Ionisation devices
AssigneeIon Science Limited
InventorsWilliam Francis Houlton Dean, Mark Julian Stockdale
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Abstract
An ionisation detector includes a third (fence) electrode (55) between the counter electrode (53) and the sensing electrode (54). The fence electrode (53) is maintained at or near the potential of the sensing electrode (54) and traps charge movement (electrolytic current) along the detector walls associated with condensation and/or contamination within the detector. In a photoionisation detector, the fence electrode is also adapted to trap photo-induced current originating from the cathode (53). Current drawn from the fence electrode (53) provides a measure of the degree of contamination or condensation within the detector and of lamp efficiency.
Claims28
An ion detector including at least one pair of counter (8) and sensing (9) electrodes at different electrical potentials measuring a plasma current between the electrodes in response to the presence of a gaseous analyte, wherein a third electrode (10) is located between the counter and sensing electrodes and is maintained at an electrical potential substantially equal to that of the sensing electrode (9).
A detector as claimed in any one of the preceding claims comprising a corona discharge detector, a photoionisation detector or a flame ionisation detector.
A detector as claimed in any one of the preceding claims measuring current collected by the third electrode (10).
A method of operating an ion detector including a chamber enclosing at least one pair of counter (8) and sensing (9) electrodes at different electrical potentials measuring a plasma current between the electrodes in response to the presence of a gaseous analyte, wherein movement of electric charge along an interior surface of a chamber surround is collected by a third electrode (10) located between the counter and sensing electrodes and maintained at an electrical potential substantially equal to that of the sensing electrode (9).
Dependencies are inferred from the claim text.