RESUMEN
In this work, headspace single-drop microextraction (HS-SDME) method and headspace (HS) method were developed and compared to determine methanol by gas chromatography with flame ionization detector (GC-FID). Several factors influencing extraction efficiency, such as extraction time, temperature, sample volume, stirring rate and extraction solvent were investigated and the optimal conditions could be obtained using 2.0 µL DMF as extractant, 45 °C as heating temperature, 5 min as extraction time, 6 mL sample volume and 1.5 g KCl as addition of salt. The obtained dynamic range of HS-SDME-GC-FID was from 0.05 to 2 mg·L-1 with the limit of detection (LOD) of 0.001 mg·L-1 and that of HS-GC-FID was from 10.0 to 400.0 mg L-1 with LOD of 0.5 mg·L-1. The relative standard deviations (RSD) of HS-SDME-GC-FID was 1.9% (n = 5, C = 0.005 mg·L-1), 4.8%(n = 5, C = 0.02 mg·L-1) and 3.3%(n = 5, C = 0.1 mg·L-1), then the RSD of HS-GC-FID was 4.4%(n = 5, C = 5 mg·L-1), 5.8%(n = 5, C = 20 mg·L-1) and 4.0%(n = 5, C = 40 mg·L-1). Clearly, compared with HS-GC-FID, HS-SDME-GC-FID possessed lower LOD and better reproducibility and both of them were applied to determine methanol in imported wine and the recoveries for the spiked samples were between 83.99 and 117.24%. Overall, HS-SDME approach was confirmed to be a more sensitive and efficient sample pretreatment method and could separate matrix effectively.
Asunto(s)
Vino , Cromatografía de Gases/métodos , Límite de Detección , Metanol , Reproducibilidad de los ResultadosRESUMEN
In this study, 3D flower-like magnetic CoFe-LDHs/CoFe2O4 was prepared by a facile urea hydrothermal method and utilized to activate peroxymonosulfate (PMS) for degrading aniline (AN). CoFe-LDHs/CoFe2O4 was systematically characterized to explore the relationship between its structure and catalytic performance. Compared with CoFe-LDHs synthesized by co-precipitation method, CoFe-LDHs/CoFe2O4 exhibited three dimensional structure and larger specific surface, which could increase the degradation efficiency of AN markedly. 96% of 10 mg L-1 AN could be eliminated by 0.3 mM PMS and 50 mg L-1 CoFe-LDHs/CoFe2O4 at initial pH 6 within 5 min and the total organic carbon (TOC) removal efficiency could be high to 52.8% in 30 min. CoFe-LDHs/CoFe2O4 can be separated by a magnet easily due to its magnetism, which makes it avoid secondary pollution and provide convenience. After recycling six times, the degradation efficiency still maintained at 92.6%. Besides, CoFe-LDHs/CoFe2O4/PMS can degrade AN in practical water samples effectively. In addition, the possible mechanism of CoFe-LDHs/CoFe2O4/PMS system for the degradation of AN was proposed. The radical scavenging experiments confirmed that SO4·-, HO· and O2·- were involved and SO4·- played a dominant role in the degradation of AN, and it was further proved by electron Paramagnetic Resonance (EPR) as well. Our findings can provide some new insights into the efficient and skillful design and application of heterogeneous catalyst for environmental remediation.
Asunto(s)
Magnetismo , Peróxidos , Compuestos de Anilina , Fenómenos Magnéticos , Peróxidos/químicaRESUMEN
Intestinal microbiota has been widely recognized to influence on their hosts with respect to digestion and absorption of nutrients, but little is known about the structure and composition of microbial communities at different growth periods of hosts as yet. In this case, 16S rRNA gene amplicon sequencing was applied to decode the microbiota architecture in four distinct intestinal compartments (duodenum, jejunum, ileum, and cecum) of both Large White pigs and Chinese Shanxi Black pigs at the weaning, nursery, and fast-growth developmental stages. In our study, the intestinal ecosystems were dynamically changing and influenced by host maturity and diets at different development stages. Species phylogenetically affiliated to phyla Firmicutes, Proteobacteria, and Bacteroidetes were abundant in both pig breeds; at the genus level, microbial communities were dominated by Prevotella, followed by Acinetobacter and Lactobacillus. Further inspection revealed that Lactobacillus was identified to be positively associated with villus height, whereas Acinetobacter and Prevotella were prone to reside in deep crypts. Furthermore, intestinal microbiota in Shanxi Black pigs had more metabolic and less infectious functions than that in Large White pigs. In short, our data present here indicated that microbiota with longitudinal diversity and lower infection in Shanxi Black pigs might contribute to the relatively stronger adaptability in comparison with Large White pigs.