Chromatographic and electroseparations of inorganic ions
Haddad, PR (2001) Chromatographic and electroseparations of inorganic ions. TrAC - Trends in Analytical Chemistry, 20 (6-7). pp. 272-273. ISSN 0167-2940
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Official URL: http://dx.doi.org/10.1016/S0165-9936(01)00086-3
The development of ion chromatography (IC) in 1975 created a revolution in the determination of inorganic ions and, to a lesser extent, low molecular weight organic ions as well. In the case of inorganic anions, their analytical determination had previously been characterised by tedious wet chemical methodology and IC opened up the possibility for the simultaneous determination of up to 10 analytes at a time, with the total analysis time being usually less than that required for a single analyte by wet chemical methods. The advantages of IC for inorganic cations were less marked because of the existence of spectroscopic methods suitable for the sensitive and simultaneous determination of these species, but IC nevertheless also became a routine tool for cation determinations.
IC has continued its development since its inception and new features have appeared at a steady pace. These improvements have embraced new columns, suppressors, detection methods and sample handling procedures, such that IC can now be applied to almost every sample type. Publications on IC continue to appear at a rate of about 250 papers each year, providing further indication of the ongoing development of the technique. It is now fair to say that IC is the analytical method of choice for inorganic anions because of its sensitivity, reproducibility and robustness. Perhaps the only disadvantages of IC are the time required for a separation to be completed and the fairly modest chromatographic efficiencies which can be achieved.
Capillary electrophoresis (CE) appeared as a viable method for the determination of inorganic and low molecular weight organic species in about 1989. The first papers created a great deal of excitement amongst IC users because of the speed of separation and very high separation efficiencies offered by CE. It was demonstrated that CE could separate over 30 analytes in the time that IC could separate two. Intense research effort was applied to the development of CE as a possible alternative for IC, but more than 10 years later we see that although CE has been accepted as a routine method for inorganic species, IC remains the major technique used for these analytes. The chief reasons for this are that IC offers somewhat better analytical ruggedness and also greater sensitivity in routine use.
In the mid-1990s it was recognised that chromatographic and electrophoretic methods could be combined by incorporating a stationary phase or pseudo-stationary phase into a capillary and to propel the mobile phase by electroosmosis rather than pressure. This hybrid technique, known as capillary electrochromatography (CEC), offered a special advantage when the chromatographic stationary phase added to the capillary was an ion exchanger, namely the ability to control separation selectivity. This advantage arose from the fact that the separation selectivities of IC and CE (as reflected by the elution order of analytes) were almost the direct opposite of each other, suggesting that combining the two techniques should provide a means to obtain any desired selectivity between the extremes offered by IC and CE. CEC methods using ion exchange stationary phases have been studied intensely over the last few years, usually with the objective of controlling selectivity.
This issue provides an overview of the determination of inorganic analytes using IC, CE and CEC. The topics have been structured to provide the reader with a broad coverage of these fields, with the number of papers devoted to each technique being roughly representative of the level of routine usage of that technique. The papers have been prepared by acknowledged experts and cover both the fundamentals and major application areas of the techniques, with an emphasis on areas of rapid development. Together, these papers provide an excellent summary of the current state of IC, CE and CEC when applied to the determination of inorganic analytes, as well as a glimpse of future directions. I hope that these papers will be a valuable resource for analytical chemists involved in the separation of inorganic analytes and I wish to extend my sincere thanks to the experts who have contributed to this special issue.
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|Deposited By:||Mr Marcus Guijt|
|Deposited On:||19 May 2008 22:05|
|Last Modified:||18 Jul 2008 20:57|
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