Resistive Capillary Coating for Stable LC/MS Ion Transfer
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Solution Overview
Problem
Existing ion transfer devices face issues with metal capillaries degrading under high temperatures and solvents in LC/MS applications, and leaded glass capillaries being unstable and expensive, while maintaining voltage drop and resistivity.
Innovation Solution
A coated capillary tube with a tunable resistance coating comprising oxides or nitrides of a metal and discrete metal particles, using atomic layer deposition (ALD) to create alternating layers of TiO2, Y2O3, Ta2O5, HfO2, Al2O3, AlN, ZrO2, or ZrN, and discrete metal particles like Ru, W, Mo, or Pt, embedded in the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If metal capillaries are used to achieve fast polarity switching, then electrical conductivity is improved, but degradation under high temperatures and solvents occurs
Solution Approach 1:
The invention uses a composite coating structure consisting of metal oxide layers (such as Al2O3, TiO2, Ta2O5) combined with discrete metal particles (such as Pt, Ru, W, Mo) embedded within the oxide matrix. This composite structure provides both the electrical conductivity needed for fast polarity switching and the thermal/chemical stability required for LC/MS applications, resolving the contradiction between speed and reliability.
2Reliability
If leaded glass capillaries are used to maintain resistivity and voltage drop, then electrical resistance is improved, but instability and drift over time occur
Solution Approach 1:
The invention changes the material composition parameters by replacing lead-based glass with a coating system comprising metal oxides and dispersed metal particles. The concentration and size of metal particles can be adjusted to achieve desired resistance values while maintaining stability. This parameter change eliminates the inherent instability of leaded glass while preserving the necessary electrical resistance for ion transfer device operation.
3Reliability
If leaded glass capillaries are used to achieve resistivity, then electrical resistance is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
The invention replaces the complex mechanical manufacturing process of making leaded glass capillaries with a deposition-based approach. A coating is applied to the inside surface of a standard capillary tube using techniques such as atomic layer deposition (ALD) or chemical vapor deposition (CVD), followed by embedding metal particles. This substitution simplifies manufacturing, reduces cost, and eliminates the need to source specialized leaded glass while achieving the required electrical resistance.
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
The coating provides stable resistivity and voltage maintenance, extending the capillary's usable lifetime and ensuring efficient ion transfer under harsh conditions.
Implementation Method 1
performing atomic layer deposition (ALD) of metal oxides or metals onto or within the capillary tube
Data Source
AI summary
A coated capillary tube having a tunable resistance in an ion transfer device, including an inlet end in communication with an atmospheric-pressure ion source, an outlet end in communication with a vacuum region of a mass spectrometer, a body elongated along an axis from the inlet end to the outlet end, and an inside surface defining a bore having an inner diameter is disclosed. The coated capillary tube also includes a resistive coating on the inside surface of the capillary tube, in which the resistive coating includes at least one layer comprising oxides or nitrides of a metal and discrete metal particles of a different metal embedded therein.