IonPac NS1 Manual
Document No. 034024-06
Page 11 of 35
Always degas and store all eluents in glass or plastic eluent bottles pressurized with helium. Only helium can be used to purge and
degas ionic eluents containing solvents, since nitrogen is soluble in solvent containing eluents.
Acetonitrile (ACN) hydrolyzes to ammonia and acetate when left exposed to basic solutions. To prevent eluent contamination
from acetonitrile hydrolysis, always add acetonitrile to basic aqueous eluents by proportioning the acetonitrile into the basic eluent
with the gradient pump. Keep the acetonitrile in a separate eluent bottle containing only acetonitrile and water. Never add the
acetonitrile directly to the basic carbonate or hydroxide eluent bottle.
3.4.1 Eluents for Reversed-Phase and Ion Suppression
A typical eluent for a reversed-phase application will contain 10% to 70% solvent. Where ion suppression is advantageous, 0.02
to 10.0 mM mineral or organic acid or base is used. If ion pair reagents are used in specific reversed-phase applications, they
typically are used at concentrations ranging from 1.0 to 10.0 mM. The chromatographic benefits of ion pair reagent concentrations
above 10 mM are generally not significant.
3.4.2 Eluents for Gradients
Gradient applications are straightforward as long as solvents and water are premixed in concentrations that allow mixing by the
gradient pump to give the required gradient ramp for your chromatography. For example, if you want to build a solvent gradient
from 10% solvent to 90% solvent, make the following eluents:
Eluent A: 10% solvent/90% water
Eluent B: 90% solvent/10% water
Then, by programming the gradient pump properly, you can go from 100% Eluent A to 100% Eluent B in a prescribed time. This
will avoid outgassing and refractive index problems associated with mixing neat solvents with water.
3.4.3 Eluents for Mobile Phase Ion Chromatography (MPIC)
All of the quaternary ammonium and sulfonic acid ion pair reagents can be used at any concentration for practical chromatographic
purposes. Buffering these reagents for column stability is not necessary.
Typical eluents for MPIC applications using suppressed conductivity detection are very similar to those used for reversed-phase
separations with respect to eluent enhancements with acids and bases, solvents and ion pair reagents. The ion pair reagents are used
in concentrations ranging from 1.0 to 5.0 mM. At higher concentrations, they may be difficult to suppress during conductivity
measurements.
The following Ion Pair Reagents are available from Dionex:
P/N 035360 Tetrabutylammonium hydroxide, 0.1 M TBAOH (MPIC-AR1)
P/N 035363 Tetrapropylammonium hydroxide, 0.1 M TPAOH (MPIC-AR2)
P/N 035361 Hexanesulfonic acid, 0.1 M HSA (MPIC-CR1)
P/N 035362 Octanesulfonic acid, 0.1 M OSA (MPIC-CR2)
3.5
Regenerant Preparation for the Self-Regenerating Suppressors
The ASRS ULTRA II when operated in the MPIC Suppression Mode requires a dilute sulfuric acid solution as the regenerant. For
detailed information on the operation of the ASRS ULTRA II, see Document No. 031956.
The CSRS ULTRA II when operated in the AutoSuppression External Water Mode requires the use of water with a specific
resistance of 10 megohm-cm or greater as the regenerant. For detailed information on the operation of the CSRS ULTRA II, see
Document No. 031956.
