Eluents generation

This chapter reviews the underlying principles of ion chromatography and its application in pharmaceutical analysis. It provides an overview of eluent systems, applications of gradients, electrolytic eluent generation, suppressors, and stationary phases. Applications of ion chromatography to the confirmation of counter ions, active ingredient analysis, competitive analysis and development work are discussed. 

FIGURE 13 Potassium hydroxide eluent generator schematic. 

The author acknowledges the helpful contributions of Yan Liu and Kannan Srinivasan. They supplied the original text for the sections on eluent generation, suppressors and trap columns, which was adapted for this chapter. 

H. SmaU, J. RivieUo, Y. Liu, N. Avdalovic. Ion chromatographic method and apparatus using a combined suppressor and eluent generator, U.S. Patent 6,027,643, 2000. 

For loading i/ith radioactive mercury the colums were pre- i/ashed i/ith nitrate solution, loaded with 2-20 ml of the active solution and again /ashed with nitrate solution. Each fraction was allowed to pass through the column under gravity with flow rate 0.2-0.5 ml/min. Generators which were not sterilized were left in the loading rack and washed with eluent, generators which were sterilized, were removed from the rack and autoclaved in nitrate or other media. 

Figure 26-6 Electrolytic KOH eluent generator for ion chromatography. [Adapted from Y. Liu, K. Sriniyasan, C. PoN, and N. Avdalovic, "Recent Developments in Electrolytic Devices tor Ion Chromatography"J. Biochem. Biophys. Methods 2004,60.205]...

The suppressors in Figure 26-4 also have been replaced by electrolytic units that generate H or OH- necessary to neutralize the eluate and require only H20 as feedstock.6 With electrolytic eluent generation and electrolytic suppression, ion chromatography has been simplified and highly automated. Readily available software can be used to simulate and optimize ion chromatographic separations.7... 

Y. Sekiguchi, A. Matsunaga, A. Yamamoto and Y. Inoue (2000). Analysis of condensed phosphates in food products by ion chromatography with an on-line hydroxide eluent generator. J. Chromatogr., 881, 639-644. 

To avoid these inconveniences, an eluent generator can be used (either acidic or basic) which is inserted, as a supplementary module, between the pump and the injector of the ion chromatograph (Figure 4.7). If the flow rate of water and the electrolytic current are known then the concentration of the eluent can be determined with precision and concentration gradients can be effected, a procedure seldom used in ion chromatography. 

Lu, Z., Liu, Y., Barreto, V., Pohl, C., Avdalovic, N., Joyce, R., and Newton, B., Determination of anions at trace levels in power plant water samples by ion chromatography with electrolytic eluent generation and suppression, J. Chromatogr. A, 956, 129-138, 2002. 

Overall, AEC is a well-developed separation technique which is widely applied for organic acid analysis. Some of the current trends include the implementation of eluent generators " development of and increased accessibility to ion chromatograph/MS systems which are now commercially available " miniamrization of complete ion chromatographic systems and the development of monolithic columns which have been used for fast analysis of inorganic... 

Figure 13.24 Three methods of suppressing mobile phase ions in IC (a) packed bed suppression—batch suppression, (b) self regenerating suppression—continuous regeneration, and (c) eluent generation from water. (Adapted with permission from Dionex Inc.)...

A combined h.p.1.c.-m.s. technique with thermospray ionization has been used for microscale structural studies on mono- and di-saccharides, methyl glycosides, and permethylated mono- to tetra-saccharides. The technique employs a reversed-phase column with aqueous ammonium formate as eluent, generates abundant M+NH ions,... 

Ion chromatography consists of the following parts (1) eluent generation system, (2) pump system, (3) sample injection system, (4) column system, (5) thermostat chamber, (6) suppressor, (7) detector and data handling system. 

Figure 2 Schematic diagram of an electrodialytic online KOH eluent generator. Based on the Dionex Eluent Generation Model EG40. Courtesy of Dionex Corporation.

Eluent generator Enrichment column Analytical column Column temperature... 

Liu, Y. Kaiser, E. Avdalovic, N. Determination of trace-level anions in high-purity water samples by ion chromatography with an automated on-line eluent generation system. Microchem. J. 1999, 62, 164-173. 

Dionex offers a just add water system for electrolyte generation and purification of commonly used eluents such as KOH and methanesulfonic acid. Eluents are generated from deionized water using an Eluent Generator (EG) cartridge and then polished of contaminants using a continuous-regeneration trap column. 

P. K. Dasgupta, Electrodialytic eluent generation and suppression ultralow background conductance suppressed... 

Figure 3.96 Schematic illustration of a cartridge for electrolytic carbonate eluent generation.

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