removes heavy metals from contaminated media at pH ≥ 3.5 within 15 min. The adsorption data were successfully fitted to the pseudo-second-order kinetic model. The preconcentration factor was 150 and maximum adsorption capacity was 36.9 mg g−1 for Cu(II), 108.8 mg g−1 for Pb(II), 30.9 mg g−1 for Zn(II), 34.32 mg g−1 for Cr(III), and 59.5 mg g−1 for Cd(II). Due to high stability in the wide range of pH, the magnetic adsorbent can be regenerated at least six times using 0.1 M HNO3. Following adsorption/desorption, determination of metal ions is provided by inductively coupled plasma optical emission spectrometry (ICP-OES) . The linear range of the proposed method is 0.1 - 200 μg L−1. The limits of detection (LOD) are 0.12 μg L−1 for Zn(II); 0.06 μg L−1 for Cd(II); 0.39 for Cu(II); 0.15 μg L−1 for Cr(III); and 0.76 μg L−1 for Pb(II). The method performance was evaluated in the analysis of environmental, tap, and wastewater samples with recoveries in the range of 94.0–104.0%.The authors received from the EU financial support under the FP7-PEOPLE-2009-IRSES (project No.247603) program. Dr. Natalia Kobylinska received financial support given by the Ministry of Education and Science of Ukraine (Grant № М-7/2019).Peer reviewe

Different approaches to the solid-phase extraction of pollutants from water and food products

Resumen del trabajo presentado al congreso Nanomaterials applied to Life Sciences (NALS), celebrado en Gijón (España) del 13 al 15 de diicembre de 2017.Control of the presence of various organic pollutants in agricultural products is one of the major issues preoccupying the regulatory agencies and industrial laboratories worldwide. The pesticides, produced by the agricultural sector, are regarded as one of the most hazardous contaminants found in the environment. They are not only toxic but also mobile and capable of bioaccumulation. Nowadays, pesticides are found in surface waters and in a growing number of aquifers, thus even if present at low concentration levels constituting a potential risk for ecosystems, drinking water quality and human health. Due to the low concentration of analytes, the complexity of some sample matrices and incompatibility of sample medium with analytical instrument a preliminary sample pre-concentration and/or separation is required. Magnetic nanoparticles have attracted significant attention because of their strong magnetic response combined with easily regulated properties via the surface modification. In this communication we report a new approach for preparation of magnetic nanoadsorbent with covalently grafted non-ionic Triton X-100 surfactant. Mesoporous Triton X-100-immobilized (Fe3O4@Triton) magnetic nanoparticles were successfully synthesized by core-shell technology and characterized using transmission electron microscopy, X-ray diffractional analysis, nitrogen physisortpion, energy-dispersive X-ray elemental analysis, vibrating sample magnetometry. The produced Fe3O4@Triton solid was employed as an adsorbent for the pre-concentration of pesticides present in water and food products before analyzing them by gas chromatography coupled with mass spectrometry GC-MS technique. The variables affecting the performance of the adsorbent in the both extraction steps such as type and volume of eluent and extraction solvent, breakthrough volume, salt addition, extraction time were thoroughly investigated. The proposed method resulted in good linearities (R2 > 0.9915) in the range of 1–10000 ng kg−1, with the limit of detection of 0.5-1.0 ng kg−1 at S/N=3, and precision of % RSD of ≤11.8. Under optimal conditions, the pre-concentration factors obtained were in the range of 2362–10593 for 100 mL of sample solution. In addition, the Quick, Easy, Cheap, Effective, Rugged, and Safety (QuEChERS) method along with the application of the novel magnetic adsorbent (Fe3O4@Triton) was applied for the monitoring of 20 organochlorine pesticides (OCPs) present in fruits and vegetables available in supermarkets of Kyiv, Ukraine. The analyses were carried out by GC-MS. The parameters of the developed analytical method, such as sensitivity, precision, linear range, the lower limits of detection and quantification, were determined for each pesticide. The results showed good linearity and the average recoveries were considered satisfactory reaching values between 69 and 110%, RSD of 2-15 %, except for hexane in strawberry, radish and watermelon samples. The OCPs were detected in strawberry (α- HCH; lindane) and radish (α, β-HCH isomers) samples. The QuEChERS method and GC-MS technique were successfully used to analyze OCPs in commercially available fruit pulps and can be applied for routine laboratory analysis.Peer Reviewe