Modulated voltage metastable ionization detector

Apparatus for quantitatively analyzing chemical constituents of a sample mixture comprising:

• a chromatograph including a tube and employing a gas carrier;
• means for inserting a sample of said mixture into said chromatograph, whereby the constituents of said mixture are separated into bands in the gas carrier as it flows through said tube;
• means for ionizing the constituents passing in bands through said tube said ionizing means including an ionization voltage input;
• power supply means providing a high voltage at an output which is adapted for connection to said ionization voltage input, whereby an ionization field is developed;
• means for detecting a change in electrical conductance caused by the presence of the various constituents as developed by said ionization means, and for providing an output signal which is representative of the constituent concentration thereof;
• and
• modulation means responsive to said output signal for controlling the amplitude of said high voltage so as to permit a maximum fixed high voltage to be present so long as said constituent concentration is below a predetermined threshold level and to cause the high voltage to vary so as to maintain said output signal substantially constant when the constituent concentration is above said predetermined level.

Apparatus for quantitatively analyzing chemical constituents of a substance comprising:

• a chromatograph including a tube and employing a gas carrier such as helium, hydrogen or nitrogen:
• means for inserting a sample of said substance into said chromatograph whereby the constituents are separated into bands interspersed in the gas carrier as it flows through said tube;
• means for ionizing the constituents passing through said tube, said ionizing means including an ionization voltage input;
• power supply means including a high voltage output adapted for connection to said ionization voltage input, whereby an ionization field is developed;
• means for measuring the change in the electrical conductance which results from the concentration of the various constituents as they pass through said ionization means, and for providing an output signal representative thereof;
• means for monitoring the change in electrical conductance caused by ionization of said constituents said monitoring means being adapted to permit a fixed high voltage to be applied from said power supply means to the ionization voltage input of said ionization means when the electrical conductance of the constituent concentration is below a predetermined level, whereby the current will vary;
• and allowing for said high voltage to vary when the electrical conductance is above said predetermined level, said high voltage varying inversely as the electrical conductance whereby the current is held substantially constant;
• and
• means for recording the variable parameter.