天然抗氧化剂茶多酚

抗氧化剂是指能防止或延缓食品成分氧化变质的食品添加剂.茶多酚是目前尚不能人工合成的纯天然、多功能、高效能的抗氧化剂和自由基净化剂,可用超临界CO2萃取法、离子沉淀提取法、树脂吸附分离法、有机溶剂萃取法提取.采用酒石酸亚铁比色法测定茶多酚含量.     

不同基质中有机氯农药提取技术及发展趋势

该文根据各种基质特点及其中有机氯农药的分布特点,对不同介质中有机氯农药的提取方法进行了归纳.着重介绍了不同基质中有机氯农药提取方法,如均质法、固相萃取法、索氏提取法、基质固相分散法、加速溶剂萃取法、超临界流体提取法、超声波提取法和微波辅助提取法等.通过详细实例,总结了上述提取方法的优缺点,并对有机氯农药提取方法做了展望...     

烟草中有机氯类农药多残留分析前处理方法对比研究

以烟草中有机氯类农药为研究对象,从检出限、回收率、重复性和色谱图4个方面系统比较了机械振荡萃取法、超声波溶剂萃取法、微波辅助萃取法和加速溶剂萃取法4种常用前处理方法。由于加速溶剂萃取法是在高温高压下进行萃取,在提取出残留农药的同时,也提取出更多的干扰物。机械振荡法、超声波溶剂萃取法和微波辅助萃取法各项结果差别较小,其中机械振荡萃取法回收率和重复性最好,但提取时间较长。考虑溶剂消耗和提取时间等方面的因素,微波辅助萃取是较理想的样品前处理方法。     

动物源性食品中小分子有机污染物的多类别多残留分析技术的研究进展

综述了近年来动物源性食品中小分子有机污染物的多类别多残留分析技术的研究进展,包括液液萃取法、加速溶剂萃取法、基质分散固相萃取法等提取方法,液液萃取法、低温冷冻法、固相分散萃取法、固相萃取法等净化方法,以及液相色谱法、质谱法、液相色谱-质谱联用等仪器分析方法。还指出了多类别多残留分析方法潜在的研究方向(引用文献64篇)。     

蒸馏-萃取法与溶剂萃取法提取杏果实香气成分的比较

采用水蒸气蒸馏一萃取法和溶剂萃取法提取杏果香成分,用气相色谱一质谱联用测定其化学成分和质量分数,并对两种提取方法进行了比较。水蒸气蒸馏一萃取法提取的杏果香成分是74种,占总峰面积的73．604％;溶剂萃取法提取的杏果香成分是32种,占总峰面积的44．677％,两者相同的成分有21种。溶剂萃取法提取的主要是烷烃类化合物,水蒸气蒸馏萃取法提取的主要化合物为G醛类、C6醇类、内酯类、萜烯醇类、酮类、烷烃类等。结果表明：水蒸气蒸馏-萃取法能较好地提取杏果实香气成分。     

天然红色素的提取研究进展

作为天然色素中的一大类,天然红色素在人们的日常生活中日益发挥着重要的作用。国内对天然红色素的提取研究起步较晚,但发展迅速。文章重点介绍了辣椒红色素、番茄红素、桑椹红色素等几种重要天然红色素的性质和提取方法,并比较了有机溶剂法、超临界CO2流体萃取法等提取方法的特点,同时对其效果和应用作了相应的展望。     

加速溶剂萃取法快速提取黄连中的生物碱

探讨了快速溶剂萃取法（ASE）提取黄连中生物碱的可行性,并比较了该方法与回流提取法和超声提取法的优越性。以黄连中盐酸小檗碱的提取率为指标,以高效液相色谱法（HPLC）为检测方法,用正交实验对快速溶剂萃取法从黄连中提取盐酸小檗碱的工作条件进行优化。最佳仪器参数：提取溶剂为80%乙醇＋0.5%HCl,提取温度为130℃,静态提取时间为10 min,提取次数为1次。快速溶剂萃取法可作为黄连中生物碱分析测定的前处理方法。     

