title: Determination of volatile components of green, black, oolong and white tea by optimized ultrasound-assisted extraction-dispersive liquid-liquid microextraction coupled with gas chromatography.
abstract: Ultrasound assisted extraction (UAE) followed by dispersive liquid-liquid microextraction (DLLME) was used for extraction and preconcentration of volatile constituents of six tea plants. The preconcentrated compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Totally, 42 compounds were identified and caffeine was quantitatively determined. The main parameters (factors) of the extraction process were optimized by using a central composite design (CCD). Methanol and chloroform were selected as the extraction solvent and preconcentration solvent, respectively .The optimal conditions were obtained as 21 in for sonication time; 32°C for temperature; 27 L for volume of extraction solvent and 7.4% for salt concentration (NaCl/H(2)O). The determination coefficient (R(2)) was 0.9988. The relative standard deviation (RSD %) was 4.8 (n=5), and the enhancement factors (EFs) were 4.0-42.6.
authors: Department of Chemistry, Faculty of Science, University of Tehran, Tehran, Iran. sereshti@khayam.ut.ac.ir
authors: Hassan
authors: H
authors: Sereshti
authors: Soheila
authors: S
authors: Samadi
authors: Mehdi
authors: M
authors: Jalali-Heravi
mesh_terms: D000704:Analysis of Variance; D002110:Caffeine; D002725:Chloroform / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D057230:Limit of Detection; D016014:Linear Models; D059627:Liquid Phase Microextraction / Q000379:methods*; D000432:Methanol / Q000737:chemistry; D009930:Organic Chemicals / Q000032:analysis* / Q000302:isolation & purification; D015203:Reproducibility of Results; D012107:Research Design; D013010:Sonication / Q000379:methods*; D013662:Tea / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D013662:Tea; D002110:Caffeine; D002725:Chloroform; D000432:Methanol