Suppressor ion chromatography

Common eluents in suppressor ion chromatography are dilute solutions of mineral acids or phenylenediamine salts for cation separations and sodium bicarbonate/sodium carbonate buffers for anion separations. These eluents are too highly conducting to be used without a suppressor column or conductivity detection. Fritz et al. [54-56] have... 

A flow scheme for the basic form of ion chromatography is shown in Fig. 7.3, which illustrates the requirements for simple anion analysis. The instrumentation used in IC does not differ significantly from that used in HPLC and the reader is referred to Chapter 8 for details of the types of pump and sample injection system employed. A brief account is given here, however, of the nature of the separator and suppressor columns and of the detectors used in ion chromatography. 

It is appropriate to refer here to the development of non-suppressed ion chromatography. A simple chromatographic system for anions which uses a conductivity detector but requires no suppressor column has been described by Fritz and co-workers.28 The anions are separated on a column of macroporous anion exchange resin which has a very low capacity, so that only a very dilute solution (ca 10 4M) of an aromatic organic acid salt (e.g. sodium phthalate) is required as the eluant. The low conductance of the eluant eliminates the need for a suppressor column and the separated anions can be detected by electrical conductance. In general, however, non-suppressed ion chromatography is an order of magnitude less sensitive than the suppressed mode. 

The experiment described illustrates the application of ion chromatography (Section 7.4) to the separation and determination of the following anions Br", Cl , NO3 and N02 It may be readily extended to include other anions, such as F , H2PC>4, and SO -. The experiment is based on the Waters ILC Series Ion/Liquid Chromatograph which does not require the use of a suppressor column. 

Figure 4.21 Exploded view of a nlcroaeBbrane suppressor and gradient elution separation of a aixture of inorgemic and organic anions by ion chromatography employing conductivity detection with a mlcromembrane suppressor.

For many years, the concept of the conductivity detector could not work, however. Ion chromatography experiments utilize solutions of high ion concentrations as the mobile phase. Thus, changes in conductivity due to eluting ions are not detectable above the already high conductivity of the mobile phase. This was true until the invention of so-called ion suppressors. Today, conductivity detectors are used extensively in HPLC ion chromatography instruments that also include suppressors. 

LC separation applying ion chromatography in combination with ion spray mass spectrometric detection was applied for the examination of a synthetic mixture of alkyl sulfonates (CnH2n+i-SO3 re = 8) and AS with different alkyl chain lengths in the selected ion monitoring (SIM) ESI-MS(—) mode [53], Selected ion current profiles provided the separation of the compounds. The ionic matrix constituents of the eluent were removed by a suppressor module prior to MS detection to improve the signal to noise (S/N) ratio. 

The use of suppressors in ion chromatography of quaternary ammonium compounds can be of advantage. These are ion exchange membranes that introduce hydroxide ions instead of the counterion present in the analyte. This simplifies the mixture and enhances the electrolytic conductivity of the sample. The effluent of the suppressor may be nebulized and subjected to field-assisted evaporation, yielding a cloud of ions suspended in the gas phase, which can be introduced into an MS analyzer designed for work at atmospheric pressure. Both the molecular weight and the structure of the quaternary cations can be determined by this method419. 

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. 

Ion chromatography is widely employed in a number of areas of pharmaceutical analysis. The high sensitivity of suppressor-based ion chromatography makes it an ideal choice for the analysis of deionized water used in the preparation of solution pharmaceuticals and as a process fluid for the preparation of pharmaceuticals. Depending upon the... 

A few DBFs, such as bromate, chlorate, iodate, and chlorite, are present as anions in drinking water. As a result, they are not volatile and cannot be analyzed by GC/MS. They are also difficult to separate by LC, but will separate nicely using ion chromatography (IC). At neutral pH, HAAs are also anions and can be separated using 1C. A number of methods have been created for these DBFs using both IC/ inductively coupled plasma (ICF)-MS and IC/ESl-MS. Fretreatment to remove interfering ions (e.g., sulfate and chloride), along with the use of a suppressor column prior to introduction into the MS interface, is beneficial for trace-level measurement. 

Haddad PR, Jackson PE, Shaw MJ. Developments in suppressor technology for inorganic ion analysis by ion chromatography using conductivity detection. Journal of Chromatography A 1000, 725-742, 2003. 

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