Early-Life Exposure to 4-Hydroxy-4'-Isopropoxydiphenylsulfone Induces Behavioral Deficits Associated with Autism Spectrum Disorders in Mice.

Exposure to bisphenol A (BPA) during gestation and lactation is considered to be a potential risk factor for autism spectrum disorder (ASD) in both humans and animals. As a novel alternative to BPA, 4-hydroxy-4'-isopropoxydiphenylsulfone (BPSIP) is frequently detected in breast milk and placental barrier systems, suggesting potential transmission from the mother to offspring and increased risk of exposure. Gestation and lactation are critical periods for central nervous system development, which are vulnerable to certain environmental pollutants. Herein, we investigated the behavioral impacts and neurobiological effects of early-life exposure to BPSIP (0.02, 0.1, and 0.5 mg/kg body weight/day) in mice offspring. Behavioral studies indicated that BPSIP exposure induced ASD-like behaviors, including elevated anxiety-related behavior and decreased spatial memory, in both male and female pups. A distinct pattern of reduced social novelty was observed only in female offspring, accompanied by significant alterations in antioxidant levels. Transcriptome analysis demonstrated that differentially expressed genes (DEGs) were mainly enriched in pathways related to behaviors and neurodevelopment, which were consistent with the observed phenotype. Besides, a decrease in the protein levels of complex IV (COX IV) across all tested populations suggests a profound impact on mitochondrial function, potentially leading to abnormal energy metabolism in individuals with autism. Additionally, changes in synaptic proteins, evidenced by alterations in synapsin 1 (SYN1) and postsynaptic density protein-95 (PSD95) levels in the cerebellum and hippocampus, support the notion of synaptic involvement. These findings suggest that BPSIP may induce sex-specific neurotoxic effects that involve oxidative stress, energy generation, and synaptic plasticity.

Stereoselective bioaccumulation and degradation of chiral pesticide hexythiazox in earthworm-soil microcosm.

The chiral pesticide hexythiazox was extensively employed in agricultural activities and has garnered growing concern for its harmful impact on the ecosystem. This study investigates the toxicodynamic earthworm at the enantiomeric level of hexythiazox. Earthworms exhibited notable enantioselectivity during the accumulation stage. Furthermore, the presence of earthworms can impact the rate of degradation and enantioselectivity of hexythiazox in soil. The accumulation of the two hexythiazox enantiomers in the earthworm adhered to the one-compartment model, whereas the elimination phase was governed by the first-order kinetics equation. Furthermore, it was discovered that there was no notable enantioselectivity observed during the elimination phase.

Epoxiconazole disturbed metabolic balance and gut microbiota homeostasis in juvenile zebrafish.

Epoxiconazole (EPX) is a broad-spectrum fungicide extensively used in agricultural pest control. Emerging evidence suggests that EPX can adversely affect different endpoints in non-target organisms. Here, the toxicity of EPX was assessed using earlier developmental stage of zebrafish as a model to investigate its effects on metabolism and intestinal microbiota after 21 days of exposure. Our findings indicated that EPX exposure resulted in physiological alterations in juvenile zebrafish, including increase in triglycerides (TG), total cholesterol (TC), low-density lipoprotein (LDL), and glycose (Glu). Nile red staining demonstrated enhanced lipid accumulation in juvenile, accompanied by a marked upregulation in the expression of genes associated with TG synthesis. Moreover, EPX led to alterations in amino acids and carnitines levels in 21 dpf (days post fertilization) zebrafish. We also observed that EPX disrupted intestinal barrier function in juvenile zebrafish, manifested by decreasing mucus secretion and changing in genes related to tight junctions. Moreover, for a more comprehensive analysis of the intestinal microbiota in 21 dpf zebrafish, the intestine tissues were dissected under a microscope for 16S rRNA sequencing analysis. The results revealed that EPX altered the structure and abundance of intestinal microflora in zebrafish, including decreased alpha diversity indices and shifted in bacteria at phylum and genus levels. Notably, the correlation analysis demonstrated strong associations between alterations in various pathogenic bacterial genera and levels of amino acids and carnitines. Overall, these findings confirm that the fungicide EPX promotes metabolic disorders and alterations in the intestinal micro-environment in 21 dpf zebrafish, shedding light on the toxicologic effects of chemicals to aquatic organisms during the development stage.

