微柱液相色谱的研究进展

介绍了微柱液相色谱（μ-LC）。从理论上简单讨论了μ-LC的柱特性、色谱洗脱效应和柱外效应等一系列问题,综述了μ-LC的柱技术的最新进展,讨论了μ-LC对仪器和附件的要求,特别是微流量输液和检测技术,还探讨了μ-LC与多维色谱、质谱等技术的联用。     

Ion-exchange chromatography of glycolatocomplexes of rare earths

Summary The ion-exchange behavior of glycolatocomplexes of the rare earths (Sc, Y and lanthanides) with 1-octanesulfonate as the hydrophobic ion has been investigated in aqueous glycolate media. The system is capable of separating adjacent light intra rare earths, La-Ce-Pr-Nd-Y-Sm, and heavy rare earths, Ho-Er-Tm-Yb-Lu-Sc, from each other with good resolution by gradient elution at room temperature. Intermediate rare earths, Dy-Tb-Gd-Eu-Sm, are difficult to separate from each other. The position of Y in the eluate is different from that found with most other eluent systems used for rare earth separations, being between Nd and Sm.     

Persistent Organic Pollutants – Are Our Methods Sensitive and Selective Enough?

Due to the exponential growth of the world population and a strong worldwide economic development, humans are increasingly exposed to chemicals. This is particularly true for persistent, toxic chemicals that accumulate in organisms including humans. The presence of these persistent organic pollutants (POPs) has been reported since the 1960s. Analytical methods developed for the determination of POPs in wildlife, food, feed, sediments, dust, air, and humans have seen a tremendous improvement in sensitivity and selectivity. Detection limits of 0.1 mg/kg for pesticides in the 1960s have decreased down to < 0.1 ng/kg for dioxins presently. On the other hand, due to new toxicological insights, authorities nowadays often demand much lower detection limits than in the early days of discovery. This paper compares the lowest effectual levels of a number of POPs with the analytical capabilities of modern laboratories in terms of sensitivity and selectivity. Methods discussed are gas chromatography (GC), including multi-dimensional GC and liquid chromatography (LC), combined with electron capture detection (for GC) or with different mass spectrometric detectors. The conclusion is that the still improving sensitivity of current methods is sufficient to allow detection of POPs at a level clearly below the lowest observable adverse effect levels. Selectivity has also improved, but given the high complexity of some of the POPs and the multitude of POPs and other chemicals to which we are exposed, further developments in selectivity are still badly needed. To limit and focus the information for regulators, an effect-directed analysis is proposed as an alternative approach.     

气相色谱近年的发展

简要阐述了近几年气相色谱(GC)的发展和特点。GC是一个成熟的技术,广泛地应用于各个领域,近几年GC的发展除了继续研究新的固定相和高性能的毛细管色谱柱之外,主要在全二维气相色谱(GC×GC)、快速GC、便携式GC仪和微型GC仪几个方面。近几年新研究的GC固定相主要集中在常温离子液体和各种环糊精的衍生物。现在GC研究者趋向于使用商品化的GC毛细管柱,而商品化的GC毛细管柱应用最多的是以含5%苯基的聚甲基硅氧烷为固定相的色谱柱。GC×GC发展迅猛,特别是关于调制器的研究,已开发出十多种调制模式,并广泛地应用于各个领域。为了适应大量样品的分析和现场分析,研究和开发了多种快速GC方法和仪器以及便携式GC仪。为了仪器的小型化和专属性检测,μGC仪的研究也稳步地发展起来。     

食品中有机酸的高效液相色谱分析法

对离子交换色谱法、离子排斥色谱法和反相高效液相色谱法分析食品中有机酸的特色和近几年的研究与应用状况作一综述。     

Displacement and spacer displacement chromatography. Alteration of spot profile in displacement thin-layer chromatography

Summary Migration of spots in displacement development was investigated using a planar stationary phase. The effects of the presence or absence of the additive substances in the carrier were demonstrated when these compounds also played a role in the competition for the binding sites of the stationary phase; however, they were not members of the displacement train.In the case of displacement chromatography, compounds A+B are well separated but located very closely to each other. Using a spacer (C) in the sample, the peaks or spots of A and B are aparted by C and their virtual separation is increased.When compounds A+B were displaced by each other as well as by the displacer, the presence of the additive compound C in the carrier (carrier-spacer) can transfer an otherwise displaced component (A) into the so-called overloaded elution region of the chromatogram. At the same time the additive compound C does not unconditionally reduce the performance of displacement chromatography.Presented at the 17th International Symposium on Chromatography, September 25–30, 1988, Vienna, Austria.     

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method

Summary The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.Symbols which specifically refer to gas chromatography (GC), to equilibrium headspace sampling (EHS) and to EHS-GC are marked by the corresponding acronym.     

