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Eriocheir sinensis is a unique freshwater crab found in China, which is well known for its rich nutrition and sweet and delicious taste. Free amino acids in Eriocheir sinensis are not only important nutrients but also are closely related to their unique taste and aroma. Therefore, the determination of the free amino acid contents in Eriocheir sinensis is of great significance for product quality evaluation, flavor research, authenticity, and origin identification. Herein we proposed an ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS)-based method for the determination of 17 free amino acids in Eriocheir sinensis. First, 5 g of the Eriocheir sinensis sample was weighed into a 50-mL polypropylene centrifuge tube. Then, 10 mL of extraction solvents was added to the centrifuge tube, and the resultant solution was mixed well using a vortex mixer. We compared a variety of solvents and finally selected 5%(v/v) perchloric acid aqueous solution as the optimum extraction solvent. The supernatant was transferred to another polypropylene centrifuge tube after centrifuging at 8000 r/min for 5 min. The extraction procedure was repeated according to the above-mentioned steps, and the extraction solution was combined with the supernatant. The extracts were then adjusted to pH 6.5 with 1 mol/L potassium hydroxide solution, and were diluted to 50 mL with water. After filtering by both qualitative filter paper and a 0.45-μm polyether sulfone syringe filter, the extracts were determined by UHPLC-HRMS. We compared three types of mobile phases and chose 0.1%(v/v) formic acid aqueous solution mixed with acetonitrile as the optimum one. Precise parent ion and ion source parameters were also optimized. The 17 analytes, viz. aspartic acid, threonine, serine, glutamic acid, proline, cystine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, arginine, glycine, alanine, and histidine, were separated on an XDB-C

The evolution of reaction phases formed in diffusion-bonded SiC/Ta–5W/SiC joints was investigated at a joining temperature of 1500–1700 °C for 10–90 min. The effects of bonding temperature and holding time on the phase evolution were found to be directly correlated with the thickness of the interfacial reaction layer when a 100-μm-thick Ta–5W interlayer was used for joining. In the case of a ~7-μm-thick reaction layer, the interfacial phase constitution consisted of a layered SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)2Si/(Ta,W)xSiy/Ta–5W structure. In the reaction layer with a thickness of ~11–26 μm, the interfacial structure evolved into SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C/(Ta,W)xSiy/(Ta,W)2Si/(Ta,W)xSiy/Ta–5W, in which an additional (Ta,W)C/(Ta,W)xSiy layer was inserted between (Ta,W)5Si3 and (Ta,W)xSiy owing to the precipitation of carbon from the (Ta,W)5Si3 layer. When the Ta–5W interlayer was fully consumed to form a stable reaction product, namely the equilibrium state, (Ta,W)xSiy and (Ta,W)2Si were eventually transformed into (Ta,W)5Si3, and the final interface structure that was obtained was SiC/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C/(Ta,W)5Si3/(Ta,W)C. This achievement will benefit the design, control, and characterization of SiC/metal interfaces.

Hydroxytyrosol (HT) and oleuropein (OL), the most abundant of the phenolic compounds in olives, have anticancer properties against breast cancer (BC). However, little attention has been paid to the mechanism of HT or OL in BC cells. The objective of this study was to identify the underlying molecular mechanisms of these compounds. ER-positive BC MCF7 and T47D cells were treated with HT and OL in combination with hepatocyte growth factor (HGF), rapamycin (Rapa, an agonist of autophagy) or 3-methyladenine (3-MA, an inhibitor of autophagy). Cell viability, metastasis capability and autophagy-related proteins were evaluated by wound healing assays, Transwell assays and Western blot. HT and OL reduced the cell viability of MCF-7 and T47D cells in a dose-dependent manner. Both cells were more sensitive to HT than OL. In addition, Rapa significantly inhibited HGF-induced migration and invasion, indicating that metastases of both BC cells could be inhibited by suppression of autophagy. Moreover, HT and OL significantly blocked HGF- or 3-MA-induced cell migration and invasion by reversing LC3II/LC3I and Beclin-1 downregulation and p62 upregulation. These findings revealed that HT and OL could suppress migration and invasion by activating autophagy in ER-positive BC cells, which might be a promising therapeutic strategy.

Ship ballast water can control the roll, trim, and draft of the ship, and thus ensuring the balance and stability of the ship in the course of sailing, and playing a vital role in the safe navigation of ships. The annual discharge of ship ballast water is very large in China. About three to five billion cubic meters of ship ballast water is discharged into offshore or inland waters every year. This water contains plankton, pathogens, and their larvae or spores. If not be handled appropriately, this will have a serious impact on the ecological environment of the discharge waters. Ballast water is usually treated by electrolysis before being discharged. Sodium hypochlorite can be generated, which can kill microorganisms; however, the by-products trihalomethanes (THMs) are cytotoxic and biotoxic. Studies have shown that THMs may cause fetal growth retardation, spontaneous abortion, or death. The concentration of THMs in drinking water is closely related to the risk of bladder cancer death. Hence, it is important to establish a method for the determination of THMs in ship ballast water. The four kinds of THMs are chloroform, dichlorobromomethane, chlorodibromomethane, and tribromomethane. At present, ship ballast water is mostly analyzed by gas chromatography (GC) using an electron capture detector (ECD) or by gas chromatography-mass spectrometry (GC-MS). Given the low boiling point of THMs, headspace injection and purge-and-trap can be used. Gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), was adopted. NCI is a soft ionization technique that shows special response to compounds bearing electronegative elements or groups. THMs contain electronegative chlorine atoms and bromine atoms. Therefore, NCI is a good choice for their analysis. The samples were processed by the headspace injection technique. The NaCl content in 10 mL sample was optimized in headspace injection. The results showed that 3.0 g NaCl was the most suitable dosage. The analytes were separated on a DB-5MS UI capillary-column (30 m×0.25 mm×1.0 μm). The target compounds were quantified by using the external standard method in selected ion monitoring (SIM) mode. The four THMs were not only well separated but also showed a high response at 0.2 μg/L. The four THMs showed good linear relationships in the range of 0.2-50 μg/L, with correlation coefficients≥0.995. The limits of quantification (LOQs

