Superheated water extraction, steam distillation and Soxhlet extraction of essential oils of Origanum onites

Superheated water extraction (SWE) at various temperatures (100, 125, 150 and 175°C), steam distillation, and Soxhlet extraction were compared in the extraction of essential oils from two samples of the plant Origanum onites, one cultivated, the other wild. C18 solid-phase extraction was used to elute the essential oils from the SWE aqueous extract. The compositions of the extracted essential oils obtained from all three methods were then characterized by comprehensive GC×GC/time-of-flight mass spectrometry (TOF/MS). The highest essential oil yields were obtained by using SWE at 150°C with a flow rate of 2 mL min^–1 and a pressure of 60 bar for 30 min: these were 3.76 and 4.11% for wild and cultivated O. onites samples, respectively, expressed as a percentage of 100 g of dry (leaf) matter. The yields obtained using SWE at 150°C were slightly higher than those from conventional methods. Steam distillation was performed for 3 h, and Soxhlet extraction was completed in 12 h. The major compounds found were borneol, terpinen-4-ol and carvacrol.     

贻贝中多氯联苯分析的前处理方法研究

针对分析贻贝中痕量多氯联苯（PCBs），比较了索氏提取（SE）和加速溶剂萃取（ASE）两种提取方法，结果表明SE对贻贝中7种PCBs（PCB28、PCB52、PCB101、PCB118、PCB153、PCB138、PCB180）回收率范围在96％～125％，ASE回收率范围在102％～115％，两者提取效果相当，但与索氏提取相比，加速溶剂萃取是一种怏速、高效的提取方法此外采用凝胶渗透色谱（GPC）分别与Florisil和C18固相萃取（SPE）小柱联用净化，GPC与Florisil柱联用净化的凹收率范围在90％-112％，GPC与C18柱联用净化的回收率范围在74％-108％，结果表明GPC与Florisil柱联增净化优于GPC与C18柱联用净化。     

液相色谱测定土壤中4种硝基苯胺类化合物

建立了索氏提取-液相色谱-紫外检测器(SE-HPLC-UV vis)测定土壤中4种硝基苯胺同系物的方法。在以Hypersil BDS C18为色谱柱,55%甲醇为流动相,流速1 mL/min,检测波长230 nm时,4种物质可以在10 min内实现良好分离。对于索氏提取,本研究指出,采用二氯甲烷作为提取剂,能极大地消除HPLC-UV vis检测中的背景干扰。在单因素实验的基础上,得出最佳的提取条件如下:温度55℃,时间8h,提取剂用量60 mL。方法回收率>90%,RSD在1.9%～4.1%之间。     

Pressurised hot-water extraction of brominated flame retardants in sediment samples

Summary A pressurised, hot-water extraction (PHWE) method was developed for brominated flame-retardants in sediments. The effect of extraction time, temperature and pressure on PHWE recovery was investigated, together with solid-phase collection parameters (trapping material, length of trapping column, eluent composition). The concentrated extracts were analysed by GC-MS. PHWE recoveries were compared with those obtained by conventional Soxhlet-extraction. In general, recoveries were much higher with PHWE than with Soxhlet.     

Aqueous extraction of polyphenols and antiradicals from wood by-products by a twin-screw extractor: Feasibility study

An efficient and eco-friendly extracting process of wood by-products (maritime pine knots and stumps and aspen knots and barks) using a twin-screw extruder has been developed. This continuous device allowed a thermo-mechanical treatment of the woody material to recover fractions containing hydrophilic polyphenols and antiradical compounds. The breakdown of woody materials and the high level of pressing of the solid/liquid mix were mainly influenced by the solvent-to-solid ratio for maritime pine knots and stumps and aspen knots, and by the solvent-to-solid ratio and the barrel temperature in the case of aspen barks. Compared to the extractives content of each by-product determined at laboratory scale, twin-screw extractions were promising for the valorisation of wood by-products and the recovery of bioactive substances.     

