Conventional Liquid Chromatography

The method for chloroacetanilide soil metabolites in water determines concentrations of ethanesulfonic acid (ESA) and oxanilic acid (OXA) metabolites of alachlor, acetochlor, and metolachlor in surface water and groundwater samples by direct aqueous injection LC/MS/MS. After injection, compounds are separated by reversed-phase HPLC and introduced into the mass spectrometer with a TurboIonSpray atmospheric pressure ionization (API) interface. Using direct aqueous injection without prior SPE and/or concentration minimizes losses and greatly simplifies the analytical procedure. Standard addition experiments can be used to check for matrix effects. With multiple-reaction monitoring in the negative electrospray ionization mode, LC/MS/MS provides superior specificity and sensitivity compared with conventional liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/ultraviolet detection (LC/UV), and the need for a confirmatory method is eliminated. In summary,... 

LC/MS/MS. LC/MS/MS is used for separation and quantitation of the metabolites. Using multiple reaction monitoring (MRM) in the negative ion electrospray ionization (ESI) mode, LC/MS/MS gives superior specificity and sensitivity to conventional liquid chromatography/mass spectrometry (LC/MS) techniques. The improved specificity eliminates interferences typically found in LC/MS or liquid chro-matography/ultraviolet (LC/UV) analyses. Data acquisition is accomplished with a data system that provides complete instmment control of the mass spectrometer. 

Banks, J.F., Jr. Quinn, J.P. Whitehouse, C.M. LC/ESI-MS Determination of Proteins Using Conventional Liquid Chromatography and Ultrasonically Assisted ESI. Anal. Chem. 1994,66.3688-3695. 

Electrochromatography involves the use of a stationary phase hence the concepts of efficiency and band broadening are similar to those that occur in conventional liquid chromatography. The efficiency, expressed in number of theoretical plates N can be obtained directly from an electropherogram using the following equation ... 

The chiral recognition mechanisms in NLC and NCE devices are similar to conventional liquid chromatography and capillary electrophoresis with chiral mobile phase additives. It is important to note here that, to date, no chiral stationary phase has been developed in microfluidic devices. As discussed above polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, proteins, crown ethers, ligand exchangers, and Pirkle s type molecules are the most commonly used chiral selectors. These compounds... 

In addition to conventional liquid chromatography, supercritical fluid chromatography (SFC), using a supercritical fluid as mobile phase (mostly scf-C02), has attracted attention in the last decades [58, 164, 168, 169]. Supercritical fluids provide a favourable medium for the transport of solutes through a chromatographic column because they resemble a gas in terms of viscosity, a liquid in terms of density, and are intermediate between these two phases in terms of diffusivity. For some physieal properties of supercritical solvents, see Section 3.2. 

In general, the use of MIPs as stationary phases in either electrochromatography or conventional liquid chromatography has to surmount important problems, such as the production of particles of reproducible size and shape, the tedious grinding-sieving process, and the need for a large amount of template molecule. 

The CCC technique is well suited for the separation of peptides and related compounds because it eliminates sample loss and denaturation caused by the solid support used in conventional liquid chromatography. The method separates multigram quantities of peptide samples using pH zone-refining CCC. 

CPC separations can be entirely interfadaUy driven analogous to conventional liquid chromatography. 

Describe a major advantage of micellar electrokinetic capillary chromatography over conventional liquid chromatography. 

During this period, many improvements have also been made in older traditional techniques. Noteworthy here is the positive impact HPLC had on conventional liquid chromatography regarding equipment and stationary phases and the significantly enhanced sensitivity of the radioactivity detectors for monitoring column effluents. 

Valaskovic, G.A. et al., Ultra-low flow nanospray for the normalization of conventional liquid chromatography/mass spectrometry through equimolar response Standard-free quantitative estimation of metabolite levels in drug discovery, Rapid Commun. Mass Spectrom., 20, 1087, 2006. 

As in conventional liquid chromatography the plate height can be expressed using a modified Van Deemter plate height equation. 

Because of its high resolving capacity, conventional liquid chromatography is an efficient tool in research, when analysis of chemically similar byproducts (secondary, tertiary, etc., complexes), metabolites or products resulting from radiolysis, is required. 

Risner, C.H. Quantitation of some tobacco anions by eluent suppressed anion exchange chromatography using conventional liquid chromatography equipment Tob. Sci. 30 (1986) 85-90. 

For what is now commonly referred to as conventional liquid chromatography separations were performed at low pressures using totally porous inorganic oxide or porous... 

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