共查询到20条相似文献,搜索用时 156 毫秒
1.
2.
3.
4.
5.
6.
固体溶质在超临界三元系统中的溶解度 总被引:1,自引:0,他引:1
溶质在超临界流体中的溶解度数据是研究超临界流体技术的基础.本文对纯组分固体溶质有夹带剂存在的超临界流体三元系统中,夹带剂增大溶质溶解度的作用进行了总结,述评了夹带剂增大溶质溶解度的机理和常用的计算模型.此外,针对两种固体混合溶质共存于超临界流体中的三元系统,讨论了混合溶质共存对彼此溶解度的影响及其相关的理论假说和计算模型. 相似文献
7.
8.
银杏叶SF-CO_2萃取物与残叶银杏黄酮的HPLC分析 总被引:3,自引:0,他引:3
银杏叶用SF -CO2 -CH3 CH2 OH体系萃取后 ,用HPLC法分析萃取物与残叶中银杏黄酮苷与黄酮苷元的含量。结果表明 ,有夹带剂时可萃取黄酮苷元 ;无论有无夹带剂银杏黄酮苷都残留在萃取残叶中。 相似文献
9.
超临界二氧化碳流体萃取中药苦参的生物总碱 总被引:8,自引:0,他引:8
超临界CO2流体萃取(CO2 SupercriticalFluidExtraction,SFE CO2)技术是一种新型分离提取技术,其选择分离效果好,提取率高,产物没有有机溶剂残留,有利于热敏性物质和易氧化物质的萃取[1]。苦参为豆科植物,是传统的清热燥湿类中药,其有效成分主要为生物碱。苦参生物碱具有抗肿瘤、平喘、升白、抗菌、抗病毒、抗原虫等多种功能[2]。由于生物碱在植物中多数以盐的形式存在,若直接用极性较弱的溶剂提取往往提取不完全,故在提取前需碱化,使之成为游离碱[3]。本实验用氨水作碱化剂,选用无水甲醇为夹带剂,… 相似文献
10.
超临界CO2萃取异甘草素的提取工艺 总被引:3,自引:0,他引:3
采用正交试验与单因素试验相结合方法对异甘草素的超临界CO2提取工艺进行了研究,并与常规索氏提取法的实验结果进行了对比。得到的最佳工艺参数为:萃取压力30 MPa、萃取温度45℃、夹带剂85%乙醇、液固比为5:1、CO2流量10 kg/h、分离压力5.5 MPa、分离温度35℃。实验结果表明,在优化的条件下,超临界CO2萃取异甘草素的提取率为0.035%,异甘草素在提取物中的质量分数为0.84%,分别是索氏提取法提取率的3.5倍,质量分数的3.0倍。超临界CO2萃取异甘草素所用时间短、溶剂用量少、提取效率高、环境友好,是一种高效、快速提取异甘草素的方法。 相似文献
11.
Contact toxicities of Acorus calamus L. (Arales: Araceae) extracts obtained from four published extraction methods: soakage, soxhlet, ultrasonic and supercritical fluid CO? (SFE-CO?), were compared in this study. Under the given extraction conditions, SFE-CO? extract exhibited the highest contact toxicity against S. zeamais of the four methods. With the SFE-CO? method, extraction temperature, pressure, time and the amount of EtOH (the extraction solvent) were identified as having a significant effect on the extract. Orthogonal experiments showed that the optimal extraction parameters were: temperature--55°C, pressure--35?MPa, time--40?min and EtOH--150?mL per 200?g of dry powder. Under these conditions, the yield was 4.12% and the LD?? of the extract against S. zeamais after 96?h of treatment was 27.26?μg?cm?2. β-asarone was the dominant component of the extract derived from the SFE-CO? method, accounting for 24.39% of the extract. These results may contribute to the designing of large-scale production processes for obtaining A. calamus extract, which proves to be an effective alternative for the control of stored product insect pests. 相似文献
12.
13.