Impacts of prothioconazole and prothioconazole-desthio on bile acid and glucolipid metabolism: Upregulation of CYP7A1 expression in HepG2 cells.

As an efficient triazole fungicide, prothioconazole (PTC) is widely used for the prevention and control of plant fungal pathogens. It was reported that the residues of PTC and prothioconazole-desthio (PTC-d) have been detected in the environment and crops, and the effects of PTC-d may be higher than that of PTC. Currently, PTC and PTC-d have been proven to induce hepatic metabolic disorders. However, their toxic effects on cellular bile acid (BA) and glucolipid metabolism remain unknown. In this study, HepG2 cells were exposed to 1-500 µM of PTC or PTC-d. High concentrations of PTC and PTC-d were found to induce cytotoxicity; thus, subsequent experimental exposure was conducted at concentrations of 10-50 µM. The expression levels of CYP7A1 and TG synthesis-related genes and levels of TG and total BA were observed to increase in HepG2 cells. Molecular docking analysis revealed direct interactions between PTC or PTC-d and CYP7A1 protein. To further investigate the underlying mechanisms, PTC and PTC-d were treated to HepG2 cells in which CYP7A1 expression was knocked down using siCYP7A1. It was observed that PTC and PTC-d affected the BA metabolism process and regulated the glycolipid metabolism process by promoting the expression of CYP7A1. In summary, we comprehensively analyzed the effects and mechanisms of PTC and PTC-d on cellular metabolism in HepG2 cells, providing theoretical data for evaluating the safety and potential risks associated with these substances.

Exposure to the fungicide prothioconazole and its metabolite prothioconazole-desthio induced hepatic metabolism disorder and oxidative stress in mice.

Prothioconazole (PTC), as a popular triazole fungicide, with its main metabolite prothioconazole desthio (PTC-d), have attracted widespread concern due to their widely use and toxicological effects on non-target organisms. However, toxic effects of study analyzed PTC and PTC-d on the hepatic metabolism of mammalian still remains unclear. In this study, we conducted the study of the C57BL/6 mice which oral exposure to 30 mg/kg PTC and PTC-d via metabolomic analysis. In the liver, the metabolomics profile unveiled that exposure to 30 mg/kg PTC and PTC-d led to significantly altered 13 and 28 metabolites respectively, with 6 metabolites in common including significant decreased d-Fructose, Glutathione, showing the change of carbohydrate, lipid and amino acid metabolism. Via the further exploration of genes related to hepatic glycolipid metabolism and the biomarkers of oxidative stress, we found that liver was potentially damaged after exposure to 5 and 30 mg/kg PTC and PTC-d. Particularly, it was proved that PTC-d caused more adverse effect than its parent compound PTC on hepatotoxicity, and high concentration PTC or PTC-d exposure is more harmful than low concentration exposure.

Effects of maternal exposure to procymidone on hepatic metabolism in the offspring of mice.

As an effective fungicide widely used in agricultural production, the excessive procymidone (PRO) residue has been detected in the environment and food. Our previous study demonstrated that PRO could destroy the intestinal barrier in mice and has a joint toxic effect. To explore the cross-generational impact of maternal exposure, 10-week-old C57BL/6 female mice were orally administrated to 10 and 100 mg/kg body weight/day of PRO during pregnancy and lactation. The offspring obtained nutrients from the maternal through the placenta and breast milk, and PRO residues were detected in the liver, intestine, and feces of F1 generation. Fecal examination found that the residual PRO had been completely metabolized when the offspring mice grew to 35 days. The drug residue of F1 generation male mice was higher than that of female mice. We attributed this result to the difference in cytochrome P450 (CYP450) enzyme expression between male and female mice. The transcriptional levels of CYP1A1, CYP1A2, CYP2D9, and CYP3A4, and CYP450 protein expression levels, were higher in female mice. Furthermore, targeted MS of plasma revealed abnormal amino acid levels. In addition, PRO-induced hepatic metabolite changes in F0 and F1-7w mice. KEGG pathway analysis further showed that PRO jointly changed the amino acid biosynthesis pathway of the maternal and offspring. In summary, these results indicated that maternal exposure to PRO during a special period would interfere with self metabolism, and offspring will also have metabolic disorders.

