Cation-exchange resin columns silver-form

Ion-exchange resins are also used as packed columns for pre-purification of samples. A characteristic example is the sample preparation of brine with the formerly used ICE suppressor (see Section 4.4), a cation exchanger in the silver form [101]. 

Stationary Phase Use prepacked macroreticular polystyrene sulfonate divinylbenzene cation-exchange resin (2% to 8% cross-linked, 8- to 25-ptm particle size), preferably in the calcium or silver form. Examples of acceptable resins are Bio-Rad Aminex HPX-87C, or equivalent, for separating DPi-DP4 saccharides, and Aminex HPX-42C and HPX-42A, or equivalent, for separating DP1-DP7 saccharides. Maintain the column at 85° during operation. 

Conductivity detection is preferred when water is used as eluent then ionizable analytes are readily detected. However, in the case where HCl is used as the eluent, the analytical column is followed by a suppressor column, packed with a cation-exchange resin in the silver form. The hydrogen ions of the eluent are exchanged for silver ions, which then precipitate chloride ions, thus removing the ions contributed by the eluent and enhancing the analyte s signal. 

Because the detection of ahphatic carboxylic acids is usually performed by measuring the electrical conductivity, suppressor systems are also used in ion-exclusion chromatography to chemically reduce the background conductivity of the acid eluent. In the past, modern membrane suppressors were not available, so packed-bed suppressor columns were used such columns contained a cation-exchange resin in the silver form. With a dilute hydrochloric acid eluent, the suppressor reaction is described as follows ... 

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