14.
Li Q Jiang C Zu Y Song Z Zhang B Meng X Qiu W Zhang L 《Molecules (Basel, Switzerland)》2011,16(10):8228-8242
Typhonium giganteum Engl. (BaiFuzi) is one of the herbs commonly used in traditional Chinese medicine against cancer. In our previous studies, 37 compounds were identified the SFE-CO(2) (supercritical fluid extraction with CO(2)) extract by GC-MS, including the four major components [β-sitosterol (40.22%), campesterol (18.45%), n-hexadecanoic acid (9.52%) and (Z,Z)-9,12-octadecadienoic acid (8.15%)]. The anti-cancer mechanisms of the SFE-CO(2 )extract from T. giganteum Engl. tubers have not been reported as yet. In this paper, the molecular mechanisms of the SFE-CO(2) extract-mediated apoptosis in SMMC-7721 cells were further examined. SFE-CO(2) extract inhibited the growth of SMMC-7721 cells in a time- and dose-dependent manner, arrested the cell cycle in the S phase and G2/M phase, and induced apoptosis. In addition, reactive oxygen species (ROS) increase, reduction of mitochondrial membrane potential, a rise in intracellular calcium levels were found in SMMC-7721 cells after treated with the extract. Western blot analysis showed that the extract caused down-regulation of Bcl-2 expression, and up-regulation of Bax expression. Moreover, caspase-3 and caspase-9 protease activity significantly increased in a dose-dependent manner. Collectively, our results showed that the SFE-CO(2) extract from T. giganteum Engl. tubers induces apoptosis in SMMC-7721 cells involving a ROS-mediated mitochondrial signalling pathway. 相似文献
15.
超声辅助液液萃取法提取烟用香精成分的研究 总被引:1,自引:0,他引:1
采用超声辅助液液萃取法(ULLE)提取某品牌烟用香精成分,GC-MS对其进行分析,研究了不同萃取剂、萃取时间和萃取温度对分析结果的影响,初步确定了最佳条件为:以二氯甲烷为萃取剂,饱和NaCl溶液作水相,室温下超声萃取5 min.又分别与同时蒸馏萃取法(SDE)和传统的液液萃取法(LLE)作以比较,对ULLE法和SDE法鉴定出的化学成分、重现性和定量值进行了对比.结果表明:超声辅助液液萃取具有操作简便、快速、节能、萃取效率高、重现性好等特点,适合于烟用香精成分的提取. 相似文献
16.
Sample pretreatment before chromatographic analysis is the most time consuming and error prone part of analytical procedures, yet it is a key factor in the final success of the analysis. A quantitative and fast liquid phase microextraction technique termed as gas purge microsyringe extraction (GP-MSE) has been developed for simultaneous direct gas chromatography-mass spectrometry (GC-MS) analysis of volatile and semivolatile chemicals without cleanup process. Use of a gas flowing system, temperature control and a conventional microsyringe greatly increased the surface area of the liquid phase micro solvent, and led to quantitative recoveries of both volatile and semivolatile chemicals within short extraction time of only 2 min. Recoveries of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and alkylphenols (APs) determined were 85-107%, and reproducibility was between 2.8% and 8.5%. In particular, the technique shows high sensitivity for semivolatile chemicals which is difficult to achieve in other sample pretreatment techniques such as headspace-liquid phase microextraction. The variables affecting extraction efficiency such as gas flow rate, extraction time, extracting solvent type, temperature of sample and extracting solvent were investigated. Finally, the technique was evaluated to determine PAHs, APs and OCPs from plant and soil samples. The experimental results demonstrated that the technique is economic, sensitive to both volatile and semivolatile chemicals, is fast, simple to operate, and allows quantitative extraction. On-site monitoring of volatile and semivolatile chemicals is now possible using this technique due to the simplification and speed of sample treatment. 相似文献
17.