A comprehensive analytical method based on gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 3-monochloropropanediol esters, 2-monochloropropanediol esters, and glycidyl esters in vegetable oils. Different parameters, such as bromination reaction temperature, bromination reaction time, derivatization reagent dosage, and derivative reaction time, were studied. The optimal conditions were as follows: 0.25 g of oil was weighed in a 10-mL glass tube, followed by the addition of 2 mL tetrahydrofuran, 25 μL of internal working standard solutions, and 30 μL of acid aqueous solution of NaBr, homogenized, and the mixture was incubated at 50 ℃ for 15 min. The reaction was stopped by the addition of 3 mL of an aqueous solution of sodium hydrogen carbonate. To separate the oil from the water phase

A method was established for the determination of eight vitamins E (

This paper reported a route to fabricate a high-performance high-entropy alloy (HEA) brazed joint with the fusion zone similar to the base metal, in which the brazing of a Ni-containing AlCoCrFeNi HEA using a novel Ni-based filler was investigated at 1150–1350 °C for 0–45 min. A microstructure similar to the base metal was received in the fusion zone through proper interface control, thus the joint shear strength obtained was approximately three times (687.2 ± 23.2 MPa) in contrast to that of the joint with the heterogenous interface (199.4 ± 2.8 MPa). The strengthening mechanism was attributed to the high-entropy solid solution, precipitation strengthening and grain refinement occurring in the joint. The highest joint strength of 687.2 ± 23.2 MPa was received at 1300 °C for 15 min with the fracture mainly happening in the base metal. The brazed joint exhibited desirable high-temperature stability with minor degradation of joint strength (∼3%) after annealing of 800 °C for 240 h. The excellent joint performances are potential for high temperature applications.

A method is proposed for the simultaneous determination of nine benzimidazole and neonicotinoid pesticides present in honey by employing automatic solid-phase extraction with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A honey sample was dissolved in a phosphate buffer (pH=7.8) followed by ultrasonic extraction. The extracts were then purified through solid-phase extraction (SPE) with hydrophilic-lipophilic balance (HLB) cartridges. Finally, nitrogen was blown on the obtained mixture, and the mixture was subsequently filtered for conducting HPLC-MS/MS analysis. Nine compounds were detected under the multiple reaction monitoring (MRM) mode, and the corresponding quantification was performed by employing the method of internal standards. The nine detected pesticides demonstrated good linearity in the range of 0.002-0.05 mg/L, with the correlation coefficient values (r2) being higher than 0.99. The limits of detection (LODs) (S/N=3) and limits of quantification (LOQs) (S/N=10) were found to be in the ranges of 0.1-1.0 μg/kg and 0.3-2.0 μg/kg, respectively. Furthermore, the results indicated that the recoveries of the nine detected pesticides range from 78.2%-101.2% at three spiked levels of 5.0, 10.0, and 20.0 μg/kg with a relative standard deviation (RSD) range of 1.3%-14.3% (n=6). Hence, the proposed method is rapid and can be employed for accurate determination of pesticide residues in large quantities of honey samples.

A method was established for the determination of amitraz (AMZ), and its metabolites semiamitraz (DMPF), 2,4-dimethylformamidine (DMF) and 2,4-dimethylaniline (DMA) in vegetables and fruits by using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The samples were diluted with 0.1 mol/L sodium hydroxide and extracted withn-hexane-isopropanol (2:1, v/v). The separation was performed on a Phenomenex Kinetex C18 column (100 mm×4.6 mm, 2.6 μm) with gradient elution using 0.1% (v/v) formic acid aqueous solution-methanol as the mobile phase. The analysis of amitraz and its metabolites were detected under electrospray positive ionization mode. The limits of quantification (LOQs) were between 0.01 and 0.4 μg/kg. The good linearities (r>0.99) were achieved for the target compounds in the range of 1.0-200.0 μg/L. The recoveries at three spiked levels (0.5, 5.0 and 20 μg/kg) in blank matrix were in the range of 62.5%-105.0% with the relative standard deviations between 7.5% and 17.6%. The method is convenient, rapid, accurate, efficient, sensitive and practical. It is suitable for the determination and confirmation of amitraz and its metabolites in vegetables and fruits, and can meet the demands of domestic and foreign regulations.

