[Simultaneous determination of 21 perfluorinated and polyfluoroalkyl substances in plant oils by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry].

Edible plant oils are a key component of the daily human diet, and the quality and safety of plant oils are related to human health. Perfluorinated and polyfluoroalkyl substances (PFASs) are pollutants that can contaminate plant oil through the processing of raw materials or exposure to materials containing these substances. Thus, establishing a sensitive and accurate analytical method for the determination of PFASs is critical for ensuring the safety of plant oils. In this study, a method based on acetonitrile extraction and solid phase extraction purification combined with ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS) was developed for the simultaneous determination of 21 PFASs, including perfluorocarboxylic acids, perfluoroalkyl sulfonic acids, and fluorotelomer sulfonic acids, in edible plant oils. The chromatographic conditions and MS parameters were optimized, and the influences of the extraction solvents and purification method were systematically studied. Plant oil samples were directly extracted with acetonitrile and purified using a weak anion-exchange (WAX) column. The 21 target PFASs were separated on a reversed-phase C18 chromatographic column and detected using a triple quadrupole mass spectrometer with an electrospray ionization source. The mass spectrometer was operated in negative-ion mode. The target compounds were analyzed in multiple reaction monitoring (MRM) mode and quantified using an internal standard method. The results demonstrated that the severe interference observed during the detection of PFASs in the co-extracted substances was completely eliminated after the extraction mixture was purified using a WAX column. The 21 target PFASs showed good linearity in their corresponding ranges, with correlation coefficients greater than 0.995. The limits of detection (LODs) and limits of quantification (LOQs) of the method were in the range of 0.004-0.015 and 0.015-0.050 µg/kg, respectively. The recoveries ranged from 95.6% to 115.8%, with relative standard deviations (RSDs) in the range of 0.3%-10.9% (n=9). The established method is characterized by simple sample pretreatment, good sensitivity, high immunity to interferences, and good stability, rendering it suitable for the rapid analysis and accurate determination of typical PFASs in edible plant oils.

Complete genome sequence of Brucella pseudintermedia ASAG-D25, isolated from the wheat ear.

Brucella pseudintermedia ASAG-D25 was isolated from the wheat ear sample in Xuzhou City, Jiangsu Province, China. The complete genome sequence of B. pseudintermedia will provide an important resource for better understanding of the genetic features of the species within the family of Brucellaceae.

Multicolor Visual Detection of Deoxynivalenol in Grain Based on Magnetic Immunoassay and Enzymatic Etching of Plasmonic Gold Nanobipyramids.

In this study, a multicolor visual method based on a magnetic immunoassay and enzyme-induced gold nanobipyramids (Au NBPs) etching was developed for deoxynivalenol (DON) detection. The magnetic beads modified with high affinity DON monoclonal antibodies were used as a carrier for target enrichment and signal transformation and the Au NBPs with excellent plasmonic optical properties were served as enzymatic etching substrates. The oxidation state TMB, which was generated through catalysis of horseradish peroxidase (HRP), induced the etching of plasmonic Au NBPs, resulting in the longitudinal peak blue-shift of local surface plasmon resonance (LSPR). Correspondingly, Au NBPs with various aspect ratios displayed a variety of individual colors which were visualized by the naked eye. The LSPR peak shift was linearly related to the DON concentration in the range of 0~2000 ng/mL and the detection limit was 57.93 ng/mL. The recovery for naturally contaminated wheat and maize at different concentrations ranged from 93.7% to 105.7% with a good relative standard deviation below 11.8%. Through observing the color change in Au NBPs, samples with overproof DON could be screened preliminarily by the naked eye. The proposed method has the potential to be applied in on-site rapid screening of mycotoxins in grain. In addition, the current multicolor visual method only used for the simultaneous detection of multiple mycotoxins is in urgent need of a breakthrough to overcome the limitation of single mycotoxin detection.

