Chromatographic methods gas-liquid

Separatory and Analytical Methods Chromatographic Methods Gas-Liquid Chromatography Thin-layer Chromatography High-pressure Liquid Chromatography Column Chromatography Electrophoresis Other Analytical Methods... 

Chromatographic Methods Gas-Liquid Chromatography High-Pressure Liquid Chromatography Column and Continuous Annular Chromatography... 

After two decades of quantitative l.c. analyses, it has been established that, when proper precautions are taken, these methods can provide accurate and reproducible results.Quantitative l.c. measurements are usually as accurate as, and often more precise than, those obtained by spectrophotometric, " paper-chromatographic, and gas-liquid-chro-matographic methods. Both external and internal standardization have been used to translate peak height or areas into quantitative, solute-concentration values. Because peak heights are easy to measure, many methods use this parameter, and, when slightly overlapping peaks or unsteady baselines are encountered, it is the method of choice. With introduction of... 

The development of accurate methods for the determination of enantiomeric purity, which began in the late 1960 s, has been critical for the assessment of enantioselective synthesis. Thus a prerequisite in the enzyme-catalyzed kinetic resolution of racemates is a precise and reliable assessment of the degree of enantioselectivity (E), enantiomeric excess (ee) and conversion (c). Among these methods are 1) polarimetric methods, 2) gas chromatographic methods, 3) liquid chromatographic methods and 4) NMR spectroscopy. The most convenient and sensitive methods used are chiral GC and HPLC. 

One of the main purposes of derivatization is the transformation of nonvolatile compounds into volatile derivatives. However, it is not the sole purpose of this treatment of analytes. Each chromatographic method [gas chromatography (GC), GC-mass spectroscopy (MS), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), etc.] being... 

International Standards Organisation (1996) Water quality - determination of certain organochlo-rine insecticides, polychlorinated biphenyls and chlorobenzenes - gas chromatographic method after liquid-liquid extraction. ISO 6468 1996. 

Gas-liquid chromatography is described by James and Martin and begins the development of instrumental chromatographic methods. Gas chromatography provided a major improvement in the separation of volatile compounds eclipsing established methods at that time. It remains the most widely used chromatographic technique for the fast and efficient separation of thermally stable and volatile compounds today. 

Spectral methods based on UV-visible spectrophotometry, laser-induced breakdown spectroscopy (LIBS), infrared (IR), Raman, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), thermoanalytical and chromatographic methods, especially liquid chromatography (LC) or gas chromatography (GC) combined with pyrolysis are most common. 

Other organic compounds Other dangerous substances include hydrocarbons (fats and oils), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins. Chromatographic methods (gas or liquid chromatography) are extensively used for separation and quantification of these groups. 

Comparative Merits of Techniques for Barbiturate Detection in Urine. Comparison of Radioimmunoassay with Thin-Layer Chromatographic and Gas-Liquid Chromatographic Methods of Barbiturate Detection in Human Urine. Comment s... 

The earliest of the chromatographic methods to be applied to trace analysis was paper chromatography, which in the later 1940s was developed as an advance on the original purely qualitative column chromatographic separations. Gas-liquid chromatography followed in due course, together with many variations of the two-dimensional techniques. 

Analytical separations may be classified in three ways by the physical state of the mobile phase and stationary phase by the method of contact between the mobile phase and stationary phase or by the chemical or physical mechanism responsible for separating the sample s constituents. The mobile phase is usually a liquid or a gas, and the stationary phase, when present, is a solid or a liquid film coated on a solid surface. Chromatographic techniques are often named by listing the type of mobile phase, followed by the type of stationary phase. Thus, in gas-liquid chromatography the mobile phase is a gas and the stationary phase is a liquid. If only one phase is indicated, as in gas chromatography, it is assumed to be the mobile phase. 

For selective estimation of phenols pollution of environment such chromatographic methods as gas chromatography with flame-ionization detector (ISO method 8165) and high performance liquid chromatography with UV-detector (EPA method 625) is recommended. For determination of phenol, cresols, chlorophenols in environmental samples application of HPLC with amperometric detector is perspective. Phenols and chlorophenols can be easy oxidized and determined with high sensitivity on carbon-glass electrode. 

Another chromatographic method is pyrolysis/gas-liquid chromatography. The sample is mixed with P205 and heated to 400°C. This technique yields the chain length distribution of the fatty acids initially used [107],... 

General Description. Liquid chromatography encompasses any chromatographic method in which the mobile phase is a liquid (c.f. gas chromatography). A variety of stationary phases and retention mechanisms are available such that a broad range of modes of separation are possible. It is worthwhile to briefly describe the important modes that find use in clinical chemistry. 

Adsorption, a surface phenomenon, is the basis of many gas or liquid mixture separation and purification methods. It is also the basis of adsorption chromatographic methods used for the analysis of complex mixtures. The knowledge of adsorption mechaiusms is useful in choosing the suitable systems providing optimum separation. 

Tokunaga R, Takahata S, Onoda M, Ishi-i T, Sato K (1974) Evaluation of the exposure to organic solvent mixture. Comparative studies on detection tube and gas-liquid chromatographic methods, personal and stationary sampling, and urinary metabolite determination. Internationales Archiv Arbeitsmedizin 33 257-267. 

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

The solvent triangle classification method of Snyder Is the most cosDBon approach to solvent characterization used by chromatographers (510,517). The solvent polarity index, P, and solvent selectivity factors, X), which characterize the relative importemce of orientation and proton donor/acceptor interactions to the total polarity, were based on Rohrscbneider s compilation of experimental gas-liquid distribution constants for a number of test solutes in 75 common, volatile solvents. Snyder chose the solutes nitromethane, ethanol and dloxane as probes for a solvent s capacity for orientation, proton acceptor and proton donor capacity, respectively. The influence of solute molecular size, solute/solvent dispersion interactions, and solute/solvent induction interactions as a result of solvent polarizability were subtracted from the experimental distribution constants first multiplying the experimental distribution constant by the solvent molar volume and thm referencing this quantity to the value calculated for a hypothetical n-alkane with a molar volume identical to the test solute. Each value was then corrected empirically to give a value of zero for the polar distribution constant of the test solutes for saturated hydrocarbon solvents. These residual, values were supposed to arise from inductive and... 

For the validation of chromatographic methods a good starting point can be found in the EURACHEM/ WELAC document on Accreditation of Chemical Laboratories [30]. ASTM Committee E19 on Chromatography covers all forms of chromatography including gas, liquid, ion and supercritical chromatography. 

Gas and liquid chromatography directly coupled with atomic spectrometry have been reviewed [178,179], as well as the determination of trace elements by chromatographic methods employing atomic plasma emission spectrometric detection [180]. Sutton et al. [181] have reviewed the use and applications of ICP-MS as a chromatographic and capillary electrophoretic detector, whereas Niessen [182] has briefly reviewed the applications of mass spectrometry to hyphenated techniques. 

N. A. Parris, Instrumental Liquid Chromatography, a Practical Manual on High-Performance Liquid Chromatographic Methods (Journal of Chromatography Library, Vol. 27), Elsevier, Amsterdam, 2nd revised ed., 1984 J. Drozd, Chemical Derivatization in Gas Chromatography (Journal of Chromatography Library, Vol. 19), Elsevier, Amsterdam, 1981 J. F. Lawrence and... 

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