Discharge Ionization Current Detector High Temperature Noise Reduction
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Solution Overview
Problem
High-boiling-point components analysis in gas chromatography using helium discharge photoionization detectors (HDPID) faces signal-to-noise ratio deterioration due to temperature-induced electric resistance changes in conventional insulating materials and gas discharge at high temperatures.
Innovation Solution
Employing sapphire or aluminum oxide with purity equal to or greater than 99.5% as insulating members and utilizing low-frequency dielectric barrier discharge to generate plasma, along with metallic O-rings and specific electrode materials to maintain airtightness and prevent oxidation, thereby reducing noise and maintaining signal integrity at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ion collecting section is heated to about 400 degrees Celsius to facilitate ionization of high-boiling-point components, then the ionization efficiency is improved, but temperature drift and noise abruptly grow at above 300 degrees Celsius, causing the background level to increase and the signal-to-noise ratio to deteriorate
Solution Approach 1:
The patent changes the material parameter of the insulating member from conventional ceramic to sapphire or aluminum oxide with specific purity (99.5% or higher). This material parameter change enables the insulating member to maintain stable electric resistance at high temperatures (400°C), preventing temperature drift and noise while allowing the ion collecting section to be heated to 400°C for improved ionization efficiency of high-boiling-point components.
2Device complexity
If conventional insulating members are used in the ion collecting section, then the device complexity is reduced, but electric resistance abruptly lowers at temperatures equal to or higher than 300 degrees Celsius, causing inadequate electrical insulation and detected as drift or noise
Solution Approach 1:
The patent specifies precise material parameters for the insulating member: sapphire or aluminum oxide with purity of 99.5% or higher. This parameter specification ensures that the insulating member maintains adequate electrical insulation performance (stable electric resistance) at high temperatures (300°C or higher), preventing false drift or noise signals while keeping the device structure relatively simple.
3Power
If high voltage pulse is applied to the plasma excitation electrode to generate plasma, then the ionization capability is improved, but gas discharge occurs at high temperatures, unnecessarily detected by the detector and causing background level to increase
Solution Approach 1:
The patent uses helium gas as the plasma generating gas, creating an inert atmosphere in the plasma generating section. This inert environment prevents unwanted gas discharge reactions that would otherwise occur at high temperatures, while still allowing effective plasma generation for ionization. The helium atmosphere ensures that only the intended plasma-related processes occur, preventing false detections and background level increases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents deterioration of the signal-to-noise ratio at high temperatures, enabling effective analysis of high-boiling-point components with improved measurement precision and reduced background noise.
Implementation Method 1
Helium gas is introduced into the plasma generating section, and a high voltage pulse is applied to the plasma excitation electrode, so that the helium gas is excited, thereby generating the plasma
Implementation Method 2
The light (vacuum ultraviolet light and the like) emitted by the plasma reaches the ion collecting section
Implementation Method 3
the light reached from the plasma generating section is cast to the sample gas, thereby ionizing the sample gas (sample ions)
Implementation Method 4
Voltage is applied to the bias electrode, generating an electric field, and the sample ions are guided to the ion collecting electrode
Implementation Method 5
the sample ions are guided to the ion collecting electrode. The ion collecting electrode collects the sample ions and detects the sample ions as an ion current
Implementation Method 6
An insulating member of, for example, ceramic (having thickness of several millimeters) is inserted between the ion collecting electrode and the bias electrode to electrically insulate one from the other
Data Source
AI summary
A discharge ionization current detector of the present invention is used for a detector for a gas chromatograph and suitable for analyzing high-boiling components. A discharge ionization current detector 10 is mainly constituted by a plasma generating section 20 and an ion collecting section 30. Regarding the ion collecting section 30, an ion collecting electrode 31 and a bias electrode 32 are arranged, and furthermore, an insulating member made of sapphire or aluminum oxide having a purity equal to or greater than 99.5% is arranged between the ion collecting electrode 31 and the bias electrode 32.