PerkinElmer CLARUS 590 GC, User Manual

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160 . Clarus 590 GC User’s Guide
for the application to be run, then again increase the bead current potentiometer to give a reading
around 0.5 mV on Range 1.
12. Allow the baseline to stabilize for 30 minutes.
13. Using the potentiometer, adjust the baseline between 0.4 and 0.6 mV at Range 1 and the bead
ready to use.
14. After conditioning the bead remove the Swagelok plug from the detector fitting and reconnect the
column.
15. Make sure the column flow is properly set. Touch the signal icon to display the detector
background produced by carrier gas flow. The bead background will be less due to cooling effects.
16. Turn the bead potentiometer dial clockwise until you achieve a reading of 0.25 mV above the "off"
reading with the detector range set to x1.
17. Once the system has stabilized, it is ready for operation.
If you are unable to achieve adequate sensitivity for your standard, increase the background of the
NPD. Increasing intervals of 0.25 mV are recommended.
Adjust the background setting to achieve the sensitivity required for your samples. For example, if
you have a concentrated sample, such as drugs, it can be analyzed with a background of 0.25 –
0.50 mV. If you have a low-level sample, such as pesticides, it may require a setting as high as 1 –
2 mV. To get the maximum life from your NPD bead, operate at the lowest setting to achieve your
required sensitivity.
NOTE: (1) The bead will be stable after operating for several hours, but it will drift in time. At the start of each
day, adjust the background reading to the setting you are using and allow a few minutes for it to stabilize.
(2) Due to the loss of alkali metal with use, the nature of the bead is to drift over time. We strongly
recommend using an internal standard for quantitative analysis.
(3) The bead can operate at higher background settings. The higher the setting, the greater the signal and
noise. Therefore, the signal to noise ratio will not increase dramatically. Operate at the lowest possible
setting to achieve the required sensitivity; this will also prolong the life of the bead.