Ion chromatography, suppressed

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. 

Wagner, H. P., Pepich, B. V., Hautman, D. P., and Munch, D. J., Analysis of 500 ng/1 levels of bromate in drinking water by direct-injection suppressed ion chromatography coupled with a single, pneumatically delivered postcolumn reagent, /. Chromatogr. A, 850, 119, 1999. 

Singh et al. [227] have determined sulfate in deep sub-surface waters by suppressed ion chromatography. 

Thiocyanate Human urine Dilution with water then passage through disposable Toyo pack ODS and IC-SP columns Suppressed ion chromatography with conductivity detection 200 nM No data Miura and Koh 1991... 

Other eluent systems in suppressed ion chromatography are typically chosen based on specific separation requirements. For routine analysis of monovalent and divalent anions, carbonate-based eluents represent a reasonable alternative to hydroxide-based eluent systems. Carbonate eluents are simple to prepare and can be useful in cases where anion analysis is only occasionally performed. It must be kept in mind, however, that carbonate lowers the detection sensitivity for anionic species and introduces significant nonlinearity into the analysis. ... 

Poovey HG, Rando RJ. 1995. Determination of chlorine and chlorine dioxide by non-suppressed ion chromatography and application to exposure assessment in the paper industry. J Liquid Chromatogr 18(2) 261-275. 

Amin M., Lim L. W Takeuchi T. Determination of common inorganic anions and cations by non-suppressed ion chromatography with column switching. Journal of Chromatography A 2008 1182 (2) 169-175. 

Erupe M. E., Liberman-martin A., Silva P. J., Malloy Q. G. J., Yonis N., Cocker D. R. Purvis-Roberts K. L. Determination of methylamines and tiimethylamine-N- oxide in particulate matter by non-suppressed ion chromatography. Journal of Chromatography A 2010 1217(13) 2070-2073. 

In suppressed-ion anion chromatography (Figure 26-4a), a mixture of anions is separated by ion exchange and detected by electrical conductivity. The key feature of suppressed-ion chromatography is removal of unwanted electrolyte prior to conductivity measurement. 

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... 

Conductivity detectors respond to all ions. In suppressed-ion chromatography, it is easy to measure analyte because eluenl conductivity is reduced to near 0 by suppression. Suppression also allows us to use eluent concentration gradients. 

In suppressed-ion chromatography, a separator column separates ions of interest, and a suppressor membrane converts eluent into a nonionic form so that analytes can be detected by their conductivity. Alternatively, nonsuppressed ion chromatography uses an ion-exchange column and low-concentration eluent. If the eluent absorbs light, indirect spectrophotometric detection is convenient and sensitive. Ion-pair chromatography utilizes an ionic surfactant in the eluent to make a reversed-phase column function as an ion-exchange column. 

Ion-Exchange and Ion Chromatography 26-1. State the purpose of the separator and suppressor in suppressed-ion chromatography. For cation chromatography, why is the suppressor an anion-exchange membrane ... 

Acid digestion followed by chemically suppressed ion chromatography. 

Barron, L. and B. Paul. 2006. Simultaneous determination of trace oxyhalides and haloacetic acids using suppressed ion chromatography-electrospray mass spectrometry. Talanta 69 621-630. 

Figure 2.10 Separation of anions in a carbonated apple juice using suppressed ion chromatography. Chromatography conditions column, AS11 with AG11 guard detector, CD20 conductivity detector with the ASRS self-regenerating suppressor in the recycle mode. (Courtesy of Dionex Corporation.)...

Bucholz et al. [91] have described a procedure for the determination of less than 1 pg L 1 of chloride, nitrite and sulphate in 2ml of rainwater sample using non-suppressed ion chromatography. Detection limits are less than 0. lmg L 1 for chloride and nitrate and 0.25mg L 1 for sulphate. The method can accomplish the simultaneous analysis of chloride, nitrate, nitrite and sulphate in less than 25min. 

Saccani, G., Tanzi, E., Pastore, P., Cavalli, S., and Rey, M. (2005). Determination of biogenic amines in fresh and processed meat by suppressed ion chromatography-mass spectrometry using a cation-exchange column. J. Chromatogr. A. 1082, 43-50. 

The main advantages of eluent suppressed ion chromatography (ESIC) are that a wide range of eluents and columns can be used, the wide dynamic range, and the higher sensitivity the main disadvantage is the periodical necessity for suppressor-column regeneration. 

McGeehan, S. L., and Naylor, D. V. (1992). Simultaneous determination of arsenite, arsenate, selenite, and selenate by suppressed ion chromatography. J. Environ. Qual. 21, 68-73. 

The process cannot be used tor strong acids or bases because these are dissociated over a wide pH range and extreme pH levels would be required for ion suppression. Ion chromatography as described in Chapter 14 was developed specifically for cases such as this. 

Suppressed ion chromatography with conductivity detection Suppressed ion chromatography with fluorescence detection... 

Miura Y, Koh T. Determination of thiocyanate in human urine samples by suppressed ion chromatography. Anal Sci, 1991 7(Suppl Proc Int Congr Anal Sci, 1991, Pt 1) 167—170. 

In suppressed ion chromatography, anions are separated on a separator column that contains a low-capacity anion-exchange resin. A dilute solution of a base, such as sodium carbonate/sodium bicarbonate or sodium hydroxide is used as the eluent. Immediately following the anion-exchange separator column, a cation-exchange unit (called the suppressor) is used to convert the eluent to molecular carbonic acid. 

For non-suppressed ion chromatography to be successful, the ion exchanger used in the separation column must have a low exchange capacity and a very dilute eluent must be used. In the separation of anions, the resin must have an exchange capacity between about 0.005 mequiv/g and 0.10 mequiv/g. Typical eluents are 1.0 x 10 M solutions of sodium or potassium salts of benzoic acid, hydroxybenzoic acid, or phtha-lic acid. These eluents are sufficiently dilute that the background conductivity is quite... 

Shortly after the invention of suppressed ion chromatography, commercial instruments for its use were made available by the Dionex Corporation. Ion chromatography became an almost overnight sensation. It now became possible to separate mixtures such as F, CF, Br", NOs and S04 in minutes and at low ppm concentrations. Analytical problems that many never knew existed were described in an avalanche of publications. 

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