基于随机聚类的复杂背景建模与前景检测算法

为了构建鲁棒的背景模型和提高前景目标检测的准确性, 综合考虑同一位置的像素点在时间上的关联性和与其相邻像素的空间关联性, 基于经典的ViBe算法中的随机聚类思想提出了一种复杂背景建模和前景检测方法. 利用样本一致性原理, 采用前n帧序列图像得到初始化背景, 避免了Ghost现象的发生; 根据实际复杂背景的动态反馈获取自适应聚类阈值和自适应更新阈值进行随机聚类, 从而实现了对动态背景的适应性; 通过全局扰动阈值和局部像素级判断阈值的结合, 实现了对光照缓慢变化、快速变化以及突然变化的免疫性, 准确地分割前景目标. 对多组数据集的测试结果表明, 本文算法较大地提高了背景模型对动态背景、光照变化及相机抖动的复杂背景的适应性和鲁棒性. 算法还能很好地适用于红外图像检测运动目标的场合, 扩展了本算法的应用范围. 在没有进行任何图像预处理和形态学后处理情况下, 得到的原始前景检测精度优于其他对比算法.     

Evaluation of Soxhlet extraction, accelerated solvent extraction and microwave-assisted extraction for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers in soil and fish samples

Three commonly applied extraction techniques for persistent organic chemicals, Soxhlet extraction (SE), accelerated solvent extraction (ASE) and microwave-assisted extraction (MAE), were applied on soil and fish samples in order to evaluate their performances. For both PCBs and PBDEs, the two more recent developed techniques (ASE and MAE) were in general capable of producing comparable extraction results as the classical SE, and even higher extraction recoveries were obtained for some PCB congeners with large octanol-water partitioning coefficients (K_ow). This relatively uniform extraction results from ASE and MAE indicated that elevated temperature and pressure are favorable to the efficient extraction of PCBs from the solid matrices. For PBDEs, difference between the results from MAE and ASE (or SE) suggests that the MAE extraction condition needs to be carefully optimized according to the characteristics of the matrix and analyte to avoid degradation of higher brominated BDE congeners and improve the extraction yields.     

Soxhlet extraction: Past and present panacea

An overview of Soxhlet extraction, the advantages and shortcomings of this centenary technique as well as the attempts to improve its performance and achievements reached is here presented. Assistance of high pressure, ultrasound or microwaves has decreased or minimized the negative characteristics of the conventional extractor. Automation of Soxhlet performance opened the door to commercialization of a number of different approaches. The evolution of Soxhlet extractor is here critically discussed, and the conclusion from this overview is that the adoption of new technologies to improve its performance converts Soxhlet extraction in almost a “panacea” in this field.     

Study of factors influencing pressurised solvent extraction of polar steroids from plant material. Application to the recovery of withanolides

Summary Pressurised solvent extraction was applied to the extraction of three withanolides from the leaves oflochroma gesnerioides. A study was carried out of the influence of various parameters on the extraction efficiency and kinetic parameters; these included the nature of the extracting solvent, its flow rate, the pressure and temperature, as well as the particle size of the plant material. The pressurised solvent extraction method compared to a conventional Soxhlet extraction showed similar recoveries and extraction selectivity but the total handling time and solvent volume were dramatically reduced.     

Comparison of extraction techniques for the isolation of explosives and their degradation products from soil

A comparison of four extraction techniques used for the isolation of 14 explosive compounds (Method 8330-Explosives) from spiked soil samples is described. Soxhlet warm extraction (SWE), pressurized solvent extraction (PSE), microwave assisted extraction (MAE) and supercritical fluid extraction (SFE) were included. The effects of basic extraction conditions – i.e. type of extraction solvent, temperature, pressure, and extraction time – were investigated. The best extraction recovery of the monitored compounds from spiked soil was obtained using pressurized solvent extraction. Recoveries of explosives using the PSE technique were in the range from 65 to 112%. Extraction recoveries by Soxhlet warm extraction and supercritical fluid extraction reached 65–99% and 52–75%, respectively. The lowest extraction recoveries (28–65%) were obtained using microwave assisted extraction. A very low extraction recovery for tetryl was observed in all cases but the best results were achieved by pressurized solvent extraction (58%).