Selective extraction of fungicide carbendazim in fruits using ß-cyclodextrin based molecularly imprinted polymers.

Considering the importance of developing a new analytical approach for pesticide residue detection for the sake of ensuring food safety, a ß-cyclodextrin based molecularly imprinted polymer was prepared for selective determination of carbendazim. The polymers consist of a porous and hollow structure demonstrating the selective abundant adsorption sites for carbendazim molecule. The selectivity and adsorption capacity of the imprinted polymers were analyzed with dispersive solid-phase extraction and analyzed with high performance liquid chromatography coupled with ultraviolet. The results of imprinted polymers were higher than non-imprinted polymers with the maximum adsorption capacity of 3.65 mg/g within 30 min of total adsorption time. The reusability of the imprinted polymers was determined to evaluate its effectiveness and stability, which proved that the polymers lost 10% efficiency within seven consecutive recycles. The developed method displayed good linearity over the concentration range of 0.05-2.0 mg/L. The recovery percentage of 81.33-97.23 with relative standard deviations of 1.49-4.66% was obtained from spiked apple, banana, orange, and peach samples with a limit of detection of 0.03 mg/L and a limit of quantification of 0.10 mg/L (signal to noise ratio = 3/10). The overall performance of the proposed method evident that this technique provided a desirable outcome and it can be used as a convenient approach, as it qualifies the analytical standards.

Surfactant-free solvothermal synthesis of Cu-MOF via protonation-deprotonation approach: A morphological dependent electrocatalytic activity for therapeutic drugs.

A copper-1,4-naphthalenedicarboxylic acid-based organic framework (Cu-NDCA MOF) with different morphologies was synthesized by solvothermal synthetic route via a simple protonation-deprotonation approach. The synthesized Cu-NDCA MOFs were analyzed by diverse microscopic and spectral techniques. The FE-SEM and TEM image results exhibited the flake-like (FL), partial anisotropic (PAT), and anisotropic (AT)-Cu-NDCA MOFs formation obtained at different pH (3.0, 7.0, and 9.0) of the reaction medium. The AT-Cu-NDCA MOF/GC electrode not only increases the electroactive surface area but also boosts the electron transfer rate reaction compared to other modified electrodes (PAT- and FL-Cu-NDCA MOFs/GCEs). Under the optimized conditions, the modified electrode (AT-Cu-NDCA MOF) exhibited a sharp oxidation peak (+ 0.46 V vs. Ag/AgCl) and higher current response for rutin. The electrode provides a wide linear range from 1 × 10-9 to 50 × 10-6 M, a low detection limit of 1.21 × 10-10 M, LOQ of 0.001 µM, and sensitivity of 0.149 µA µM-1 cm-2. The AT-Cu-NDCA MOF/GC electrode exhibited good stability (RSD = 3.52 ± 0.02% over 8 days of storage), and excellent reproducibility (RSD = 2.62 ± 0.02% (n = 3)). The modified electrode was applied to the determination of rutin in apple, orange, and lemon samples with good recoveries (99.79-99.91, 99.24-99.69, and 99.53-99.83, respectively). Graphical abstract Anisotropic structure of Cu-NDCA MOFs and its modification on glassy carbon electrode for ultra-sensitive determination of rutin in fruit samples.

Direct molecular imprinting technique to synthesize coated electrospun nanofibers for selective solid-phase microextraction of chlorpyrifos.

Molecularly imprinted-electrospun nanofibers based on the use of poly(vinyl alcohol) were fabricated and used as a new sorbent for solid-phase microextraction of chlorpyrifos. The molecularly imprinted nanofibers were prepared by electrospinning and direct molecular imprinting of polymeric nanofibers. Poly(vinyl alcohol) was used as the functional and electrospun polymer. Chlorpyrifos was used as a template molecule, and glutaraldehyde as the cross-linker. Detection was performed by ion mobility spectrometry equipped with a secondary electrospray ionization source. The molecularly imprinted fiber has a selectivity and extraction efficiency better than the fiber fabricated using the conventional method of encapsulating MIP particles in electrospun nanofibers. Parameters affecting the extraction efficiency such as ionic strength, stirring rate, extraction time, and temperature were evaluated. The dynamic range of the method was in the range of 0.5-200 µg L-1 with the limit of detection of 0.1 µg L-1. The intra- and inter-day relative standard deviations of the method were 4 and 9%, respectively. The fiber-to-fiber reproducibility for three different fibers is 5%. The spiking recoveries from spiked apple, cucumber, and water samples were in the range of 82-112%. Graphical abstract Molecularly imprinted-electrospun nanofibers were fabricated based on the direct molecular imprinting technique and used as a new SPME fiber coating for selective extraction of chlorpyrifos from fruits and water samples prior its determination by secondary electrospray ionization-ion mobility spectrometry.

