Column chromatography sample introduction

Gas chromatography (GC) is the most common and successful method of soil-gas analysis. The detection limits are about 1-10 ppb by volume. The basic components of a gas chromatographic system are a carrier gas and a flow control system, a column packed with a gas-separating material, an oven for temperature control of the column, a sample introduction device, a detector and a recording system (Fig. 8-8). 

Kolb, B. and Pospisil, P. (1985) Headspace gas chromatography (HSGC) with capillary columns, in Sample Introduction in Capillary Gas Chromatography (ed. P. Sandra), Huethig Verlag, Heidelberg, pp. 191-216. 

Z. Fiu and J. B. Phillips, Farge-volume sample introduction into narrow-hore gas chromatography columns using thermal desorption modulation and signal averaging , /. Microcolumn Sep. 2 33-40 (1990). 

The limited sample capacity and low carrier gas flow rates characteristic of open tubular column gas chromatography give rise to certain difl icultles in sample introduction. Direct sample... 

Principles and Characteristics As mentioned already (Section 3.5.2) solid-phase microextraction involves the use of a micro-fibre which is exposed to the analyte(s) for a prespecified time. GC-MS is an ideal detector after SPME extraction/injection for both qualitative and quantitative analysis. For SPME-GC analysis, the fibre is forced into the chromatography capillary injector, where the entire extraction is desorbed. A high linear flow-rate of the carrier gas along the fibre is essential to ensure complete desorption of the analytes. Because no solvent is injected, and the analytes are rapidly desorbed on to the column, minimum detection limits are improved and resolution is maintained. Online coupling of conventional fibre-based SPME coupled with GC is now becoming routine. Automated SPME takes the sample directly from bottle to gas chromatograph. Split/splitless, on-column and PTV injection are compatible with SPME. SPME can also be used very effectively for sample introduction to fast GC systems, provided that a dedicated injector is used for this purpose [69,70],... 

SFE-SFC operation consists of extraction, trapping, and transfer to the column for chromatography. Concentration of the solutes of interest before sample introduction to SFC may be achieved by ... 

The //PLC system described in this chapter is equipped with 24 parallel columns for liquid chromatography, each with its own sample introduction port and exit port for connection to detectors of choice (UV absorbance and/ or fluorescence). Flow from a binary solvent delivery system is divided evenly across 24 channels and results in 1/24 of the programmed pump flow rate through each column (i.e., total flow of 300 /zL/ min will produce a flow of 12.5 /zL/ min in each column). Samples are introduced to the columns by a multichannel autosampler configured to sample from either 96-or 384-well SBS standard plates. Figure 6.2 depicts a general view of the system. 

LIQUID CHROMATOGRAPHY. An analytical method based on separation of the components of a mixture in solution by selective adsorption. All systems include a moving solvent, a means of producing solvent motion (such us gravity or a pump I, a means ol sample introduction, a fractionating column, and a detector. Innovations in functional systems provide the analytical capability for operating in three separation modes (1) liquid-liquid partition in which separations depend on relative solubilities of sample components in two immiscible solvents (one of which is usually water) 12) liquid-solid adsorption where the differences in polarities nf sample components and their relative adsorption on an active surface determine tile degree ol separation (2) molecular size separations which depend on the effective molecular size of sample components ill solution. 

With regard to terminology, we will use FI to mean flow injection as described above with an injection valve for sample introduction. Similarly, we will use SI as described above to mean sequential injection in which solutions are pulled into a holding coil via a multiposition valve, and pushed out through this valve to the separation system. The combination of a SI fluid-handling system with a separation column can be called SI chromatography. Some papers apply FI and SI terms more loosely to flow-based systems that may or may not follow these formal fluid-handling approaches as just defined. 

Z. Liu and J. B. Phillips, Sample introduction into a 5 pan i.d. capillary gas chromatography column using an on-column thermal desorption modulator , J. Microcolumn Sep. 1 159-162(1989). 

Penton, Z. (1991). Optimization of samples introduction parameters for determination of pesticides by capillary gas chromatography using a two column, two detector system. J. Assoc. Off. Anal. Chem., 74(5) 872-875. 

Liquid chromatography (LC) is the most commonly used technique for trace element speciation with ICP-MS detection. The mobile phase flow rates used with most LC techniques (0.5-2.0 mL min-1) are compatible for ICP-MS introduction using conventional sample introduction systems (pneumatic nebulization with cross flow and concentric nebulizers and double-pass spray chambers). An interface, known as a transfer line, must be constructed to allow connection between the outlet of the LC column and the nebulizer of the ICP-MS. Inert plastic tubing is commonly used for this purpose with the inner diameter and length kept to 20-50 cm in order to minimize peak broadening. 

The isolation of atropine, scopolamine, and cocaine occurred long before the development of modern analytical techniques. Gas chromatography was the first instrumental technique available in the field of separation science and thus it is not surprising that these alkaloids were firstly analyzed by GC despite their low volatility. With the advent of capillary columns and the proliferation of various sample introduction and detection methods, GC has evolved as the dominant analytical technique for screening, identification, and quantitation of tropane alkaloids of plant origin as well as in biological fluids. The state-of-the-art of GC analysis of tropane alkaloids has been the subject of two comprehensive reviews [45,58]. We shall therefore mainly focus on publications which have appeared since 2002. 

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