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2.6
Operating Guidelines
2.6.1
Mobile Phases
Solvent quality significantly affects both detection limits and instrument
performance. To ensure optimal performance of the Dionex PDA, observe
the following precautions.
Strong bases can etch the fused silica windows of the flow cell. If the
mobile phase is a base, make sure the mobile phase concentration
does not exceed 0.1 M. If the concentration of the base is greater than
50 mM, disconnect the separator column and flush the system with
deionized water for 5 minutes at 1.0 mL/min immediately after the
analysis. If strong base remains in the cell for 1 to 2 days, the cell
windows may need to be replaced (see
Do not use a PEEK flow cell with normal phase or chlorinated
solvents; these solvents will damage the cell.
Do not use a stainless steel flow cell with low pH solutions; these
solutions may cause corrosion, contamination, and metal leaching.
•
Prepare all mobile phases with spectroscopy-grade solvents, reagent-
grade chemicals, and ASTM Type I (18 megohm-cm) filtered,
deionized water that meets the specifications listed in
•
Degas all mobile phases before use and maintain them in a degassed
state.
•
Mobile phase pH affects not only the retention time of the separation,
but the sample absorbance and the background absorbance of the
mobile phase. If an analysis employs chemical suppression and
compound detection techniques, compare the UV cutoff of the mobile
phase before and after the suppressor to see whether it is
advantageous to locate the Dionex PDA ahead of the suppressor. This
location also limits suppressor exposure to backpressure.
•
When changing from a buffer to a different operating mobile phase,
be sure the solvents are miscible and will not induce precipitation of
the buffers. Flush the cell with deionized water immediately after the
analysis.
Doc. 065378-01 1/12
2 • Description
Section
5.5).
Table
B-1.
25
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