RESUMO
Fe3O4-grafted nitrogen-doped graphene (Fe3O4/N-G) nanomaterials were synthesized by chemical co-precipitation method, and its adsorption properties were discussed preliminarily.It was demonstrated that the adsorption of parachlormetaxylenol on Fe3O4/N-G was not limited to uniform monolayer adsorption and the adsorption kinetic followed the pseudo-second-order kinetic mode.Then, an ultrasound-assisted magnetic solid-phase extraction with Fe3O4/N-G as the magnetic adsorbent has been developed for the determination of four compounds including triclosan, chloroxylenol, hexachlorobenzene and 2,2′,4,4′,5,5′-hexachlorobiphenyl in environmental water samples, in combination with gas chromatography coupled to tandem mass spectrometry.Several factors related to extraction efficiencies, such as the amount of adsorbent, extraction time, sample pH and desorption conditions were investigated.The proposed preparation procedure was as follows: 6.0 mg of Fe3O4/N-G was dispersed into 100 mL of water sample under ultrasound.After 15 s, the Fe3O4/N-G carrying four compounds was separated from the water sample by an external magnetic field.Then, the targets were eluted from Fe3O4/N-G with 3 mL of ethanol and 2 mL of dichloromethane, sequentially.Finally, the eluent was dried under a mild stream of nitrogen and reconstituted with methanol and dichloromethane (1∶1, V/V) for the subsequent GC-MS/MS analysis.Under the optimized condition, an excellent linearity was observed in the range of 0.1-10 ng/L for the four compounds, with the correlation coefficients ranging from 0.9983 to 0.9999.The limits of detections (S/N=3) ranged from 0.05 to 0.6 ng/L and the limits of quantity (S/N=10) ranged from 0.2 to 2.4 ng/L.The mean recoveries at three spiked levels ranged from 68.2% to 99.6%.The relative standard deviations (RSDs) of intraday and interday were in the range of 3.3%-6.9% and 3.4%-9.4% (n=6), respectively.The proposed method was demonstrated to be simple and feasible for the trace analysis of antimicrobial agents and organochlorine contaminants in environmental water samples.
RESUMO
<p><b>OBJECTIVE</b>To determine the structures and contents of the volatile components of flowers of Fritillaria thunbergii, and investigate the effects of operation modes on its volatile components.</p><p><b>METHOD</b>The volatile oils were first obtained by the hydrodistillation assay and then submitted to gas chromatography-time-of flight mass spectrometry (GC-TOF-MS) analysis.</p><p><b>RESULT</b>More than 60 peaks were resolved, and 39 of which were identified quantitatively and qualitatively based on high-resolution spectra and compounds library screening. Among these identified components, the octadecatrienoic acid methyl esters were major components in the unprocessed flowers, while some aromatic aldehydes and ketones, such as benzeneacetaldehyde and 1-(2-hydroxy-5-methylphenyl)-ethanone, were prominent components in the flowers both dried in the fluidized bed and in shadow. In addition, the flowers dried in the fluidized bed were more fragrant than other flowers.</p><p><b>CONCLUSION</b>The component and contents closely related to their processing mode, and the fluided bed drying may be a best choice to process the flowers of F. thunbergii.</p>