[Determination of 118 pesticide residues in urine by ultra-high performance liquid chromatography-tandem mass spectrometry].

Pesticide residues in food and their hazardous effects have attracted much attention given the increased and widespread use of pesticides. The long-term consumption of food containing pesticide residues is an important pathway for the gradual accumulation of pesticides in the human body. Urine is often monitored as a biological sample for low-dose exposure to pesticides, and urine collection is a relatively convenient sampling technique in general population research. In order to effectively monitor residual levels of multiple pesticides in human urine and provide an important technological approach for health risk assessment, a rapid screening and confirmatory detection method for 118 pesticides in urine was established using QuEChERS method as a pretreatment combined with ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS). The 118 pesticides analyzed included organophosphorus, carbamate, neonicotinoid, and strobilurin fungicides and other widely used pesticides. Following systematic optimization of the pretreatment process, LC separation conditions, and MS/MS parameters, 118 pesticides were extracted from urine samples and analyzed within 2 h. In brief, the target analytes in 5 mL urine samples were extracted with 10 mL of acetonitrile and added with 5 g of anhydrous MgSO4 and 1 g of NaCl as water-removal and salting-out agents, respectively. After centrifugation, 6 mL of the supernatant was cleaned using the QuEChERS method with 300 mg of C18, 300 mg of primary secondary amine (PSA) and 900 mg of anhydrous MgSO4 as the purification adsorbent. After nitrogen blowing and solubilization, the 118 target analytes were separated on a ZORBAX Eclipse Plus C18 analytical chromatographic column (100 mm×2.1 mm, 1.8 µm) with gradient elution using (A) 0.01% formic acid aqueous solution (containing 2 mmol/L ammonium formate) and (B) 0.01% formic acid methanol solution (containing 2 mmol/L ammonium formate) as mobile phases. The gradient elution program was as follows: 0-0.5 min, 5%B; 0.5-1.5 min, 5%B-20%B; 1.5-2.5 min, 20%B-50%B; 2.5-8.0 min, 50%B-80%B; 8.0-9.0 min, 80%B-98%B; 9.0-11.0 min, 98%B; 11.0-11.5 min, 98%B-5%B; 11.5-15.0 min, 5%B. The analytes were then determined by UHPLC-MS/MS with positive/negative ion switching in dynamic multiple-reaction monitoring mode and quantified using the external standard method. The results indicated that the proposed method can determine 118 pesticides in urine simultaneously and rapidly. The limits of detection and limits of quantification were 0.10 and 0.50 µg/L, respectively, and the matrix effects were less than 20%for all targeted compounds. The recoveries of the 118 pesticides in urine were between 70.2% and 104% at three spiked levels of 0.50, 1.00, and 5.00 µg/L, and the relative standard deviations ranged from 2.8% to 9.3%. The method was applied to 10 actual urine samples, and the results revealed the presence of six pesticides, including thiamethoxam, clothianidin, acetamiprid, dinotefuran, isoproturon, and dimethomorph, with contents ranging from

Simultaneous Analysis of 53 Pesticides in Safflower (Carthamus tinctorius L.) by Using LC-MS/MS Coupled with a Modified QuEChERS Technique.

OBJECTIVE: An optimized quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique was investigated and compared with the conventional QuEChERS technique for the simultaneous analysis of fifty-three pesticide residues in safflower using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). METHOD: Graphitic carbon nitride (g-C3N4) consisting of a major amount of carbon and nitrogen with a large surface area was used as a QuEChERS adsorbent instead of graphitized carbon black (GCB) for safflower extraction purification. Validation experiments were performed using spiked pesticide samples, and real samples were analyzed. RESULTS: The linearity of the modified QuEChERS technique was evaluated with high coefficients of determination (R-2) being higher than 0.99. The limits of detection were <10 µg/kg. The spiked recoveries ranged from 70.4% to 97.6% with a relative standard deviation of less than 10.0%. The fifty-three pesticides exhibited negligible matrix effects (<20%). Thiamethoxam, acetamiprid, metolachlor, and difenoconazole were detected in real samples using an established method. CONCLUSION: This work provides a new g-C3N4-based modified QuEChERS technique for multi-pesticide residue analysis in complex food matrices.

A new core-shell magnetic mesoporous surface molecularly imprinted composite and its application as an MSPE sorbent for determination of phthalate esters.

