Synthesis of azo-linked covalent organic polymers for pipette tip solid-phase extraction of sedative residues from animal tissues samples.

Azo-linked covalent organic polymers (ACOPs) were synthesized by a simple azo reaction, with 2,2'-bis(trifluoromethyl)benzidine and 1,3,5-trihydroxybenzene as the monomers. The preparation process was mild, green, and environmental-friendly, avoiding the use of high temperature, metal catalysis, and harmful organic reagent. The obtained ACOPs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and Brunauer-Emmett-Teller. With the prepared ACOPs as adsorbent, a method of pipette tip solid-phase extraction-liquid chromatography-tandem mass spectrometry detection (PTSPE-LC-MS/MS) was proposed for the analysis of target sedatives in animal tissues. Furthermore, the parameters for the extraction of five sedatives, including the amount of adsorbent, pH value, ion strength, elution solvent and volume, were investigated. Under the optimized conditions, the linear dynamic range was found from 0.1 to 10.0 µg kg-1, and the limits of detection were ranged from 0.02 to 0.1 µg kg-1. The method was assessed by the analysis of target sedatives in animal tissues, and the recoveries for the spiked pork muscle and pork liver samples were 84-102% and 83-101%, respectively. The results show that the developed method of PTSPE-LC-MS/MS with ACOPs as adsorbent is efficient for the analysis of trace sedatives in animal tissues.

Detection of azithromycin residue in broiler feathers by liquid chromatography-tandem mass spectrometry.

In the study, a sensitive and reproducible method for the quantitative analysis of azithromycin in broiler feather samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Feather samples were rinsed after being wrapped in medical gauze, then chopped and then added to 5% (v/v) ammonia in methanol solution for ultrasonic extraction. The extract was purified by the combination of commercial polymeric microparticles (Oasis MCX) and Fe3O4 nanoparticles. The LC separation was performed on an Agilent Eclipse plus C18 column. Multiple reaction monitoring was used for the selective detection of azithromycin. The good linearity curve of azithromycin in feather sample was in the range from 1.0 µg kg-1 to 100.0 µg kg-1 with 0.9935 of correlation coefficient. And the limit detection and limit of quantification was 0.5 µg kg-1 and 2.0 µg kg-1 in spiked feather samples. The recoveries of azithromycin were 85.2-94.7% with the relative standard deviation less than 10%. The established method is simple, rapid, sensitive and specific, and could meet the need of government and enterprises to monitor the illegal use of azithromycin in livestock and poultry breeding.

[Seasonal and Spatial Variations of Microcystins and Their Relationships with Physiochemical and Biological Factors in Poyang Lake].

