非平衡塔板理论的几个问题

本文用非平衡方法对塔板理论进行了重新处理,导出了描述塔板过程的统一方程（平衡或非平衡）如下：（注：符号ｐｆ（ｒ,ｎ）表示交换ｎ次后第ｒ号塔板流动相中的物质分数;符号ｑｆ（ｒ,ｎ）表示交换ｎ次后第ｒ号塔板固定相中的物质分数）经计算机数值计算,得到如下初步结果：（１）色谱峰是不对称峰,其形状与流速有关。流速增大,不对称性将增大。流速的改变,也会引起峰形的其它改变。（２）色谱峰的峰宽与流速有关。流速增大,峰宽（以塔板数为量纲）将增大。（３）色谱峰的峰高与流速有关。流速增大,峰高将减小。     

流动注射分析中试样分散的对流—扩散理论

用两种方法求解适合于单一平直管道且无化学反应的流动注射分析（ＦＩＡ）体系的对流－扩散方程，得到了述塞状进样在管道中分散后的浓度分布公式，从而得到Ｆ曲线，讨论了反应管和采样管的内径和长度、流速和扩散系数对峰形和分散度的影响；采用数值法解出半峰宽和扩散系数的关系，提出了两种测定扩散系数的方法，为ＦＩＡ体系的设计和指示物质、操作条件的选择提供了理论依据。     

磁化后掺水乳化重油分散度的实验研究

乳化重油的分散相（水）微粒大小对重油掺水乳化燃烧技术的应用效果有很大影响,本人在过去实验的基础上,用光学反射显微镜法对磁场作用下掺水乳化重油中分散相（水）的分散度进行了测定,研究了乳化重油的分散度与磁场强度、温度以及流速之间的关系,实验结果表明：磁化后有利于乳化重油的微细化,且效果比较显著;温度的升高有利于分散相（水）的微细化,兼顾能耗和燃油的发泡、沸腾现象,以及磁化后温度的升高对分散度的影响减少,有一个合理的温度范围;磁化后分散度与流速的关系呈峰值关系,本实验中流速较佳值为8m/s;磁场强度的增大也有利于微细化,磁场强度太高或太低均不会取得太好的处理效果,在1000GS－1400GS范围内为宜。     

温度对流动注射分析中溶液分散影响的研究

本文从理论和实验两方面进行了温度对流动注射分析中溶液分散影响的研究。结果表明,随着溫度升高,峰高值增大,半峰宽减小,保留值延长,峰面积则基本不变。增大进样体积和流速能够减小温度对峰高、半峰宽和保留时间的影响程度。     

测定青霉素浓度的流动注射分析系统及其特性的研究

基于青霉素在青霉素酶的作用下会水解生成青霉素酸，降低了系统的ｐＨ值，一个青霉素流动注射分析系统在我们实验室建立起来了。大量的实验结果表明，青霉素浓度与［Ｈ￣＋］输出峰面积成正比，与［Ｈ￣＿］输出峰高成非线性关系，青霉素浓度的峰面积计算法比峰高计算法具有更高的准确性。     

流动注射分析中试样分散的对流-扩散理论

用两种方法求解适合于单一平直管道且无化学反应的流动注射分析(FIA)体系的对流-扩散方程,得到了描述塞状进样在管道中分散后的浓度分布公式,从而得到F曲线。讨论了反应管和采样管的内径和长度、流速和扩散系数对峰形和分散度的影响;采用数值法解出半峰宽与扩散系数的关系,提出了两种测定扩散系数的方法,为FIA体系的设计和指示物质、操作条件的选择提供了理论依据。     