Four PQQ-Dependent Alcohol Dehydrogenases Responsible for the Oxidative Detoxification of Deoxynivalenol in a Novel Bacterium Ketogulonicigenium vulgare D3_3 Originated from the Feces of Tenebrio molitor Larvae.

Deoxynivalenol (DON) is frequently detected in cereals and cereal-based products and has a negative impact on human and animal health. In this study, an unprecedented DON-degrading bacterial isolate D3_3 was isolated from a sample of Tenebrio molitor larva feces. A 16S rRNA-based phylogenetic analysis and genome-based average nucleotide identity comparison clearly revealed that strain D3_3 belonged to the species Ketogulonicigenium vulgare. This isolate D3_3 could efficiently degrade 50 mg/L of DON under a broad range of conditions, such as pHs of 7.0-9.0 and temperatures of 18-30 °C, as well as during aerobic or anaerobic cultivation. 3-keto-DON was identified as the sole and finished DON metabolite using mass spectrometry. In vitro toxicity tests revealed that 3-keto-DON had lower cytotoxicity to human gastric epithelial cells and higher phytotoxicity to Lemna minor than its parent mycotoxin DON. Additionally, four genes encoding pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases in the genome of isolate D3_3 were identified as being responsible for the DON oxidation reaction. Overall, as a highly potent DON-degrading microbe, a member of the genus Ketogulonicigenium is reported for the first time in this study. The discovery of this DON-degrading isolate D3_3 and its four dehydrogenases will allow microbial strains and enzyme resources to become available for the future development of DON-detoxifying agents for food and animal feed.

Risk screening of mycotoxins and their derivatives in dairy products using a stable isotope dilution assay and LC-MS/MS.

An liquid chromatography-tandem mass spectrometry method coupled with a stable isotope dilution assay was established for the simultaneous detection of 17 mycotoxins and their derivatives (aflatoxins B1 , B2 , G1 , G2 , M1 , and M2 ; fumonisins B1 and B2 ; ochratoxin A; zearalenone; zearalanone; α-zearalanol; α-zearalenol; T-2 toxin; deoxynivalenol; deepoxy-deoxynivalenol; and sterigmatocystin) in milk and dairy products. The mycotoxins were extracted with acidified acetonitrile and the lipids were removed using a Captiva EMR-lipid column. The average recoveries of the target compounds from samples spiked at three different concentrations were 67-102%, and the relative standard deviations of the peak areas were less than 10%. Limits of quantification (S/N = 10) of 0.004-1.25 µg/kg were achieved, which are significantly lower than the maximum levels allowed in various countries and regions for each regulated mycotoxin. Milk and yogurt products from local markets and e-commercial platforms were analyzed using the optimized method. The screening showed that aflatoxin M1 , deoxynivalenol, fumonisins B1 and B2 , and zearalenone could be found in milk and yogurt products, especially those products also containing grains or jujube ingredients, indicating that there is a risk of mycotoxins in dairy products.

[Simultaneous determination of five mycotoxins in various grains and their products by liquid chromatography-tandem mass spectrometry with isotope internal standard].

A rapid method was established for the determination of zearalenone (ZON), nivalenol (NIV), deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ACDON) and 15-acetyl-deoxynivalenol (15-ACDON) in various grains and their products by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted by acetonitrile-water (84:16, v/v), and cleaned-up by multifunctional column without any further step. The separation was carried out on an Acquity UPLC® BEH C18 column (100 mm×2.1 mm, 1.7 µm) with gradient elution using acetonitrile-water as mobile phases. The analytes were quantified by isotope internal standard method. The correlation coefficients (r2) were all above 0.99. The limits of detection (LODs, S/N=3) ranged from 5 µg/kg to 20 µg/kg. The recoveries of the five mycotoxins spiked in blank grain and its product samples varied from 84.2% to 114.5%, with the relative standard deviations (RSDs) of 0.4%-9.9% (n=6). The method is accurate, efficient, sensitive and practical.

