Development of an Enhanced Total Ion Current Chromatogram Algorithm to Improve Untargeted Peak Detection

Area of Science:

• Analytical Chemistry
• Chromatography
• Mass Spectrometry

Background:

• Accurate analyte peak detection is crucial for data analysis, often relying on the total ion current chromatogram (TIC).
• Standard TIC analysis frequently misses low-abundance peaks due to signal limitations and background noise.
• Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) generates complex datasets.

Purpose of the Study:

• To develop and evaluate an enhanced TIC algorithm for improved peak detection in GC × GC-TOFMS data.
• To overcome the limitations of standard TIC analysis in identifying low-signal analytes.
• To enhance the sensitivity and scope of untargeted metabolomic profiling.

Main Methods:

• An 'enhanced TIC algorithm' was developed, utilizing the full mass spectral dimension to identify signals above background noise.
• The algorithm processes GC × GC-TOFMS data by zeroing background noise and summing analytical signals.
• Method validation involved serial dilutions of a test mixture, analysis of yeast metabolite extracts, and chromatographic simulations.

Main Results:

• The enhanced TIC algorithm recovered 62% and 93% of peaks at 1 and 10 parts-per-million (ppm) dilutions, respectively, compared to 0% and 45% for standard TIC.
• Analysis of yeast metabolite extracts revealed 33-64% more peaks using the enhanced TIC compared to the standard TIC.
• Simulations demonstrated that enhanced TIC processing improved the accuracy of statistical overlap theory (SOT) modeling for low signal-to-noise chromatograms.

Conclusions:

• The enhanced TIC algorithm offers a significant improvement in peak discovery for GC × GC-TOFMS data analysis.
• This method effectively detects analytes obscured by background noise, increasing the depth of chemical information obtained.
• The enhanced TIC algorithm is a valuable tool for improving untargeted metabolomics and other complex mixture analyses.