基于积分渐进展开的气相色谱重叠峰快速解析法

论文提出用积分渐进展开解析气相色谱重叠峰,该方法有3个主要步骤：首先将谷峰或肩峰分成两个积分区域,得到一个子区域的积分方程和一个重叠峰面积的代数方程;然后用数值积分求出这两个方程计算中所需要的峰面积,再用积分渐进公式将积分方程展开成代数方程;最后,将这两个方程与峰高约束方程联立后,得到一个非线性代数方程组,用Gauss-Seidel迭代可以快速求解方程组,方程收敛的最大迭代次数不超过20次。仿真和实验结果表明,解析的峰高和峰面积误差均很小,峰面积最大误差低于6.44%,峰高的最大误差约为6.80%。由于该算法精度高,效率高,所以这个方法可以用于气相色谱重叠峰和一般色谱峰的实时在线解析。     

高效液相色谱峰压缩中灵敏度增加值与峰压缩因子的关系研究

以从塔板理论得到的色谱流出曲线为基础,推导了高效液相色谱(HPLC)双流动相分离场中实现峰压缩时,峰压缩因子(峰压缩后的半峰宽与未进行峰压缩时的半峰宽的比值)和峰高表示的灵敏度变化(峰压缩后的峰高与未进行峰压缩时的峰高的比值)的关系,结果表明峰高表示的灵敏度增加值等于峰压缩因子的倒数.并用色氨酸、香豆素、苯和2-硝基酚在不同速率差实现堆积时的相关参数进行了验证.实验结果表明,这些化合物在各个峰压缩条件下的峰压缩因子倒数和实际灵敏度增加值相等,实验结果与理论推导结果一致.考察了该关系式在实际样品测定中的应用,结果表明灵敏度增加值等于峰压缩因子的倒数,这也与理论部分的结果一致.     

土木香内酯的电化学研究

用单扫示波极谱法，在０１ｍｏｌ／ＬＬｉＣｌ中，土木香内酯有两个极谱还原波：Ｐ１（－１４１Ｖ）和Ｐ２（－１５１Ｖ）（ｖｓ．ＳＣＥ），峰Ｐ１的峰高与浓度在４３×１０－７～１２×１０－６ｍｏｌ／Ｌ和１３×１０－６～１５×１０－５ｍｏｌ／Ｌ范围内呈线性关系，可进行定量分析，用标准加入法能作定性分析，其检测限为２６×１０－７ｍｏｌ／Ｌ。测定了中药土木香中总内酯的含量，其结果令人满意。实验证明土木香内酯的电极过程为带有吸附性的不可逆的逐级电子反应过程，另外，还证明了Ｈ２Ｏ２可催化峰Ｐ１和羟基自由基可催化峰Ｐ２，讨论了土木香内酯清除由邻苯三酚自氧化产生的活性氧自由基（Ｏ－·２）的作用。     

混合表面活性剂存在下用溴邻苯三酚红紫外光度法测锑

在ＯＰ－１０及ＣＴＡＢ混合表面活性剂存在下，锑（Ⅲ）与溴邻苯三酚红形成的络合物在紫外区及可见区的均有很强的吸收峰，就峰高和半宽度而言，紫外区的吸收峰无论是在优化不审非优化条件下皆比同一体系在可见区的吸收峰更适合于Ｓｂ（Ⅲ）的测定，为此，本文建立了在混合表面活性剂存溴邻苯三酚红在紫外区（３１２ｎｍ）测定Ｓｂ（Ⅲ）的分光光度方法，在优化条件下，Ｓｂ（Ⅲ）在０～４０μｇ／１０ｍＬ内符合比耳定律，摩尔吸光     

Segmental flow-injection analysis: device and applications

A segmental flow-injection system which possesses features of both flow-injection analysis (FIA) and continuous-flow analysis (CFA) has been built. The whole sample zone is segmented by only two air bubbles. A valve has been designed to inject the sample and the bubbles into the carrier stream in a quantitative way. The position of the segmentation can be accurately controlled and the amount of the air introduced is minimized (only 5% of the bubbles in CFA) so that the stability of flow-rate can be improved. In this system, longer residence times (10 min or more) and higher reaction temperatures (up to 95 °C) can be obtained without loss of peak height or loss of sampling frequency in comparison with FIA. Owing to the good reproducibility the determination can still be performed when the equilibrium stare is is not obtained. The determination of total amino acids in tea with ninhydrin reagent, ammonia in natural water with phenol-sodium hypochlorite reagent and trace amounts of Cu(II) and V(V) by means of catalytic spectrophotometry are given as examples.     

