Radiant energy – Invisible radiant energy responsive electric signalling – Including a radiant energy responsive gas discharge device
Patent
1996-09-30
1998-09-08
Porta, David P.
Radiant energy
Invisible radiant energy responsive electric signalling
Including a radiant energy responsive gas discharge device
250379, G01N 2766
Patent
active
058048286
ABSTRACT:
Electron capture detector for use with an effluent stream from a gas chromatograph includes an ionization cell and a sample inlet system connected to the ionization cell for providing an effluent fluid having a sample concentration therein. In the preferred constant-current, variable frequency mode of operation, a cell current is measured and compared to the reference current. The pulse rate is then adjusted to maintain a constant cell current. The pulse rate is converted to a voltage, processed according to a novel linearization formula, and recorded. The ionization cell includes a radioactive ionization source and the ionization cell defines an optimized cell volume in which the electron capture reaction is forced to occur according to a concentration mode of operation. Improved sensitivity in the electron capture detector may be achieved by restricting the effective radioactivity in the ionization cell to be in the range of 0.5 to 3 milliCuries, and preferably in the range of 1 to 2 milliCuries. The ionization cell volume is substantially reduced while the aforementioned effective level of radioactivity is nonetheless maintained. Linearization of the electron capture detector is obtained by overcoming and/or compensating for several sources of nonlinearity by: (1) forcing the detector to operate in only the concentration mode of operation, and (2) processing the signal derived from the detector response so as to compensate for a heretofore unrealized logarithmic decay of the response factor at higher sample rates.
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Dudley Mark Z.
Hanig Richard
Hewlett--Packard Company
Porta David P.
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