[Isolation and identification of impurities in the natural vitamin E].

Two impurities in the natural vitamin E extracted from oil deodorizer distillate were separated and characterized by high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The impurities were purified and collected by normal-phase HPLC. The accurate masses were determined using FTICR-MS and fragmentation behavior was studied by GC-MS. The results showed that the impurities had identical MS spectra and similar electron impact (EI) fragmentation patterns. Based on the spectra, the structures of the two impurities were proposed as the enantiomers of sesamin. The presented method is rapid and effective, and can be applied for the food safety to the vitamin E manufacturing industry.

[Determination of phthalate plasticizers in daily foods and their migration from food packages].

A total of 16 phthalates in food samples (beverage, milk and wine) were analyzed by y gas chromatography-mass spectrometry (GC-MS) combined with the sample preparation of liquid-liquid extraction and dispersive solid-phase extraction ( dSPE ) . The limits of detection (LODs, S/N=3) for the 16 phathalates were fairly good, ranging form 0.005 to 0.025 mg/L. The relative standard deviations (RSDs) of the peak areas were less than 2%, showing good repeatability. In addition, the recoveries of phthalates in various matrices were generally ranging from 60% to 110%. In conclusion, the developed method can help the trace analysis of phthalates in beverage, wine and milk. In order to strictly investigate the migration of phthalates from the daily food packages like plastic wraps and storage bags, iso-octane was used as the simulant of fatty foods. The migration determined using the above aptimized method showing the significant migration exsting in plastic wraps and some unqualified products in current market is not meeting the national regulations about the migration limits of phthalates.

[Determination of nitrogen compounds in catalytic gasolines by gas chromatography-nitrogen chemiluminescence detection].

A method for the separation and determination of nitrogen compounds in catalytic gasolines by gas chromatography-nitrogen chemiluminescence detection (GC-NCD) was established. The effects of the flow rate of carrier gas and the oven temperature on the resolution were studied. More than 20 nitrogen compounds, including amines, pyridine, aniline, 2-methyl aniline, 3-methyl aniline, 4-methyl aniline, quinoline, and indole, in catalytic gasoline were identified based on the retention time of some pure nitrogen compounds and by gas chromatography-mass spectrometry. The relative standard deviations of the peak areas of main nitrogen compounds in a catalytic gasoline sample were less than 2.5% and the detection limits for nitrogen were 1.0 mg/L under the chosen conditions. The linear ranges were 1.0-100 mg/L nitrogen for each nitrogen compound. The correlation coefficients were more than 0.998. The method can be successfully applied for the determination of each nitrogen compound in different catalytic gasolines.

[Distribution determination of nitrogen compounds in catalytic diesel oil using gas chromatography].

The method for the separation and determination of nitrogen compounds in catalytic diesel oil using gas chromatography-nitrogen chemiluminescence detection (GC-NCD) was established. The effects of the flow rate of carrier gas and oven temperature on the resolution were studied. More than 80 nitrogen compounds (such as aniline, alkyl anilines, quinoline, indole, alkyl indoles, carbazole, alkyl carbazoles) in catalytic diesel oil were enriched using a Al2O3 column and identified based on the retention time of some pure nitrogen compounds and the retention index of nitrogen compounds on GC-NCD. The relative standard deviations of the peak areas of main nitrogen compounds in catalytic diesel oil were lower than 8%. The detection limit (S/N = 3) for nitrogen of carbzole was 1.0 mg/L under the chosen conditions. The linear range of nitrogen was 1.0 - 600 mg/L for each nitrogen compound. The correlation coefficient was more than 0.998. The recoveries of four nitrogen compounds (aniline, quinoline, indole, carbazole) in catalytic diesel oil were in the range of 89.5% - 99.8%. The method can be applied for the determination of each nitrogen compound in different catalytic diesel oils.

