微机用于柱色谱条件的优化选择——正交试验设计及方差分析评价

多因素的“正交试验设计”,能用较少的试验次数获得尽可能全面的信息,且能在各因素都变化的条件下比较并较快地找到好的试验点,因而也被用于分析测试的条件选择。试验结果用方差分析可以判断各因素影响的大小和确定控制因素,但手工计算十分费时,应用微型计算机可以解决繁复的数字运算。 我们利用正交表L_(18)(2~1×3~7)安排试验,选择微粒填充柱色谱的最佳操作条件,     

正交试验设计法简介

一项科学试验要达到预期的目的,除有正确的指导思想外,还和方法十分有关。试验安排得好,次数不多就能获得成效;如果试验的计划安排不妥,盲目试验,不仅增加试验次数,延长周期,造成人力、物力、时间上的浪费,而且有时还会导致试验的失败。     

分析测试中的试验设计和优化方法 一、正交试验设计

近年来,试验设计和优化方法越来越受到分析测试人员的注意。它是研究如何科学地安排试验,以最少的人力物力消耗取得更多的或更全面的分析信息。试验安排得好,事半功倍;反之,则事倍功半,甚至达不到预期的效果。目前试验设计和优化方法还没有象统计检验、方差分析、回归分析等统计方法那样受到人们应有的重视。为了引起大家对这一问题的注意,我们将在本刊陆续分专题向大家介绍分析测试中实用的试验设计和优化方法。总共分六个专题介绍:正交试验设计;正艾多项式回归设计;均匀设计;单纯形优化法;多因素试验优化方法和用信息参量作为优化的评价指标。我们期望这些专题将对大家的工作有所裨益。     

多因素综合试验的单纯形优化法及其在分析测试上的应用

在分析测试工作中,常常会遇到多因素交互影响的问题,为寻求最佳工作条件,不少人已熟用正交试验法。但是,正交试验法与单纯形法比较起来还有某些不足之处。一是单纯形法所确定的最佳条件普遍比正交试验法更加理想,而且试验次数还少一些;二     

用正交设计制作酶过程曲线的方法

用正交设计制作酶过程曲线的方法郭慧云，张立，李彬，刘兰英（吉林大学分子生物学系，长春１３００２３）正交设计￣［１］，是用正交表安排多因素试验、用统计数学原理进行数据分析的一种科学方法。为培养学生的实际工作能力，应让本科生在专门化实验课中得到使用该方法...     

利用正交试验设计法培养学生化学实验能力的研究

正交试验设计法作为一种科学地安排多因素实验问题的方法,在优化实验条件、开展化学教学实验研究方面,已经显示了其积极作用,那 么它对于培养学生解决实验问题的能力是否有促进作用呢?为此我们设计了如下实验来研究此问题。     

正交试验结合响应面法优化诃子多糖提取工艺

采用正交试验结合响应面法优化诃子多糖的提取工艺,以诃子多糖的提取率为指标,以固液比、提取温度、提取时间和提取次数为因素,正交试验初步筛选工艺参数,响应面法做进一步优化.结果表明,多糖提取的最佳工艺条件为固液比1∶28,提取温度69℃,提取时间1h,提取次数3次,各项指标相对误差均小于2%,应用响应面法可减少诃子多糖提取时间.     

尿素包合法分离分析月见草油的脂肪酸组成包合参数的优化

研究月见草油在尿素包合过程中脂肪酸组成的变化,对包合参数进行优化。设计单因素试验和正交试验,利用气相色谱法检测月见草油被包合前后包合物中脂肪酸的组成。单因素试验表明,包合时间延长、包合温度降低、包合次数增加有利于尿素包合,最佳点依次为36 h,–15℃,4次。正交试验表明,60 h,–15℃,包合3次为最佳工艺。该条件下γ-亚麻酸纯度达78.996 4%。包合时间、包合温度及包合次数对尿素包合法分离月见草油中γ-亚麻酸的影响均为显著。     