A method was developed for the simultaneous determination of 10 perfluorinated carboxylic acid compounds in water by gas chromatography-mass spectrometry coupled with negative chemical ionization (GC-NCI-MS). Perfluorinated carboxylic acid compounds were derivatized by trifluoro-N-methyl-N-(trimethylsilyl) acetamide (MSTFA) as the trimethylsilyl derivatization reagent. The water sample was purified and enriched through a weak anion exchange solid phase extraction column and analyzed via GC-NCI-MS. The sample pretreatment, derivation and instrument conditions were optimized. The results showed that the linearity of the 10 perfluorinated carboxylic acid compounds was good in the range of 0.1-10 mg/L with correlation coefficients of 0.9956-0.9993. The limits of detection (LODs) and limits of quantification (LOQs) were 0.5-1.5 μg/L and 1.5-4.5 μg/L, respectively. The spiked recoveries of the blank samples ranged from 70.2% to 112.6% with the relative standard deviations (RSDs) between 2.1% and 14.5% (n=6). The method is simple, sensitive, accurate and precise, and can be used to detect the 10 perfluorinated carboxylic acid compounds in water.

A method was established for the determination of five acylpyrazole pesticide residues in edible vegetable oils using gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The pesticides were extracted from a sample with acetonitrile under freezing conditions. A simple cleanup step known as QuEChERS was then conducted. After being identified by GC-NCI-MS, the extracts were quantified using an external standard method that employs a matrix correction standard curve. The linearity of the method was good between 20 and 1000 μg/L, and all limits of quantification were less than 2 μg/kg. Recoveries of all pesticides were in the range of 82.7%-112.4% at the three spiked levels of 0.01, 0.02, and 0.05 mg/kg, and all relative standard deviations were not more than 12.3%. Therefore, this method can be used to determine the residues of acylpyrazole pesticides in edible vegetable oils.

A simple and rapid gas chromatography-mass spectrometry (GC-MS) method was developed and validated for the simultaneous determination of α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols in vegetable oils. In this study, tedious sample pretreatments like saponification and derivatization, which are commonly used in previously published related methods, were not adopted. Tocopherols and tocotrienols were isolated from oil samples by ultrasonic extraction with methanol, then centrifuged and the supernatant was directly injected into the GC-MS system for analysis. The results showed that α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols were well separated within 14 minutes. The instrumental limits of detection and quantification ranged from 0.3 to 2.5 ng mL−1 and from 1.0 to 8.3 ng mL−1, respectively. Calibration curves were well correlated (r2 > 0.99) within the concentration range of 10 to 1000 ng mL−1 for all eight compounds. Recovery tests were carried out by spiking virgin olive oil with standards at three concentration levels (10, 50 and 250 mg kg−1), in which the average recoveries (n = 6) varied from 83.7% to 117.2%, with relative standard deviations ranging between 1.9% and 7.5%. The proposed method proved to be simple, sensitive and accurate, and was successfully applied to the determination of tocopherols and tocotrienols in vegetable oils.

A method was established for the determination of fipronil and its metabolites in eggs and egg products with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The targets were extracted from samples with acetonitrile, and followed by a simple cleanup step known as dispersive solid-phase extraction QuEChERS. The extracts were determined by GC-NCI-MS, and quantified by external standard method with matrix correction standard curves. The recoveries were in the range of 87.0% to 99.3% at four spiked levels (0.1, 2.0, 4.0 and 20.0 μg/kg), and all RSDs were not more than 12.7% for the four analytes. The linearity of the method was good between 0.005 and 0.10 mg/L, and all LOQs were less than 0.10 μg/kg. So this method can be used to determine the residues of fipronil and its metabolites in eggs and egg products.

A modified quick, easy, cheap, effective, rugged, and safe sample preparation method combined with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI/MS) has been developed for the determination of 7 dinitroaniline herbicide residues in complex matrices (garlic, olive oil, scallion, leek and chili). Dinitroaniline residues were extracted with hexane-saturated acetonitrile. After the cleanup with the dispersive solid-phase extraction, the extract was analyzed by GC–NCI/MS in selected ion monitoring mode. Two isotope internal standards (trifluralin-d 14 and pendimethalin-d 5) were employed for quantification. Compared with electron ionization (EI) mode, the superiorities of NCI in sensitivity and selectivity were investigated. Limits of the detection of 7 dinitroanilines were in the range of 0.014–0.096 μg kg−1, and there were no interfering peaks (unlike in EI) in the complex matrices. Recoveries of 7 dinitroanilines in five matrices at three spiked levels (10, 20 and 40 μg kg−1) ranged from 61 to 126 % and the relative standard deviations were all below 12 %.

A simple and efficient method based on a novel solid phase extraction (SPE) cartridge and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) was developed for the determination of clenbuterol residue in pork. The minced pork sample was ultrasonically extracted by 5% (v/v) perchloric acid and centrifuged at 10 000 r/min for 15 min, then the supernatant was purified by an SMCX cartridge, which is a novel SPE column based on homemade silica matrix with two mixed modes of reversed-phase and strong cation exchange, for the selective enrichment and purification of the analyte. The linear range of the method was 0.25 - 50 microg/kg with a correlation coefficient of 0.998 2. The average recoveries ranged from 62.2% to 72.0% at the three spiked levels of 1.25, 12.5 and 50 microg/kg with the relative standard deviations (RSDs) between 4.2% and 6.1%. The limit of detection (S/N = 3) was 0.05 microg/kg. The method is simple, fast and can be extended to enrich and determine beta-agonist drugs.

