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The NPD requires periodic cleaning. In most cases, this only involves the collector
and the jet. Agilent provides brushes and wires that simplify the cleaning of all detector
parts. The brushes are used to dislodge particulates clinging to the metal surfaces.
A fine wire is used to clean the jet opening of particulates. Do not force too large a wire
or probe into the jet opening or the opening will become distorted. A loss of sensitivity
or poor peak shape may result if the opening is deformed. The various parts can be
ultrasonicated after cleaning with a brush. Eventually the jet needs to be replaced,
so it is strongly recommended to have spare jets on hand.
Over time, residue from the bead or sample can build up in the collector and cause
baseline problems. You should clean the collector after you have damaged the bead
two or three times.
The metal C-rings wear slightly with each assembly and disassembly. After several
assemblies and disassemblies (five or more), the rings may not seal effectively, causing
an erratic baseline. A ceramic insulator and seal kit is available. Always cool the detector
to near-ambient when changing seals and insulators.
Because there is no flame in the NPD, the jet does not collect silica and soot as does
the FID jet. Although you can clean the jet, it is ususally more practical to simply replace
dirty jets with new ones. If you do clean the jet, use the cleaning wire, taking care not
to damage the inside of the jet. You can also use a sonicator bath to clean the jet.
Cleaning and Replacement
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