Advances in Chemical Suppression...regenerant flow became restricted if the fiber swelled, resulting...

Table of Contents

Leading the Way in Chemical

Suppression

Packed-Bed Chemical

Suppressors

Hollow Fiber Suppressors

MicroMembrane Suppressor

Self-Regenerating Suppressor

Electrolytically and Chemically

Regenerated Suppressors

Atlas Suppressor

Specialty Electrolytically


Leading the Way

History of Chemical Suppression

Advances in

Chemical Suppression

Table of Contents


Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Leading the Way in Chemical Suppression

We invite you to learn more about suppression technology and advances in ion analysis. In 1975, packed-bed chemical suppression was introduced and modern ion chromatography was born. Chemical suppression was revolutionary because it reduced background conductivity, enhancing ion detection. With packed-bed chemical suppression, chemists achieved sensitivity and selectivity from low parts-per-billion (μg/L) to parts-per-million (mg/L) levels.

In 1981, we continued to lead in suppression technology by introducing hollow fiber suppressors. These suppressors allowed continuous, rather than off-line regeneration used in packed-bed suppression. The Thermo Scientific™ Dionex™ MicroMembrane Suppressor (MMS) was introduced in 1985, delivering greater dynamic capacity and allowing the use of gradient elution. In 1992, we introduced the Thermo Scientific™ Dionex™ Self-Regenerating Suppressor (SRS) with Auto-Suppression. These suppressors used electrolysis as the source of regenerant ions, eliminating the need to make and handle corrosive regenerant solutions.

In 2003, we took suppressor technology a step further with the Dionex SRS ULTRA II suppressors The Dionex SRS ULTRA II suppressor provided ultralow noise, low and stable backgrounds, superior dynamic capacity, and broad dynamic range. Today, the Thermo Scientific™ Dionex™ ERS™ 500 Electrolytically Regenerated Suppressor and the Thermo Scientific™ Dionex™ CRS™ 500 Chemi-cally Regenerated Suppressor represent the state-of-the-art in suppressor technology. The Dionex ERS 500 and Dionex CRS 500 suppressors are designed to preserve the highly efficient peak shapes of the new 4 µm columns, are even more tolerant to high backpressures over extended periods of time and are more tolerant of high temperatures.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Packed-Bed Chemical Suppressors

A packed-bed suppressor uses a column body packed with a very high capacity ion-exchange resin.The resin is a cation-exhcange resin in the acid form for anion suppressors or anion-exchange resin in the hydroxide form for cation suppressors. Packed-bed suppressors have finite capacity and must be taken off-line and regenerated regularly. Often they also have a very large internal volume, comparable to the separator column itself, resulting in band dispersion.

The Thermo Scientific Dionex packed-bed chemical suppressors (Thermo Scientific Dionex SC-1 and Dionex SC-2 suppressors) were designed to be operated with weak eluents to maximize the time between regenera-tion steps. The Dionex SC-1 and Dionex SC-2 suppressors were discon-tinued in 1997.

The Metrohm MSM and MSM II suppressors are based on the packed-bed chemical suppression technology and are still in use to this day. In order to minimize band dispersion the MSM and MSM II have relatively low capacity, but solve this by using three suppressors which are rotated in a revolver-like device between injections. While the first one is in use, the second is being regenerated, and the third is being rinsed.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way



A hollow fiber suppressor uses a capillary (hollow fiber) that is packed with glass beads and wound onto a spool that is placed into a chamber filled with regenerant solution. The capillary is made from an ion-exchange material that allows ions to migrate into and out-of the capillary. For anion hollow fiber suppressors, the capillary wall is a cation-exchange material in the acid form. For cation hollow fiber suppressors, the capillary wall is an anion-exchange material in the hydroxide form. Regenerant solution is continually pumped through the regenerant chamber to keep it from becoming exhausted, while eluent is passed through the capillary.

The Dionex hollow fiber suppressor was the first continuously regenerated suppressor ever commercialized. The suppressor never needed to be taken off-line and regenerated, allowing continuous operation of the system even with moderate strength eluents. However, key disadvantages of the hollow fiber suppressor were that it easily ruptured and often the regenerant flow became restricted if the fiber swelled, resulting in excess noise. The Dionex hollow fiber suppressor was discontinued in 1989 as the more robust micro-membrane based devices become popular.