A gas chromatography–mass spectrometry (GC–MS) multi-residue method with different ionization modes has been developed for the determination of 23 organochlorine pesticides and ten polychlorinated biphenyls (PCBs) in crayfish. The approach was based on an extraction with acetonitrile saturated by hexane (containing 0.1 % acetic acid), followed by a dispersed solid-phase extraction cleanup with primary secondary amine and octadecylsilane, and finally analyzed by GC–MS/MS operated in electron impact (EI) and positive chemical ionization (PCI), and GC–MS in negative chemical ionization (NCI), respectively. An isotope internal standard, DDT-D8, was used for quantification. These three GC–MS procedures were validated and compared using crayfish samples fortified at three levels (5, 10 and 20 ng/g). Good linearity, accuracy, precision and sensitivity were achieved by all three ionization modes with recoveries in the range of 70 to 112 %, relative standard deviations (RSDs) below 10 % and limits of detection (LODs) in the range of 0.002 to 8 ng/g. Extremely high selectivity was obtained by both EI- and PCI-MS/MS, while PCI was more sensitive to compounds containing nitro and carbonyl groups, and EI was a better choice for dieldrin, endosulfan, and its metabolites. NCI-MS had the highest sensitivity but lower anti-interference ability and was not suitable for the determination of DDTs and PCBs. These three ionization modes can be used as complementary and alternative in routine GC–MS analysis of organochlorine pesticides and polychlorinated biphenyls in food.

An analytical method with the technique of QuEChERS (quick, easy, cheap, effective, rugged and safe) and gas chromatography (GC)/mass spectrometry (MS) in negative chemical ionization (NCI) has been developed for the determination of 17 pyrethroid pesticide residues in troublesome matrices, including garlic, onion, spring onion and chili. Pyrethroid residues were extracted with acidified acetonitrile saturated by hexane. After a modified QuEChERS clean-up step, the extract was analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode. An isotope internal standard of trans-cypermethrin-D(6) was employed for quantitation. Chromatograms of pyrethroids obtained in all these matrices were relatively clean and without obvious interference. The limits of detection (LODs) ranged from 0.02 to 6 μg kg(-1) and recovery yields were from 54.0% to 129.8% at three spiked levels (20, 40 and 60 μg kg(-1) for chili, and 10, 20 and 30 μg kg(-1) for others) in four different matrices depending on the compounds determined. The relative standard deviations (RSDs) were all below 14%. Isomerization enhancement of pyrethroids in chili extract was observed and preliminarily explained, especially for acrinathrin and deltamethrin.

A method has been developed for rapid untargeted screening and determination of unknown contaminants in aquatic products by high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry. The samples were extracted by acetonitrile, dried under nitrogen, dissolved in methanol-water (3:7, v/v), and analyzed via the full MS scan/data dependent MS2mode during the screening process. The Trace Finder software was used to match the precise mass, the isotope abundance ratio, the fragment ion to search for unknown contaminants in aquatic samples. The optimized QuEChERS method is used to purify the samples when quantifying. The quantitative analyses of triazole, caffeine, and ethoxyquinoline were performed via the target-MS2mode. The correlation coefficients of the three compounds in fish and shrimp samples were higher than 0.99 in the linear range of 5-1000 μg/L. The limit of detection was 1 μg/kg, and the limit of quantitation was 5 μg/kg. The average recoveries were between 70.5% and 90.9% with the relative standard deviations ranging from 5.4% to 12.8%. The screening method has the advantages of fast, accurate, and high throughput; when combined with the quantitative method, it can be used to screen and determine unknown contaminants in the actual aquatic products.

For the determination of organo-tin residues in edible vegetable oil, a method was developed based on gas chromatography-mass spectrometric (GC-MS) with positive chemical ionization (PCI). The edible oil samples were first dissolved by cyclohexane-ethyl acetate (1:1, v/v), and then purified by gel permeation chromatography (GPC). After derivatization by sodium tetraethylborate, the samples were analyzed by GC-MS with PCI source in the single ion monitor (SIM) mode. The seven organo-tin compounds showed good linear relationships in the range of 20-2000 μg/L and the correlation coefficients exceeded 0.99. The limits of quantitation (LOQs) and the average recoveries of the seven organo-tin compounds were 0.3-1.2 μg/kg and 66.2%-103.2%, respectively, and the relative standard deviations were less than 11.5% at three spike levels (0.05, 0.10, and 0.20 mg/kg). The method showed good linearity and high sensitivity and can be used for the determination of organo-tin residues in edible vegetable oil.

A liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of chloramphenicol (CAP) in royal jelly. Royal jelly samples were first denatured with lead acetate solution, and the CAP was extracted with solid-phase extraction before separation by liquid chromatography. A triple-quadrupole mass spectrometer operated in the negative electrospray ionization and selected-reaction monitoring mode was used for the detection of CAP. For method validation, royal jelly samples were fortified at CAP levels between 0.1 and 10.0 μg/kg; at these levels, recovery values (internal standard-corrected) ranged from 93.3 to 105.0%, and the within-laboratory reproducibility (relative standard deviation) was ≤9.1%. The decision limit was 0.07 μg/kg, and the detection capability was 0.1 μg/kg.

