China 
Africa 
Explore chapters and articles related to this topic
Analytical Process Systems
Published in Dale R. Patrick, Stephen W. Fardo, Industrial Process Control Systems, 2021
Dale R. Patrick, Stephen W. Fardo
The functional elements of a modern chromatographic instrument are shown in the block diagram in Figure 7-11. The basic components of this system apply to both gas and liquid chromatography. The method of analysis in this case is a discrete-sample laboratory procedure. Analysis begins when a representative sample is injected into the sampling port of the instrument. The sample also enters the mobile phase of the operation at this time. Pressure reduction and temperature stabilization are usually achieved in the sampling port. ‘The sample then goes into a constant- volume loop, where it is held and eventually injected into the chromatographic column. The column effluent or output is then monitored by a system detector that changes chemical information into an electrical signal. The signal is amplified and applied to a recorder, computer memory, or graphic display.
Mobile Phase Effects in Reversed-Phase and Hydrophilic Interaction Liquid Chromatography
Published in Nelu Grinberg, Peter W. Carr, Advances in Chromatography Volume 57, 2020
In high-performance liquid chromatography, the stationary phase is usually a bed of fine solid particles with narrow size distribution, densely packed in a metal, glass or plastic tube – a chromatographic column. The particles may be either fully or only partially porous, such as core-shell columns with a layer of the stationary phase chemically bonded to a support material. On the contrary, monolithic columns do not contain particles; instead, a continuous chromatographic bed fills the full inner column volume. The mobile phase (eluent) is a liquid, usually a mixture of two or more solvents (often containing suitable additives) forced through the column by applying elevated pressure in HPLC. The sample compounds move at different velocities along the column, together with – but more slowly than – the mobile phase. The elution process ideally leads to the eventual sample separation. The separated compounds appear at different times at the outlet from the column as the elution waves (peaks) monitored by a detector attached to the outlet of the column. The elution (retention) time, tR, of the peak maximum is a characteristic property of each sample compound, depending on the distribution constant between the stationary and the mobile phases in the chromatographic column. Hence, the tR, or the retention volume VR, is a useful tool for solute identification.
Downstream Processing
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
In gas chromatography (GC) or liquid chromatography (LC), the eluent (fluid) enters the column/solvent that carries the analyte. The eluate is in the mobile phase leaving the column. The stationary phase consists of immobilized support particles or on the inner wall of the column tubing. For example, silica layer is used in thin layer chromatography; silica gel, alumina, chromosorb, etc. are used in a gas chromatography column. The mobile phase of gas chromatography is gas, which carries the sample through the column, e.g., nitrogen, hydrogen, helium, etc. Similarly, in liquid chromatography, liquid is used as the mobile phase. The mobile phase passes through the chromatography column (the stationary phase) where the sample interacts with the stationary phase and is separated. Retention time is the time taken by an analyte to pass through the system (from the column inlet to the detector) under the operating conditions. A chromatogram is the visual output of the chromatograph. Different peaks on the chromatogram correspond to the different components present in the sample. It is basically a plot of detector signal versus retention time. The signal is proportional to the concentration of the specific analyte separated. A chromatography system is shown in Fig. 11.13.
Non-targeted metabolomics in sport and exercise science
Published in Journal of Sports Sciences, 2019
Liam M. Heaney, Kevin Deighton, Toru Suzuki
Chromatography uses the affinity of molecules to a stationary phase for deconvolution of complicated matrices that contain many hundreds of metabolites (e.g., plasma/serum). As the metabolites pass along the chromatographic column, their varying affinities to the stationary phase cause them to exhibit different times between entry and exit of the analytical column. These properties cause metabolites to be separated and introduced into the mass spectrometer at intervals, thereby reducing the complexity of each MS scan. Decreased analytical complexity, through separation of molecules, improves metabolite identification through the reproducibility of metabolite retention times when chromatographic conditions are maintained across analytical runs. GC also offers the use of Kovát’s retention index (Kováts, 1958), where a series of homologous alkanes provide comparative retention time data across different chromatographic conditions. These retention indices can be compared to published values (e.g., the National Institute of Standards and Technology (NIST) mass spectral library) for more confident identification of analytes.