RESUMEN
A method to analyze the volatile components in Minnan oolong tea was developed based on headspace solid phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOF MS). Volatile compounds of 48 oolong tea samples with different qualities and production seasons from five varieties (Tieguanyin, Huangjingui, Benshan, Maoxie and Meizhan) were extracted by HS-SPME and analyzed by GC×GC-TOF MS. More than 2 000 peaks were obtained from each sample, and 51 common compounds were tentatively identified by comparison with the standard mass spectrum databases, retention indices and structure spectra. The projection score of the common compounds obtained from principal component analysis ( PCA) had presented a straightforward classification trend for different oolong tea varieties. In addition, 9 compounds which had significant impact on the classification were selected by stepwise discriminate analysis, and used as variables to establish four discriminated functions by Fisher's discriminate analysis (FDA). The accuracy for the recognition of 48 samples was 97. 9%. The results had demonstrated the feasibility of the method to be used to discriminate the oolong tea varieties.
Asunto(s)
Té/química , Compuestos Orgánicos Volátiles/análisis , Análisis Discriminante , Cromatografía de Gases y Espectrometría de Masas , Microextracción en Fase SólidaRESUMEN
An effective method was developed and applied to determine the residues of ten pesticides of pyrazoles and pyrroles in tea by accelerated solvent extraction coupled with gas chromatography-tandem mass spectrometry (ASE-GC-MS/MS). The samples were extracted with ethyl acetate-hexane (1:1, v/v) for 5 min at 1.03 x 10(7) Pa and 100 degree C for one cycle. Then, they were purified by Envi-Carb/PSA column, and eluted by ethyl acetate-hexane (1:1, v/v). The analytes were determined by GC-MS/MS and quantified by external standard method. The limits of quantification were 0.003 mg/kg for fenpyroximate, 0.001 mg/kg for fipronil-sulfide, 0.002 mg/kg for fipronil, 0.005 mg/kg for fipronil-sulfone, 0.002 mg/kg for chlorfenapyr, 0.006 mg/kg for flusilazole, 0.001 mg/kg for difenzoquat, 0.001 mg/kg for pyraflufen-ethyl, 0.000 3 mg/kg for tebufenpyrad and 0.005 mg/kg for tolfenpyrad. The results show that the proposed method is sensitive and accurate for the determination of the ten pesticide residues.
Asunto(s)
Cromatografía de Gases y Espectrometría de Masas/métodos , Residuos de Plaguicidas/análisis , Pirazoles/análisis , Pirroles/análisis , Té/química , Contaminación de Alimentos/análisis , Microextracción en Fase Líquida/métodos , Solventes/química , Espectrometría de Masas en Tándem/métodosRESUMEN
A high performance liquid chromatographic (HPLC) method has been developed for the determination of quinoxyfen residue in various food matrixes including soybean, cauliflower, cherry, mushroom, wine, tea, honey, pork liver, chicken and eel. The analyte was extracted by ethyl acetate, and then purified with aminopropyl solid phase extraction (NH2 SPE) cartridge. Post-extraction gel permeation chromatography (GPC) was used for animal (except honey) and fishery products prior to NH2 SPE cleanup. The average recoveries and relative standard deviations (RSDs) for the analysis of all samples fortified in the range of 0.010 - 5.0 mg/kg were in the ranges of 82% - 96% and 3.2% - 11.8%, respectively. Good linearity was obtained in the concentration range from 0.050 to 50.0 mg/L. The limit of detection was 0.010 mg/kg. The proposed method was successfully applied to the analysis of quinoxyfen residue in various food samples.