Direct Construction of Peaks from Free Induction Decay Curves for Gas Chromatography–Molecular Rotational Resonance Spectroscopy without Fourier Transforms

Abstract

The concept of coupling gas chromatography with molecular rotational resonance spectroscopy (GC-MRR) was introduced in 2020, combining the separation capabilities of GC with the unparalleled specificity of MRR. In this study, we address the challenge of the high data throughput of MRR spectrometers, as GC-MRR spectrometers can generate thousands to millions of data points per second. In the previous GC-MRR studies, a free induction decay (FID) measurement was Fourier transformed to generate each point on the chromatogram. Such extensive calculations limit the performance, sensitivity, and speed of GC-MRR. A direct approach is proposed here to extract peak intensity from FID using the Gram–Schmidt vector orthogonalization method. First, analyte-free FIDs are used to construct a basis set representing the instrument’s background noise, and then the remaining FIDs are orthogonalized to this fixed basis set. Each FID yields a single intensity value after Gram–Schmidt orthogonalization. The magnitude of the orthogonalized analyte FID is the signal intensity plotted in the chromatogram. This approach is computationally much faster (up to 10 times) than the conventional Fourier transform algorithm, is at least as sensitive as the FT algorithm, and maintains or improves the chromatographic peak shape. We compare the sensitivity, linearity, and chromatographic peak shapes for the Fourier transform and Gram–Schmidt approaches using both synthetically generated FIDs and instrumental data. This approach would allow the summed peak intensity to be displayed essentially in real-time, following which identified peaks can be further investigated to identify and quantify the species associated with each.

Solving Advanced Task-Specific Problems in Measurement Sciences with Generative AI

“…The experimental details and data collection parameters for the microwave spectrum of benzyl acetate are provided in the reference . The low-resolution source microscopy images of vascular bundles and GATTA cells were obtained under Creative Commons Attribution 4.0 International License from the work of Eilers and Ruckenbusch ().…”

“…The experimental details and data collection parameters for the microwave spectrum of benzyl acetate are provided in the reference. 29 The low-resolution source microscopy images of vascular bundles and GATTA cells were obtained under Creative Commons Attribution 4.0 International License from the work of Eilers and Ruckenbusch (http://creativecommons.org/licenses/by/4.0/). The Raman spectrum was simulated on a sigmoidal baseline, and the peaks were represented as pure Gaussian functions (SI-3).…”

“…Chirped pulse microwave spectrometry is a recent gas-phase technique 29,36,37 to distinguish all types of isomers, such as isotopomers and isotopologues, with a permanent dipole moment. Rotational spectrometry is extremely sensitive to the 3D mass distribution within the molecule.…”

“…It was windowed with a Hamming window, and the purple region underwent the FFT process to generate a onesided magnitude corrected MRR spectrum (Figure 2E) of benzyl acetate as desired. 29 The generated code will work for any FID in MRR.…”

“…In this study, we chose four recently published scientific papers from multiple analytical chemistry subfields: spectroscopy, bioimaging, chromatography, and electroanalytical chemistry. − The reported specific tasks therein were then accomplished with the assistance of an LLM instead of human researchers to explore the capabilities of ChatGPT-4, a Microsoft-backed OpenAI platform. All papers included high-level mathematical concepts not covered in analytical sciences and require advanced training in mathematics for full implementation.…”