Dielectric barrier discharge ionization detector

A dielectric barrier discharge ionization detector for ionizing and detecting a sample component in a sample gas by using plasma induced by an electric discharge within a gas passage through which a plasma generation gas containing argon is passed, the detector comprising:

• a) a dielectric tube made of a dielectric material and containing an upstream section of the gas passage;
• b) an electrically grounded tube-line tip member made of metal, for introducing the plasma generation gas into the dielectric tube;
• c) a high-voltage electrode attached to an outer wall of the dielectric tube;
• d) an electrically grounded upstream-side ground electrode attached to the outer wall of the dielectric tube and located upstream of the high-voltage electrode as well as downstream of the tube-line tip member in a flow direction of the plasma generation gas;
• e) an electrically grounded downstream-side ground electrode attached to the outer wall of the dielectric tube and located downstream of the high-voltage electrode in the flow direction of the plasma generation gas;
• f) an AC power source connected to the high-voltage electrode, for applying an AC voltage between the high-voltage electrode and the upstream-side ground electrode as well as between the high-voltage electrode and the downstream-side ground electrode so as to induce a dielectric barrier discharge within the gas passage and thereby generate plasma;
• and
• g) a charge-collecting section located downstream of the downstream-side ground electrode, forming a downstream section of the gas passage, including a sample-gas introducer for introducing a sample gas into the downstream section, and a collecting electrode for collecting ions generated from a sample component in the sample gas by light emitted from the plasma,
• wherein:
• a semiconductor film is formed on an inner wall of the dielectric tube over an area where the high-voltage electrode is attached and/or an area located downstream of the aforementioned area and upstream of the charge-collecting section;
• and
• when the largest length of the downstream-side ground electrode which allows a creeping discharge to occur between the high-voltage electrode and the charge-collecting section under the condition that the downstream-side ground electrode is located between the high-voltage electrode and the charge-collecting section is defined as an initiation distance for a creeping discharge between the high-voltage electrode and the charge-collecting section, a length of the downstream-side ground electrode in the flow direction is longer than the initiation distance for a creeping discharge between the high-voltage electrode and the charge-collecting section.

A dielectric barrier discharge ionization detector for ionizing and detecting a sample component in a sample gas by using plasma induced by an electric discharge within a gas passage through which a plasma generation gas containing argon is passed, the detector comprising:

• a) a dielectric tube made of a dielectric material and containing an upstream section of the gas passage;
• b) an electrically grounded tube-line tip member made of metal, for introducing the plasma generation gas into the dielectric tube;
• c) a high-voltage electrode attached to an outer wall of the dielectric tube;
• d) an electrically grounded upstream-side ground electrode attached to the outer wall of the dielectric tube and located upstream of the high-voltage electrode as well as downstream of the tube-line tip member in a flow direction of the plasma generation gas;
• e) an electrically grounded downstream-side ground electrode attached to the outer wall of the dielectric tube and located downstream of the high-voltage electrode in the flow direction of the plasma generation gas;
• f) an AC power source connected to the high-voltage electrode, for applying an AC voltage between the high-voltage electrode and the upstream-side ground electrode as well as between the high-voltage electrode and the downstream-side ground electrode so as to induce a dielectric barrier discharge within the gas passage and thereby generate plasma;
• and
• g) a charge-collecting section located downstream of the downstream-side ground electrode, forming a downstream section of the gas passage, including a sample-gas introducer for introducing a sample gas into the downstream section, and a collecting electrode for collecting ions generated from a sample component in the sample gas by light emitted from the plasma,
• wherein:
• a semiconductor film is formed on an inner wall of the dielectric tube over an area where the high-voltage electrode is attached and/or an area located upstream of the aforementioned area as well as downstream of the tube-line tip member;
• and
• when the largest length of the upstream-side ground electrode which allows a creeping discharge to occur between the high-voltage electrode and the tube-line tip member under the condition that the upstream-side ground electrode is located between the high-voltage electrode and the tube-line tip member is defined as an initiation distance for a creeping discharge between the high-voltage electrode and the tube-line tip member, a length of the upstream-side ground electrode in the flow direction is longer than the initiation distance for a creeping discharge between the high-voltage electrode and the tube-line tip member.