Atmospheric Pressure Ionization Apparatus Gas Flow Design
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Solution Overview
Problem
Conventional atmospheric-pressure ionization techniques face challenges in achieving a stable and uniform heating environment within the ionization chamber, leading to unstable sample sprays and contamination of mass spectrometers due to neutral droplets, which disrupts the ionization process and reduces sensitivity.
Innovation Solution
The API apparatus features a housing with a flared structure and a gas passage that directs a stream of drying gas in a radial direction, optimizing gas flow and heating, and includes a secondary electrode with a cylindrical portion to reduce turbulence and stagnation zones, ensuring a smooth and heated environment for ionization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a stream of drying gas is introduced into the ionization chamber to assist evaporation and sweep solvent away, then solvent removal is improved, but gas turbulence is created that disrupts the sample spray
Solution Approach 1:
The gas passage is designed to direct drying gas to specific locations within the ionization chamber where solvent removal is most needed, rather than introducing gas uniformly throughout the chamber. This localized approach removes solvent effectively while minimizing disruption to the sample spray in other regions.
Solution Approach 2:
The gas flow is directed along the sampling axis (axial direction) rather than perpendicular to it, utilizing a different spatial dimension to achieve solvent removal without creating turbulence that would disrupt the spray trajectory.
2Productivity
If the drying gas velocity is increased to improve solvent evaporation, then evaporation efficiency is improved, but gas turbulence increases that disrupts the sample spray
Solution Approach 1:
High velocity gas flow is confined to specific regions where evaporation is needed, while other regions maintain lower gas velocities to preserve spray stability. The gas passage geometry creates zones of different flow characteristics.
Solution Approach 2:
The gas flow utilizes the axial dimension along the sampling axis to achieve evaporation efficiency without creating radial turbulence that would disrupt the spray. The flow direction is changed from perpendicular to parallel with the spray axis.
3Device complexity
If the ionization chamber geometry and components are configured conventionally, then device simplicity is maintained, but low-pressure gas stagnation zones are created that perturb the sample spray
Solution Approach 1:
The ionization chamber is divided into distinct functional regions: an ionization region for sample introduction and ion formation, and a drying region for solvent removal. This segmentation allows optimization of each region's gas flow characteristics without compromising the other.
Solution Approach 2:
The gas passage introduces drying gas along the axial dimension rather than from the sides, creating a co-flow configuration that eliminates stagnation zones and maintains continuous gas movement through the chamber.
4Quantity of substance
If drying gas is directed to sweep solvent away from the sampling orifice, then solvent removal is improved, but the majority of the ionization chamber remains unheated
Solution Approach 1:
The drying gas stream serves multiple functions simultaneously: it sweeps solvent away from the sampling orifice, provides heating through its thermal energy, and maintains a uniform temperature distribution throughout the ionization chamber. This multi-functionality resolves the trade-off between solvent removal and heating uniformity.
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
This configuration enhances the stability of the sample spray, reduces contamination, and increases the sensitivity of the mass spectrometer by improving the ionization efficiency and maintaining a uniformly heated environment, resulting in a higher ion signal intensity.
Implementation Method 1
a gas passage that is configured for directing a stream of gas from a gas source to the chamber in a radial direction relative to the sampling axis
Implementation Method 2
A voltage potential is applied between the needle and a secondary electrode (or counter-electrode) in the ionization chamber to establish an electric field within the ionization chamber
Implementation Method 3
The droplets undergo a process of desolvation or ion evaporation as they travel through the ionization chamber. As solvent contained in the droplets evaporates, the droplets become smaller.
Implementation Method 4
The electric field induces charge accumulation at the surface of the liquid at or near the tip of the needle, and the liquid sample is discharged from the needle in the form of highly charged droplets (electrospray)
Data Source
AI summary
An atmospheric pressure ionization apparatus includes a chamber, an ion inlet structure, an electrode, a sample emitter, and a gas passage. The ion inlet structure includes a sampling orifice. The electrode includes an electrode bore. An ionization region is defined between the ion inlet structure and the electrode. The flared structure is coaxially disposed about the ion inlet structure, and extends along an outward direction that includes a radial component relative to the sampling axis. The sample emitter is oriented at an angle to the sampling axis for directing a sample stream toward the ionization region. The gas passage directs a stream of gas from a gas source to the chamber. The flared structure and the wall cooperatively form an outward-directed portion of the gas passage that extends annularly about the sampling axis and along the outward direction. The gas flows through the outward-directed portion, around the flared structure, and toward the ionization region and the electrode bore.