Maternal Sodium p-Perfluorous Nonenoxybenzene Sulfonate Exposure Disturbed Lipid Metabolism and Induced an Imbalance in Tyrosine Metabolism in the F1 Generation of Mice.

The toxicity of perfluorinated compounds (PFCs) to mammals has recently received increasing attention. However, the effects of maternal sodium p-perfluorous nonenoxybenzene sulfonate (OBS) exposure during pregnancy and lactation on the liver function of dams (F0) and offspring (F1) mice are still unknown. The results demonstrated that maternal OBS treatment could not only induce lipid metabolism dysfunction but also disrupt amino acid metabolism in the liver of F0 and F1 generations. OBS had marked accumulation in the liver, and the serum and liver triglyceride (TG) levels increased in the F0 and F1 generations after maternal OBS exposure. Moreover, maternal OBS exposure changed the transcriptional levels of genes related to lipid metabolism (fatty acid (FA) synthesis, TG synthesis, and transport) and induced changes in the amino acid level in dams and 20-day-old mice offspring (F1-20 d). Additionally, the regulation of lipid metabolism by OBS was mainly dependent on the activation of peroxisome proliferator-activated receptor γ (PPARγ) and cluster of differentiation 36 (CD36). Interestingly, OBS could also disturb tyrosine (TYR) metabolism by increasing the TYR level and downregulating fumarate acetoacetate hydrolase (FAH). Together, these results indicated that the liver can be perceived as the major target tissue of OBS, which strongly affected metabolic function and ultimately led to an imbalance in the metabolism of lipids and TYR. In summary, maternal OBS exposure during pregnancy and lactation has toxic effects on the hepatic metabolism of dams and offspring, indicating that the toxic effects could obviously cross generations of mice, and we should pay more attention to understanding the health risk to both dams and offspring.

Sub-chronic exposure to antibiotics doxycycline, oxytetracycline or florfenicol impacts gut barrier and induces gut microbiota dysbiosis in adult zebrafish (Daino rerio).

Antibiotics are widely used in the treatment of bacterial infections and as food additives in the livestock industry. The wide usage of antibiotics causes residues in animal products, like milk, eggs and meat. A number of studies have reported that antibiotic residues exist at high concentrations in watercourses around the world. Doxycycline (DH), oxytetracycline (OTCC) and florfenicol (FF) are the three most commonly used veterinary antibiotics in China. However, studies of the toxic effects of DH, OTCC and FF are limited. In this study, six-moth-old healthy male adult zebrafish were exposed to 0, 10, 30, 100 µg/L DH, OTCC or FF for 21 days. After exposure, some biochemical parameters changed significantly, including total cholesterol (TC), triglyceride (TG), pyruvate and acid phosphatase (ACP). In addition, mucus secretion in the gut decreased and the transcription of related genes also decreased significantly. Moreover, the composition of microbiota in the gut changed significantly. DH, OTCC and FF exposure caused the decrease of diversity of gut microbiota. The relative abundance of Proteobacteria increased significantly after OTCC and FF exposure and Fusobacteria decreased in all antibiotic-treated groups. Further functional prediction analysis also suggested changes in gut microbiota in the OTCC and FF-treated groups, especially those linked to metabolism. To support this idea, we confirmed that some glycolipid related genes also increased significantly in the liver of adult zebrafish after antibiotic exposure. According to these results, DH, OTCC or FF exposure could cause the gut microbiota dysbiosis and dysfunction, and hepatic metabolic disorder in adult male zebrafish.

Similar Antimicrobial Resistance of Escherichia coli Strains Isolated from Retail Chickens and Poultry Farms.