A confirmatory method was established for the determination of trifluralin residue in aquatic products and edible oils with the technique of offline disperse solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry (DSPE-GC-MS/NCI). Trifluralin was extracted from aquatic products and edible oils with acetonitrile, and liquid-liquid partitioning formed by adding anhydrous magnesium sulfate followed by a simple cleanup step known as dispersive solid-phase extraction. The aliquot was analyzed by GC-MS/NCI using isotope internal standard method. The method was reliable and stable. The recoveries of trifluralin were in the range from 80% to 100% at three spiked levels of 1.0, 2.0, and 3.0 microg/kg, and the RSDs were not more than 10.3%. The linearity of method was good from 1 to 40 microg/L, and the LOD was 0.02 microg/kg. This method can be used as a conclusive evidence method for the determination of trifluralin residue in aquatic products and edible oils.

A method was established for the determination of 17 pyrethroid pesticide residues in vegetables using QuEChERS (quick, easy, cheap, effective, rugged and safe) clean-up method and gas chromatography-mass spectrometry (GC-MS) with negative chemical ionization (NCI). The pyrethroid pesticides in the sample were extracted with acetonitrile. After QuEChERS clean-up with a mixture of primary secondary amine and graphitized carbon black packings, the extract was analyzed by GC-NCI-MS in selected ion monitoring (SIM) mode. An isotope internal standard of cypermethrin was employed to the quantification. The limits of quantification ranged from 0.02 to 5 microg/kg. The recoveries of the pyrethroid pesticides spiked in three different matrixes (peas, broccoli and Chinese onion green) at four spiked levels of 10, 20, 30 and 100 microg/kg were from 71.0% to 139.0%, and the relative standard deviations were less than 12.8%. This method can be used as a conclusive evidence method of the 17 pyrethroid pesticide residues in vegetables.

A method for the simultaneous determination of fenbutatin oxide, triphenyltin and cyhexatin in apples and cabbages was developed by gas chromatography-mass spectrometry coupled with two different ionization techniques, electron impact (EI) ionization and positive chemical ionization (PCI). At first, the samples were digested by hydrobromic acid, and extracted by acetone-hexane (1:2, v/v). The extracts were derivatized by sodium tetraethylborate as the derivatization reagent, and cleaned up by the Florisil SPE columns. Finally, the samples were analyzed by GC-EI/MS and GC-PCI/MS in selected ion monitoring (SIM) mode. The results showed that good linearities were obtained with correlation coefficients (r2) greater than 0.997 for fenbutatin oxide in the range of 75-500 μg/L in both foods, triphenyltin in the range of 50-1000 μg/L in cabbages and 50-500 μg/L in apples and cyhexatin in the range of 50-1000 μg/L in the two foods. The accuracy was checked at three spiked levels (50, 100 and 200 μg/kg) in cabbages and apples. The limits of detection (LODs, S/N=3) were 0.01-0.05 mg/kg (EI) and 0.01-0.02 mg/kg (PCI), and the limits of quantifications (LOQs, S/N=10) were 0.03-0.16 mg/kg (EI) and 0.02-0.06 mg/kg (PCI). The average recoveries ranged from 59.24%-97.36% (apples) and 50.54%-94.54% (cabbages) in the mode of EI, and the corresponding values were 65.38%-95.86% and 62.56%-90.44% in the mode of PCI. The relative standard deviations (RSDs) were all less than 6.9% (n=6). The PCI method can be used to improve the accuracy in comparing with the EI, in terms of good selectivity and high sensitivity.

A method for the determination of characteristic compound 3,5-dimethoxybenzoate-4-diglucoside (leptosperin) in manuka honey was developed by automatic on-line solid phase extraction-liquid chromatography-high resolution mass spectrometry (SPE-LC-HRMS). The samples were separated on a Dikma Diamonsil Plus C18 column (150 mm×4.6 mm, 5 μm) using the mobile phases of 0.1% (v/v) formic acid aqueous solution and acetonitrile with gradient elution. The compound was detected with negative electrospray ionization (ESI-) in Target-MS2 mode. The results showed that the linear range was 0.5-100.0 mg/L, the correlation coefficient was 0.9993. The limit of detection (LOD, S/N ≥ 3) and limit of quantification (LOQ, S/N ≥ 10) of the method was 3 mg/kg and 10 mg/kg, respectively. The recoveries at the spiked levels of 50.0, 100.0, 200.0 mg/kg (10.0, 20.0, 50.0 mg/kg in black locust samples) were in the range of 82.0%-95.2% with the relative standard deviations ranging from 2.7% to 9.7% (n=6). The proposed method was applied to 95 mature honey samples from hives in New Zealand including 12 different kinds and 50 commercial honey samples from four different countries. The method is fast, sensitive and accurate to provide technical support to solve the judgment of the manuka honey imported from New Zealand.

