Capillary column overview

A modern gas chromatograph, whether configured for packed or capillary column use, consists of several basic components. All of them must be properly chosen and operated for successful analysis. These are pneumatics and gas-handling systems, an injection device, an inlet, a column oven and column, a detector and a data system. Since the inception of GC in the 1950s, instrumentation has evolved significantly as new techniques and technologies were developed. This section provides an overview of the major components of a modern gas chromatograph, with details about how to choose components based on analytical needs, and applications. 

This overview concerns the new chromatographic method - capillary electrochromatography (CEC) - that is recently receiving remarkable attention. The principles of this method based on a combination of electroosmotic flow and analyte-stationary phase interactions, CEC instrumentation, capillary column technology, separation conditions, and examples of a variety of applications are discussed in detail. 

Several protocols can be used to fabricate packed bed structures for use in CEC. In this chapter, we will discuss the packing techniques and column fabrication protocols that have been used for packing particulate material. We concentrate, therefore, on the different approaches used to deliver chromatographic particles into the capillary column. We present an overview of the different packing protocols available to the practitioner, as well as of the CEC column fabrication method, as performed in our laboratory. Our own experiences, practices, and views regarding packing procedures are also provided, when appropriate. 

Later, packed columns were replaced by capillary columns and perchlorination techniques were used less frequently. However, a congener-specific determination of PCTs was still not possible due to the high number of PCTs present in environmental and technical samples. An overview of columns and conditions used in more recent studies is given in Table 3. The stationary phases used are generally non-polar and semi-polar. As with packed columns a condition is a sufficiently high maximum allowable temperature to enable elution of all PCTs. 

Overview. The capillary column IGC technique was used to determine the partition coefficients and diffusion coefficients of a number of solvents (methanol, acetone, methyl acetate, ethyl acetate, propyl acetate, benzene, toluene, and ethylbenzene) in poly(methyl methacrylate). Measurements below the glass transition temperature were obtained for the PMMA/methanol system. 

An overview of capillary gas chromatography is presented. Selected environmental applications, such as PCB s in water, PAH s in airborne particulate matter, and TCDD s at the part-per-trillion level illustrate the separation and analysis of complex mixtures. The chromatographic performance, characteristics, and trade-offs of packed and capillary columns are described in terms of permeability and efficiency, sample capacity, choice of stationary phase, high temperature capabilities, quantitative accuracy, and the development of GC separation methods. 

See also Capillary Electrophoresis Overview. Chir-optical Analysis. Liquid Chromatography Column Technology Mobile Phase Selection Reversed Phase Instrumentation Amino Acids. Mass Spectrometry Peptides and Proteins. Nuclear Magnetic Resonance Spectroscopy Techniques Nuclear Overhauser Effect. Proteins Traditional Methods of Sequence Determination Foods. 

Ettre, L.S. (2002) The evolution of capillary column gas chromatography a historical overview, in A Century of Separation Science (ed. H.J. Issaq), Marcel Dekker, Inc.,... 

Most users of a modem capillary column regard it as a high-precision and sophisticated device and purchase columns from a vendor. Few give any thought to the steps involved in column preparation. Their number one priority is understandably the end result of accurate and reproducible chromatographic data that the column can provide. In this section, an overview of deactivation and coating of a fused-silica column with stationary phase is discussed. 

Polysiloxanes are the most widely used stationary phases for packed- and capillary-column GC. They offer high solute diffusivities coupled with excellent chemical and thermal stabilities. The thorough review of polysiloxane phases by Haken (105) and the overview of stationary phases for capillary GC by Blomberg (106,107) are strongly recommended readings. 

This book is organized into five sections (1) Theory, (2) Columns, Instrumentation, and Methods, (3) Life Science Applications, (4) Multidimensional Separations Using Capillary Electrophoresis, and (5) Industrial Applications. The first section covers theoretical topics including a theory overview chapter (Chapter 2), which deals with peak capacity, resolution, sampling, peak overlap, and other issues that have evolved the present level of understanding of multidimensional separation science. Two issues, however, are presented in more detail, and these are the effects of correlation on peak capacity (Chapter 3) and the use of sophisticated Fourier analysis methods for component estimation (Chapter 4). Chapter 11 also discusses a new approach to evaluating correlation and peak capacity. 

An important step in the transfer of an LC fraction to the GCxGC separation is the elimination of the solvent. Typical peak widths at baseline in LC are around 40 s. At four transfers across a peak and an LC column diameter of 2.1mm, viz. a flow rate of 200nL/min, the corresponding fraction volume is approximately 35 pL. Clearly, special precautions are needed for introducing such a volume into a capillary GC(xGC) system. Since the LC separation mode used in LCxGCxGC is very likely to be a Normal Phase LC separation, the introduction of such a volume is feasible. It actually is rather straightforward, especially if the compounds of interest are not too volatile. A detailed discussion of methods for large-volume injection in GC is beyond the scope of the present chapter. For an excellent overview of such methods, see Mol et al. s work published several years ago [22]. 

A An Overview of Electrophoresis 867 30B Capillary Electrophoresis 868 30C Applications of CE 875 30D Packed Column Electrochromatography 30E Field-Flow Fractionation 884 Questions and Problems 888... 

Figure 7 Overview of the strategy of immobilized salen-type catalysts by (a) on-column reaction GC, (b) on-column reaction capillary electrophoresis (CE)Zelectrokinetic chromatography (EKS), (c) flow-through microreactor, and (d) coated glassware.

The heart of any enantioseparation by liquid chromatography is a chiral column packed with a CSP or rarely a chiral selector immobilized on the wall of a capillary. A CSP consists of a chiral selector and an inert carrier. Both constituents are equally important for the separation performance. The chromatographic literature reports several himdreds of chiral compoimds applied as chiral LC selectors. A more or less complete overview of all materials applied as chiral selectors is impossible within the framework of this short chapter. In principle, any chiral compound possessing the ability to interact noncovalently with chiral molecules has the potential to be used as chiral selector in liquid chromatography. A chiral selector has to meet a set of characteristics that depend on the goal of the separation as well as the mode and technique used. The advantages and bottlenecks of the major classes of commercially available CSPs are summarized in Table 4.1. 

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