Antimicrobial resistance (AMR) is a major public health challenge and spreads through humans, animals, and the environment. Many reports show that AMR genes (ARGs) or phenotypes can be transferred from food animals to humans. However, the level and correlation of AMR in different nodes of the poultry meat supply chain are still poorly understood. Herein, 225 Escherichia coli isolates were recovered from chilled chicken samples from markets (123) and chicken fecal samples from farms (102) in Zhejiang Province, China. The dominant sequence types (STs) were ST155 (8.89%), ST48 (7.56%), and ST10 (7.11%), which are common in chicken and fecal samples. Antimicrobial susceptibility testing (AST) analysis showed that the E. coli isolates from fecal samples and retail chickens were resistant to ampicillin (61.77% and 63.42%, respectively) and trimethoprim (56.87% and 52.85%). Moreover, 36.59% of the E. coli isolates from chilled chickens and 39.22% of the isolates from fecal samples were resistant to three or more antimicrobial agents. A total of 59 ARGs were identified in sequenced E. coli genomes, including the mcr-1 gene involved in colistin resistance. The E. coli from farms and markets could be clustered in the same branch according to core single nucleotide polymorphisms. In addition, toxin genes astA and hlyE were also predicted in 86.5% (32/37) and 13.5% (5/37) of the above genomes, respectively. Taken together, these findings demonstrated that E. coli isolates from markets and farms showed similar AMR patterns, suggesting that E. coli strains in markets may originate from farms.

Characterization of an NDM-5 carbapenemase-producing Escherichia coli ST156 isolate from a poultry farm in Zhejiang, China.

BACKGROUND: The emergence of carbapenem-resistant Enterobacteriaceae strains has posed a severe threat to public health in recent years. The mobile elements carrying the New Delhi metallo-ß-lactqtamase (NDM) gene have been regarded as the major mechanism leading to the rapid increase of carbapenem-resistant Enterobacteriaceae strains isolated from clinics and animals. RESULTS: We describe an NDM-5-producing Escherichia coli strain, ECCRA-119 (sequence type 156 [ST156]), isolated from a poultry farm in Zhejiang, China. ECCRA-119 is a multidrug-resistant (MDR) isolate that exhibited resistance to 27 antimicrobial compounds, including imipenem and meropenem, as detected by antimicrobial susceptibility testing (AST). The complete genome sequence of the ECCRA-119 isolate was also obtained using the PacBio RS II platform. Eleven acquired resistance genes were identified in the chromosome; four were detected in plasmid pTB201, while six were detected in plasmid pTB202. Importantly, the carbapenem-resistant gene blaNDM-5 was detected in the IncX3 plasmid pTB203. In addition, seven virulence genes and one metal-resistance gene were also detected. The results of conjugation experiments and the transfer regions identification indicated that the blaNDM-5-harboring plasmid pTB203 could be transferred between E. coli strains. CONCLUSIONS: The results reflected the severe bacterial resistance in a poultry farm in Zhejiang province and increased our understanding of the presence and transmission of the blaNDM-5 gene.

A high-throughput screening method for determination of multi-antibiotics in animal feed.

A high-throughput method based on ultrasonic-assisted extraction, 96-well plate thin-film microextraction was established to determinate 18 antibiotics in animal feed. In this method, the extraction was implemented by ultrasonic-assisted extraction for 30 min with disodium ethylenediaminetetraacetic acid-McIlvaine buffer (pH 5) containing 6% sodium chloride w/v, purified by thin-film microextraction and combined with 96-well plate system to improve the efficiency. Optimization of thin-film microextraction conditions was performed by methods of single factor and response surface, and finalized as: condition time: 20 min; adsorption time: 55 min; washing time: 5 s with water; desorption time: 30 min with acetonitrile/water (8:2, v/v) containing 0.1% formic acid v/v. Evaluation of different extractive phases showed that polystyrene-divinylbenzene-polyacrylonitrile was the optimum coating. The analysis was performed by ultra-high performance liquid chromatography with tandem mass spectrometry. Recovery, inter- and intraday precision, linearity, limit of detection, and quantitation were evaluated. The average recoveries of 18 antibiotics were 66.6-93.5% at three spiked levels, intraday precision was 1-8.4%, and interday precision was 3.0-16.4%. The linearity was good for r2  > 0.99. Limits of detection and quantification were found in the range of 1-14 and 4-48 µg/kg, respectively.

Degradation of triadimefon and residue levels of metabolite triadimenol: tracing rapeseed from harvesting and storage to household oil processing.

