Anion Exchange-Reversed Phase

FIGURE 8.3 Schematic diagram of an AEX x RPLC instrument. Reprinted with permission from Holland and Jorgenson (1995), copyright 1995, American Chemical Society. 

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Tjemberg, A., Edlund, P. O., and Noren, B., Screening of eltanolone metbolites in dog urine by anion-exchange/reversed phase liquid chromatography and mass spectrometry, /. Chromatogr. B, 715, 395, 1998. 

IAA Glycine max partition Gossypium hirsutum Sephadex-GlO Phaseolus vulgaris others anion exchange reverse phase-C adsorption fluorescence electro- chemical (61)... 

Ionic Acidic Anion-exchange Reversed phase ion-pair... 

A comparison of anion-exchange, reversed phase and reversed phase ion-pair modes for the separation of small oligonucleotides concluded that anion-exchange provides the best resolution although column life-time may be shorter (Haupt and Pingoud, 1983). 

Sulfonic acids Alkylsulfonates, C < 8, toluene, xylene, benzene sulfonates Alkylsulfonates, C > 8, aromatic sulfonates Ion exclusion, anion exchange Ion pair, anion exchange + reversed phase Amperometry, conductivity Conductivity... 

The second method uses preconcentration to increase the analyte concentration in the absorption solution to detectable levels prior to analysis. One example is the use of solid-phase extraction with an anion exchange column as a pretreatment technique to remove interference from the sample matrix and to enhance the detection sensitivity prior to determination of the concentrated iodide anion through reversed phase high-performance liquid chromatography (HPLC) using an ultraviolet (UV) detector. The results show more than 90% recovery and good reproducibility for the determination of trace iodine in iodine-enriched eggs. 

Because of the development of analytical methods for determination of MC, especially in last decade, the most widespread analytical techniques for their determination are commercialized enzyme-linked immunosorbent assays and HPLC with diode array detectors of anion-exchange columns for this purpose were only sporadically reported with UV detection and isocratic or gradient ° elution. For anion-exchange stationary phase functionalized with diethylaminoethylene groups, better resolution for LR and YR was reported than for Cl8 columns.For separation of cyanobacterial toxins, including MC-LR and -RR, hydrophilic interaction HPLC with gel Amide-80 column and amide C16 column providing comparable resolution to that of conventional reversed-phase Cl8 columns were applied. 

GW Schieffer, GP Wheeler, CO Cimino. Determination of folic acid in commercial diets by anion-exchange solid-phase extraction and subsequent reversed-phase HPLC. J Liq Chromatogr 7 2659-2669, 1984. 

Hplc techniques are used to routinely separate and quantify less volatile compounds. The hplc columns used to affect this separation are selected based on the constituents of interest. They are typically reverse phase or anion exchange in nature. The constituents routinely assayed in this type of analysis are those high in molecular weight or low in volatility. Specific compounds of interest include wood sugars, vanillin, and tannin complexes. The most common types of hplc detectors employed in the analysis of distilled spirits are the refractive index detector and the ultraviolet detector. Additionally, the recent introduction of the photodiode array detector is making a significant impact in the analysis of distilled spirits. 

Naphthalenedisulfonate-acetonitrile as the only mobile phase with a silica column coated with a crosslinked aminofluorocarbon polymer has proven to be an effective combination for the separation of aliphatic anionic surfactants. Indirect conductivity and photometric detection modes are used to monitor these analytes. The retention of these surfactants is found to depend on both the ionic strength and the organic solvent content of the mobile phase. The mechanism of retention is considered to be a combination of both reverse phase and ion exchange processes. Selective separation of both alkanesulfonates and... 

Wheat samples are extracted with dilute ammonia on the ASE200. The extracts are amended with isotopically labeled internal standards. The extracts are purified by sequential octadecyl reversed-phase solid-phase extraction (Cig SPE) and ethylenediamine-iV-propyl anion exchange (PSA) SPE. The samples are analyzed by LC/MS/MS. This method determines crop residues of flucarbazone-sodium and A-desmethyl flucarbazone with a limit of quantitation (LOQ) of 0.01 mgkg for each analyte. 

Amino -(CHj),NH2 Normal, reversed phase and weak anion exchanger... 

Purification of double-stranded DNA on micropellicular anion exchange and reversed-phase materials has been reviewed.43 Micropellicular phases adsorb only at the surface and have no internal pores. For this reason, the surface area and hence the capacity of micropellicular phases tends to be low. Using small particles (1-3 p in diameter) increases the surface area but may be impractical for preparative work above the mg scale. 

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