A method for rapid screening of fipronil and its metabolites in egg and egg products was developed by liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF MS). The samples were extracted by acid-acetonitrile, cleaned up by PRiME HLB SPE. The separation was performed on a Poroshell 120 EC C18 column (150 mm×3 mm, 2.7 μm) with gradient elution using water and acetonitrile as mobile phases. The target compounds were monitored under negative ionization mode with electrospray ionization (ESI) source and two databases of accurate mass and fragment ions were created. The matrix effects in four kinds of egg and egg products were considered and the quantification was carried out by internal standard method. The results demonstrated that the linear ranges were from 0.1 to 5 μg/L with good correlation coefficients (r2>0.99). The limits of detection (LODs, S/N>3) and limits of quantitation (LOQs, S/N>10) were 0.2 μg/kg and 1 μg/kg, respectively. The recoveries of fipronil and its metabolites in different matrixes spiked with 1, 2 and 5 μg/kg varied from 82.6%-98.1%, and the relative standard deviations (RSDs) were between 3.8%-9.9% (n=6). The method can effectively correct the ionization suppression. It is sensitive, accurate and suitable for the rapid screening of fipronil, fipronil sulfide, fipronil sulfone and fipronil desulfinyl in egg, egg noodle, cake and mayonnaise.

A simple and efficient method based on a novel solid phase extraction (SPE) cartridge and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) was developed for the determination of clenbuterol residue in pork. The minced pork sample was ultrasonically extracted by 5% (v/v) perchloric acid and centrifuged at 10 000 r/min for 15 min, then the supernatant was purified by an SMCX cartridge, which is a novel SPE column based on homemade silica matrix with two mixed modes of reversed-phase and strong cation exchange, for the selective enrichment and purification of the analyte. The linear range of the method was 0.25 - 50 microg/kg with a correlation coefficient of 0.998 2. The average recoveries ranged from 62.2% to 72.0% at the three spiked levels of 1.25, 12.5 and 50 microg/kg with the relative standard deviations (RSDs) between 4.2% and 6.1%. The limit of detection (S/N = 3) was 0.05 microg/kg. The method is simple, fast and can be extended to enrich and determine beta-agonist drugs.

Connexin 43 (Cx43) is the predominant isoform of gap junction proteins in the working myocardium. In the heart, mitogen-activated protein (MAP) kinases are implicated in regulating Cx43 remodeling; however, their precise roles remain obscure. Mitogen-activated protein kinase kinase 4 (MKK4) is a critical component of the stress-activated MAP kinase signaling pathway. We have previously demonstrated that MKK4 antagonizes cardiomyocyte hypertrophy. Herein, we investigate the role of MKK4 in regulating Cx43 expression in cardiomyocytes. We found that knockdown of MKK4 expression or inhibition of its kinase activity in neonatal rat cardiomyocytes (NRCMs) significantly reduced phenylephrine-induced Cx43 expression. Furthermore, two activator protein-1 (AP-1) binding elements in the Cx43 promoter region were identified as being responsible for the MKK4-regulated Cx43 expression. Consistently, we also detected heterogeneously reduced Cx43 expression and attenuated zonula occludens-1 (ZO-1) content in the hearts of MKK4 cardiomyocyte-specific knockout mice (MKK4cko) following pressure overload. To test whether heterogeneously reduced Cx43 expression contributes to ventricular arrhythmic vulnerability, MKK4cko and control mice were subjected to pressure overload followed by programmed electrical stimulation (PES). 6 of 13 MKK4cko mice, but none of the controls, developed ventricular tachycardia. Epicardial activation mapping recorded from the MKK4cko hypertrophied heart showed ventricular activation delay. Mathematical models have simulated that the spatially heterogeneous decrease in Cx43 causes slowed ventricular conduction and fragmented wave propagations leading to re-entrant excitations. Collectively, these data reveal a novel role for MKK4 in regulating Cx43 expression and preventing hypertrophy-associated arrhythmogenesis.

A method for the determination of cyanuric acid (CYA) in milk and milk powder was developed using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS). The target analyte was extracted from samples by acetonitrile, and the proteins were precipitated at the same time. The supernatant was cleaned up and enriched with a strong anion exchange column, analysed by HPLC-MS/MS with an AX column, and quantified by internal standard method. Good linearity was obtained in the range of 50-2000 microg/L. The recoveries were all ranged from 97% to 121% at three levels, 200, 500 and 1000 microg/kg, and the relative standard deviations (RSDs) were all below 4.8%. Limit of quantification (LOQ) was 200 microg/kg. The method has high accuracy and precision, the operation is fast, easy and suitable for the determination of CYA in milk and milk powder.

A screening method was developed for the determination of 107 pesticide residues in vegetables using off-line dispersive solid-phase extraction (DSPE) and gas chromatography-tandem mass spectrometry (GC-MS/MS). The pesticides interested were extracted from the samples with acetonitrile (saturated by n-hexane) containing 1% acetic acid and simultaneously separated by liquid-liquid partitioning with adding anhydrous magnesium sulfate plus sodium acetate following by a simple cleanup step known as dispersive solid-phase extraction. The extracts were determined by GC-MS/MS using external standard method. The method was reliable and stable that the recoveries of almost all pesticides were in the range from 60% to 130% at the spiked level of 10 microg/kg into four vegetable matrixes (garlic, green bean, radish 8 and spinach) and the relative standard deviations (RSDs) were all not more than 15.3%. The linearity of the method was good between 0.05 mg/L and 1 mg/L, and all limits of quantification (LOQs) less than 10 microg/kg. The method is selective with no interference, especially in the complicated garlic matrix.

