窄内径多孔层开管柱的制备及在液相色谱中的应用

近年来,微纳分离技术由于其内在的优势而受到越来越多的关注.多孔层开管柱是一种重要的微分离柱形式,与粗内径的多孔层开管柱(>25μm)相比,窄内径的多孔层开管柱具有更高的分离效率和更低的试剂消耗量.本文综述了内径≤25μm的窄内径多孔层开管毛细管柱的制备方法、与质谱检测联用技术以及在液相色谱中的应用研究进展,对其发展前景进行了展望.     

New developments and experiences with glass capillary column production and sampling techniques

Summary An introductory discussion is given on the manufacture of glass capillary columns, including details of the methods of column testing and of the properties of the inner surfaces of glass capillaries. As a result a simple method for the testing of various kinds of support surfaces is presented which allows stepwise control of the column making procedure. A new kind of pretreatment of soft glass surfaces with HCl and HF at 450°C is described which allows the production of non-polar columns with much improved tailing behaviour for strongly polar solutes. Concerning capillary column sampling a new technique of direct sampling without previous vaporisation of the sample outside the column is presented together with a double column system for selective sampling of complex mixtures.     

A micro electron capture detector for temperature programmed analysis with capillary columns for a wide range of applications

Summary The electron capture detector (ECD) has become a indispensable and widely used tool for the detection of halogenated compounds in gas chromatography. The ECD is successfully used for routine analysis particularly in the field of environmental survey, residue determination in the food and agriculture chemistry and even more so in clinical chemistry. However, its application with high resolution glass capillary columns revealed a substantial drawback of existing ECD's, primarily the relatively large internal detector volume. The micro ECD described, with its very small cell volume (140 mm³), particularly designed for use with high resolution capillary columns, minimizes drastically the loss of separation efficiency since diffusion effects are negligible. The micro ECD permits the use of splitless or split injection techniques, as well as temperature programmed analysis to optimize sample separation. Very stable baseline and low noise conditions lower the detection limits considerably (2 pg Lindane full scale). The micro ECD can be operated either with direct current, pulsed frequency or constant current modes. Examples demonstrating the capabilities of this detector include the detection of halogenated organic volatiles in water at subnanogram levels, the determination of PCB's and pesticide residues in food as well as selected analysis in clinical chemistry, such as bile acids and amino acids in body fluids.     

Radio-gas chromatography on wide-bore capillary columns equipped with a synchronized accumulating radioisotope detector

A gas chromatographic system with wide-bore capillary columns and synchronized accumulating radioisotope detector (SARD) was developed. A direct injection method and constant-flow regulation were applied. The performance of wide-bore capillary columns was good and the correspondence of the resolution obtained with SARD and that with mass detection was excellent. It was proved that the apparatus could detect of the order of 1 pg of 3H-labelled substances (3.7 TBq/mmol) and compete in terms of sensitivity with gas chromatography-mass spectrometry.     

530μ大口径毛细管柱在气相色谱分析中的潜力

详细讨论了大口径毛细管柱的优点及其在许多常规分析中的应用以替代填充柱的可能性,列举出了在国内的一些成功的应用实例,还阐述了大口径柱的进样等技术和推广大口径柱存在的一些问题。     

Arsenic speciation by capillary gas-liquid chromatography

Specific environmentally significant arsenic compounds are determined by capillary gas-liquid chromatography. Inorganic (arsenite, arsenate) and organic (monomethylarsonate, dimethylarsinate) arsenicals are measured as the corresponding methylthioglycolate derivatives, which are simultaneously separated on wide-bore borosilicate glass and fused-silica columns under conditions of temperature programming. Inorganic arsenate and arsenite cannot be differentiated by the derivatization technique. Flame-ionization and electron-capture detection are evaluated. A simple and rapid sample preparation procedure is used for water, urine, blood, and tissue.     

Glass capillary column with nematogenic liquid crystals as stationary phases for separating polycyclic aromatic hydrocarbons

Summary Use of the homologues and analogues of nematogenic liquid crystals of the type N,N-bis(p-methoxylbenzylidene)-,-bi-p-toluidine (BMBT) as stationary phases in glass capillary columns is described. These stationary phases are very useful for resolving closely related, rigid solute isomers of three-, four- and five-ring PAH. With these columns it is possible to achieve faster and more complete separation of PAH compared with packed columns with a liquid crystalline stationary phase.     

Some applications of capillary gas chromatography in the chemical industry

About three years ago, fused silica capillary columns were introduced in the Quality Control Laboratory of the Shell refinery/chemical complex at Pernis. In general, long, thick-film, wide-bore capillary columns are used together with low split ratios and hydrogen as carrier gas. These conditions enable the analysis of relatively large sample amounts, resulting in low detection limits for the minor components without overloading by the major components, while still maintaining a satisfactory resolution. A number of applications are shown, such as the analysis of complex mixtures, the determination of trace impurities and the analysis of residual volatiles in polymers.     

