PerkinElmer CLARUS 590 GC, Руководство пользователя

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Detectors . 49
ECD
The Electron Capture Detector (ECD) is the most sensitive detector available for the analysis of
electrophilic compounds such as chlorinated hydrocarbons found in pesticide residues. It is
concentration-sensitive and nondestructive.
The ECD cell contains a nickel foil in a cylinder through which the carrier gas flows. The coating of the
foil's inner surface contains the radioactive isotope Nickel-63 and has a nominal sensitivity of 15 mCi. To
optimize detector response, make-up gas is combined with column effluent.
Beta particles emitted from the isotope ionize the carrier gas. The resultant ions and electrons travel to
the collector anode assembly under the influence of a pulsed polarizing voltage applied between the
source and the collector. The pulse frequency is varied to maintain a constant average current. The
presence of an electron absorbing species in the detector decreases the current as the absorbed
electrons form ions, which travel more slowly than electrons. The pulse frequency of the polarizing
supply is automatically controlled to maintain a constant current and is used to form the detector output
signal.
The ECD works with nitrogen carrier or makeup gas or a carrier or makeup gas mixture of 95%
argon/5% methane. When using capillary columns at low flows (5 mL/min or less), helium or hydrogen
may be used as the carrier gas provided nitrogen or argon/methane is used as the make-up gas. A cross
section view of an ECD is shown below.
The 63 Ni radioactive foil coating and requires careful handling to ensure that it does not create a safety
hazard. In order to prevent a Thermal Runaway risk, the GC shuts down if any heated zone exceeds
470º C. If this occurs, the following message appears:
Warning
Instrument Shutdown
Thermal Runaway xxxxxx zone
Call your PerkinElmer service representative
Instrument shutdown also occurs if there is a PRT (Platinum Resistance Thermometer) or MPU (Micro
Processor Unit) failure. In this case, the following message appears:
Instrument Shutdown
xxxx zone PRT error
Call your PerkinElmer service representative
The ECD works with nitrogen carrier or makeup gas or a carrier or makeup gas mixture of 95% argon/5%
methane. When using capillary columns at low flows (5 mL/min or less), helium or hydrogen may be used as
the carrier gas provided nitrogen or argon/methane is used as the make-up gas.
The following screens show the Active Method screen and the corresponding settings in the Configuration
screen.