Temperature - HP 5890 Series II Plus Reference Manual

Detector Systems
Electron capture detector (ECD)
Considerations for packed column operation
Either N or Ar containing 5 or 10% CH , may be used as carrier gas.
N yields somewhat higher sensitivity, but it is accompanied by higher
noise; minimum detectable limit is about the same. N sometimes
produces a negative solvent peak. Ar/CH gives greater dynamic range.
The carrier gas must be dry and O •free.Moisture and O traps are
strongly recommended for highest sensitivity. Because plastic tubing is
permeable to many gases, use copper tubing for all connections.
Total flow into the detector must be at least 20 ml/min to prevent peak
tailing.
Considerations for capillary column operation
H carrier gas (with N makeup gas) gives best column performance.
Ar/CH as makeup gas may also be used. For most purposes, 60 ml/min of
makeup gas is satisfactory. For very fast runs this can be increased to 100
ml/min to sharpen peaks, but some sensitivity will be lost since the ECD
is a concentration•dependentdetector.
H or He carrier gas affords the best column performance with reduced
retention times. Ar/CH or N makeup gas is used in the range of
30-60 ml/min. Since the ECD is a concentration dependent detector,
reduced sensitivity is obtained at higher flow rates.
Moisture and O traps for carrier gas are essential with capillary/ECD
operation.

Temperature

Some compounds exhibit strong dependence of response to detector
temperature. The effect may be either positive or negative. Different
detector temperatures may be tried, always remaining above the oven
temperature, to determine the effect on sensitivity. Generally a detector
temperature between 250-300 C is satisfactory for most applications.
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