IonPac NS1 Manual
Document No. 034024-06
Page 10 of 35
Avoid creating high viscosity pressure fronts that may disrupt the column packing when the eluent solvent is changed.
To
do this, equilibrate the column for approximately 10 minutes with an eluent containing only 5% of the current solvent type (e.g.,
methanol). Exchange this eluent for an eluent with 5% of the new solvent type (e.g., acetonitrile) and then equilibrate the column
and allow the system to stabilize (approximately 10 minutes). Next, run a 15-minute gradient from 5% of the new solvent type to
the highest percentage that will be used during the new analysis protocol.
Solvents can be added to the ionic eluents used with IonPac NS1 columns to modify the ion exchange process or improve sample
solubility. The solvents used must be free of ionic impurities. However, since most manufacturers of solvents do not test for ionic
impurities, it is important that the highest grade of solvents available be used. Currently, several manufacturers are making ultrahigh
purity solvents that are compatible for HPLC and spectrophotometric applications. These ultrahigh purity solvents will usually
ensure that your chromatography is not affected by ionic impurities in the solvent. At Dionex, we have obtained consistent results
using High Purity Solvents manufactured by Burdick and Jackson and Optima® Solvents by Fisher Scientific.
When using a solvent in an ionic eluent, column generated back pressures will depend on the solvent used, concentration of the
solvent, the ionic strength of the eluent and the flow rate used. The column back pressure will vary as the composition of water-
methanol and water-acetonitrile mixture varies. The practical back pressure limit for the IonPac NS1 columns is 4,000 psi (27.57
MPa).
The IonPac NS1 can withstand common HPLC solvents in a concentration range of 1–100%. Solvents and water should be
premixed in concentrations which allow proper mixing by the gradient pump and to minimize outgassing. Ensure that all of the
inorganic chemicals are soluble in the highest solvent concentration to be used during the analysis.
Table 3
HPLC Solvents for Use with IonPac NS1 Columns
Solvent
Maximum Operating Concentration
Acetonitrile
100%
Methanol
100%
2-Propanol
100%
Tetrahydrofuran
20%
3.3.4 Acid Modifiers
Mineral acids such as HCl, H
2
SO
4
, and HNO
3
can be used at concentrations as high as 1.0 N to acidify eluents.
3.3.5 Base Modifiers
Bases such as NaOH, KOH, and NH
4
OH can be used up to 1.0 N to alkalify eluents.
3.4
Preparing Eluents that Contain Solvents
When mixing solvents with water remember to mix solvent with water on a volume to volume basis. If a procedure requires an
eluent of 90% acetonitrile, prepare the eluent by adding 900 mL of acetonitrile to an eluent reservoir. Then add 100 mL of
deionized water or eluent concentrate to the acetonitrile in the reservoir. Using this procedure to mix solvents with water will
ensure that a consistent true volume/volume eluent is obtained. Premixing water with solvent will minimize the possibility of
outgassing.
NOTE
When purging or degassing eluents containing solvents, do not purge or degas the eluent excessively since it is
possible that a volatile solvent can be “boiled” off from the solution.