水体中合成麝香检测方法的研究进展

合成麝香被广泛应用于个人护理产品和生活用品中,在环境中的污染程度呈逐年上升的趋势,准确测定环境中合成麝香的含量具有重要意义。综述了水体中合成麝香的前处理方法(包括固相萃取法、固相微萃取法、液液萃取法、液液微萃取法、索氏提取法、超声辅助提取法、加速溶剂萃取法和QuEChERS等)和仪器分析方法(包括气相色谱-质谱法、气相色谱-串联质谱法、高效液相色谱法、液相色谱-串联质谱法和新型荧光光谱法等),并对相关研究领域的发展趋势进行了展望(引用文献52篇)。     

气相色谱分析样品的提取与富集技术

对几种常用或新近发展起来的气相色谱分析样品的提取和富集方法如固相萃取法、吹扫——捕集法、热解析法等作了简要论述，着重讨论了它们的应用特点、优缺点，并对这几种提取、富集方法进行了比较。     

GC-MS法测定ABS木塑材料中十溴二苯醚

建立了索氏提取和超声萃取-GC-MS法测定丙烯腈-丁二烯-苯乙烯共聚物(ABS)木塑材料中十溴二苯醚的分析方法。通过正交试验分析提取溶剂、样品质量和提取时间三个因素的显著性,并优化了参数。在优化条件下,索氏提取和超声萃取法的平均回收率均大于80%,精密度均小于10%。经F检验和T检验显著性统计,两种前处理方法的精密度和准确度不存在差异。相对于传统的索氏提取法,超声萃取法具有操作简单、溶剂用量少和省时的特点,可以较好的应用于木塑材料中十溴二苯醚检测。     

Graph Neural Networks with Multiple Feature Extraction Paths for Chemical Property Estimation

Feature extraction is essential for chemical property estimation of molecules using machine learning. Recently, graph neural networks have attracted attention for feature extraction from molecules. However, existing methods focus only on specific structural information, such as node relationship. In this paper, we propose a novel graph convolutional neural network that performs feature extraction with simultaneously considering multiple structures. Specifically, we propose feature extraction paths specialized in node, edge, and three-dimensional structures. Moreover, we propose an attention mechanism to aggregate the features extracted by the paths. The attention aggregation enables us to select useful features dynamically. The experimental results showed that the proposed method outperformed previous methods.     

树脂法提取茶多酚的研究

本文研究了用大孔吸附树脂由茶叶提取茶多酚的方法。通过对树脂的筛选，确定了NK-S3树脂对茶多酚吸附-解吸性能良好；选择由乙醇、乙酸乙酯和水组成的混合液为脱附剂；研究了流速对吸附、脱附性能的影响，并解决了茶水的前处理问题。     

Orthogonal transformations for feature extraction in chemical pattern recognition

A crucial point in pattern recognition methods is the extraction of features to determine the pattern vectors. Orthogonal transformations, e.g., Fourier, Walsh and Haar, are investigated as preprocessing methods for feature extraction. The theoretical considerations and conclusions are compared with computational results obtained by applying different pattern recognition methods to two different but similar collections of low-resolution mass spectra.     

PA／XDA膜包络复合树脂对茶多酚、咖啡碱的吸附分离

研制了XDA负载PA膜包络体的复合树脂,并用于茶叶提取液中茶多酚、咖啡碱的分离。通过对复合工艺,如溶剂配比、PA担载量及添加剂加入量的研究,提出了复合树脂制备的优惠工艺条件。该复合树脂具有良好的吸附、洗脱性能。将溶解度参数理论用于脱附剂的选择,实验结果与理论分析相一致。     

利用27Al NMR研究茶多酚与铝形成配合物的形态

采用27Al NMR技术,研究了不同茶叶中茶多酚与铝形成配合物的形态。考察了在不同pH值和配体/金属(L/M)下铝的存在形态,系统地研究了焦性没食子酸、儿茶酚等官能团模拟化合物与铝的配位体系中铝的形态,探讨了配体取代基的个数与焦性没食子酸-铝配合物的δ27Al的关系,获得了非常有意义的规律,并确定了茶多酚与铝配合物的结构。     

Comparison of techniques for the extraction of the hypotensive drugs geniposidic acid and geniposide from Eucommia ulmoides

The extraction of geniposidic acid and geniposide from Eucommia ulmoides was carried out by Soxhlet extraction, enzyme-assisted aqueous extraction, semi-bionic extraction and supercritical fluid extraction techniques and the extracts were analyzed by high performance liquid chromatography. The results showed that the best methods for extraction of geniposidic acid and geniposide are enzyme-assisted aqueous extraction and semi-bionic extraction. Compared with various extraction methods, the semi-bionic extraction was more efficient, yielding the highest amount of geniposidic acid and geniposide. In semi-bionic extraction, no organic solvent was used. Semi-bionic extraction was performed at the same pH as that of the human body. The results indicated that semi-bionic extraction was the best method for large-scale efficient extraction of geniposidic acid and geniposide from plant materials. The supercritical fluid extraction process required more time than the other methods, and gave the lowest yields of geniposidic acid and geniposide.     