The SeQuant SAMS™ was introduced in Sweden in 1987 and uses the same principles for suppression as the original Dionex hollow fiber suppressors.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way



The SeQuant™ CARS™ uses the same principle as the AutoRegen accessory to allow continuous regeneration of a SAMS™ for months of unattended operation.

In 1999, we introduced a new mode of operation for the Dionex MMS suppressor: Displacement Chemical Regeneration (DCR). In DCR mode, the effluent from the detector is used to push regenerant through the Dionex MMS suppressor regen chambers, eliminating the need for pressurized bottles or external pumps, ensuring a continuous, pulse-free flow of regenerant. The DCR mode of operation has become the recommended alternative to AutoRegen.

A Dionex MMS suppressor uses a pair of membranes separating a central eluent chamber from regenerant chambers on either side. The chambers are filled with functionalized ionically charged screens. In an anion Dionex MMS suppressor, the membrane itself as well as screens are cation exchangers in the acid form. In a cation Dionex MMS suppressor, the charge is reversed.

The Dionex MMS suppressor had substantially increased capacity compared to the hollow fiber suppressor, allowing continuous operation with moderate to strong eluents. The Dionex MMS suppressor was also more robust.

AutoRegen for the Dionex MMS Suppressor

Introduced in 1987, the AutoRegen module allows continuous operation of a Dionex MMS suppressor for up to 2000 hours without the need to refill the regenerant solution, depending on the strength of the eluent being suppressed. The AutoRegen accessory is comprised of a pump, a regenerant reservoir and an AutoRegen cartridge. The pump is used to recirculate regenerant from the reservoir through the AutoRegen cartridge to the Dionex MMS suppressor and back to the reservoir. In a Dionex AMMS suppressor for example, sulfuric acid regenerant is converted to sodium sulfate during the suppression process. The AutoRegen anion cartridge contains a high capacity cation-exchange resin in the acid form; thus sodium sulfate is converted back to sulfuric acid before re-entering the Dionex AMMS suppressor.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way



A Dionex SRS Self-Regenerating Suppressor has a very similar con-struction to a Dionex MMS suppressor, but electrodes are added to the regenerant chambers. By connecting a power supply to the electrodes and passing current through the suppressor, regenerant ions are gener-ated inside the suppressor from water, negating the need to provide a chemical regenerant; this is known as AutoSuppression. To provide water for the electrolysis reaction, a constant flow of water is passed through the regenerant chambers.

The Dionex SRS suppressor has the highest capacity of any constantly regenerated suppressor, allowing full suppression of gradient eluents. Furthermore, by using the detector waste as regenerant, a constant flow of water is provided without the need for any secondary pumping system. This suppressor set a new standard for ease-of-use.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Electrolytically and Chemically Regenerated Suppressors

In 2013, the Dionex SRS Self-Regenerating Suppressor was renamed to Dionex ERS Electrolytically Regenerated Suppressor with the release of the Dionex ERS 500 suppressor. A Dionex ERS suppressor is constructed differently compared to a Dionex SRS suppressor, although the principles of operation remain the same. In a Dionex ERS suppressor, the membranes are sealed against a PEEK preform using o-rings. This increases the backpressure tolerance of the suppressor, and stabilizes its tolerance over long periods of time. The screen in the eluent pathway is eliminated in favor of a planar packed-bed of ion-exchange resin. This increases the static capacity of the suppressor ten-fold compared to the Dionex SRS suppressor, making the suppressor more robust to strong sample matrices.

Other improvements include linear eluent flow to preserve the peak shape efficiency, particularly when used with 4 µm columns, serial regenerant flow for better gas sweep out, and matched eluent to regenerant chamber construction to allow for faster electrolytic regeneration after exhaustion.