Glass capillary gas chromatography of highly polar solutes like diols,acids and amines deactivation of fused silica and pretreated alkali glass support surfaces

Summary The method of support surface deactivation by PSD (alkylpolysiloxane degradation) at temperature between 300 and 450°C previously described was used to deactivate both fused silica and alkali glass surfaces of capillary columns. The latter surfaces had to be pretreated before deactivation with aqueous HCl leaching or by the dealkalisation method using flowing HCl gas at 450°C and subsequent rinsing with water for alkali removal. Excellent alkylpolysiloxane columns with regard to tailing and irreversible adsorption of highly polar solutes have been obtained on both fused silica and the pretreated alkali glass. Fused silica does not require pretreatment before deactivation by the PSD-method, however. Good polyethyleneglycol (Carbowax 20 M) columns can also be obtained by coating the two types of surfaces when no deactivation is necessary. Deactivation by the PSD method cannot be applied in this case because polar stationary liquids do not adhere to alkylpolysiloxane deactivated surfaces. Sample capacity problems arising when separating highly polar solutes with non-polar stationary phases have also been investigated.     

Micropreparative system for enrichment of capillary GC effluents

An automated system for preparative gas chromatography with capillary columns is described. The effluet from the capillary column is switched to the FID detector or to the traps by means of a Live-T switching device. The pneumatics is controlled by a microprocessor so that repetitive sampling can be performed over a period of days in order to enrich sufficient amount of material for NMR or other spectroscopic methods. The effluent containing the compounds is collected in glass tubes filled with column packing material (e.g. Chromosorb coated with 3% OV - 101, crosslinked). The trap temperatue can be adjusted from + 20°C to ? 80°C, depending on the trapping material and volatility of trapped substances. The analysis of enriched substances or chromatographic fractions can be performed by thermal desorption of the same traps or by solven elution. The recovery of enriched substances is higher than 90%. High capacity and resolution for enrichment of trace components are obtained with the aid of a double column-double oven system. Examples of such applications are given.     

Capillary Column Inlet System for the Gas Chromatography of Biological Samples

Abstract

A glass injection system consisting of a packed precolumn and gasphase splitter has been developed for the introduction of derivatized biological samples on glass capillary columns. The precolumn provides complete sample evaporation before the splitter zone, traps contaminating nonvolatiles, and prevents decomposition or adsorption of components. In addition, a carrier gas control system is described that permits stable and repeatable adjustment of split ratio and capillary inlet pressure.

The linearity of the splitter has been established using a hydrocarbon mixture covering the range of methylene unit (MU) values in which the steroid derivatives are eluted.     

Evaluation of fused-silica capillary columns for GC/ECD analysis of chlorinated hydrocarbons listed in EPA method 8120

Four mega-bore, one wide-bore, and one narrow-bore fused-silica capillary columns were evaluated for their applicability to the GC/ECD analysis of 22 chlorinated hydrocarbons, some of which are currently targeted by EPA Method 8120. No one column can resolve all 22 compounds investigated here. Four compounds (two pairs) are coeluting on the SPB-35, DB-210, DB-WAX, and DB-519 fused-silica capillary columns, five compounds (two groups) are coeluting on the DB-1301 fused-silica capillary column, and ten compounds (five pairs) are coeluting on the SPB-5 fused-silica capillary column. The analysis time varies between 30 and 50 min. The order of elution of the chlorinated benzenes seems to depend on their boiling points rather than on the polarity of the liquid phase. The retention times of an additional nine chlorinated toluenes, eight chlorinated xylenes, and five chlorinated naphthalenes are also reported. Electron capture detector linearity is reported for the DB-210 fused-silica capillary column. Five brominated compounds were investigated as possible internal standards for Method 8120.     

Preparative gas chromatography with glass capillary columns

The present paper describes an automated system for preparative gas chromatography with glass capillary columns, controlled by a microprocessor. The effluent from the capillary column is divided by a pneumatically controlled splitter and any desired split ratio between traps and detector can be obtained. Moreover, a second pneumatic control allows instantaneous change-over to a different split ratio, thus minimizing loss of material during collection. The effluent containing the compounds of interest is passed through a multiple manifold and collected in coiled glass capillary traps. To ensure maximum trapping efficiency even for very small amounts of material, the inner walls of the capillary traps are wetted with a suitable solvent, which gives a quantitative recovery of micro- and nanogram amounts of material. After repetitive sampling, sufficient amounts of material can be obtained for NMR spectroscopy and possibilities exist to enrich trace components with the aid of a double column system. Two examples of such applications are given, employing mixtures of both synthetic and natural origin.     

Glass Capillary Columns In The Gas Chromatographic And Gas Chkomatocraphic-Mass Spectrometry Determination Of Trace Levels Of Kepone In Natural Waters

Abstract

The application of high-resolution glass capillary columns to the analysis for Kepone in environmental samples by gas chromatography and gas chromatography-mass spectrometry is described. Glass capillary columns make possible the rapid screening and analysis of Kepone at a lower detection limit of 2 ng/L in natural waters. However, even with the aid of glass capillary columns, electron capture determinations for Kepone are suDJect to error. The use of isopropanol in solutions containing Kepone was found to reduce the variability of the Kepone detector response by as much as six times. A discussion concerning the intricacies of Kepone analysis in natural waters is given.     