The system evaluation strategy in practice,allowing direct estimation of peak heights and limits of detection in HPLC

Summary The novel system evaluation strategy recently developed describes an HPLC system in terms of two parameters, that ideally are independent of the test conditions. These describe the peak height response, or dilution, occurring in the column and the system. Limits of detection (LOD’s) can thus also be calculated. System parameters, (e.g. cell length, external dispersion), chromatographic parameters (e.g. retention, column length, flow-rate), and sample parameters (e.g. sample volume & absorptivity), are all included. Consequently this approach is applicable to the chromatographer and LC system designer alike. The system evaluation strategy was previously demonstrated under typical chromatographic conditions, on two HPLC systems, and systematic changes were studied. In principle this is applicable to any compound under any chromatographic conditions, on any column. This is now to be investigated further, under a wide range of conditions, and applied to the calculation of an LOD in a real LC analysis.     

Confluent streams in flow injection analysis

The addition of a confluent stream increases the mean length of the sample zone and simultaneously decreases the involved concentrations. Simple equations describing these effects under ideal mixing conditions are proposed. The effects of the confluent stream on the overall sample dispersion may be more or less compensated, depending on the decrease in the post-confluence dispersion. When this compensation is almost total, a paradoxical situation occurs, in which the recorded peak height becomes practically unaffected by variations in the flow rate of the merging stream. In this situation, the peak width approaches a limiting value which is independent of the injected volume and of the flow rate of the confluent stream. Limiting values for the peak width and for the mean length of the sample zone are postulated. When the post-confluence dispersion is negligible, the effects of the confluence appear in the recorded peak. The confluent stream addition reduces the overlap between successive sample zones. The site of the confluence may be an important dispersion factor. A saturation index is proposed and practical implications are discussed.     

Contribution of axial dispersion to band spreading in perfusion chromatography

A new interpretation of the band spreading data in perfusion chromatography is proposed by investigating the relative importance of axial dispersion in perfusive beds. Elution chromatography of proteins (bovine serum albumin and lysozyme) under non-retained conditions on two kinds of reversed-phase perfusive supports (POROS R1/H and POROS R2/H), which have different pore structures, were carried out to obtain the axial dispersion data. The Knox equation and some empirical correlations for dispersion coefficients in porous media were applied to correlate the experimental data. The influences of particle properties, solute molecular sizes and flow velocity on the dispersion coefficient were elucidated. Axial dispersion was recognised to be the main contributor to peak broadening in perfusion chromatography. The dependence of the height equivalent to a theoretical plate on flow-rate was found to be the result of the velocity dependence of the axial dispersion. The dispersion coefficient in a perfusive column can be well represented both by a power-law relationship and a correlation derived based on stochastic theory. Pursuant to these, it was found that pore size distribution of the perfusive particles and solute molecular size are important parameters, which influenced the dispersion results significantly.     

Comparison of Aqueous,Micellar and Microemulsion Carriers in Flow Injection Analysis. The Base Hydrolysis of Acetylsalicylic Acid

Abstract

The potential applicability of surfactant solutions as carrier streams in flow injection analysis is examined. The reaction rates determined for the base catalyzed hydrolysis of acetylsalicylic acid in aqueous, micellar and microemulsion solutions show a rate enhancement of 40% for the static microemulsion system when compared to the aqueous solution. However, when the identical microemulsion solution is employed as a carrier stream in flow injection analysis with ultraviolet detection, this enhancement in rate is not observed. To our knowledge, all previous work employing microemulsions in FIA has been concerned only with detection enhancement, here we present direct comparisons between aqueous and microemulsion carriers concerning rates of reaction, peak dispersion and analytical figures of merit. The loss in relative sensitivity can be traced to the increased dispersion in the microemulsion system (D = 14.36) when compared to the aqueous carrier (D = 12.52). Additionally, an increased skewness was observed in the peaks obtained with a microemulsion carrier, yielding further information about the physical dispersion process occuring in the sample plug.     

