Table of Contents
Advertisement
Dionex VWD Operator's Manual
•
Strong bases can etch the 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
ASTM Type I (18 megohm-cm) filtered, deionized water for
5 minutes at 1.0 mL/min immediately after the analysis.
•
Mobile phase pH affects not only the retention time of the separation,
but the sample absorbance and the background absorbance of the
mobile phase.
•
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 a buffer-compatible solvent (in most
cases, ASTM Type I (18 megohm-cm) filtered, deionized water)
immediately after the analysis. Do not allow buffers to remain in the
cell for extended periods.
2.5.3
Mobile Phase Delivery System
The pumping system should deliver continuous flow while ensuring good
mixing of the solvent (if gradient elution is used). Fluctuations in pump
backpressure can cause baseline noise. If the signal noise is found to be
regular and cyclical, monitor the pump for pressure fluctuations. Refer to
the pump manual for troubleshooting information.
The plastics present in some solvent delivery systems are not fully
compatible with the solvents commonly used in chromatography.
Therefore, plastic components may dissolve and thus impair UV
detection.
For UV operation, these guidelines are recommended:
•
The solvent reservoir should be glass.
•
All tubing connections should be made of materials suitable for IC or
HPLC applications (e.g., PEEK, stain les steel, Tefzel
as required for the operating pressure and application.
•
Some pump seals incorporate a band spring to preload the seal during
the vacuum stroke of the piston. The band spring should be stainless
steel, a fluoropolymer (Kalrez
known quality.
20
®
or fluorosilicone), or other material of
®
, or titanium),
Doc. 065377-01 1/12
Advertisement
Table of Contents