铜合金中磷的分光光度测定——多因素正交试验法的应用

铋盐催化、抗坏血酸还原钼蓝光度法测定微量磷的方法,已在钢铁分析中得到广泛应用,但从不少资料的报导来看,一些主要试剂如钼酸铵、抗坏血酸、铋盐等的用量及酸度范围都不同程度地存在差异。本文为拟定铜合金中磷的分析方法,在影响因素较多的情况下,选用四水平五因素正交表L_(16)(4~5)安排试验程序,进行多因素正交试验,经16次试验即获得酸度条件及各试剂用量的最佳配比,从而缩短了条件试验时间,在灵敏度、稳定性等方面都收到较好效果。试验     

白屈菜提取工艺的初步研究

研究了白屈菜的提取工艺。采用正交试验法,以总生物碱得率为指标,考察乙醇浓度（A）、乙醇用量（B）、提取时间和次数（C）三个因素对白屈菜提取工艺的影响。结果表明,优化的白屈菜提取工艺为A2B2C2,即取白屈菜切成小段,加6倍量80％乙醇,加热回流提取2次,每次2h。经验证,本最佳工艺比酸水提取法好。     

神经网络在共混物改性中的应用

采用神经网络研究了PP/POE共混物的冲击性能,通过温度、配比与冲击强度的正交试验设计得出的数据来验证神经网络的效果。将10℃、20℃和30℃的实验数据用于学习训练,将0℃的实验数据用于预测。同时通过调节不同的参数得出三种不同结构神经网络模型分别进行预测。通过测试表明,神经网络对于共混改性的预测具有较好的效果。将神经网络方法用于聚合物共混改性的数据分析,能明显减少实验次数,提高实验效率,快速完成共混材料的产品配方设计,并得出了该网络类型下的模型参数调控的大致方向,表明对于小样本数据,较少的隐藏层与神经单元数量能取得更好的预测效果。     

Analytical utility of coupled transport across a supported liquid membrane Selective preconcentration of zinc

A liquid membrane comprising 5-10% bis(2,4,4-trimethylpentyl)phosphinic acid in dodecane that is supported between an aqueous sample at pH 4.7-6.0 and a 0.1M HCl receiver results in uphill transport of Zn(II) from the sample into the receiver. With 2 ml of receiver, a 5 cm(2) membrane and 60 min dialysis time, Zn(II) is preconcentrated by a factor of ca. 13 when the initial concentration in the sample is in the range 1.5 x 10(-7)-1.5 x 10(-4)M. The enrichment factor is directly proportional to time up to 30 min since the transport rate of Zn(II) across the membrane is constant over this period. At longer times the flux is slowed as the system begins to approach equilibrium. The presence of other metals such as Cu(II), Co(II), Ni(II), Cd(II), Pb(II) and Fe(II) does not change the enrichment factor for Zn(II), even when the interferent is at a concentration high enough for the rate of transport (nmole/min) of the interferent and Zn(II) to be about the same. The flux of Zn(II) was about 40 times that of Cu(II) and 100 times that of Co(II) when their concentrations in the sample were equal. The other metal ions examined are not significantly transported.     

Motion of a disordered polypeptide chain as studied by paramagnetic relaxation enhancements, 15N relaxation, and molecular dynamics simulations: how fast is segmental diffusion in denatured ubiquitin?