A method was developed for the determination of 20 kinds of pesticide residues in soybeans and corn with the technique of offline disperse solid-phase extraction and gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The pesticides interested were extracted twice from the samples with acetonitrile. The combined extract was concentrated to dryness and redissolved in acetonitrile, then cleaned up by dispersive solid-phase extraction with sorbents of N-propyl ethylene diamine (PSA), graphited carbon black, and C18, and determined and confirmed by GC-NCI/MS. The recoveries of all pesticides were in the range of 70%-130% at three spiked levels (5, 10 and 20 microg/kg), and the relative standard deviations were below than 17%. The linearity of the method was good in the concentration range of 20-400 microg/L, and limits of quantification (LOQs) were no more than 2 microg/kg. The method is selective well with no interference and suitable for the confirmatory of pesticide residues in soybeans and corn.

A confirmatory method is proposed for the determination of 12 azole fungicide residues in beans and corn with the technique of offline disperse solid phase extraction (DSPE) and gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The pesticides interested were extracted from the samples with acetonitrile containing 1% acetic acid and simultaneous liquid-liquid partitioning formed by adding anhydrous magnesium sulfate plus sodium acetate followed by a simple cleanup step known as dispersive solid-phase extraction. The aliquot was determined and confirmed by GC-NCI/MS using external standard method. The recoveries of all pesticides were between 70% and 130% at the three spiked levels, 10 microg/kg, 20 microg/kg and 40 microg/kg. The relative standard deviations were less than 13.9%. The linearity of method was good from 50 to 1 000 microg/L. The limits of quantification (LOQ) were less than 8 microg/kg. The method is selective with no interference and is suitable for the confirmatory of pesticide residues in beans and corn.

A method for the simultaneous analysis of 19 quinolone residues, enrofloxacin, ciprofloxacin, norfloxacin, ofloxacin, difloxacin, oxolinic acid, flumequine, sarafloxacin, sparfloxacin, danofloxacin, fleroxacin, marbofloxacin, enofloxacin, orbifloxacin, pipemidic acid, pefloxacin, lomefloxacin, cinofloxacin, and nalidixic acid in honey was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). In comparison of the three different extraction methods, i.e. acid solution coupled with cation-exchange solid-phase extraction cartridge (PCX), neutral buffer solution coupled with a reversed-phase extraction cartridge (HLB) and alkali solution coupled with a strong anion-exchange solid-phase extraction cartridge (PAX), the third method was finally used. The cartridge was then applied to accumulate and purify the target analytes from the sample matrices in one step. The HPLC separation was performed on a C18 column with a linear gradient elution program of methanol and 0.1% formic acid solution as the mobile phase. Selective reaction monitoring (SRM) was used for the selective detection of 19 quinolones. The linearity of all the 19 quinolones in the range from 1 microg/L to 100 microg/L had correlation coefficient greater than 0.991. In the detection of spiked samples, the detection limit of the method was 1.0 microg/kg for all the 19 quinolones, and the recoveries were 71% - 118% with the relative standard deviations of 4.2% - 6.7%. Internal standard calibration was used for the quantitative analysis.

A method was developed for the determination of cyflufenamid residue in carrots by solid phase extraction-gas chromatography-negative chemical ionization mass spectrometry (SPE-GC-NCI/MS). Cyflufenamid residue was extracted with ethyl acetate from carrots. The extract was cleaned-up by an active carbon SPE column connected to a neutral alumina SPE column. The analysis was carried out by the GC-NCI/MS with selected ion monitoring mode. The recoveries of cyflufenamid in carrot samples were in the range from 74.9% to 94.6% at four spiked levels, 0.005, 0.01, 0.02, 0.04 mg/kg, and the relative standard deviations (RSD) were less than 9.7% for inter-days. The linearity of the method was good in the range from 10 to 1000 ng/mL, and the limit of detection (LOD) was 0.001 mg/kg, and the limit of quantitation (LOQ) was 0.005 mg/kg. The method is selective without interference and is suitable for the determination and confirmation of cyflufenamid residue in carrots.

A confirmatory method is presented for the determination of triadimenol residue in foods by dispersive solid phase extraction-gas chromatography-negative chemical ionization mass spectrometry (SPE-GC-NCI/MS). Triadimenol residue was extracted from different food samples, such as snow pea, carrot, orange, bean, spinach, oolong tea, rice, beef, longsnout catfish, royel jelly, red swamp crayfish, bee honey etc with acetonitrile containing 1% acetic acid and simultaneous liquid-liquid partitioning formed by adding anhydrous magnesium sulfate plus sodium acetate, followed by a simple clean-up step known by dispersive solid-phase extraction. The aliquot was determined and confirmed by gas chromatography-negative chemical ionization mass spectrometry using external standard method. The average recoveries at the three spiked levels (0.005, 0.010 and 0.020 mg/kg) in different samples ranged from 70% to 110%, and the relative standard deviations were lower than 12.0%. The linearity of detection ranged from 0.050 to 0.750 mg/L. The detection limit of the method was 0.001 mg/kg and the limit of quantification was 0.003 mg/kg. The method is selective with no interference and suitable for confirmatory of triadimenol residue in 12 categories of foods.

