Focusing agents and calibration transportability
Inventors
Rubenstein, H. Mitchell • Qualley, Anthony
Assignees
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Publication Number
US-12099045-B2
Publication Date
2024-09-24
Expiration Date
2037-03-07
Abstract
A thermal desorption tube for chromatography and mass spectrometry analysis. The thermal desorption tube includes a sorbent and a plurality of focusing agents loaded at known, relative amounts onto the sorbent. Each focusing agent is a compound that chromatographically elutes within a retention time similar to a retention time of a target analyte and has a mass spectrum similar to a mass spectrum of the target analyte. The thermal desorption tube is configured to be further loaded with a sample having the target analyte.
Core Innovation
The invention relates to a thermal desorption tube for chromatography and mass spectrometry analysis comprising a sorbent and a plurality of focusing agents loaded at known, relative amounts onto the sorbent. Each focusing agent is a compound that chromatographically elutes with a retention time similar to that of a target analyte and has a mass spectrum similar to the target analyte. The tube is configured to be further loaded with a sample having the target analyte to facilitate identification and enhanced quantification.
The invention addresses the problem of wide variability and lower reliability in quantifying chemical warfare agents and toxic industrial chemicals/materials during field analysis. Existing portable gas chromatograph-mass spectrometer devices demonstrate significantly higher relative standard deviation (RSD) values of about 70% compared to an industry standard of about 30% or less. This elevated uncertainty exists even with internal standards present in the instruments, and data variability occurs intra- and inter-instrumentally.
The invention provides a method and system to overcome these challenges by embedding focusing agents with known relative amounts into the sorbent media of the thermal desorption tubes. These focusing agents provide internal calibration that correlates chromatographically and spectrally with the target analytes, enabling improved data quality, reduced variability, and calibration transportability across different instruments and field locations.
Claims Coverage
The patent includes two independent claims directed to methods of comparing amounts of a target analyte using calibration transportability with thermal desorption tubes embedded with focusing agents.
Use of thermal desorption tubes with embedded focusing agents to enable cross-instrument comparison
Obtaining first and second thermal desorption tubes comprising a sorbent with a plurality of focusing agents loaded at known, relative amounts. The focusing agents chromatographically elute at the same retention time as the target analyte and have a similar mass spectrum. Both tubes have the same focusing agents at the same known relative amounts, are further loaded with target analyte samples, desorbing the focusing agents in a chromatography and mass spectrometry instrument, and analyzing these samples on separate instruments to compare the amounts of the target analyte.
Injection timing of the internal standard relative to desorption for improved calibration
Injecting an internal standard not included among the focusing agents either after desorption or immediately prior to desorbing the focusing agents in the chromatography and mass spectrometry instrument. This internal standard is distinct from the embedded focusing agents and is used in the analysis process to improve the quantification and comparison of target analyte amounts between different thermal desorption tubes and instruments.
The inventive features focus on the preparation and use of thermal desorption tubes embedded with focusing agents that chromatographically and spectrally mimic the target analyte, enabling reliable sample analysis and direct comparison across different instruments and locations. The timing of internal standard injection relative to desorption further refines the calibration method.
Stated Advantages
Significantly reduced variability in field measurements, with relative standard deviation (RSD) reduced from approximately 70% to less than 20%, improving data reliability beyond industry standards.
Enables accurate quantification and comparison of target analytes across multiple instruments and different field locations through embedded focusing agents with known relative amounts.
Provides in-situ calibration that compensates for variability and anomalies in conventional internal standard dosing and instrumentation, improving robustness of field portable instrumentation.
Enhances stability of calibration standards over time and under varying environmental conditions including elevated temperatures, supporting effective field and laboratory analysis.
Reduces the need for on-site analytical expertise, facilitating deployment by field personnel and first responders with improved quantitative results.
Documented Applications
Identification and enhanced quantification of chemical warfare agents (CWAs) using portable gas chromatograph-mass spectrometer systems such as the HAPSITE ER.
Field analysis and quantification of toxic industrial chemicals/materials (TIC/TIM) with improved calibration transportability and data quality.
Use in chromatographic analytical techniques including gas chromatography and liquid chromatography coupled with mass spectrometry for volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs).
Application in environmental and military surveillance contexts for detecting hazardous chemical agents across multiple field sites and instruments.
Extending techniques to various adsorbent media and sampling devices, including tubes, dosimeters, and impingers, across multiple analytical configurations.
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