Operating instructions

Charged Aerosol Detectors
Corona Veo and Corona Veo RS
Operating Instructions Page 41
4.5 General Guidelines for Detector Operation
The following sections offer general guidelines for detector operation.
4.5.1 Mobile Phase
Mobile phase quality significantly affects detection limits and detector performance. A careful
consideration in the selection of the components of the mobile phase will be extremely useful
in minimizing baseline noise and optimizing the performance during analysis. This section
describes general guidelines for the use of the mobile phase with the detector.
To ensure optimal performance of the detector, observe the following guidelines:
• Prepare all mobile phases with HPLC-grade (or better) solvents- and reagent-grade
chemicals.
Tip: It is recommended to use water from an ultra-pure deionized source, which
typically has low conductivity and high resistivity.
• Use only mobile phases that contain water, solvents and modifying reagents of the
highest purity available.
• The stability of the mobile phase may decrease over a period of time. Use freshly
prepared mobile phase on a daily basis.
Tip: It is recommended to use online degassers for HPLC systems with the
detector. In some cases, it may be necessary to use helium sparging and/or
sonication during mobile phase preparation in order to achieve optimum
results.
• Take care to minimize non-volatile particulates and/or additives from the mobile phase.
The detector will produce a response to non-volatile particulate matter contained in the
mobile phase.
• Use solvents with minimal residue after evaporation. If a particular solvent causes
problems due to particulates, try a different grade or a different vendor. Be aware that
some solvents contain stabilizing agents that may cause elevated baseline noise.
• When you change from a buffer to a different operating mobile phase, be sure the
solvents are miscible and will not induce precipitation of the buffers.
• Only use volatile mobile phase additives (buffers, solvents, etc.). Buffers such as acetic
or formic acid and their ammonium salts are typical. Use additives (e.g. trifluoroacetic
acid (TFA, HFBA)) at concentrations below 0.3 %. Avoid using carbonates,
bicarbonates, sulfates, phosphates or other non-volatile buffers.