Novel modified carbon nanotubes as a selective sorbent for preconcentration and determination of trace copper ions in fruit samples.

In this work, multiwalled carbon nanotubes were reacted with N-[3-(triet-hoxysilyl)propyl]isonicotinamide to prepare pyridine-functionalized carbon nanotubes. This novel sorbent was characterized by infrared spectroscopy, thermal and elemental analysis, and scanning electron microscopy. Functionalized carbon nanotubes were applied for the preconcentration and determination of copper ions using flame atomic absorption spectrometry. Various parameters such as sample pH, flow rate, eluent type and concentration, and its volume were optimized. Under optimal experimental conditions, the limit of detection, the relative standard deviation, and the recovery of the method were 0.65 ng/mL, 3.2% and 99.4%, respectively. After validating the method using standard reference materials, the new sorbent was applied for the extraction and determination of trace copper(II) ions in fruit samples.

An advanced ratiometric molecularly imprinted sensor based on metal ion reoxidation for indirect and ultrasensitive glyphosate detection in fruit.

An indirect and ultrasensitive ratiometric molecularly imprinted (MIP) sensor, based on metal ion reoxidation, is introduced for glyphosate (GLY) determination in fruit. As high-performance signal amplification substrates, carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) are conveniently modified on GCE. The artificial antibody-MIP membrane, presents typical three-dimensional structure to GLY template. Built-in reference methylene blue (MB) is directly electropolymerized on MWCNTs-Au/GCE. Particularly, Cu2+ and GLY interestingly form chelate complex, and the Cu2+ (ICu) in Cu(Ⅱ)-GLY-complex can be reoxidized, and indirectly quantizes GLY. The reference signal (IMB) presents noteworthy stability with different GLY levels, and the ratiometric readout (ICu/IMB) is recognized as a more trustworthy indicator to quantize GLY. Proposed sensor presents broad range as 1.73 âˆ¼ 400 ng/mL, and limit of detection is well found as 0.24 ng/mL (S/N = 3). Finally, as-fabricated method is verified with standard HPLC in real-fruit-sample, and the errors and recovery rates are calculated as 3.4% âˆ¼ 6.7% and 94.4% âˆ¼ 104.6%, respectively.

Triazine-based porous organic framework as adsorbent for solid-phase microextraction of some organochlorine pesticides.

Triazine-based porous organic frameworks (POFs) were constructed through a Friedel-Crafts reaction of cyanuric chloride (CC) with triphenylamine (TPA) monomers. The obtained POFs (CC-TPAs) were explored as the solid-phase microextraction (SPME) fiber coatings for the extraction of the organochlorine pesticides (OCPs). It was found that the mesoporous volume of the CC-TPAs was the main factor for their SPME adsorption performance. The CC-TPA-based fiber was successfully used for the SPME of the OCPs from fruit samples (apple, peach and pear). With the help of gas chromatography-micro-electron capture detection, the CC-TPA-based SPME method showed high enrichment factors (146-456), low limits of detection (0.032-0.090 ng g-1), good linearity (0.11-20 ng g-1, r2 > 0.991) and satisfactory repeatability (relative standard deviations <10.5%) for the OCPs. The method recoveries for spiked OCPs at the concentrations of 0.5, 2.0 and 10.0 ng g-1 in fruit samples were in the range of 86.0-114.0%, 83.5-116.5% and 81.1-118.6%, respectively. The CC-TPA coated fiber was stable enough for 100 extraction cycles without significant loss of the extraction efficiency.