An analytical method of solid phase extraction-gas chromatography-mass spectrometry with two different ionization techniques was established for simultaneous determination of 12 acetanilide herbicide residues in tea-leaves. Herbicides were extracted from tea-leaf samples with ethyl acetate. The extract was cleaned-up on an active carbon SPE column connected to a Florisil SPE column. Analytical screening was determined by the technique of gas chromatography (GC)-mass spectrometry (MS) in the selected ion monitoring (SIM) mode with either electron impact ionization (EI) or negative chemical ionization (NCI). It is reliable and stable that the recoveries of all herbicides were in the range from 50% to 110% at three spiked levels, 10 microg/kg, 20 microg/kg and 40 microg/kg, and the relative standard deviations (RSDs) were no more than 10.9%. The two different ionization techniques are complementary as more ion fragmentation information can be obtained from the EI mode while more molecular ion information from the NCI mode. By comparison of the two techniques, the selectivity of NCI-SIM was much better than that of EI-SIM method. The sensitivities of the both techniques were high, the limit of quantitative (LOQ) for each herbicide was no more than 2.0 microg/kg, and the limit of detection (LOD) with NCI-SIM technique was much lower than that of EI-SIM when analyzing herbicides with several halogen atoms in the molecule.

A method is presented for the determination of difenoconazole residue in all kinds of foods by solid phase extraction-gas chromatography-negative chemical ionization mass spectrometry (SPE-GC-MS/NCI). Difenoconazole residue was extracted with ethyl acetate from different samples, such as perilla leaves, carrots, spinach powder, rice, gram, jasmine flower tea, oolong tea, strawberries, sauce, bee honey, beef, chicken and eels, etc. The extracts were cleaned-up by active carbon SPE column connected to alumina neutral SPE column or Florisil SPE column only. Analytical screening was determined by the technique of GC-MS/NCI on selected ion monitoring mode. The recoveries of difenoconazole in most samples were in the range from 70% to 120% at three spiked levels, 0.01 mg/kg, 0.04 mg/kg and 0.10 mg/kg, and the relative standard deviations (RSDs) were below 9.5%. The linearity of the method is good from 0.02 to 1.00 mg/L, and limit of detection (LOD) was 0.000 5 or 0.001 mg/kg for different type samples. The method is selective without interference and is suitable for determination and conformation of difenoconazole residue in all kinds of foods.

A confirmatory method is presented for the determination of acrylamide in different food products by gas chromatography-mass spectrometry (GC-MS). The method is based on the extraction of acrylamide with and methanol, and purification with Carrez I zinc sulfate) and Carrez II (potassium hexacyanoferrate) solution, followed by bromination onto the acrylamide double bond. The derivative was extracted with ethyl acetate/hexane (4: 1, v/v), and converted to the stable 2-bromopropenamide by dehydrobromination using 10% triethylamine, then analyzed by GC-MS, employing 13C3-acrylamide as internal standard. In-house validation data for flour and bread showed good accuracy and precision of the method. The recoveries of acrylamide in the French fries and bread were all in the range from 80% to 110% after correction of analyte loss by the internal standard at three spike levels of 0.02, 0.05 and 0.2 mg/kg, and relative standard deviations (RSDs) no more than 12.7%. The limits of detection for flour and bread were estimated at 5 microg/kg.

A method was developed for the determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The honey and royal jelly samples were treated with different preparation methods as the result of the different components. The honey sample was extracted with ethyl acetate and cleaned up with primary second amine, and the royal jelly sample was extracted with acetonitrile-water (1:1, v/v), and cleaned up with a C18 solid-phase extraction column. Finally, the extracts of the honey and royal jelly were analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode separately. External standard calibration method was used for quantification. The linearities of calibration curves of the four insecticides were good with the correlation coefficients greater than 0.99 in the range of 50-500 microg/L. The limits of the detection (LODs) of the four insecticides were in the range of 0.12- 5.0 microg/kg, and the limits of the quantification (LOQs) were in the range of 0.40-16.5 microg/kg. The recoveries of the four insecticides spiked in honey and royal jelly at three spiked levels (10, 15 and 20 microg/kg) were in the range of 78.2 -110.0%, and the relative standard deviations (RSDs) were all below 14%. The sensitivity and selectivity of this method were good with no interfering peaks. The proposed method is simple quick and effective to analyze the four insecticide residues in honey and royal jelly.

A reversed-phase high performance liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method was developed for the determination of 4-chlorophenoxyacetic acid, 6-benzylaminopurine, enrofloxacin and norfloxacin residues in sprouts and source beans. The sample was extracted by acetonitrile containing 0.1% acetic acid and concentrated. The chromatographic analysis was carried out on a C18 column with methanol and 0.1% formic acid solution as the mobile phases in gradient elution program. The MS analysis was set in electrospray ionization mode and separated to two segments of positive and negative modes. The precursor ions were m/z 189.9, 226.1, 359.9 and 320.1, while the product ions for quantification were m/z 127.0, 91.2, 315.9 and 276.2 for 4-chlorophenoxyacetic acid, 6-benzylaminopurine, enrofloxacin and norfloxacin, respectively. The calibration curves showed good linearity in the range of 5 - 200 microg/L with correlation coefficients more than 0.995. The limits of detection (LODs) were 1 microg/kg and the limits of quantification (LOQs) were 5 microg/kg for the four compounds spiked in mung bean sprouts and mung beans. The recoveries of the four compounds spiked at three levels of 5.0, 10.0 and 20.0 microg/kg ranged from 70% to 91%, with the relative standard deviations (RSDs) less than 14%. The method established is accurate, sensitive, simple, and has considerable advantages in the analysis of the four kinds of illegal additive residues in sprouts and beans simultaneously.