银杏叶中黄酮类化合物的提取、纯化及测定方法的研究进展

对应用于银杏叶中黄酮类化合物的提取方法、纯化方法和测定方法的现状(主要在1999～2011年间发表的文献)及相关的原理和方法的特点作了综述。     

Modern microextraction techniques for natural products

Natural product analysis has gained wide attention in recent years, especially for herbal medicines, which contain complex ingredients and play a significant clinical role in the therapy of numerous diseases. The constituents of natural products are usually found at low concentrations, and the matrices are complex. Thus, the extraction of target compounds from natural products before analysis by analytical instruments is very significant for human health and its wide application. The commonly used traditional extraction methods are time-consuming, using large amounts of sample and organic solvents, as well as expensive and inefficient. Recently, microextraction techniques have been used for natural product extraction to overcome the disadvantages of conventional extraction methods. In this paper, the successful applications of and recent developments in microextraction techniques including solvent-based and sorbent-based microextraction methods, in natural product analysis in recent years, especially in the last 5 years, are reviewed for the first time. Their features, advantages, disadvantages, and future development trends are also discussed.     

A new approach to untargeted integration of high resolution liquid chromatography–mass spectrometry data

Because of its high sensitivity and specificity, hyphenated mass spectrometry has become the predominant method to detect and quantify metabolites present in bio-samples relevant for all sorts of life science studies being executed. In contrast to targeted methods that are dedicated to specific features, global profiling acquisition methods allow new unspecific metabolites to be analyzed. The challenge with these so-called untargeted methods is the proper and automated extraction and integration of features that could be of relevance. We propose a new algorithm that enables untargeted integration of samples that are measured with high resolution liquid chromatography–mass spectrometry (LC–MS). In contrast to other approaches limited user interaction is needed allowing also less experienced users to integrate their data. The large amount of single features that are found within a sample is combined to a smaller list of, compound-related, grouped feature-sets representative for that sample. These feature-sets allow for easier interpretation and identification and as important, easier matching over samples. We show that the automatic obtained integration results for a set of known target metabolites match those generated with vendor software but that at least 10 times more feature-sets are extracted as well. We demonstrate our approach using high resolution LC–MS data acquired for 128 samples on a lipidomics platform. The data was also processed in a targeted manner (with a combination of automatic and manual integration) using vendor software for a set of 174 targets. As our untargeted extraction procedure is run per sample and per mass trace the implementation of it is scalable. Because of the generic approach, we envision that this data extraction lipids method will be used in a targeted as well as untargeted analysis of many different kinds of TOF-MS data, even CE- and GC–MS data or MRM. The Matlab package is available for download on request and efforts are directed toward a user-friendly Windows executable.     

HPLC and GC-MS determination of bioactive compounds in microwave obtained extracts of three varieties of Labisia pumila Benth

Microwave extraction of phytochemicals from medicinal plant materials has generated tremendous research interest and shown great potential. This research highlights the importance of microwave extraction in the analysis of flavonoids, isoflavonoid and phenolics and the antioxidant properties of extracts from three varieties of the Malaysian medicinal herb, Labisia pumila Benth. High and fast extraction performance ability, equal or higher extraction efficiencies than other methods, and the need for small samples and reagent volumes are some of the attractive features of this new promising microwave assisted extraction (MAE) technique. The aims of the present research were to determine the foliar phenolics and flavonoids contents of extracts of three varieties of L. pumila obtained by a microwave extraction method while flavonoid, isoflavonoid and phenolic compounds were analyzed using RP-HPLC. Furthermore, the antioxidant activities were measured by the DPPH and FRAP methods and finally, the chemical composition of the crude methanolic extracts of the leaves of all three varieties were analyzed by GS-MS.