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Detectors
Because of its high sensitivity, the NPD requires very pure gases (99.999% or better).
We strongly recommend that moisture and hydrocarbon traps be used on the carrier gas
and all detector gases, including the detector hydrogen, air, and makeup gases. Dirty
gases will not only give poor chromatographic performance, but will shorten the bead
life as well.
Gas Purity
Measuring NPD Flows
1. Set the bead voltage to 0.0 V.
2. Cool the NPD to 100°C.
3. Remove the bead and store it carefully until re-installation.
4. Insert the NPD flowmeter adapter tool into the NPD collector.
5. Attach the flow-measuring insert to the NPD flowmeter adapter tool.
6. Place the flowmeter tubing over the flow-measuring insert to begin measuring flows.
For more information about gas
purity and selection, including the
Renewable Gas Purification System,
see pages 3-12.
Gas Flow
The hydrogen, air and makeup gas flows should be measured frequently. They can drift
over time or be changed unintentionally without knowledge of it occurring. Each gas flow
should be measured independently to obtain the most accurate values. NPDs are very
sensitive to changes in the gas flows and consistent flows are necessary to maintain
performance levels.
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