Dionex was the first company to patent chemical suppression in 1975, and has continued to expand the capabilities of suppression technology by inventing state-of-the-art electrolytic suppression in 1992. Suppression works two ways to achieve the absolute best sensitivity and corresponding lowest detection limits for inorganic analyses; it increases the analyte signal while simultaneously decreasing the background noise. Today we offer a full line of choices tailored to meet the needs of our customers. Suppression greatly enhances sensitivity (signal-to-noise ratio) by:
Decreasing background eluent conductivity, which lowers noise
Increasing analyte conductivity, which increases signal
Eliminating sample counterions
Electrolytic suppression based on Reagent-Free TM Ion Chromatography (RFIC TM ) with AutoSuppression® technology only from Dionex
SRS® 300 Self-Regenerating Suppressor
The SRS 300 Self-Regenerating Suppressor is our best selling general-purpose electrolytic suppressor. This suppressor is a true workhorse, serving virtually all ion chromatography (IC) applications for both anions and cations. For anions, the preferred eluent is hydroxide. With our unique "Just Add Water" RFIC technology, your ionic sample is detected by conductivity in high-purity water. What AutoSuppression means for you is ease-of-use; there is no need to make up regenerant because the suppressor is constantly being regenerated by the continuous electrolysis of water.
Atlas® Electrolytic Suppressor (AES®)
The AES is our premier carbonate eluent suppressor.The Atlas Electrolytic Suppressor (AES) is a rugged suppressor for eluents for both anion and cation IC analysis.This suppressor equilibrates quickly and efficiently on a day-to-day basis. It has a limited capacity of 25 mN at 1.0 mL/min.
MicroMembrane TM Suppressor (MMS TM 300)
The MicroMembrane Suppressor (MMS 300) is a robust chemical suppressor for eluents containing solvents and the most difficult of sample matrices. The anion ion-exclusion suppressor (AMMS®-ICE 300) is used primarily for chemical suppression of eluents required for weak acid analysis.
Suppressors from Dionex
All suppressor models come in both anion and cation versions, except the AMMS-ICE. In addition, many of the suppressors come in both 2- and 4-mm versions to correspond to the column size. When it comes to suppression, Dionex is decades ahead of the competition.
The figure above demonstrates the effect of suppression. The example is simple anion ion chromatography with NaOH eluent. When the analytes F–, Cl–, and SO4 2– elute from the column, they are still in the NaOH eluent, which is fully ionized and highly conductive. If a suppressor is not used, the conductivity detector trace looks like the top panel. In this chromatogram, small analyte peaks are superimposed on the high sodium hydroxide background.
The suppressor behaves like a cation exchanger and replaces the sodium counterions with hydronium ions. Thus, the analytes leave the suppressor in a water solution. Water is only weakly ionized so the background conductivity is now very low (see the lower panel). The analyte response is also enhanced because the hydronium counterion is approximately 7 times more conductive than the sodium counterion.
Cation suppression operates by an analogous mechanism in which the cation suppressor acts as an anion exchanger.
The SRS and the MMS are high-capacity suppressors capable of suppressing eluents for all IC separations, including gradients. The Atlas has a lower suppression capacity applicable to carbonate, methanesulfonic acid, and some sulfuric acid applications.
Eluents containing solvents should not be used with the Atlas. Low levels of solvent in the eluent are acceptable when using an SRS in the external water mode only, or an MMS. Higher levels of solvents in the eluent require the use of the MMS suppressor.