Poyang Lake is the largest freshwater lake in China and an important drinking water source for Jiangxi Province. Since the year 2000, toxic cyanobacteria have been observed frequently in Poyang Lake. In this study, water samples were collected in the lake quarterly (April 2012, August 2012, October 2012, and January 2013) to examine the spatial and seasonal variations in the concentrations of microcystins (MCs; MC-RR, -YR, and -LR) and their relationships with physiochemical and biological factors. MCs were determined by ultra-high-performance liquid chromatography-electrospray ionization tandem triple quadrupole/mass spectrometry (UPLC-MS/MS). MC-RR (accounting for 75.01% and 71.34% of intracellular MC (IMC) and extracellular MC (EMC) concentrations, respectively) was the most dominant variant in Poyang Lake, followed by MC-LR (accounting for 21.95% and 24.97% of IMC and EMC concentrations, respectively), while MC-YR was detected in low concentrations (accounting for 3.01% and 3.69% of IMC and EMC concentrations, respectively). Total MC concentrations (IMC + EMC, TMC) ranged from 0.49 to 3517.85 ng·L-1, with an average of 337.43 ng·L-1 and only 2.53% (2 out of 79 water samples) of the water samples contained MCs concentrations exceeding the drinking water guideline level of 1 ng·L-1 for MC-LR proposed by World Health Organization (WHO). IMC concentrations showed significant relationships with Microcystis biomass (r=0.47, P<0.01), Oscillatoria biomass (r=0.68, P<0.01), Cyanobacteria biomass (r=0.56, P<0.01), and Chl-a (r=0.28, P<0.01), but no significant correlation was found between intracellular MC concentration and Anabena biomass (P>0.05), suggesting that Microcystis and Oscillatoria might be the main MCs-producing cyanobacteria in Poyang Lake. In addition, IMC concentrations were positively correlated with water temperature (r=0.51, P<0.01), transparence (r=0.69, P<0.01), Fe (r=0.43, P<0.01), and Zn contents (r=0.43, P<0.01), and negatively correlated with TN (r=-0.44, P<0.01), TP (r=-0.29, P<0.01), NH4+-N (r=-0.33, P<0.05), NO2--N (r=-0.28, P<0.05), Ca (r=-0.34, P<0.01), and Mg(r=-0.35, P<0.05), while no significant correlations were observed between IMC concentrations and pH, PO43--P, NO3--N, electrical conductivity, permanganate index, and Cu content (P>0.05). These results indicated that light intensity (represented by transparence), nitrogen, phosphorus, and water temperature might be the regulating factors of MCs production in Poyang Lake and trace elements (Fe, Zn, Ca, and Mg) can influence the MC production to a certain extent. IMCs and EMCs exhibited similar seasonal variations in Poyang Lake. The highest values of IMCs (531.87 ng·L-1) and EMCs (232.44 ng·L-1) were observed in summer. The concentrations of IMCs and EMCs in autumn were 31.97 ng·L-1 and 6.49 ng·L-1, respectively. Low concentrations were observed in spring (0.55 ng·L-1 and 0.88 ng·L-1 of IMCs and EMCs, respectively) and winter (0.69 ng·L-1 and 4.14 ng·L-1 of IMCs and EMCs, respectively). The highest IMCs and EMCs values of Poyang Lake in summer were 2298.08 ng·L-1 and 1219.77 ng·L-1, respectively, and the lowest values were 92.53 ng·L-1 and 38.80 ng·L-1, respectively. Overall, the concentrations of IMCs in eastern bays, the vicinity of Songmen Mountain, Banghu Lake, and its outlet were higher than those in other regions. However, the spatial distributions of EMCs in Poyang Lake were different from those of IMCs. EMCs concentrations in the vicinity of Songmen Mountain, Banghu Lake, and its outlet were higher than those in other regions.

Complete mitochondrial genome of the natural pentaploid loach, Misgurnus anguillicaudatus (Teleostei: Cypriniformes: Cobitididae).

The complete mitochondrial genome of the natural pentaploid loach Misgurnus anguillicaudatus is a circular molecule of 16,643 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and two main noncoding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 918 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the pentaploid M. anguillicaudatus.

Complete mitochondrial genome of Schizopygopsis malacanthus (Teleostei: Cypriniformes: Cyprinidae).

The complete mitochondrial genome of Schizopygopsis malacanthus is a circular molecule of 16,677 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 main non-coding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 938 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the S. malacanthus.

Simultaneous determination of Se, trace elements and major elements in Se-rich rice by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) after microwave digestion.

A quick and accurate method was devised to determine Se, As, Ba, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn in Se-rich rice samples by microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS). Spectral interferences on Se were eliminated using methane as a reaction gas in the dynamic reaction cell (DRC). Rhodium was used as an internal standard to compensate for sample matrix effects. A rice-certified reference material (CRM) (GBW 10010) was used to verify the accuracy of the method. The method detection limits were 0.001-0.03 mg/kg, analyte recoveries were 85-108% and precisions (RSDs) ranged from 2.1% to 5.8%. Correlation analysis showed that the Se concentrations in the Se-rich rice samples correlated well with the Cu concentrations (r=0.53, p<0.05).