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chromatography is a separation method based on the difference in interactions between the components of the sample dissolved in a fluid phase (gas or liquid) and the stationary phase. The driving force of the transport between the phases is the difference in chemical potential. The retention in the stationary phase (partition) depends on the interactions of the molecules, ions, atoms of the sample. As a consequence, their average velocity will be different, and they leave the stationary phase separated. The separated components are detected based on their physical or chemical properties. The stationary phase can be solid or liquid. The mobil phase can be gas, supercritical fluid or liquid. Depending on the mobil phase the chromatographic techniques are classified as gas chromatography, supercritical fluid chromatography and liquid chromatography. (Source: Balla J.: Analytical applications of gas chromatography. Budapest, 1987) All of these chromatographic techniques are widely used for characterization of various mixtures, e.g. environmental samples in site assessment, technology monitoring, etc.

gas chromatography

gas chromatography is an analytical technique employing a gaseous mobile phase that separates mixtures into their individual components. The stationary phase can be solid or immobilized liquid. The separation is based on dynamic sorption-desorption processes. Compounds volatilized without decomposition can be separated. The technique is not suitable for the separation of ionic compounds and of large molecules like proteins, peptides, polysacharides, etc. (Source: Balla J.: Analytical applications of gas chromatography. Budapest, 1987)

In environmental analysis gas chromatography is applied for the measurement of volatile and semivolatile organic compounds (VOC and SVOC, resp.) in air, in surface and subsurface water, as well as in potable water, in soil, of residual content of a chemical in food, in animal and plant samples. It is applied for identification of the source of the contamination, the transport of contaminants, bioaccumulation, assessment of contaminated sites, technology monitoring, etc.

liquid chromatography
a chromatographic technique which employs a liquid mobile phase. The separation is based on the partition of components between the mobile and the stationary phase. The High Performance liquid chromatography (HPLC) is widely used in the environmental analysis.
thin layer chromatography
a chromatographic technique employing a porous medium of glass or plastic coated with a stationary phase. The sample, e.g. an extract is spotted near the bottom of the medium and placed in a chamber with solvent (mobile phase). The solvent moves up on the effect of capillary forces in the medium and separates the components of the extract, based on affinities for the medium and solvent.
UV detector in liquid chromatography
detection system in liquid chromatography based on absorption of ultraviolet light. Based on their absorbance spectra certain compounds such as PAHs can be identified. The absorbance is proportional to the quantity (concentration) of the analyte.