BACKGROUND: Triadimefon is a fungicide used in agriculture to control fungal diseases such as sclerotinia sclerotiorum. RESULTS: In field trials, rape plants were sprayed with triadimefon at three different dosages during the flowering period. The degradation of triadimefon and the residue levels of its metabolite, triadimenol, in rapeseed obtained from harvesting, storage, and household oil processing were traced and evaluated. The pesticides were determined by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) at each processing step. Triadimefon degraded completely and only its metabolite, triadimenol, was detected in rapeseed after harvesting. The stability of triadimenol in rapeseed was studied at weekly storage intervals, from 0 to 7 weeks at ambient temperature (25 °C) and freezing temperature (-20 °C), respectively. Storage temperature had an important influence on the residue levels of triadimenol. The processing factor (PF) was defined as the ratio of pesticide residue levels in rapeseed to rapeseed oil levels during household oil processing. The average PF of triadimenol was about 0.96 for a hot pressing technique and 0.88 for a cold pressing technique. CONCLUSION: Different storage conditions and food processing could reduce the pesticide level to a greater or lesser extent. However, it is not easy to eliminate or significantly weaken triadimenol once triadimefon has degraded completely. © 2018 Society of Chemical Industry.

Syringe cleanup with UHPLC-MS/MS for nitroimidazoles and steroids detection in manure-based fertilizers.

A syringe-dispersive solid-phase extraction method was developed for the determination of seven nitroimidazoles and nine steroids in manure-based fertilizers by ultra-high performance liquid chromatography with tandem mass spectrometry. Methanol and acetonitrile were used to extract the sample, and mixed dispersive sorbents dispersed in the syringe were used for purification. The extract was separated with an HSS-T3 column and detected in positive or negative multiple reaction monitoring mode. Under the optimal conditions, the recoveries of the 16 compounds ranged from 70.3 to 112.3% at the four spiked levels (3, 10, 20, and 50 µg/kg) and the relative standard deviations ranged from 1.0 to 12.4%. The limits of detection and quantification were 0.22-0.86 and 0.73-2.87 µg/kg, respectively. This method is simple, fast, and reliable, and can be used to simultaneously screen and determine nitroimidazoles and steroids in manure-based fertilizers.

Detection of 13 mycotoxins in feed using modified QuEChERS with dispersive magnetic materials and UHPLC-MS/MS.

An analytical method for the simultaneous determination of 13 mycotoxins in feed by magnetic dispersive solid-phase extraction combined with ultra-high performance liquid chromatography and tandem mass spectrometry was developed. The samples were extracted with acetonitrile/water (80:20, v/v, containing 3% acetic acid), and separated by centrifugation after salting-out, and then treated with magnetic adsorbents to remove interferences. The separation of target mycotoxins was performed on an ACQUITY UPLC HSS T3 column using a mobile phase consisting of 1 mmol/L ammonium acetate with 0.1% formic acid and methanol by gradient elution. Good linearities for the 13 mycotoxins were achieved with correlation coefficients over 0.99, and the recoveries of mycotoxins were in the range of 89.3-112.6% at spiking at levels of 5, 20, and 100 µg/kg, with relative standard deviations of 0.9-10.4%. Based on the functional magnetic materials (MDN@Fe3 O4 , PSA@Fe3 O4 , ZrO2@ Fe3 O4 ) applied in dispersive solid-phase extraction, the pretreatment process is more convenient and it is beneficial to reduce the experimental cost by reusing the recycled magnetic materials. It is a simple, rapid, and environmentally friendly analytical method for the determination of mycotoxins in feed.

Bioaccumulation and Distribution of Hexabromocyclododecane Isomers in Duck Tissues.

