共查询到18条相似文献,搜索用时 62 毫秒
1.
自茶叶中提取咖啡因实验教学探索与研究 总被引:8,自引:0,他引:8
自茶叶中提取咖啡因是大学有机化学实验教学中关于天然产物提取的经典实验,目前国内高校大多采用文献[1]进行实验教学,但该文献中关于咖啡因提取液炒干时的状态,加入生石灰以中和丹宁酸的量及升华时沙浴的温度等方面不准确,从而在实验教学中经常出现升华产物色泽不好、咖啡因晶体颗粒短小、甚至无升华产物等现象。为此,笔者经过多年的教学探索与研究,使上述问题得到较好解决。 相似文献
2.
3.
4.
5.
6.
茶叶中咖啡因的超临界流体分析 总被引:6,自引:0,他引:6
用超临界流体法 (SFC)测定茶叶中的咖啡因 ,在二氧化碳流动相中加入体积分数为 5 %的甲醇后 ,得到了良好的分离效果。该方法具有样品前处理简单 ,共存组分不干扰测定 ,分析速度快等优点 ,可以用于茶叶中咖啡因的快速分析。 相似文献
7.
8.
树脂对茶多酚与咖啡因的吸附分离 总被引:7,自引:1,他引:7
从低档绿茶末的水提取液中,利用离子交换,吸附树脂成功地分离出茶多酚与咖啡因,并详细考察了其交换与吸附性能。与其它方法相比,该树脂法具有产品收率高,成本低廉等特点。 相似文献
9.
模拟退火神经网络用于药物液相色谱梯度分离条件的优化。使用均匀设计法以乙腈在线性梯度展开时的初始浓度和线性梯度的斜率为优化参数,对六种药物混合体系进行优化。采用退火神经网络方法建立了有效的分离条件预测模型。对神经网络模型所预测的最佳分离条件进行试验,分离结果满意。模拟退火神经网络可有效地用于药物液相色谱分离条件的优化。 相似文献
10.
11.
To replace costly and time-consuming experimentation in laboratory, a novel solubility prediction model based on chaos theory, self-adaptive particle swarm optimization (PSO), fuzzy c-means clustering method, and radial ba- sis function artificial neural network (RBF ANN) is proposed to predict CO2 solubility in polymers, hereafter called CSPSO-FC RBF ANN. The premature convergence problem is overcome by modifying the conventional PSO using chaos theory and self-adaptive inertia weight factor. Fuzzy c-means clustering method is used to tune the hidden centers and radial basis function spreads. The modified PSO algorithm is employed to optimize the RBF ANN connection weights. Then, the proposed CSPSO-FC RBF ANN is used to investigate solubility of CO2 in polystyrene (PS), polypropylene (PP), poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA), respec- tively. Results indicate that CSPSO-FC RBF ANN is an effective method for gas solubility in polymers. In addition, compared with conventional RBF ANN and PSO ANN, CSPSO-FC RBF ANN shows better performance. The values of average relative deviation (ARD), squared correlation coefficient (R2) and standard deviation (SD) are 0.1071, 0.9973 and 0.0108, respectively. Statistical data demonstrate that CSPSO-FC RBF ANN has excellent prediction capability and high-accuracy, and the correlation between prediction values and experimental data is good. 相似文献
12.
基于近红外光谱的人工神经网络研究STR基因座分型方法 总被引:1,自引:0,他引:1
以D16S539基因座的3种(9-9、9-11、11-11)基因型为例,设计引物扩增包含该多态性位点的1段DNA片段,获得了3种基因型建模样本各50个.基于近红外光谱(NIRS)结合误差反向传播人工神经网络(BPANN)建立了测定短串联重复序列(STR)基因型的判别模型,所建立的判别模型的校正均方根残差和预测集均方根误差分别为0.082 5、0.072 5,预测准确率均为100%.该方法不需任何前处理,只需一步PCR扩增和NIRS检测即可实现STR基因型判别,具有简单、快速、低成本等优点. 相似文献
13.
人工神经网络法用于高效毛细管电泳分离条件优化的研究 总被引:9,自引:1,他引:8
把人工神经网络(ANN)法应用于高效毛细管电泳(HPCE)分离条件的优化,给出了反向传播(BP)的ANN模型的具体算法。用正交试验法同时考察了缓冲溶液组成、浓度、pH值和有机添加剂浓度等实验因素对HPCE分离合成色素和防腐剂的影响,采用误差反向传播方法建立了有效的ANN预测模型,预测最佳分离条件,获得了满意的分离结果。 相似文献
14.
15.
Siripon Anantawaraskul Mahapon Toungsetwut Ratchadaporn Pinyapong 《Macromolecular Symposia》2008,264(1):157-162
An artificial neural network (ANN) is applied to determine appropriate parameters in copolymerization of ethylene and 1-octene via metallocene catalytic system for producing a copolymer with desired chain microstructures. The polymerization parameters of interests are polymerization temperature, ethylene pressure, and the amount of hydrogen used. The ANN used is a feed-forward network with a back propagation learning method and has a 5-6-6-3 architecture. When comparing with both training and testing experimental data sets, it was found that ANN can provide a good guesstimation of polymerization parameters. 相似文献
16.
Huixian Wei Jianguo Ma Zhengwu Wang 《Journal of Dispersion Science and Technology》2013,34(3):319-326
Formulation optimization of emulsifiers for preparing multiple emulsions was performed in respect of stability by using artificial neural network (ANN) technique. Stability of multiple emulsions was expressed by the percentage of reserved emulsion volume of freshly prepared sample after centrifugation. Individual properties of multiple emulsions such as droplet size, δ, viscosity of the primary and the multiple emulsions were also considered. A back‐propagation (BP) network was well trained with experimental data pairs and then used as an interpolating function to estimate the stability of emulsions of different formulations. It is found that using mixtures of Span 80 and Tween 80 with different mass ratio as both lipophilic and hydrophilic emulsifiers, multiple W/O/W emulsions can be prepared and the stability is sensitive to the mixed HLB numbers and concentration of the emulsifiers. By feeding ANN with 39 pairs of experimental data, the ANN is well trained and can predict the influences of several formulation variables to the immediate emulsions stability. The validation examination indicated that the immediate stability of the emulsions predicted by the ANN is in good agreement with measured values. ANN therefore could be a powerful tool for rapid screening emulsifier formulation. However, the long‐term stability of the emulsions is not good, possibly due to the variation of the HLB number of the mixed monolayers by diffusion of emulsifier molecules, but can be greatly improved by using a polymer surfactant Arlacel P135 to replace the lipophilic emulsifier. 相似文献
17.
18.
人工神经网络用于高效液相色谱分析条件的优化 总被引:12,自引:1,他引:11
本文采用人工神经网络的线性网络法(LMS)优化高效液相色谱的分析条件,考察了样本集类型和不同初始权值对优化结果的影响。结果表明,模拟的精度与样本集类型有关,而在一定置信区间与初始权值无关。 相似文献