In 2014, the Dionex MMS MicroMembrane Suppressor was renamed to Dionex CRS Chemically Regenerated Suppressor with the release of the Dionex CRS 500 suppressor. The same design concept as a Dionex ERS suppressor is used, however there are no electrodes as the suppressor is regenerated chemically, and length of the suppressor is increased in order to preserve dynamic capacity.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Atlas Suppressor

A Thermo Scientific™ Dionex™ Atlas™ Suppressor uses a small column body packed with a series of monolithic ion-exchange disks through which the eluent is passed. The ends of the column body are separated from regenerant chambers by ion-exchange membranes. The regenerant chambers contain electrodes that are used to generate the regenerant ions from water. When current is applied to the electrodes, an electric field pushes the regenerant ions lengthwise through the column body counter-current to the eluent flow.

The Dionex Atlas suppressor has relatively low capacity compared to the Dionex ERS or Dionex CRS suppressor, but operates with noise levels similar to a Dionex CRS suppressor and ease-of-use similar to a Dionex ERS suppressor. Despite its low capacity, the Dionex Atlas suppressor is very well suited to a wide range of applications, particularly isocratic carbonate and methanesulfonic acid eluents.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Sometimes one-size does not fit all, so Thermo Scientific manufactures a number of Electrolytically Regenerated Suppressors that have been optimized for particular applications. These include the Thermo Scientific™ Dionex™ AERS™ 500 Carbonate suppressor, the Thermo Scientific™ Dionex™ ERS™ 500e suppressor and Thermo Scientific™ Dionex™ ERD™ 500 Electrolytically Regenerated Desalter. These suppressors are based on the Dionex ERS 500 suppressor platform but have design modifications to improve their performance in certain applications.

The Dionex AERS 500 Carbonate suppressor is designed to reduce noise levels when operating with carbonate eluents. Noise is reduced up to 5-fold compared to a Dionex AERS 500 suppressor. The Dionex ERS 500e suppressor is optimized for use with external water mode. It incorporates regenerant flow optimizations that make pneumatic delivery easier to control, as well as improved sweep out of electrolytic by-products produced when solvents or borate is used as an eluent. The Dionex ERD 500 desalter is a high-capacity variant of the Dionex ERS 500 suppressor designed to desalt high ionic strength eluents commonly employed with carbohydrate analyses. It is used in conjunction with HPAE-PAD systems that need to interface with mass spectrometric detectors, or fraction collectors.

Specialty Electrolytically Regenerated Suppressors

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Learn more at www.thermoscientific.com

Leading the Way

As ion chromatography (IC) technology advances over the years, some suppressors are discontinued to ensure that customers performing ion analysis use the best available technology. The hollow fiber suppressor was discontinued in 1989, and the packed-bed suppressor was discontinued in 1997. The AutoRegen accessory was discontinued in 2005, although AutoRegen cartridges are still available. Today, the Dionex ERS 500 and Dionex CRS 500 suppressors are the industry standard.

Thermo Scientific solutions have been at the forefront of every innovation in suppressor technology. These advances have made IC easier and more reliable, allowing chemists to consistently achieve better results. It is not surprising that IC users look to us for suppressor innovations, and those advances are ongoing. Our pursuit of optimal suppression has yielded the Dionex ERS 500, Dionex AERS 500 Carbonate, Dionex ERS 500e, and Dionex CRS 500 suppressors. The innovation of suppression technology will not stop there.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way



Year Product

1975 – 1997Packed-Bed Chemical Suppressors (Dionex SC-1 and Dionex SC-2)

In 1975 the face of ion analysis was changed forever. Packed-bed chemical suppression was introduced to chemists worldwide. Chemical suppression was revolutionary because it reduced background conductivity and simultaneously enhanced the detection of ions; however, the suppressor needed to be periodically taken off-line to be regenerated.

1981 – 1989

Hollow Fiber Suppressors (Thermo Scientific Dionex FS1 and Thermo Scientific Dionex FS2)

Improving on the limited capacity of the packed-bed chemical suppressors, hollow fiber suppressors were introduced in 1981 which allowed continuous regeneration, eliminating the need for off-line regeneration. In 1984 a second generation hollow fiber suppressor was introduced; this was little more than a cosmetic improvement.

1985 – 1994Dionex MMS MicroMembrane Suppressor

A few years later in 1985, the Dionex MMS MicroMembrane suppressor was introduced. These suppressors possessed much greater dynamic capacity, increasing the flexibility of IC by allowing the use of gradient elution. The Dionex MMS suppressor was replaced by the Dionex MMS II suppressor in 1994.

