Optimizing column-to-column retention time alignment in high-speed gas chromatography by combining retention time...

Area of Science:

• Analytical Chemistry
• Chromatography
• Chemometrics

Background:

• High-speed gas chromatography (HS-GC) is crucial for analyzing complex mixtures.
• Nominally identical columns often exhibit retention time shifts, complicating data analysis.
• Accurate alignment of chromatograms is essential for reliable classification and comparison.

Purpose of the Study:

• To optimize chromatogram alignment for HS-GC data.
• To evaluate the effectiveness of retention time locking (RTL) and correlation optimized warping (COW) for aligning data from nominally identical columns.
• To improve sample classification using principal component analysis (PCA) by minimizing column-specific variations.

Main Methods:

• Three sample mixtures were analyzed using HS-GC on four nominally identical columns.
• Chromatograms were analyzed without alignment, with COW alone, with RTL alone, and with RTL followed by COW.
• Principal component analysis (PCA) and degree-of-class separation (DCS) were used to assess alignment effectiveness.

Main Results:

• Unaligned data showed high column-to-column variation (DCScol=76.1).
• RTL alone (DCSsam=4.7, DCScol=4.2) and COW alone (DCSsam=1.9, DCScol=1.7) provided insufficient alignment.
• The combined RTL and COW approach significantly improved sample classification (DCSsam=32.5) and minimized column effects (DCScol=0.4).

Conclusions:

• Retention time locking (RTL) provides essential first-order correction for retention time mismatches between identical GC columns.
• Correlation optimized warping (COW) further refines alignment, optimizing sample classification by PCA.
• The sequential application of RTL followed by COW is a robust strategy for accurate data analysis in HS-GC, even with column variations.