Metal organic frameworks-derived magnetic nanoporous carbon for preconcentration of organophosphorus pesticides from fruit samples followed by gas chromatography-flame photometric detection.

In this work, magnetic nanoporous carbons (MNPCs) based on Zn/Co-MOFs was synthesized via a facial one-step carbonization method. The prepared MNPCs exhibited high specific surface areas, good chemical stability and high extraction efficiency for interest organophosphorus pesticides (OPPs). The good extraction performance of the MNPCs for interest OPPs can be primarily attributed to π-π interaction and hydrophobic interaction between MNPCs and OPPs. Based on it, MNPCs-based MSPE-GC-FPD method was established for the quantification of five OPPs in fruit samples. The main experimental conditions for MSPE of five target OPPs were investigated systematically and optimized, such as the desorption solvent and volume, extracted volume, ionic strength, extraction time and desorption time. Under the optimal conditions, the limits of detection (LODs, S/N = 3) were found to be in the range of 0.018 (ethion) -0.045 (malathion) µg/L. The linearity was 0.05-100 µg/L for phorate, diazinon, ethion and 0.1-100 µg/L for malathion, fenthion respectively. The reproducibility of the method was in the range of 3.5-9.7%. The recovery experiments were carried out by spiking target OPPs at three concentration levels to validate the accuracy of the proposed method, and the recoveries for target OPPs were 84-116%. The results show that the proposed method in this work can be successfully used to analyze OPPs residue in fruit sample.

Chemically modified halloysite nanotubes as a solid-phase microextraction coating.

Halloysite nanotubes were modified in three simple steps including etching, hydroxylation and amino grafting. The sol-gel technique was used for the chemical bonding of the modified halloysite nanotubes (MHNTs) to fused-silica support. The MHNTs, as a novel adsorbent was applied as a SPME coating. Diazinon, parathion and fenthion were selected as the model compounds to study the extraction efficiency of the coating. Gas chromatography-corona discharge ion mobility spectrometry was applied for the analysis of the extracted analytes. The parameters influencing the extraction efficiency of the method, such as stirring rate, salt effect, extraction temperature and time were optimized. The results showed that the MHNTs fiber had better extraction efficiency than the commercial SPME (PA, PDMS, and PDMS-DVB), bare silica, silica-based HNTs and HNTs-titanium dioxide fibers. The limits of detection were found to be in the range of 0.01-0.03 µg L-1. The limits of quantification were in the range of 0.03-0.07 µg L-1. Also, a good linearity in the range of 0.03-3.0, 0.07-2.0 and 0.03-3.0 µg L-1, was found for diazinon, fenthion and parathion, respectively. The method precision was lower than 7.0 and 8.7% as the intra- and inter-day relative standard deviations, respectively. Agricultural wastewater, cucumber and apple were chosen as the real samples. The spiking recovery values were between 84 (±9) and 97% (±6). The results showed that the method was applicable and suitable for real samples analysis.

Zirconium (IV)-based metal organic framework (UIO-67) as efficient sorbent in dispersive solid phase extraction of plant growth regulator from fruits coupled with HPLC fluorescence detection.

A stable zirconium (Ⅳ)-based metal organic frameworks (UIO-67) material possessing good chemical, thermal and water stability was synthesized and applied as a sorbent for the dispersive solid phase extraction (DSPE) of 8 plant growth regulators (PGRs) in fruit samples. Fluorescence labeling combined with high performance liquid chromatography fluorescence detection (HPLC-FLD), was used to quantify the target analytes. Characterization of the UIO-67 material was performed by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The experimental parameters, such as amount of UIO-67, type and volume of eluting solvent, adsorption and desorption time, were optimized. Under the optimized conditions, good linearity was observed in the range of 10-1000 pmol/mL with R(2)>0.9989. The limits of detection and limits of quantification were in the range of 0.21-0.57ng/mL and 0.81-1.91ng/mL, respectively. The intra-day and inter-day precisions (based on the relative standard deviation, n=3) of the PGR derivatives were under 3.1% and 5.3% respectively and the accuracies of the method for the PGRs were in the range from 89.3% to 102.3%. The developed method was successfully applied to analyze PGRs residues in fruit samples. The proposed method is proved to be simple, environment-friendly and inexpensive and it is feasible to directly use UIO-67 as sorbent to extract targets by varying conditions.