[Determination and distribution of sulfur compounds in coked gasoline by gas chromatography-sulfur chemiluminescence detection].

The method for the separation and determination of sulfur compounds in coked gasoline by gas chromatography-sulfur chemiluminescence detection (GC-SCD) was established. Seventy-four sulfur compounds including hydrogen sulfide, mercaptans, sulfides, disulfides, thiophene, alkyl thiophenes, benzothiophene, alkyl benzothiophenes in a coked gasoline sample were identified by standard samples and past identified results. The retention indexes of different sulfur compounds in coked gasoline under programmed temperature condition were calculated based on the retention times of hydrosulfide, ethyl mercaptan, n-propyl mercaptan, thiophene, 2-methyl thiophene, 2-ethylthiophene, 2-propylthiophene, C4-thiophene (t(R) = 40.28 min), benzothiophene, and methylbenzothiophene (t(R) = 58.13 min). The relative standard deviations of the determination results of main sulfur compounds (isopropyl mercaptan, n-propyl mercaptan, n-butyl mercaptan, 2-methylthiophene, 3-methylthiophene, 2, 4-dimethylthiophene, 2,3,4-trimethylthiophene) in coked gasoline were less than 5%, and the detection limit for sulfur was 0.05 mg/L. The linear range of sulfur was 0.2 - 400 mg/L for each sulfur compounds (r2 = 0. 999). The contents of sulfur compounds, especially the content of mercaptan, are much more than those in the catalytic gasoline. There is also a big difference in the sulfur contents between 2-methylthiophene and 3-methylthiophene. The data can be useful for the study of hydrodesulfurizing catalyst and industrial process planning.

[Primary study on determination of the size distribution of nanoparticles by capillary zone electrophoresis].

The separation of polystyrene (PS) latex in sizes of 50 nm and 125 nm has been carried out using capillary zone electrophoresis (CZE). The effects of experimental parameters including pH, the concentration of buffer and the voltage, on the separation were investigated. The optimum electrophoretic conditions were as follows: 8.00 mmol/L NaH2PO4 (adjusted to pH 8.00 with ammonia) as buffer, applied voltage of 26 kV and detection wavelength of 214 nm. The relative standard deviation of the migration time and the peak area of PS50 were 0.3% and 4.7%, respectively. The separation was found to be size-dependent. Larger particles exhibited longer migration time. Stable dispersion condition of PS particles in aqueous solution was obtained by adding PS particles into the buffer.

[Determination of sulfur compounds in fluid catalytic cracking gasoline by gas chromatography with a sulfur chemiluminescence detector].

A method for the separation and determination of sulfur compounds in fluid catalytic cracking gasoline (FCC gasoline) by gas chromatography with a sulfur chemiluminescence detector (GC-SCD) was established. Fifty eight sulfur compounds including mercaptan, sulfide, disulfide, thiophene, alkyl thiophenes, benzothiophene and alkyl benzothiophenes were identified based on their retention indexes and the data obtained from gas chromatography with an atomic emission detector (GC-AED). The effects of flow rate of carrier gas and oven temperature were discussed. Detection reproducibilities of main sulfur compounds (thiophene, n-butyl mercaptan, 2-methylthiophene, 3-methylthiophene, 2,4-dimethylthiophene) in FCC gasoline were satisfactory (RSDs were no more than 5.0%) and detection limit for sulfur was 0.1 mg/L. Using thiophene and benzothiophene as testing samples, it was determined that response factor was independent of the molecular structure of sulfur compounds. The linear range was 0.5-800.0 mg/L sulfur with a correlation coefficient of 0.999.

[Determination of particle size distribution of nano-particles by capillary zone electrophoresis].

A new method was established for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). The data processing method for acquiring size distribution from primary electropherogram was investigated. The relative standard deviation of migration time was deduced by using dimethyl sulfoxide (DMSO) as an internal standard. Scattering effect of nano-particles was studied and a correction equation was established to correct this influence. The experimental results showed that the correction method was effective. After correction, the measuring results for the mixed samples with different mass ratios of PS50 and PS125 were almost the same with their theoretical values and the relative deviation was reduced from 35% to 5%. This method for the determination of size distribution is satisfactory.

