DAPCI System Tapered Tip Ionization
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Solution Overview
Problem
Current methods for detecting explosives, chemical warfare agents, and biological toxins face challenges such as requiring sample manipulation, being slow, and failing to ionize non-volatile and thermally unstable analytes effectively, especially under ambient conditions.
Innovation Solution
A desorption atmospheric pressure chemical ionization system using a high-voltage electrode with a tapered tip and a high-speed gas flow of solvent vapor ions, which directs gaseous solvent ions towards a substrate to ionize analytes without droplets, allowing for rapid and specific analysis without sample preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional desorption ionization methods are used, then ionization of analytes can be achieved, but operation under vacuum conditions is required and sample manipulation is needed
Solution Approach 1:
The invention changes the operating pressure parameter from vacuum to atmospheric pressure, enabling direct ionization of analytes on surfaces without requiring vacuum conditions. This is achieved through a corona discharge ionization source that operates effectively at atmospheric pressure, eliminating the need for complex vacuum systems and sample manipulation procedures
Solution Approach 2:
The invention replaces mechanical sample manipulation systems (wiping, thermal desorption apparatus) with a corona discharge ionization field that directly ionizes analytes in place. The corona discharge creates reactive ions that can extract and ionize analyte molecules from surfaces without physical contact or thermal processing
2Measurement precision
If thermal desorption/gas phase ionization is used, then detection of picked-up compounds can be achieved, but the method is slow and requires manual sample transfer
Solution Approach 1:
The corona discharge ionization source performs preliminary ionization action directly at the sample location without requiring sample transfer. Analytes are ionized in place on the surface, and the resulting ions are directly introduced into the mass spectrometer, eliminating the time-consuming steps of manual sample transfer and thermal desorption
Solution Approach 2:
The invention extracts only the essential function of ionization from the complex thermal desorption process. By using corona discharge to directly ionize analytes on the surface, it removes the unnecessary steps of thermal heating, vaporization, and manual sample handling, achieving rapid detection while maintaining detection precision
3Reliability
If electrospray ionization is used, then ionization of analytes can be achieved, but significant sample manipulation is required
Solution Approach 1:
The invention replaces the complex electrospray mechanical system (nebulizer, capillary, high voltage source requiring sample introduction) with a corona discharge system that ionizes analytes directly on the surface. This substitution eliminates the need for sample dissolution, injection, and nebulization steps, significantly reducing device complexity and sample manipulation requirements
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 system provides high sensitivity, specificity, and rapid response times for detecting trace analytes, including explosives and toxins, with no sample handling, enabling effective analysis of non-volatile and thermally unstable compounds.
Implementation Method 1
a wire, needle, or other elongated electrode having a tip, which can be tapered, is connected to a high voltage power supply... The gaseous solvent vapor is ionized in close proximity to the tip by virtue of the high voltage applied to the electrode
Implementation Method 2
A vapor of a solvent is mixed into the annular gas flow surrounding the electrode. The high-speed flow of gas and solvent vapor ions extending outward from the capillary is directed toward a substrate
Data Source
AI summary
A desorption atmospheric pressure chemical ionization (DAPCI) system delivers a primary ion beam composed of an inert, high velocity gas and solvent ions to a surface to effect desorption and ionization of both volatile and non-volatile species present on surfaces. A electrode having a tapered tip is connected to a high voltage power supply. The tapered tip projects outward from a capillary carrying a high-speed flow of gas. A vapor of a solvent is mixed into the annular gas flow surrounding the needle. The gaseous solvent vapor is ionized in close proximity to the tapered tip by virtue of the high voltage applied to the electrode. The high-speed flow of gas and solvent vapor ions extending outward from the capillary is directed toward a substrate on which an analyte of interest may have been deposited. The solvent vapor ions can blanket the surface of the analyte causing a static charge build up that facilitates ion desorption and additionally can provide positive ion adducts of the analyte freed from the substrate surface that can be directed toward an atmospheric intake of a mass spectrometer or other instrument capable of studying the analyte.