Optimized data analysis algorithm for on-site chemical identification using a hand-held attenuated total reflection...

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Chemical Defense

Background:

• Field-portable spectroscopy is crucial for rapid on-site chemical identification.
• Distinguishing target analytes from complex environmental matrices remains a significant challenge.

Purpose of the Study:

• To develop and validate an algorithm for identifying specific chemical warfare agents (CWAs) using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy.
• To assess the algorithm's performance in the presence of common interfering materials found in field conditions.

Main Methods:

• Utilized a field-portable ATR FT-IR spectrometer for spectral data acquisition.
• Developed a spectral comparison algorithm that calculates similarity (distance) between analyte and reference spectra at selected frequencies.
• Optimized the algorithm to identify O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioic acid (VX), sarin (GB), and sulfur mustard (HD).
• Employed receiver operating characteristics (ROC) analysis to determine probabilities for detection (PD) and false alerts (PF).

Main Results:

• The algorithm, using an average distance approach across multiple frequencies, achieved high detection probabilities (PD) for VX (90%), GB (90%), and HD (90%).
• Low false alert probabilities (PF) were recorded: 0% for VX, 0% for GB, and 1% for HD.
• The average distance method proved significantly more effective than analyzing individual spectral frequencies.
• Algorithm performance was validated across various combinations of spectral peaks.

Conclusions:

• The developed algorithm provides a reliable method for the on-site identification of predetermined analytes, specifically CWAs, amidst interfering substances.
• The ATR FT-IR approach combined with the spectral comparison algorithm offers a robust solution for chemical threat detection in diverse environments.