Contribution of adsorption to rentension data in capillary gas chromatography part II. Non-polar stationary phases

Summary The influence of adsorption on the dependence of retention data upon film thickness of the non-polar stationary phases OV-101 and Apiezon L coated on glass (series of capillary columns with non-deactivated and Carbowax 20 M deactivated surface) and fused silica has been studied. Limiting values of Kovats indices, I, of solutes which exhibit tendency to hydrogen bonding are calculated for each series of columns.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Factors affecting reproducibility in the manufacture of glass and siliceous glass open tubular (capillary) columns

Summary Column characteristics affecting the chromatographic behavior of glass and siliceous glass (fused silica) capillary columns include the dimensional uniformity of the column, the physical and chemical characteristics of the column wall and the characteristics of the liquid phase. In the case of the coated column the uniformity and thickness of the liquid phase film are the most important criteria affecting column reproducibility. The paper discusses these factors and their influence on column performance.Presented in part at the Symposium on Standardized Materials for Chromatography, 181 st National American Chemical Society Meeting, Atlanta, Georgia, March 29–April 3, 1981.     

Radio gas chromatography on capillary columns using a multi-column system (column-switching)

Summary A gas chromatographic system with capillary columns (fused silica) for the analysis of radiolabelled compounds is described. The system presented is based on a dual column gas chromatograph equipped with column switching facllity and a variable splitter at the column outlet combined with a dead-volume free adapter for the radioactivity monitor for continous measurement of radioactivity in the column effluent. The first column works as a separation column and the second is roughly shortened and used as a feed to the mass detector. The adjustment of the split ratio is regulated by the inlet pressures for the carrier gas supplying both columns. For mass detection all conventional systems can be used. Detection of radioactivity by a gas proportional counter (system based on a combustion technique). Three flow modes can be adjusted: a) total column effluent to the mass detector or b) to the radioactivity monitor, and c) simultaneous flow (dependent on the chosen split ratio) to mass-and radioactivity detectors. The system was developed for use in clinical chemistry and tested with labelled and unlabelled steroids. The method for peak identification by means of relative retention times and methylene units was possible also for radioactive peaks when a heart cutting technique was used. The radio gas chromatographic system presented allows the development of radiochromatograms with the same peak characteristics as in conventional capillary gas chromatography.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Mixed phases of Superox 20M and OV-1 in fused silica and glass capillary gas chromatography

Summary Mixed phases of Superox 20M and OV-1 can be coated homogeneously on the untreated wall of fused silica capillary columns. Excellent columns with regard to efficiency, inertness and thermal stability can be obtained. (CE>95% and MAOT250°). The polarity and selectivity were ascertained with Rohrschneider-Reynolds probes and a capillary polarity test mixture. The analysis of an essential oil mixture illustrates the possibilities of mixed phases in practical capillary GC.     

Reproducibility of glass open tubular columns in a production environment — Two years of experience

Summary The problems associated with the preparation of glass open tubular (capillary) columns are well documented in the literature. These problems are even more evident if column production is done on a routine basis, in a production environment. On the other hand, from the point of the user who wants to rely on a supplier, the reproducible quality of the columns is crucial. Here quality does not only mean efficiency but also refers to the reproducibility of the average liquid film thickness (capacity ratio) and the relative retention, as well as the tube treatment influencing the polarity of the column tube. In a paper published one year ago [1] our investigation concerning the reproducibility of the column manufacturing process was reported. The present paper continues this investigation. Four different columns will be considered: two types of OV-101 columns with thin and thick liquid film as well as columns prepared with Carbowax 20M and DEGS liquid phases. The consistency of their characteristics and efficiency will be investigated. Column characteristics include the capacity ratio which is directly related to the thickness of the liquid phase film. Column efficiency is investigated with help of the HETP and peak resolution. The effective and theoretical plate numbers are compared and the incorrectness of the assumption that the former is better suited for column testing is demonstrated. Relative retention reproducibility of even difficult peak pairs shows the consistency of column wall treatment. Finally, the consistency and performance of shorter columns obtained by the breaking of long columns will be discussed.Paper presented at the Second International Symposium on Glass Capillary Chromatography, Hindelang, Allgäu, Federal Republic of Germany, May 2–6, 1977.     

Quantitation of aniline in water,urine and serum by isotopic dilution mass fragmentography

Summary A method for trace analysis of aniline in water, urine and serum samples is presented. Internal standardisation with d₅-aniline, extraction, derivatisation with dimethylthiophosphinic chloride, gas chromatographic separation on a glass capillary column and mass fragmentographic quantitation are essential steps of the analytical procedure. A detection limit of 20 pg/ml in water and 500 pg/ml in urine or serum is achieved.Presented at the 14th International Symposium on Chromatography London, September, 1982