Advances in arsenic speciation techniques

The present review describes the speciation techniques of arsenic. The principal advanced techniques discussed are gas chromatography, reversed-phase liquid chromatography, ion chromatography, capillary electrophoresis. Some other techniques are also mentioned. The extraction procedures of arsenic species from unknown samples are also discussed. Arsenic speciation is summarized in tabular form and optimizing parameters are also discussed.     

A micellar liquid chromatographic method for quality control of pharmaceutical preparations containing tricyclic antidepressants

Summary Micellar liquid chromatography methods for quality control of pharmaceutical preparations (capsules, pills, tablets, injections) containing the tricyclic antidepressants amineptine, amitriptiline, clomipramine, doxepin, imipramine, melitracen and nortriptyline alone or together with other CNS drugs like diazepam, medazepam and perphenazine are described. The methods using micellar solutions of cetyltrimethylammonium bromide as mobile phases and UV detection are rapid and reproducible. Due to the versatility of interactions in micellar liquid chromatography, it is possible determine highly hydrophobic compounds such as TCAs in a short time using mobile phases containing low organic solvent concentrations and usual flow rates, in contrast with the RP-HPLC methods proposed for these compounds. Samples preparation only requires solution and adequate dilution with the mobile phase before injection into the chromatographic system.     

Potentiometric detection of monovalent anions separated by ion chromatography using all solid-state contact PVC matrix membrane electrode

Summary An all solid-state contact tubular PVC-matrix membrane electrode has been applied for potentiometric detection of inorganic and organic monovalent anions using phosphate and hydrogen phosphate eluents at low concentrations. This is a “monovalent detection method” as the selectivity of the electrode towards monovalent anions results in some other anions being undetected unless the concentration of those other anions is higher than 10⁻³ mol dm⁻³ in the sample solution injected. It takes only eight minutes to complete the separation with a good resolution. Theoretical and practical considerations are discussed, and in particular, sensitivity, linearity, detection limit and dynamic behaviour are presented. The use of an all solid-state contact bromide-selective electrode as a detector offers so far the best simultaneous sensitivity toward all anions when compared with other detection methods. Determination of Cl⁻ and NO₃ ⁻ ions in river, rain and drinking water samples without any further sample preconcentration has been successfully achieved. The detection limit is sub-ppb for most of anions in a 20 μL injection volume.     

应用电子计算机求解色谱过程动力学方程

提出采用计算机求取色谱过程动力学方程解的方法。在此基础上考察了在Ｌａｎｇｍｕｉｒ吸附等温线情况下色谱柱效率、色谱峰的偏态、峰态与分酸系数、流动相线速、进样量之间的关系,从而明确指出,动力学过程是使色谱峰峰形拖尾的一个原因,但不是主要原因。实践中观察到的峰非对称性现象主要是分配系数非线性所致。     

Bioanalysis of fluorouracil applying liquid chromatography and valve switching

Summary Fluorouracil has been analyzed with a reversed-phase ion-pair liquid chromatographic system applying PRP-1 as the stationary phase. A valve switching technique was applied for the separation of the analyte and some other chemotherapeutic agents. The described procedure gives a rapid screening for the analyte in urine and plasma samples without interferences from late eluting solutes. Biological samples are pretreated by means of a liquid-liquid extraction resulting in a recovery of about 52% for plasma and urine with minimum detectable amounts of about 5ng/ml. The sensitivity and the selectivity of the procedure allows the monitoring of fluorouracil in body fluids and subsequent pharmaco-kinetic studies of the fluoropyrimidine.     

Centrifugal partition chromatography – A review of recent applications and some classic references

Countercurrent chromatography, based on liquid–liquid partitioning, has many technological variants. One of them is centrifugal partition chromatography, introduced by Wataru Murayama and Kanichi Nunogaki in 1982. This technique, like other countercurrent chromatography techniques, is based on the phenomenon of liquid–liquid partitioning between two immiscible liquid phases that stay at equilibrium. But the significant difference between this technique and others is the retention mechanism of stationary phase. In the case of centrifugal partition chromatography, this mechanism is based on hydrostatic force, formed by the centrifugal field in the rotor in one‐axis centrifuge. Sometimes that allows more control of stationary phase, for example, when aqueous two‐phase and other difficult solvent systems are used. However, the efficiency of the separation in centrifugal partition chromatography is also affected by a variety of parameters dependent on the sample properties in the solvent system, physical properties of the solvent system, parameters of the instrument, and the method. This article includes also recent ideas for improvements to the technique and broadening its application (e.g., (multiple) dual‐mode or elution–extrusion procedure, pH‐zone‐refining centrifugal partition chromatography, ion‐exchange centrifugal partition chromatography, online and offline coupling of centrifugal partition chromatography).     

