Thermo Scientific DSQ II, Hardware Manual

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3
Troubleshooting
Linearity Symptoms
138 DSQ II Hardware Manual Thermo Scientific
Linearity Symptoms
Linearity symptoms occur when a plot of intensity versus concentration of a known
compound are not uniform throughout the curve, or vary from their expected peaks. Poor
instrument operating conditions can cause linearity problems. Additionally, certain
compounds do not give a desired linear response due to chromatographic activity.
A well-maintained instrument will provide good linear response over a wide range of
concentration for most compounds. Like any instrument, however, the DSQ II has a
saturation point.
Perform routine injector and column maintenance to minimize linearity problems. Usually, a
hardware fault that affects linearity will show different symptoms than those that might be
attributed to linearity.
Calibration plots not sufficiently linear.
Possible Solutions
• Standards are too concentrated. Use split injection technique to decrease amount of
sample, lower emission current to reduce sensitivity, or lower detector gain.
• Ion volume, lenses, or prefilter are dirty. Clean the ion volume, lenses, and prefilter, as
described in “Cleaning the Ion Source, Lenses and Prefilter” on page 45 .
• Injection port liner or capillary column is dirty. Change the injection port liner and trim
the capillary column.
• Capillary column stationary phase is too thin for high concentration samples. Use a
higher capacity capillary column with a thicker stationary phase and/or use a split
injection technique.
• The capillary column is bad. Replace capillary column.