Molecular dynamics (MD) simulations have been widely used to analyze dynamic conformational equilibria of folded proteins, especially in relation to NMR observables. However, this approach found little use in the studies of disordered proteins, where the sampling of vast conformational space presents a serious problem. In this paper, we demonstrate that the latest advances in computation technology make it possible to overcome this limitation. The experimentally validated (calibrated) MD models allow for new insights into structure/dynamics of disordered proteins. As a test system, we have chosen denatured ubiquitin in solution with 8 M urea at pH 2. High-temperature MD simulations in implicit solvent have been carried out for the wild-type ubiquitin as well as MTSL-tagged Q2C, D32C, and R74C mutants. To recalibrate the MD data (500 K) in relation to the experimental conditions (278 K, 8 M urea), the time axes of the MD trajectories were rescaled. The scaling factor was adjusted such as to maximize the agreement between the simulated and experimental (15)N relaxation rates. The resulting effective length of the trajectories, 311 μs, ensures good convergence properties of the MD model. The constructed MD model was validated against the array of experimental data, including additional (15)N relaxation parameters, multiple sets of paramagnetic relaxation enhancements (PREs), and the radius of gyration. In each case, a near-quantitative agreement has been obtained, suggesting that the model is successful. Of note, the MD-based approach rigorously predicts the quantities that are inherently dynamic, i.e., dependent on the motional correlation times. This cannot be accomplished, other than in empirical fashion, on the basis of static structural models (conformational ensembles). The MD model was further used to investigate the relative translational motion of the MTSL label and the individual H(N) atoms. The derived segmental diffusion coefficients proved to be nearly uniform along the peptide chain, averaging to D = 0.49-0.55 × 10(-6) cm(2)/s. This result was verified by direct analysis of the experimental PRE data using the recently proposed Ullman-Podkorytov model. In this model, MTSL and H(N) moieties are treated as two tethered spheres undergoing mutual diffusion in a harmonic potential. The fitting of the experimental data involving D as a single adjustable parameter leads to D = 0.45 × 10(-6) cm(2)/s, in good agreement with the MD-based analyses. This result can be compared with the range of estimates obtained from the resonance energy transfer experiments, D = 0.2-6.0 × 10(-6) cm(2)/s.     

Four-level orthogonal array design as a chemometric approach to the optimization of polarographic reaction system for phosphorus determination

It is the purpose of the present work to provide information on the four-level orthogonal array design and data analysis for the optimization of analytical procedures. In the theoretical part, the construction and characteristics of the OA(16)(4(5)) matrix is described in detail, followed by the data analysis strategy, in which the significance of the different factors is quantitatively evaluated by an analysis of variance (ANOVA) method including per cent contribution, and the difference among four levels for each factor is determined by Duncan's multiple F test. Furthermore, a third-order polynomial model representing response surface is established to estimate the effects for the factors with significant influences. In the application part, the proposed four-level orthogonal array design and data analysis method were applied to optimize polarographic reaction system for phosphorus determination. By conducting 16 preplanned experiments that span the maximum working range of the system, the best experimental conditions for achieving the largest response can be obtained. The expected value for each experimental trial calculated by the third-order regression equation established is in good agreement with the corresponding experimental value. To confirm the validity of the optimization procedure, additional experiments using the recommended conditions were performed. The results demonstrate that satisfactory results can be acquired. Therefore, the proposed four-level orthogonal array design as a chemometric approach to optimize the polarographic reaction system for phosphorus determination is rather efficient and effective.     

全钒液流电池用磺化聚醚醚酮/锂皂石质子膜的结构及性能

通过溶液流延法制备了磺化聚醚醚酮/锂皂石(SPEEK/Lap)复合膜, 对其物理化学性质、 机械性能、 化学稳定性及单电池性能进行了测试. 在SPEEK基质中引入的Lap有效改善了复合膜的质子传导率、 溶胀率和机械性能. 当Lap添加量(质量分数)从0.2%增到1.5%时, 复合膜的质子传导率随之增加(19.9~23.6 mS/cm). SPEEK/Lap-0.2复合膜的自放电时间为57.2 h, 是Nafion 117膜的2.4倍和纯SPEEK膜的1.5倍. 在80 mA/cm ²电流密度下, SPEEK/Lap-0.2复合膜的电压效率(VE, 86.5%)和能量效率(EE, 84.0%)明显高于Nafion 117膜(VE: 83.8%, EE: 80.7%)和纯SPEEK膜(VE: 81.4%, EE: 78.9%). 同时, SPEEK/Lap-0.2复合膜经100次充放电循环测试后具有良好的循环稳定性和结构稳定性.     