Smart templates for peak pattern matching with comprehensive two-dimensional liquid chromatography

Comprehensive two-dimensional liquid chromatography (LCxLC) generates information-rich but complex peak patterns that require automated processing for rapid chemical identification and classification. This paper describes a powerful approach and specific methods for peak pattern matching to identify and classify constituent peaks in data from LCxLC and other multidimensional chemical separations. The approach records a prototypical pattern of peaks with retention times and associated metadata, such as chemical identities and classes, in a template. Then, the template pattern is matched to the detected peaks in subsequent data and the metadata are copied from the template to identify and classify the matched peaks. Smart Templates employ rule-based constraints (e.g., multispectral matching) to increase matching accuracy. Experimental results demonstrate Smart Templates, with the combination of retention-time pattern matching and multispectral constraints, are accurate and robust with respect to changes in peak patterns associated with variable chromatographic conditions.     

Diffusion coefficients from stopped-flow gas chromatography

Summary Mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas. The other component A is injected in a small amount instantaneously at the closed end of the column with the detector placed at the other end. By repeatedly stopping and then restoring after a short time the flow of B, narrow extra peaks are produced on the chromatographic elution curve, owing to diffusion of A into B. An equation is derived giving the area under the curve of each stop-peak as a function of time of the corresponding stop. Plotting the experimental data according to this equation permits the determination of the diffusion coefficient of A into B. Some results obtained by this method show negligible variations with changes in the experimental parameters.     

Determination of Morphological Properties of Swellable Solids by Size Exclusion Chromatography

Many technically interesting porous solids, e.g. ion exchangers or adsorbents for catalysis, are swellable polymers, i.e. the pore structure depends on the solvent medium. A method based on exclusion chromatography, permits determination of the pore size and pore size distribution in the swollen state.—Size exclusion chromatography, also referred to as gel permeation, gel filtration, or molecular sieve chromatography, is a widely employed method for the separation of dissolved substances—mostly polymer mixtures—according to their molecular size. Porous solids are used as stationary phase. Conversely, pore sizes and other structural data can be determined by exclusion chromatography. This application requires a series of standards (polymer samples) of known molecular weight. As a simple and rapid method, it has already proven valuable for such determinations in the case of rigid solids; in the case of swellable solids, this constitutes the sole method by which the pore structure can be characterized: classical methods require dry samples.     

LC-MS of enzymatic peptic haemoglobin hydrolysate produced at the pilot-plant level

Summary A method is described for the ready identification of any peptide isolated from a complex peptic haemoglobin hydrolysate produced on the pilot-plant scale. A combination of size exclusion and reversed-phase, high-performance liquid chromatography have proved to be a useful strategy for fractionation of such a mixture. This technique enabled pure peptides from the total hydrolysate to be obtained. Amino acid analysis and fast atom bombardment mass spectrometry provided the accurate composition and molecular weight of any isolated peptide. Molecular weights are compared with those deduced from size-exclusion chromatography (SEC) and the usefulness of SEC is discussed. The procedure described in this study will be useful for acquiring a better knowledge of such an hydrolysate and could be extended to other crude protein digests.Presented in part at the 8th International Biotechnology Symposium, July 17–22, 1988, Paris, France.     

高分子冠醚毛细管柱的性能研究

本文报道了3种新的聚硅氧烷侧链冠醚作气相色谱固定液,并涂渍成弹性石英毛细管柱,这种毛细管柱具有优良的色谱性能,它们具有柱效高,热稳定性好,选择性强的特点,适于分离各种异构体。     

Comparison of analytical methods for the quality control of a new formulation containing soy extract and melatonin

Three analytical methods have been developed and compared for the quality control of a new formulation (Soymen GN(R) capsules) containing soy extract and melatonin for the treatment of menopausal symptoms. The first method is based on MEKC with diode-array detection, using a mixture of basic carbonate buffer (95%) and methanol (5%), containing 55 mM SDS, as the BGE. The second method is an HPLC method with UV detection at 260 nm. The third method is an HPLC method coupled to amperometric detection which is carried out at an oxidation potential of +0.8 V. In both HPLC systems, the chromatographic separation is obtained on an RP C18 column using a mixture of ACN and an acidic phosphate buffer (25:75 v/v) as the mobile phase. A feasible pretreatment procedure with a methanol/water mixture has been implemented to achieve the quantitative extraction of the main soy isoflavones and of melatonin from the capsules. The results obtained with the three methods are in good agreement with each other and satisfactory in terms of linearity (r(2) >0.9996), precision (RSD <5.4%) and accuracy (recovery >97%). Thus, each of the three analytical methods seems to be suitable for the simultaneous analysis of the main soy isoflavones and melatonin in the new commercial formulation.