In this study, a new core-shell magnetic mesoporous surface molecularly imprinted polymer (Fe3O4@SiO2@mSiO2-MIPs) which has specific adsorption and rapid adsorption rate for phthalate esters (PAEs) was prepared by a convenient method. Based on this composite as a magnetic solid phase extraction (MSPE) material, a rapid, efficient and sensitive matrix dispersion magnetic solid-phase extraction gas chromatography-mass spectrometry method (DMSPE-GC/MS) was developed for the determination of PAEs in multiple liquid samples. It is the first time that Fe3O4@SiO2@mSiO2-MIPs have been prepared by bonding amino groups on the surface of a double layer silicon substrate with diisononyl phthalate (DINP) as virtual template and 3-(2-aminoethyl)-aminopropyl trimethoxymethylsilane (TSD) as functional monomer. FT-IR, TEM, EDS, SEM, XRD, BET and VSM were used to characterize the composite. The adsorption isotherm and kinetics of Fe3O4@SiO2@mSiO2-MIPs showed that it possessed fast adsorption rates (approximately 5 min to reach equilibrium), high adsorption capacities (523.9 mg g-1) and good recognition of PAEs. The real samples were preconcentrated by Fe3O4@SiO2@mSiO2-MIPs, under the optimum DMSPE-GC/MS conditions. Validation experiments showed that the method presented good linearity (R 2 > 0.9971), satisfactory precision (RSD < 5.7%) and high recovery (92.1-105.8%), and the limits of detection ranged from 1.17 ng L-1 to 3.03 ng L-1. The results indicated that the novel method had good sensitivity, high efficiency and wide sample application and was suitable for the determination of PAEs in liquid drink samples such as water, alcohol, beverages and so on.

Retro Baeyer-Villiger reaction: thermal conversion of the [60]fullerene-fused lactones to ketones.

The conversion of the [60]fullerene-fused lactones to ketones with triflic anhydride as an unusual reductant under aerobic conditions has been achieved in excellent yields. The present thermal retro Baeyer-Villiger reaction from lactones to ketones has no precedents. In addition, the unique ring-opened peroxy [60]fullerene derivatives can be obtained by the electrochemical reactions of the synthesized [60]fullerene-fused ketones.

Unexpected Diels-Alder reaction of [60]fullerene with electron-deficient ferrocenes as cyclopentadiene surrogates.

The unexpected Diels-Alder reaction of [60]fullerene (C60) with ferrocenes bearing electron-withdrawing groups as cyclopentadiene surrogates has been developed to selectively afford single isomers of [2 + 4] cycloadducts of C60. Mechanistic studies indicate that cyclopentadienes are in situ generated from electron-deficient ferrocenes in the presence of an oxidant and an acid, followed by [2 + 4] cycloadditions with dienophiles. A Michael addition reaction using a Grignard reagent has been utilized to transform the Diels-Alder adducts of C60 into more stable fullerene derivatives.

Magnetic solid-phase extraction based on sulfur-functionalized magnetic metal-organic frameworks for the determination of methylmercury and inorganic mercury in water and fish samples.

A novel magnetic metal-organic frameworks (Fe3O4@UiO-66-SH) was successfully prepared by coating Fe3O4 nanospheres with sulfur-functionalized UiO-66. The Fe3O4@UiO-66-SH possesses both the magnetic properties of Fe3O4 and the diverse properties of metal-organic framework (MOF) in one material, which has the superiority of high surface area, easy-operation and strong adsorb ability with mercury, is used for the magnetic solid-phase extraction of methylmercury (MeHg+) and inorganic mercury (Hg2+) in water and fish samples. The analyzes were conducted by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The different pretreatment conditions influencing the extraction recoveries of Hg2+ and MeHg+, including adsorbent amount, pH, extraction time, elution solvent, elution volume, desorption time, co-existing ions and dissolved organic materials were investigated. Under the optimized conditions, the limits of detection (LODs) of Hg2+ and MeHg+ for water samples were 1.4 and 2.6 ng L-1, and the limits of quantification (LOQs) of Hg2+ and MeHg+ for water samples were 4.7 and 8.7 ng L-1. The enrichment factors (EFs) were 45.7 and 47.6 fold for Hg2+ and MeHg+, respectively. The accuracy of the proposed method was demonstrated by analyzing the certified reference material of fish tissue (GBW10029) and by determining the analyte content in spiked water and fish samples. The determined values were in good agreement with the certified values and the recoveries for the spiked samples were in the range of 84.5-96.8%.

