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11.
12.
Summary A simplex method for determining the constantsS andk
o from the equation lnk’=lnk
o−S ϕ (was developed and applied to the reversed phase separation of high molar mass polystyrenes using gradients of any curvature.
Experimental retention times described using the equation had a standard deviation of 1.1%. The inclusion of a quadratic term
in the equation was found to be unwarranted. BothS and lnk
o varied linearly with ln molar mass. The logarithm of peak width of an eluting polystyrene peak was found to be a linear function
of the mobile phase composition at elution. The slope was equal toS. 相似文献
13.
Leonid M. Blumberg 《Journal of separation science》1993,16(1):31-38
In linear chromatography (i.e. chromatography performed in the absence of sample overloading), when the plate height of a column is roughly uniform along its length, variations in the velocities of solutes are the only possible causes of erosion of efficiency. The sources of these variations (variations in capacity ratio and in the density of the mobile phase, etc.) play no direct role in the erosion of efficiency except through their effect on solute velocities. In other words, what eventually causes the erosion of efficiency is merely variation in the time required for solutes to traverse equally small segments of a column. Significant erosion can only arise from abrupt and deep deceleration of solutes in one or several relatively small segments of a column. If erosion of efficiency caused by pressure gradients in linear SFC is to be large, the depth and the sharpness of the deceleration of a solute must go beyond that hitherto confirmed experimentally. Many relevant examples are analyzed graphically. 相似文献
14.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
15.
Dietger Leyendecker Dagmar Leyendecker Franz P. Schmitz Ernst Klesper 《Chromatographia》1987,23(1):38-42
Summary In supercritical fluid chromatography (SFC), the elution behavior of styrene oligomers in pentane depends greatly on the degree of oligomerization, n. The influence of capacity ratio, k, on the lower oligomers up to about n=11 resembles the behavior of other substrates of low molecular weight, like aromatic hydrocarbons. Thus, with pentane of 100 bar and below, minima are found in plots of k versus temperature. In contrast, the k of oligomers of higher molecular weight (n>11) increase monotonously with increasing temperature. The studies were performed using oligostyrene fractions obtained by semipreparative SFC fractionation. 相似文献
16.
The purpose of this paper is to present a new primal extreme point algorithm for solving assignment problems which both circumvents and exploits degeneracy. The algorithm is based on the observation that the degeneracy difficulties of the simplex method result from the unnecessary inspection of alternative basis representations of the extreme points. This paper characterizes a subsetQ of all bases that are capable of leading to an optimal solution to the problem if one exists. Using this characterization, an extreme point algorithm is developed which considers only those bases inQ. Computational results disclose that the new algorithm is substantially more efficient than previously developed primal and primal-dual extreme point (simplex) methods for assignment problems. 相似文献
17.
Paul G. Mezey 《Theoretical chemistry accounts》1985,67(1):43-61
The family of all possible reaction mechanisms on a potential surface has an algebraic structure with potential applications in quantum chemical molecular design and synthesis planning.Transformation properties and equivalence relations of reaction paths on potential energy hypersurfaces lead to a topological definition of reaction mechanisms. The family of all fundamental reaction mechanisms on the hypersurface has a group structure,the fundamental group of an appropriately defined topological space. Isomorphism and homomorphism relations between fundamental groups of reaction mechanisms are used to characterize the chemically important topological properties of various subsets of a hypersurface, or those of different excited state hypersurfaces. 相似文献
18.
The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium
was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair,
lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization
rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization
with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid
chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to
reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results
showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent
with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the
cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence
of ferrous ion was also necessary together with the lactate and sulfate substrates. 相似文献
19.
Summary Plots of capacity factor and retention time vs. elution solvent composition were proved to be useful to interpret the retention
behavior of Kepone and its metabolites in a reversed-phase solid-phase extraction and to optimize the elution solvent. The
percent recovery of Kepone was largely improved when the solvent was optimized. The standard deviations of the results of
extractions were also improved upon the optimization of the solvent. 相似文献
20.
在政府推进部门预算制度和财政拨款管理制度改革的大环境下,国家自然科学基金逐渐采用预算管理制度,因此需要平衡资助计划和支出预算.本文在建立科学基金计划和预算的协调模型中,提出计划批准对年度支出敏感度的概念,设计了对经费使用的计划和支出纵横两维拨付的动态监控方法.并且通过模型的计算,可以快速给出综合考虑资助计划发展和使用经费有效两个方面因素的多种方案,供决策者参考. 相似文献