System Description
3
SCD and NCD User Manual
43
simultaneous detection of hydrocarbon components using a
single column without splitting. For this reason, Agilent offers
an optional FID adapter to mount the burner assembly onto an
FID for the simultaneous collection of FID and SCD
chromatograms. During dedicated SCD operation, 100 % of the
column effluent passes through the burner to the detector.
During simultaneous detection, approximately 10 % of the FID
exhaust gases are drawn into the burner through a restrictor,
which reduces SCD sensitivity to approximately 1/10 of the
signal observed in a dedicated SCD burner.
NCD chiller
For NCD, the detector uses a Peltier cooler to lower the PMT
temperature, which in turn reduces noise. This chiller cools the
PMT relative to the current ambient temperature. Higher
laboratory ambient temperatures may result in higher PMT
temperatures. Fluctuations in ambient temperature may result
in fluctuations in PMT temperature.
Since noise and response determine the MDL, the efficiency of
the chiller can influence the MDL. Depending on the ambient
temperature, the chiller may not be able to maintain a
sufficiently cool temperature in the PMT, and XCD noise will
increase, therefore increasing the MDL.
Because chiller efficiency depends on the ambient temperature
inside the detector and in the laboratory, the chiller setpoint
does not impact detector readiness. A GC run can start
regardless of whether or not the chiller has cooled the GC to
setpoint.