Suppressor operation modes

Figure 25.2 (bottom panel) contains the MS/MS spectrum of thioredoxin with the precursor suppressor ON and optimized for precursor (10,000 laser shots). The data collected were with the default MS-MS 2 kV Positive Sensitivity operating mode with the CID OFF (i.e., no target gas in collision cell) and the timed ion selector (TIS) set at a resolution of 100 Da with a 1.0 bin size for the digitizer. 

Figure 3.110 Flow diagram of a micromembrane suppressor operated in the pressurized bottle mode.

AutoSuppression with external water supply. In this operation mode, the deionized water needed for electrolysis is provided externally. Usually, a pressurized reservoir is used that is, water is delivered pneumatically to the regenerant chambers of the suppressor. Gases formed during the electrolysis process are diverted to waste together with the aqueous effluent containing the cations and other suppressor products. The conductivity cell effluent is also diverted to waste. 

Depending on the apphcation, a self-regenerated suppressor can also be operated in three diiferent modes, which were described in Section 3.6.4. The most common mode of operation for the CSRS 300 is AutoSuppression in the recycle mode, in which the conductivity cell effluent is used as the source for the required deionized water (see Figure 3.116 in Section 3.6.4). Because in this case an external chemical regenerant such as tetrabutylammonium hydroxide is unnecessary, cost of ownership is significantly reduced, and suppressor operation is simplified. However, this mode of operation can be used only for applications that use pure aqueous eluents. 

In 2001, a third type of suppressor -Atlas Electrolytic Suppressor (AES) - was introduced. The Atlas suppressor is a continuously regenerated suppressor operated in the recycle mode and designed for optimal performance with conventional methanesulfonic acid (MSA) eluents. Able to suppress up to 25mmol/L... 

Depending on the application, a self-regenerating suppressor can be operated in three different modes. 

In case organic solvents need to be added to the mobile phase, AutoSuppression with external water supply is recommended as the mode of operation, to avoid the recycling of degradation products from organic solvents under electrolysis conditions this would increase noise and background conductivity. But even under those conditions, the organic solvent content in the mobile phase is limited to 40% (v/v). The CSRS 300 self-regenerating suppressor can be operated at temperatures up to 40 °C. 

The recommended and most commonly used mode of operation is the AutoSuppression recycle mode. In this mode of operation, eluent flows from the eluent outlet of the suppressor into the conductivity cell and is then recycled back through the CCES 300 regenerant chambers. This eliminates the need for an external source of regenerant water but limits the regenerant flow rate to the eluent flow rate. The AutoSuppression recycle mode should only be used for solvent-free mobile phases. 

A micromembrane suppressor for ion-exclusion chromatography has been introduced under the trade name AMMS-ICE. Its structure corresponds to the systems developed for anion and cation exchange chromatography (see Sections 3.6.3 and 4.3.3). However, in its mode of operation, it corresponds to the AFS-2 hollow fiber suppressor. An AMMS-ICE micromembrane suppressor also contains membranes that are compatible with water-miscible organic solvents. Therefore, it is used for the analysis of long-chain fatty acids, which are separated on a non polar stationary phase in a weakly acidic medium with methanol or acetonitrile as mobile phase components. In this case, a dilute potassium hydroxide solution is used as the regenerant. With respect to the ion-exchange... 

Weigh out accurately 0.7 g of dried cement into a 250 cm beaker. Disperse in water, add 10 cm cone. HCl and 150 cm hot water. Bring to the boil and keep hot for 5 minutes. Cool and transfer quantitatively to a 250 cm volumetric flask and make up to the marie. Dissolve in a 100 cm aliquot 0.191 g purest KCI and in another 100 cm aliquot 0.254 g purest NaCl. These chlorides are added as ionisation suppressors. Use the atomic spectrophotometer in the emission mode and measure the readings for the two solutions, using the manufacturer s recommended operating conditions. Use calibration standards to find [K] and [Na]. Calculate from the results of spectrophotometry the percentages of oxides of the elements determined. 

Bond and Wallace [10] described a microprocessor-based chromatographic system which they used for the simultaneous and automated determination of Pb(II), Cd(II), Hg(II), Co(II), Ni(II), and Cu(II). Reverse-phase was used to separate in situ formed di-thiocarbamate complexes, and the system could operate continuously and unattended for periods of several days using spectrophotometric detection, and slightly less time using electrochemical detection with background suppression because this mode required frequent suppressor regeneration. 

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