Basic HTML Version
HID - SRI Instruments
HID - Helium Ionization Detector
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Universal (except neon)
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Detect from 1-2 % down to 10 ppm
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Requires only helium carrier and make-up gas
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Perfect complement to the TCD!
The Helium Ionization Detector is a "universal" detector which responds to all molecules except neon. The HID is
particularly useful for volatile inorganics like NOx, CO, CO
2
, O
2
, N
2
and H
2
which do not respond on the
or
other detectors. Unlike an FID, the HID needs no hydrogen or air. Requiring only helium carier and make-up gas, the
HID delivers sensitivity in the low ppm range. For labs that are reluctant to store hydrogen fuel gas for safety reasons,
the helium-only HID is a significant advantage.
The HID is especially useful in combination with a
The TCD is not sensitive enough to detect low
ppm concentrations, while the HID saturates in the low percent range. When using both detectors in series, it is possible
to cover 10ppm to 100%.
Unlike other HID designs, the SRI HID can be easily disassembled for cleaning. The HID incorporates robust,
easily servicable electrodes which support a low current arc through the helium make-up gas flow. This elevates the
helium to a metastable state. When the metastable helium molecules collide with sample molecules as they elute from
the column, the sample molecules are ionized and attracted to a collector electrode, amplified and output to the data
system. Our HID features a window through which the low current arc is visible, so it is easy for the operator to verify that
the detector is functioning.
This chromatogram
shows the SRI HID