Chimuka L van Pinxteren M Billing J Yilmaz E Jönsson JÅ 《Journal of chromatography. A》2011,1218(5):647-653
A selective extraction technique based on the combination of membrane assisted solvent extraction and molecularly imprinted solid phase extraction for triazine herbicides in food samples was developed. Simazine, atrazine, prometon, terbumeton, terbuthylazine and prometryn were extracted from aqueous food samples into a hydrophobic polypropylene membrane bag containing 1000μL of toluene as the acceptor phase along with 100mg of MIP particles. In the acceptor phase, the compounds were re-extracted onto MIP particles. The extraction technique was optimised for the type of organic acceptor solvent, amount of molecularly imprinted polymers particles in the organic acceptor phase, extraction time and addition of salt. Toluene as the acceptor phase was found to give higher triazine binding onto MIP particles compared to hexane and cyclohexane. Extraction time of 120min and 100mg of MIP were found to be optimum parameters. Addition of salt increased the extraction efficiency for more polar triazines. The selectivity of the technique was demonstrated by extracting spiked cow pea and corn extracts where clean chromatograms were obtained compared to only membrane assisted solvent extraction or only molecularly imprinted solid phase extraction. The study revealed that this combination may be a simple way of selectively extracting compounds in complex samples. 相似文献
18.
H. Steinwandter 《Fresenius' Journal of Analytical Chemistry》1992,343(12):887-889
Summary For the determination of pesticide residues 10 fruit and vegetable samples and 2 wheat samples with unknown spray history were extracted by the micro on-line extraction technique using the binary solvent system water + ethyl acetate as the extracting agent. The results of this proposed micro extraction were compared with already tested methods and it was found that the micro ethyl acetate method was equally effective. The reduction of solvents and chemical waste by miniaturization of analytical procedures is an important step for environmental protection. 相似文献
19.
Supercritical fluid extraction (SFE) with CO(2), a clean and rapid alternative to conventional organic solvent extraction techniques, was investigated for the extraction of 2,4-D from soils using a variety of pre-extraction soil treatments to enhance extraction recoveries. Initial experiments with silylation, ion-pairing, methyl esterification, and ionic displacement are reported. Methyl esterification and ionic displacement during SFE proved to be the most promising approaches for quantitative extraction. Although the SFE procedures were not fully optimized, comparison between SFE and a standard Soxhlet extraction method demonstrated the potential for improving analytical measurement for highly polar pesticides in soil by modifying SFE-CO(2) extraction with derivatizing reagents and ionic solutions. 相似文献
20.
Efficiency of supercritical fluid extraction for determining 4-nonylphenol in municipal sewage sludge. 总被引:3,自引:0,他引:3
When the sewage sludge containing the persistent, lipophilic, metabolite 4-nonylphenol (4-NP) has been disposed of in the environment it's toxic nature can lead to serious health risks to human beings and can also affect plants and aquatic organisms. Supercritical fluid extraction (SFE) is a new and powerful technique for extracting the organic contaminants from the solid phase. The present study was conducted to investigate optimal conditions for the quantitative extraction of 4-NP by SFE and to determine the concentration of 4-NP in municipal sewage sludge. The effect of several parameters such as temperature, pressure, static extraction time, dynamic extraction time, CO2 flow-rate, sample mass and modifier on the extraction were investigated. The optimal conditions for the extraction of the spiked sample were fluid pressure 97 bar, temperature 40 degrees C, flow-rate 3.0 ml/min, static extraction time 2 min, dynamic extraction time 5 min and modifier methanol (0.5 ml). Extracts were analyzed by gas chromatography-mass spectrometry. Concentration of 4-NP in the anaerobically degraded sludge of the De-Haw Sewage Treatment Plant in Taiwan was found to be 243.9 mg/kg. The extraction efficiency of the SFE method was compared with the conventional Soxhlet extraction method. The overall recovery of the SFE method was found to be greater and the results indicate that SFE is an efficient method for extracting 4-NP from sewage sludge. 相似文献