A copper-promoted synthesis of epoxy-bridged [60]fullerene-fused lactones and further derivatization.

A facile copper-promoted decarboxylative annulation of [60]fullerene (C60) with two identical α-oxocarboxylic acids via an unprecedented cascade addition pathway has been exploited to synthesize the unique epoxy-bridged C60-fused lactones for the first time. Further transformations into the rare epoxy-bridged C60-fused hemiacetals and bicyclic-fused 1,2,3,4-adducts as well as application in a perovskite solar cell device of the obtained products have also been demonstrated. The structures of the epoxy-bridged C60-fused lactones and derived reductive products have been unequivocally established by single-crystal X-ray crystallography. Plausible reaction mechanisms leading to the observed products are proposed.

Computational design and synthesis of molecular imprinted polymers for selective solid phase extraction of sulfonylurea herbicides.

A high-efficiency approach for the synthesis of molecularly imprinted polymers has been developed and further for the solid-phase extraction of sulfonylurea herbicides in food samples. Molecular simulation approach combined chemometric selected metsulfuron-methyl (MSM) and 2-trifluoromethyl acrylic acid (TFMAA) as the template and the monomer to synthesize the molecularly imprinted polymers (MIPs). Experimental validation confirmed that the MSM-imprinted polymers showed a higher selectivity and affinity to sulfonylurea herbicides. The optimized molecularly imprinted solid-phase extraction (MISPE) conditions, including loading, washing, and eluting conditions, were established. The developed MISPE technology combined HPLC-MSMS was successfully used for the determination of sulfonylurea herbicides in foods. Compared with commercial SPE columns, MISPE showed high affinity, excellent selectivity and low matrix effect. The recoveries of sulfonylurea herbicides spiked in four matrices were between 86.4% and 100.2%, with the relative standard deviations (RSD) in the range of 0.9%-10.5%.

Magnetic C60 nanospheres based solid-phase extraction coupled with isotope dilution gas chromatography-mass spectrometry method for the determination of sixteen polycyclic aromatic hydrocarbons in Chinese herbal medicines.

C60-based magnetic nanospheres were synthesized by coating Fe3O4 nanospheres with silica, then modifying with 3-aminopropyltriethoxysilane as a linker and a C60 fullerene stationary phase. The morphologies, magnetic properties, infrared absorption and carbon content of magnetic nanospheres were studied by TEM, VSM, FTIR and carbon and sulfur analyzer. The magnetic nanospheres were employed for the magnetic solid-phase extraction (MSPE) of 16 polycyclic aromatic hydrocarbons (PAHs) in nine Chinese herbal medicines. The analyses were conducted by isotope dilution gas chromatography-mass spectrometry. The main parameters influencing the extraction, including extraction solvent, adsorbent amount, and extraction time were optimized. Method validation showed that the limit of detection (LOD) was 0.02-0.11 µg/kg, and the limit of quantification (LOQ) was 0.07-0.36 µg/kg. The spiked recoveries rates for 16 PAHs in white peony root were 84.7-107.2%. The relative standard deviation (RSD) was 1.7-8.4%. The established method was further used for the determination 16 PAHs in nine Chinese herbal medicines. Total content of 16 PAHs varied from 73.6 µg/kg (fructus lycii) to 2172.6 µg/kg (astragalus root). The results indicate that the pollution of PAHs in Chinese herbal medicines is serious. The established method can effective detect PAHs contamination in Chinese herbal medicines.

A retro Baeyer-Villiger reaction: electrochemical reduction of [60]fullerene-fused lactones to [60]fullerene-fused ketones.

A highly efficient electrochemical reduction of [60]fullerene-fused lactones to [60]fullerene-fused ketones, a formal process of retro Baeyer-Villiger reaction, has been achieved for the first time. The electrochemically generated dianionic [60]fullerene-fused lactones can be transformed into [60]fullerene-fused ketones in the presence of acetic acid in 85-91% yields. Control experiments have been performed to elucidate the reaction mechanism. The products have been characterized with spectroscopic data and single-crystal X-ray analysis. Moreover, the electrochemical properties have also been investigated.

