Suppressor cartridge

Self-regenerating suppressor cartridge incorporating an electrolysis cell, (a) For anionic analytes, (b) For cationic analytes. 

Recently, Karmarkar reported an impressive dual IC-flow injection analysis (FIA) method for the sequential determination of anionic (nitrate and phosphate) and cationic (ammonium) nutrients in wastewater samples. The dual system was based upon the use of an anion exchange column (Lachat QS-A5) and two detectors, one suppressed conductivity detector using a Lachat Instruments QE-Al small suppressor cartridge, which is regenerated between samples, and a second visible absorbance detector. Upon injection of the sample the conductivity detector was switched off line and the nonretained ammonium was passed through the analytical column and detected by the visible absorbance detector, following an on hne colorimetric reaction. The conductivity detector was then immediately switched on hne to detect the retained nutrient anions. The method reported detection limits for phosphate of 0.006 mg/1 phosphate. 

The only possibility to limit the steadily increasing back pressure caused by the continuing precipitation of silver chloride in the suppressor column was to cut off the exhausted part of the cartridge after some days of operation. 

Another suppression device uses a packed-bed suppressor in disposable cartridges. A device with soUd-phase electrochemical cells called Electrically Regenerated Ion Suppression (ERIS) is marketed by Alltech [9]. A degassing unit for removing CO2 from suppression of carbonate is included in a more recent suppressor. Metrohm markets a column suppressor module that uses two suppressor columns. One is regenerated while the other is being used. When the first is exhausted then the other is available for eluent suppression. 

When the chromatographic conditions for the analysis of inorganic anions are taken as a basis, the lifetime of the ion-exchange cartridge is about 780 h. Even if this cartridge is already changed as suggested when it is expended to 90%, the suppressor system can be operated for about 30 days without any interruption. 

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