[Determination of average particle diameter and size distribution of ultra-fine beta zeolite by capillary zone electrophoresis].

A new method was developed for the determination of average particle diameter and size distribution of ultra-fine beta zeolite by capillary zone electrophoresis (CZE). The dispersion and stabilization conditions of ultra-fine beta zeolite powder in suspensions were investigated by measuring the isoelectric point (IEP) of the powder suspension. Stable dispersion condition of beta zeolite ultrafine particles in aqueous solution was obtained by adding beta zeolite into the buffer (1.25 mmol/L NaHCO3-5 mmol/L Na2CO3, pH 10.82). The calibration equation between migration time and particle size was established to obtain the data of particle diameter by relating the beta zeolite diameters determined by laser particle sizer with the migration time from electropherogram of beta zeolite through the cumulative percentage of particle distribution. The calibration equation between particle size and amount was also established to correct the deviation of the response caused by particle size as the special relating principle suggested in the paper. The method is advantageous in small sample quantity required, low cost and short measurement period for each individual analysis.

[Study on distribution of nitrogen compounds in catalytic diesel oil by gas chromatography-atomic emission detector].

The method for the separation and determination of nitrogen compounds in a typical catalytic diesel oil by gas chromatography-atomic emission detector (GC-AED) was established. Seventy-three nitrogen compounds (including aniline, alkyl anilines, quinoline, indole, alkyl indole, carbazole, alkyl carbazole) in the catalytic diesel oil were qualified based on the retention times of some pure nitrogen compounds and the retention indices of nitrogen compounds. Effects of pressures of various reagent gases on peak area of main nitrogen compounds in diesel oil were examined as well. The pressures of reagent gases were optimized. Retention indices of different nitrogen compounds under temperature programmed condition were calculated. Reproducibilities of peak areas of main nitrogen compounds in the catalytic diesel oil were no more than 8.0%. The detection limit for nitrogen was 1.0 mg/L under specific conditions. The linear range was 2.0 - 600 mg/L for each nitrogen compound and correlation coefficient was greater than 0.998. The method can be successfully applied in the determination of nitrogen compounds in different catalytic diesel oils.

[Determination of sulfur compounds in catalytic diesel oil by gas chromatography with atomic emission detector and its applications].

The method for separation and determination of sulfur compounds in catalytic diesel oil by gas chromatography with atomic emission detector (GC-AED) was established. More than 130 sulfur compounds (including alkyl thiophenes, benzothiophene, alkyl benzothiophenes, dibenzothiophene, alkyl dibenzothiophenes) in catalytic diesel oil were qualified based on the retention time of some pure sulfur compounds and the retention indexes of sulfur compounds. The effects of oven temperature, heating rate and sample amount on resolution and effective plate number were investigated. Retention indexes of different sulfur compounds under temperature programmed condition were calculated. The relative standard deviations of peak areas of main sulfur compounds in catalytic diesel oil were no more than 5.0%, detection limit for sulfur was 0.1 mg/L under chosen conditions. Because response factor was independent on the molecule structure of the sulfur-containing compound, the content of each sulfur compound was determined quantitatively using thiophene as sulfur standard sample. The linear range was 2 mg/L-1,000 mg/L sulfur, and the correlation coefficient was 0.997. The method is successfully applied for the determination of the contents of sulfur compounds in six different catalytic diesel oils (Fujian catalytic diesel oil, Yanshan catalytic diesel oil, Zhongdong diesel oil, Zhenhai catalytic diesel oil, Zhenhai Changsan oil and Zhenhai Changer oil). Distributions of sulfur compounds in different catalytic diesel oils were obtained by GC-AED.