Gas Delivery System for Mass Spectrometer Cells
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Solution Overview
Problem
Inductively coupled plasma mass spectrometers with collision/reaction cells face challenges in rapidly switching between vented-cell and pressurized-cell modes due to slow fill times and signal stabilization, leading to reduced sample throughput and increased operational costs at low flow rates.
Innovation Solution
The implementation of a gas delivery system utilizing three-way valves and vacuum system configurations to purge gas lines between mass flow controllers and the gas manifold, reducing gas flow over-shoot and enabling faster switching between operational modes by minimizing pressure differences across valves, thus reducing the internal leakage requirements and improving fill times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas is delivered to collision/reaction cell at low flow rates to achieve precise pressure control, then measurement precision is improved, but fill time increases significantly reducing productivity
Solution Approach 1:
The system pre-fills a gas reservoir to a predetermined pressure before analysis begins. This preliminary action stores gas in advance, so when analysis mode is activated, the gas can be delivered immediately at high flow rates without waiting for slow fill processes, thus resolving the contradiction between precise pressure control and fast sample throughput.
Solution Approach 2:
The invention extracts the gas storage function from the main analysis system by introducing a separate gas reservoir. This reservoir can be filled independently at low flow rates when precision is needed, then rapidly dispense gas to the collision/reaction cell during analysis, separating the precision filling process from the high-speed analysis process.
2Productivity
If gas flow rate is increased to reduce fill time and improve productivity, then sample throughput is improved, but gas flow over-shoot increases causing signal instability
Solution Approach 1:
The gas reservoir acts as an intermediary between the gas source and the collision/reaction cell. It buffers the gas flow, allowing high flow rates during transfer while maintaining stable pressure in the cell. The reservoir's larger volume absorbs flow variations, preventing over-shoot and signal instability even when gas is delivered rapidly.
Solution Approach 2:
The system cushions against gas flow over-shoot by using the gas reservoir as a buffer. The reservoir's volume provides a cushion that absorbs sudden pressure changes and flow variations, preventing the harmful effects of over-shoot while allowing high flow rates to be used for fast filling during analysis.
3Productivity
If switching between vented-cell and pressurized-cell modes is performed rapidly to increase sample throughput, then productivity is improved, but switching time remains long due to slow fill and stabilization
Solution Approach 1:
The gas reservoir is pre-filled with the required amount of gas before switching to pressurized-cell mode. This preliminary preparation eliminates the time-consuming fill process during mode switching, allowing rapid transition between vented and pressurized modes while maintaining high sample throughput.
Solution Approach 2:
The system dynamically adapts gas delivery based on operational mode. During mode switching, the pre-filled reservoir enables rapid pressure changes. The system can quickly transition between vented and pressurized modes by controlling when gas is delivered from the reservoir, optimizing both switching speed and sample throughput.
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 approach significantly reduces switching times from minutes to seconds, enhancing data availability, increasing sample throughput, and lowering analysis costs by eliminating gas flow over-shoot and stabilizing the analytical signal more quickly.
Implementation Method 1
The collision/reaction cell is vented to the vacuum system
Implementation Method 2
minimizing pressure differences across valves
Data Source
Figure 1
Figure 2
AI summary
A gas delivery system for a cell-based mass spectrometer includes a mass flow controller having an input coupled to a gas source. A three-way valve includes an input coupled to an output of the mass flow controller, a first output coupled to a vacuum system, and a second output normally coupled to a reaction or collision cell. A cell is positioned inside a vacuum chamber of the mass spectrometer where the second output of the three-way valve is coupled to an inlet of the cell and the mass flow controller provides a gas to the cell that increases a pressure inside the cell relative to the pressure in the vacuum chamber.