Eighty ducks (Sheldrake, Anas platyrhynchos) from Zhejiang Province, China were fed capsules containing commercialized hexabromocyclododecanes (HBCDs) at low (0.8 mg/kg/day) or high (1.6 mg/kg/day) exposure level, or only maize starch for 21 days. Then the next 21 days was set as depuration period. Ducks were euthanizated at 0, 7, 14 and 21 days after last dose and ten duck tissues including skin, tongue, intestines, heart, gizzard, muscle, liver, lung, brain and blood were sampled, separately. Three HBCDs including α-HBCD, ß-HBCD and γ-HBCD in duck tissue samples were analyzed. At the end of depuration period, the total HBCDs concentration in skin was significantly higher than those in the other tissues (p < 0.05). The elimination rates of the three isomers in skin, tongue, intestines, heart, gizzard and brain were in the order ß- > γ- > α-HBCD. The enantioselectivity of three HBCDs enantiomers was also studied in ten duck tissues. It was shown that the EF (enrichment factor) for two γ-HBCD enantiomers was significant lower than 0.5 (p < 0.05) in gizzard, heart, muscle, tongue, intestinal and liver at the end of depuration day, showing a selective accumulation of (+)-γ-HBCD in these tissues. This study provided a reference for evaluation on the accumulation of the persistent contamination of HBCDs in edible poultry.

Etoxazole is Metabolized Enantioselectively in Liver Microsomes of Rat and Human in Vitro.

Acaricide etoxazole belongs to the ovicides/miticides diphenyloxazole class, affecting adults to lay sterile eggs by inhibiting chitin biosynthesis possibly. The reverse-phase HPLC-MS/MS method was used to determine the etoxazole enantiomers. The enantioselective degradation behavior of rac-etoxazole in liver microsomes of rat and human in vitro with NADPH was dramatically different. The t1/2 of (R)-etoxazole was 15.23 min in rat liver microsomes and 30.54 min in human liver microsomes, while 21.73 and 23.50 min were obtained for (S)-etoxazole, respectively. The Vmax of (R)-etoxazole was almost 5-fold of (S)-etoxazole in liver microsomes of rat in vitro. However, the Vmax of (S)-etoxazole was almost 2-fold of (R)-etoxazole in liver microsomes of human in vitro. The CLint of etoxazole was also shown the enantioselectivity on the contrary in liver microsomes of rat and human. These results indicated that the metabolism of two etoxazole enantiomers was selective in liver microsomes of rat and human in vitro, and enantioselectivity in the two kinds of liver microsomes was in the difference in degradation performance. The reason might be related to the composition and content involved in the enzyme system.

Chromatography column comparison and rapid pretreatment for the simultaneous analysis of amantadine, rimantadine, acyclovir, ribavirin, and moroxydine in chicken muscle by ultra high performance liquid chromatography and tandem mass spectrometry.

In this work, a chromatography column comparison and rapid pretreatment development were carried out. A multi-class method was built based on the quick, easy, cheap, effective, rugged, and safe pretreatment method with hydrophilic interaction ultra high performance liquid chromatography and tandem mass spectrometry for the high-throughput analysis of five antivirals in chicken muscle. The HSS T3 column, BEH HILIC column and BEH Amide column were studied, and their chemical functionalities and chromatographic separation effectiveness were compared. The BEH Amide column was selected to perform the mass spectrometry analysis under the hydrophilic interaction chromatography mode. First, a different strategy without adding MgSO4 and NaCl into the muscle samples was considered. Then, different concentrations of formic acid, acetic acid, and ammonia in acetonitrile were compared for better extraction efficiency. Nine sorbents (C18 , PSA, NH2 , Florisil, Alumina-B, Alumina-N, PestiCarb, NANO, and NANO-NH2 ) were studied. The optimized procedure consisted of the use of 10% acetic acid in acetonitrile for the extraction solvent and NANO-NH2 for clean-up. NANO-NH2 had not been applied in other matrix and pollutants so far. The developed method provided favorable trueness, precision, and acceptable matrix effect. Meanwhile, the method was sensitive, the limits of detection of amantadine, rimantadine, acyclovir, ribavirin, and moroxydine achieved were 0.56, 0.50, 0.30, 2.22, and 0.51 µg/kg, respectively, and were successfully applied for the routine detection of antivirals in the chicken samples.

Simultaneous determination of sulfonamides and metabolites in manure samples by one-step ultrasound/microwave-assisted solid-liquid-solid dispersive extraction and liquid chromatography-mass spectrometry.