[Determination of 39 veterinary drug residues in Procambarusclarkii by ultra-high performance liquid chromatography-quadrupole-time of flight mass spectrometry].

An ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) method was developed for determination of 39 veterinary drugs in Procambarusclarkii. Samples were extracted with acidified acetonitrile and purified with enhanced matrix removal-lipid (EMR-Lipid) adsorbent and graphitized multi-walled carbon nanotubes (GMWNTs). Extracts were analyzed by UHPLC-Q-TOF-MS. Target compounds were screened according to accurate mass, isotopic ratio, and retention time, and confirmed by library search. Target analytes were quantified using the chromatographic peak area of each compound. For each of the drugs of interest, calibration curves were linear in their respective ranges with correlation coefficients greater than 0.99. The limits of quantification (LOQs) were 3-15 µg/kg. The recoveries for target compounds spiked in Procambarusclarkii ranged from 62.4% to 105.8%, with relative standard deviations (RSDs) ranging from 2.5% to 13.5%. This method is simple, rapid, accurate, and suitable for simultaneous determination of 39 veterinary drugs, including sulfonamides, quinolones, and triphenylmethane, extracted from Procambarusclarkii.

Magnetic solid-phase extraction based on [60]fullerene functionalization of magnetic nanoparticles for the determination of sixteen polycyclic aromatic hydrocarbons in tea samples.

[60]Fullerene functionalized magnetic nanoparticles (Fe3O4@SiO2@C60) were prepared and characterized by transmission electron microscope, vibrating sample magnetometer and infrared spectroscopy. The Fe3O4@SiO2@C60 was then applied for the magnetic solid-phase extraction of 16 priority pollutants polycyclic aromatic hydrocarbons (PAHs) in tea samples. The analyses were performed on gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) mode. Parameters affecting the extraction, including sorbent amount, desorption solvent, salt concentration, pH and extraction time were investigated. Under optimized conditions, the developed method based on Fe3O4@SiO2@C60 gave detection limits of 0.8-14.3 ng L-1, and quantification limits of 2.6-47.6 ng L-1 for 16 PAHs, respectively. The spiked recoveries of the target PAHs in tea samples ranged from 92.4% to 106.9%. The intra-day and inter-day relative standard deviations (RSDs) were lower than 8.7% and 10.6%, respectively. These results demonstrated that the established method could be applied to the analysis of PAHs at trace level in tea samples.

Synthesis of [60]Fullerene-Fused Spiroindanes by Palladium-Catalyzed Oxidative Annulation of [60]Fullerene with 2-Aryl Cyclic 1,3-Dicarbonyl Compounds.

A convenient and facile palladium-catalyzed reaction of [60]fullerene (C60) with 2-aryl cyclic 1,3-dicarbonyl compounds via the enolate-directed sp(2) C-H activation and sp(3) C-H functionalization has been exploited to synthesize the novel and rare C60-fused spiroindanes for the first time. This reaction is easy to perform with broad substrate scope and provides diversified products in 20-50% yields. A plausible reaction mechanism involving the palladium-catalyzed enolate-directed C-H activation and subsequent cyclization has been proposed, and the electrochemistry of the C60-fused spiroindanes has also been investigated.

Ferric Perchlorate Promoted Reaction of [60]Fullerene with N-Sulfonyl Aldimines: Synthesis and Functionalization of Fulleroxazolidines.

The rare fulleroxazolidines 2 were successfully synthesized by the facile ferric perchlorate promoted reaction of [60]fullerene with various N-sulfonyl aldimines 1. Further functionalization of fulleroxazolidines by arenes in the presence of boron trifluoride afforded 1,4-bisarylation products 4. A possible reaction mechanism for the formation of the fulleroxazolidines is proposed.

Palladium-catalyzed decarboxylative annulation of 2-arylbenzoic acids with [60]fullerene via C-H bond activation.

A convenient and highly efficient palladium-catalyzed decarboxylative annulation of 2-arylbenzoic acids with [60]fullerene has been exploited to synthesize the novel and scarce [60]fullerene-fused dihydrophenanthrenes. The use of Lewis acid ZnCl2 is crucial for the success of the present formal [4 + 2] annulation reaction. Plausible reaction pathways leading to the observed products have been proposed, and the electrochemistry of the fullerene products has also been investigated.