Injection-port derivatization coupled to GC-MS/MS for the analysis of glycosylated and non-glycosylated polyphenols in fruit samples.

Polyphenols, including glycosylated polyphenols, were analyzed via a procedure based on injection-port derivatization coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS). The polyphenols in lyophilized fruit samples were extracted with an acidified MeOH mixture assisted by ultrasound. Samples were dried under vacuum, and carbonyl groups were protected with methoxylamine. Free hydroxyl groups were subsequently silylated in-port. Mass fragmentations of 17 polyphenol and glycosylated polyphenol standards were examined using Multiple Reaction Monitoring (MRM) as the acquisition mode. Furthermore, in-port derivatization was optimized in terms of optimal injection port temperature, derivatization time and sample: N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) volume ratio. A C18 solid-phase-extraction clean-up method was used to reduce matrix effects and injection liner degradation. Using this clean-up method, recoveries for samples spiked at 1 and 10µg/g ranged from 52% to 98%, depending on the chemical compound. Finally, the method was applied to real fruit samples containing the target compounds. The complete chromatographic runtime was 15min, which is faster than reported for recent HPLC methods able to analyze similar compounds.

A novel nanomagnetic task specific ionic liquid as a selective sorbent for the trace determination of cadmium in water and fruit samples.

A selective sorbent was prepared for the simultaneous separation and preconcentration of cadmium ion from water and fruit samples, prior to determination by flame atomic absorption spectrometry (FAAS). The sorbent was synthesized by combining of Fe3O4 magnetic nanoparticles (MNPs) and Aliquat(®)336 thiosalicylate, [A336][TS], a thiol-containing task specific ionic liquid (TSIL). The high affinity of TSIL toward the target compound as well as the magnetic behavior of Fe3O4 was combined to provide an efficient and simple magnetic sorbent for solid-phase extraction (SPE). The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). The important parameters influencing the extraction efficiency such as pH, sorbent dosage, extraction and desorption conditions were studied and optimized. Under the optimum conditions, the calibration curve was linear in the range of 2.5-260 ng mL(-1) and good linearity (R(2)>0.996) was obtained. The limit of detection (LOD) and enrichment factor (EF) of the method were found to be 0.5 ng mL(-1) and 50, respectively. The relative standard deviations (RSDs %) were less than 3.1 (n=6) for the target analyte. In this method, only small amounts (20mg) of adsorbent were needed to obtain satisfactory extraction recoveries within 20 min. Finally, the proposed method was successfully applied for the trace determination of cadmium ions in fruit (apple, orange and banana) and water samples. Good spike recoveries, varied within the range of 95-109%, confirmed the good performance of the method in real sample analysis.

Application of solvent-assisted dispersive solid phase extraction as a new, fast, simple and reliable preconcentration and trace detection of lead and cadmium ions in fruit and water samples.

In this research, a new sample treatment technique termed solvent-assisted dispersive solid phase extraction (SA-DSPE) was developed. The new method was based on the dispersion of the sorbent into the sample to maximize the contact surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by injecting a mixture solution of the sorbent and disperser solvent into the aqueous sample. Thereby, a cloudy solution formed. The cloudy solution resulted from the dispersion of the fine particles of the sorbent in the bulk aqueous sample. After extraction, the cloudy solution was centrifuged and the enriched analytes in the sediment phase dissolved in ethanol and determined by flame atomic absorption spectrophotometer. Under the optimized conditions, the detection limit for lead and cadmium ions was 1.2 µg L(-1) and 0.2 µg L(-1), respectively. Furthermore, the preconcentration factor was 299.3 and 137.1 for cadmium and lead ions, respectively. SA-DSPE was successfully applied for trace determination of lead and cadmium in fruit (Citrus limetta, Kiwi and pomegranate) and water samples. Finally, the introduced sample preparation method can be used as a simple, rapid, reliable, selective and sensitive method for flame atomic absorption spectrophotometric determination of trace levels of lead and cadmium ions in fruit and water samples.