Peak Profile Analysis in High Field Asymmetric Wave Ion Mobility Spectrometry

High field asymmetric wave ion mobility spectrometry (FAIMS) is a powerful tool to detect and characterize gas-phase ions, while the unsolvable partial differential equation of ions moving in ion drift tube poses a big challenge to FAIMS spectral peak analysis. In this work, a universal and effective model of FAIMS spectral peak profile has been proposed by introducing ion trajectory and loss height. With this model, the influence of the structure of ion drift tube, dispersion voltages, compensation voltages, and carrier gas flow rate on the FAIMS spectral peak characteristics like peak shape, full width at half maximum and peak height is analyzed and discussed. The results show that the influence of different factors on the FAIMS spectral peak profile can be qualitatively described by the model which agrees with the experimental data.     

Flow-rate dependence of post-column reaction chromatographic detectors and optimization of reactor length for slow chemical reactions

In high-performance liquid chromatography, use of any post-column reactor invariably involves a compromise between the conditions needed to obtain complete reaction and avoidance of excessive dispersion by band broadening in the reactor. Flow rate and the reactor geometry interact to establish the final chromatographic performance. Based on the flow-rate dependence of the peak area and peak height, post-column detectors constitute a distinct class of detectors which differ from mass-flow and concentrations-sensitive detectors such as the flame ionization and absorbance detector, respectively. The concept of reactor length optimization is developed for first-order chemical reactions in a post-column detector. The findings are applicable to both chromatographic and flow-injection systems.     

Studies on peak width measurement-based FIA acid-base determinations

Summary Studies on Peak Width Measurement-Based FIA Acid-Base Determinations Peak width measurement is employed to determine strong acid or base concentrations by injection into an aqueous indicator flowstream. Investigated parameters include concentration and pK of the indicator, dimensions and nature of the dispersion tube, signal level employed for peak width measurement, sample volume, carrier flow rate, viscosity of the carrier stream and the diffusion coefficient of the analyte.     

Investigation of carbon dioxide modified supercritical and near supercritical carrier streams for flow injection systems

Since flow injection (FI) is a dilution technique, efforts have been undertaken to minimize online dilution or dispersion. Solutes in supercritical fluids exhibit increased diffusion coefficients which have been shown to decrease dispersion of the sample zone. This work investigates the use of supercritical fluids (or CO₂ modified fluids) as carrier streams for FI. Both a non-reacting tracer and an online chemical reaction were employed to investigate the behavior of solutes in supercritical and near critical systems. Further, these results are compared to those obtained in the system studied with a conventional carrier stream. Plots of peak response vs% CO₂ modifier increase with a sharp break at moderate modifier composition (20–30%). Plots of peak variance vs% CO₂ modifier show decreased variance with increasing % modifier. The system was also optimized with regards to temperature and pressure. The optimized system displayed improved limits of detection and decreased variance relative to 0% CO₂ modifier carrier streams.     

Effective on-line coupling of HPLC and flame-AAS by means of hydraulic high pressure nebulization

Summary Hydraulic high pressure nebulization is used as an effective way of on-line coupling of HPLC to flame-AAS for speciation of metal compounds in the ng range. Compared to coupling with a conventional nebulizer a signal enhancement by a factor of 7.5 (peak height) and 10.1 (peak area) for copper is obtained. Using an injected volume of 50 μL the detection limits for Cu, Fe, Ni and Cd are below 0.1 μg/mL (=5ng) and for Mg below 0.01 μg/mL (=0.5ng). The effects of HPLC flow-rate and nebulization nozzle diameter on the signal peak height have been investigated. The performance of the system is demonstrated using speciation of iron. A base-line separation of Fe(II) and Fe(III) is achieved within two minutes. Also species changes (Fe acetate to Fe citrate) can be analysed using the proposed system.