| The research on bioactive components of traditional Chinese herbal medicine is helpful to its pharmacological study and clinical application. The extraction of the bioactive components is one of the key points. Traditional extraction methods are usually time-consuming, laborious and expensive. Application of modern extraction techniques, such as ultrasonic-assisted extraction and microwave-assisted extraction or the novel extraction mode such as dynamic extraction and its on-line combination with detection, make the analytical progress more rapid. At the same time, the solvent and sample consumption decreased and the optimization of the extraction process is accelerated.Food safety is a point of concern in recent years. In extraction of the harmful ingredients in food, the commercial high-pressure microwave device is applicable in a wide range of and easy to promote. This method is rapid and effective. The solvent and sample consumption decreased.Moreover, multiple parallel samples can be handled at a time. In addition combination with other purification technique would make the method selective and reduce the matrix interference.In the second chapter, an on-line method, based on coupling dynamic ultrasonic assisted extraction (DUAE), continuously sampling the suspension of sample and solvent, high performance liquid chromatographic separation with diode, array detection(on-line continuous flow-DUAE-HPLC), has been developed for the determination of the flavonoids, including baicalin, baicalein and wogonin, from the root of Scutellaria baicalensis Georgi. Variables influencing the DUE were evaluated by orthogonal test. The extraction yields of baicalin, baicalein and wogonin in the roots of Scutellaria baicalensis georgi obtained from five different cultivated areas are 73.8-131.5μgmg-1 (RSD≤6.24%),6.8-15.9μgmg-1 (RSD≤5.36%) and 4.4-14.3μgmg-1 (RSD≤5.30%), respectively. The limits of detection for baicalin, baicalein and wogonin are 0.30,0.37 and 0.41μgmL-1, respectively. Linearity is from 0.55 to 109μgmL-1 for baicalin, from 0.51 to 105μgmL-1 for baicalein and from 0.53 to 102μgmL-1for wogonin. Compared with off-line continuous flow-DUE, the proposed method would be more convenient for the determination of the analytes and the rapid optimization of the extraction process. The extraction yields of flavonoids obtained by the proposed method are comparable with those obtained by dynamic microwave assisted extraction, static ultrasonic extraction and reflux extraction. The result indicated that the proposed method is suitable to determine the active components in Chinese herbal medicine.Dynamic microwave-assisted extraction (DMAE) of flavonoids in root of Scutellaria baicalensis Georgi was described. A TM010 microwave resonant cavity was employed as energy coupler. Several parameters of DMAE, including concentration, flow rate and volume of extraction solvent and irradiation power, were optimized. The extraction was performed under the optimum conditions for the extraction of total flavonoids. UV-Vis spectrophotometry was applied to determination the total flavonoids. The determination of the main bioactive components, including baicalin, baicalein and wogonin, was performed by HPLC. The extraction yields of flavonoids obtained by DMAE were comparable with those obtained by pressurized microwave assisted extraction (PMAE), ultrasonic extraction (UE), soxhlet extraction (SE), and reflux extraction (RE), indicating that DMAE was a good alternative method for extraction of flavonoids in Radix Scutellarie.An on-line method, based on coupling dynamic microwave extraction (DMAE), continuously sampling the suspension of sample and solvent, high performance liquid chromatographic separation with diode array detection (on-line continuous flow-DMAE-HPLC), has been developed for the determination of the lignans, including schisandrin A, schisantherin A and deoxyschizandrin and anthraquinones pigment including shikonin andβ,β'-dimethylacrylshikonin from Arnebia euchroma (Royle) Johnst. A modified household microwave oven was employed as energy coupler. Variables influencing the DMAE were evaluated by orthogonal test. The extraction yields of schisandrin A, schisantherin A and deoxyschizandrin in Schisandra chinensis (Turcz.) Baill. are 4.24-6.84μgmg-1(RSD≤5.58％),0.68- 0.86μgmg-1(RSD≤4.31%) and 0.58-0.95μg mg-1(RSD≤3.87%); The extraction yields of schisandrin A, schisantherin A and deoxyschizandrin in Schisandra sphenanthera Rehd. etWils are 0.13-0.26μgmg-1 (RSD≤5.25%),2.46-7.42μg mg-1 (RSD≤4.33%) and 1.04-1.65μgmg-1 (RSD≤5.58%). The extraction yields of shikonin andβ,β'-dimethylacrylshikonin in Arnebia euchroma (Royle) Johnst obtained from four different cultivated areas are 0.66-0.92μg mg-1 (RSD≤5.43%) and 3.02-8.88μg mg-1(RSD≤5.84%). The limits of detection for schisandrin A, schisantherin A and deoxyschizandrin shikonin andβ,β'-dimethylacrylshikonin 0.86,0.90,0.27,0.42 and 0.92μmL-1,respectively. Linearity is from 0.74-186μg mL-1for schisandrin A, from 0.82-204μg mL-1 for schisantherin A and from 0.94-236μg mL-1for deoxyschizandrin,from 1.22 to 266μg mL-1 for shikonin,from 0.78 to 234μgmL-1 forβ,β'-dimethylacrylshikonin. Compared with off-line continuous flow-DUE, the proposed method would be more convenient for the determination of the analytes and the rapid optimization of the extraction process. The extraction yields of flavonoids obtained by the proposed method are comparable with those obtained by dynamic microwave assisted extraction, static ultrasonic extraction and reflux extraction. The result indicated that the proposed method is suitable to determine the active components in Chinese herbal medicine.A method for determining triazine herbicides in infant nutrient cereal-based foods by pressurized microwave-assisted extraction (PMAE), coupled with high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS), is described. The key parameters of PMAE, including extraction solvent, extraction time and temperature, were optimized. The isolation of the target compounds from the matrix was found to be efficient when 2 g of nutrient cereal samples was extracted with 20 mL of methanol for 10 min at 105℃. Final determination was accomplished by HPLC-ESI/MS. The recoveries from 66.2 to 88.6% were obtained for three compounds at fortification levels (5-500μg kg-1) with relative standard deviations (R.S.D.)≤12.62%. Compared with atmospheric pressure microwave-assisted extraction (AMAE), ultrasonic extraction (UE) and soxhlet extraction (SE), the proposed method was more efficient, faster and more straightforward and required no additional cleanup steps. When the proposed method was applied to the aged spiked nutrient cereal samples, the results indicated that, although the recoveries of analytes were much lower than those obtained from fresh spiked samples, they were nevertheless satisfactory for the quantitative analysis of practical samples.A method for determining Sudan (I-IV) dyes in powdery condiments and ready meals) by pressurized microwave assisted extraction (PMAE) in combination with high performance liquid chromatography-diode array detection (HPLC-DAD) is described. Considering the presence of interfering substances especially for paprika color (oleoresin) in the powdery condiments extracts, solid-phase extraction (SPE) was also coupled to the proposed methods, when the powdery condiments was extracted. The key parameters of PMAE, including extraction solvent, extraction time and the temperature, were optimized. The isolation of the target compounds from the matrix was found to be efficient when 1g powdery condiments was extracted with 20ml of ethanol for 10 min at 90℃or 2g ready meal samples was extracted with 20ml of ethanol for 8 min at 90℃。Final determination was accomplished by HPLC-DAD. The recoveries from 61.51% to 93.92% were obtained for four compounds at fortification levels (100-500μgkg-1) with relative standard deviations (R.S.D.)≤6.88%. Compared ultrasonic assisted extraction (UAE) and soxhlet extraction (SE), the proposed method was more efficient and faster. |
PDF Full Text Request