An in-line matrix cleanup method was used for the simultaneous extraction of 15 sulfonamides and two metabolites from manure samples. The ultrasound/microwave-assisted extraction (UMAE) combined with solid-liquid-solid dispersive extraction (SLSDE) procedure provides a simple sample preparation approach for the processing of manure samples, in which the extraction and cleanup are integrated into one step. Ultrasonic irradiation power, extraction temperature, extraction time, and extraction solvent, which could influence the UMAE efficiency, were investigated. C18 was used as the adsorbent to reduce the effects of interfering components during the extraction procedure. The extracts were concentrated, and the analytes were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) without any further cleanup. The isotopically labeled compounds sulfamethoxazole-d 4, sulfamethazine-d 4, sulfamonomethoxine-d 4, and sulfadimethoxine-d 6 were selected as internal standards to minimize the matrix effect in this method. The recoveries of the antibiotics tested ranged from 71 to 118 % at the three spiking levels examined (20, 200, and 500 µg · kg(-1)). The limits of detections were 1.2-3.6 µg · kg(-1) and the limits of quantification were 4.0-12.3 µg · kg(-1) for the sulfonamides and their metabolites. The applicability of the method was demonstrated by analyzing 30 commercial manure samples. The results indicated that UMAE-SLSDE combined with LC-MS/MS is a simple, rapid, and environmentally friendly method for the analysis of sulfonamides and their metabolites in manure, and it could provide the basis for a risk assessment of the antibiotics in agricultural environments.

Enantioselective Degradation of (2RS, 3RS)-Paclobutrazol in Rat Liver Microsomes.

Paclobutrazol, with two stereogenic centers, but gives only (2R, 3R) and (2S, 3S)-enantiomers because of steric-hindrance effects, is an important plant growth regulator in agriculture and horticulture. Enantioselective degradation of paclobutrazol was investigated in rat liver microsomes in vitro. The degradation kinetics and the enantiomer fraction were determined using a Lux Cellulose-1 chiral column on a reverse-phase liquid chromatography-tandem mass spectrometry system. The t1/2 of (2R, 3R)-paclobutrazol is 18.60 min, while the t1/2 of (2S, 3S)-paclobutrazol is 10.93 min. Such consequences clearly indicated that the degradation of paclobutrazol in rat liver microsomes was stereoselective and the degradation rate of (2S, 3S)-paclobutrazol was much faster than (2R, 3R)-paclobutrazol. In addition, significant differences between the two enantiomers were also observed in enzyme kinetic parameters. The Vmax of (2S, 3S)-paclobutrazol was more than 2-fold of (2R, 3R)-paclobutrazol and the Clint of (2S, 3S)-paclobutrazol was higher than that of (2R, 3R)-paclobutrazol after incubation in rat liver microsomes. These results may have potential implications for better environmental and ecological risk assessment for paclobutrazol.

Simultaneous determination of florfenicol with its metabolite based on modified quick, easy, cheap, effective, rugged, and safe sample pretreatment and evaluation of their degradation behavior in agricultural soils.

A simple and simultaneous method for the determination of florfenicol and its metabolite florfenicol amine in agricultural soils using modified quick, easy, cheap, effective, rugged, and safe sample pretreatment and reversed-phase high-performance liquid chromatography with tandem mass spectrometry is presented. Florfenicol and its metabolite florfenicol amine residues in agricultural soils were extracted with alkalized acetonitrile and an aliquot was cleaned up with Si(CH2)3NH(CH2)2NH2 and C18 sorbent, which were powder materials. High-performance liquid chromatography with tandem mass spectrometry was applied to simultaneously determine the level of florfenicol and florfenicol amine in agricultural soils. Excellent linearity was achieved for florfenicol and florfenicol amine over a range of concentrations from 0.1-500 µg/L with coefficients more than 0.99. Average recoveries at four different levels (0.005, 0.05, 0.5, and 5.0 mg/kg) for florfenicol and florfenicol amine ranged from 73.6-94.9% with relative standard deviations of 2.9-12.5%. The limits of detection for florfenicol and florfenicol amine in agricultural soils were 2.0 µg/kg, and the limits of quantification were 6.0 µg/kg. Based on this method, the degradation behavior of florfenicol and its metabolite florfenicol amine in three soils (Nanchang, Hangzhou, and Changchun) under sterilized and native conditions was investigated and the transformation rate of florfenicol amine from florfenicol was evaluated.