聚苯乙烯负载席夫碱Mo(Ⅵ)配合物合成、表征及其在环己烯环氧化反应中的催化活性

合成了聚苯乙烯负载乙二胺缩水杨醛席夫碱与Mo(Ⅵ)的配合物,并对其结构进行了表征.该配合物催化环己烯环氧化反应与小分子配合物MoO₂(acac)₂相比,具有更优良的催化活性和选择性;建立了催化剂中Mo分析和环氧环己烷气相色谱分析新方法;探讨了配合物及环氧环己烷合成过程诸因素的影响;优化了环氧环己烷合成条件,即以n(t-BuOOH)=0.1mol计,n(C₆H₁₀)∶n(t-BuOOH)=3∶1,溶剂5mL,反应温度80℃,时间60min.在该条件下,环氧环己烷收率(以t-BuOOH计)99.2%以上,质量分数约99.5%(GC检测).催化剂循环使用5次后,未见活性明显下降,环氧环己烷收率(以t-BuOOH计)仍接近99%.     

Peroxide dynamic crosslinking in impact modification of polypropylene with polybutadiene

Polypropylene was blended with polybutadiene in an internal mixer in order to improve its toughness. The rubber content ranged from 10 to 20 wt. % and dicumyl peroxide (DCP) was added to provide required radicals for dynamic crosslinking of polybutadiene, and for in-situ compatibilization of the phases. This was done using two sequences of mixing. In addition, zinc dimethacrylate was utilized as a co-agent to control chain scission of PP, enhance the interfacial reactions and increase compatibility of the components. In obtaining the optimum blend, the Taguchi orthogonal experimental design was applied and results of Izod impact strength test were concordantly related to crystallinity of the polypropylene, morphology of the blends and reactions that may occur. The impact strength was increased about four times at best in comparison to the neat polypropylene, showing versatility of this way of toughening which may be improved further.     

山楂叶中熊果酸提取工艺研究

以熊果酸的提取率为指标,采用单因素与正交实验相结合的方法对提取工艺进行了优化,得到最佳提取参数为:乙醇体积分数95%、提取温度85℃、提取时间110min、液固比5:1、提取次数3次。在该条件下,熊果酸提取率为93.47%。该工艺简单合理,为工业生产提供了理论参考。     

Statistical experimental design for bioprocess modeling and optimization analysis

The statistical design of experiments (DOE) is a collection of predetermined settings of the process variables of interest, which provides an efficient procedure for planning experiments. Experiments on biological processes typically produce long sequences of successive observations on each experimental unit (plant, animal, bioreactor, fermenter, or flask) in response to several treatments (combination of factors). Cell culture and other biotech-related experiments used to be performed by repeated-measures method of experimental design coupled with different levels of several process factors to investigate dynamic biological process. Data collected from this design can be analyzed by several kinds of general linear model (GLM) statistical methods such as multivariate analysis of variance (MANOVA), univariate ANOVA (timesplit-plot analysis with randomization restriction), and analysis of orthogonal polynomial contrasts of repeated factor (linear coefficient analysis). Last, regression model was introduced to describe responses over time to the different treatments along with model residual analysis. Statistical analysis of biprocess with repeated measurements can help investigate environmental factors and effects affecting physiological and bioprocesses in analyzing and optimizing biotechnology production.     

Local order and dynamics in supercooled water: a study by IR spectroscopy and molecular dynamic simulations

Micron-sized water droplets in a cryogenic flow tube were probed by IR spectroscopy. The analysis of the IR spectra suggests that there is a relative increase of about 30% in the fraction, f(L), of low density domains in water on cooling over the temperature range between 300 and 240 K. The results derived from the experiments agree qualitatively with those of molecular dynamics (MD) simulations in terms of the increase in the f(L) values. The MD simulations show that the intensities of the mode at about 100 cm(-1) for the molecules in the low density domains are reduced in comparison to the average, while the intensities and frequencies of the librational mode at 600 cm(-1) are increased. Furthermore, the reorientations (dielectric relaxation times) in these domains are found to be somewhat slower, pointing to the fact that these low density "cages" live longer than the average local molecular environments in supercooled water.