1991 Dionex MMS (2 mm) Suppressor

The Dionex MMS (2 mm) suppressor was the first commercially available suppressor designed for flow-rates typically found in systems using 2 mm i.d. columns. The Dionex MMS (2 mm) suppressor differed from the standard Dionex MMS (4 mm) suppressor in that the internal volume was reduced by halving the path length; thus the packaging was also smaller.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


Year Product

1992 – 1997

Dionex SRS I Self-Regenerating Suppressor and Dionex MMS II Suppressor

Based on the successful design of the Dionex MMS suppressor, the Dionex SRS suppressor with AutoSuppression was introduced in 1992. These suppressors used electrolysis as the source of regenerant ions for suppression, which eliminated the need to make and handle corrosive regenerant solutions altogether. The Dionex SRS I suppressor was superseded in 1997. The Dionex MMS II suppressor was a significant improvement in the Dionex MMS suppressor design. Improved membranes led to lower backgrounds and higher efficiencies. The Dionex MMS II suppressor was replaced by the Dionex MMS III suppressor in 1998.

1997 – 1998 Dionex SRS II Suppressor

The Dionex SRS II suppressor had a very similar construction to the original Dionex SRS I suppressor, but improvements were made to the screen designs in the cation version to increase solvent compatibility and overall efficiency. The Dionex SRS II suppressor was replaced by the Dionex SRS ULTRA suppressor in 1998.

1998 – 2003Dionex SRS ULTRA Suppressor and Dionex MMS III Suppressor

The Dionex SRS ULTRA suppressor implemented an optimized eluent channel to reduce spiking and improve efficiencies. A new gasket design led to improved backpressure tolerance. In the cation version new screens were employed to improve current efficiency and thus decrease noise. The Dionex SRS ULTRA suppressor was replaced by the Dionex SRS ULTRA II suppressor in 2003.

The Dionex MMS III suppressor was the first Dionex MMS suppressor to use the same packaging and materials as the Dionex SRS suppressor. The 2 mm version used the same channels as the Dionex SRS suppressor, improving efficiency. Other optimizations led to higher capacity and faster start-up times. The Dionex MMS III suppressor was replaced by the Dionex MMS 300 suppressor in 2007.

2001 Dionex Atlas Suppressor

In 2001, a new concept in suppression technology was introduced with the Dionex Atlas Electrolytic Suppressor. The patented design of the Dionex Atlas suppressor resulted in much faster daily start-up times and lower noise. The Dionex Atlas suppressor has a significantly reduced capacity compared to Dionex MMS and Dionex SRS suppressors; however, it is still ideal for many applications.

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Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


2003 – 2007 Dionex SRS ULTRA II Suppressor

The Dionex SRS ULTRA II suppressor implemented a new solvent cleaned gasket design that further reduced noise, improved efficiencies, and decreased start-up times. The cation version also implemented a new regenerant channel design that further improved performance. The Dionex SRS ULTRA II suppressor was replaced by the Dionex SRS 300 suppressor in 2007.

2007 – 2013Dionex SRS 300 and Dionex MMS 300 suppressors

The Dionex SRS 300 and Dionex MMS 300 suppressors were designed to increase the backpressure tolerance by a factor of 3 compared to previous generations of micromembrane based suppressors. They implemented a design that improved regenerant sweep-out, leading to lower noise and faster start-up times. Improvements in membrane materials also improved noise performance for the Dionex SRS 300 suppressor, particularly when operated in recycled eluent mode.

2013 – 2014Dionex ERS 500 and Dionex CRS 500 Suppressors

The Dionex ERS 500 and Dionex CRS 500 suppressors use a totally different construction compared to previous generations. The membranes are sealed against a PEEK preform using o-rings to improve backpressure tolerance over longer periods of time. The screen in the eluent pathway is eliminated in favor of a planar packed bed of ion-exchange resin to improve start-up time and static capacity. And the eluent is introduced into the suppressor in a linear fashion to preserve the peak shape efficiency of 4 µm columns.

Year Product

Table of Contents


Suppression

Packed-Bed Chemical

Suppressors






Atlas Suppressor



Leading the Way


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Advances in Chemical Suppression...regenerant flow became restricted if the fiber swelled, resulting...

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