VaporFit: an open-source software for accurate atmospheric correction of FTIR spectra.

This paper introduces VaporFit, an open-source software for automated atmospheric interference correction in Fourier-transform infrared (FTIR) spectroscopy, based on a refined correction algorithm. It significantly improves the accuracy and reproducibility of chemical and biological FTIR analysis by effectively removing variable contributions from water vapor and carbon dioxide that often obscure spectral features. Unlike traditional methods relying on subtraction of a single reference spectrum, which struggle with atmospheric variability, VaporFit employs a multispectral least-squares approach to automatically optimize subtraction coefficients based on multiple atmospheric measurements recorded throughout the experiment. The software provides a user-friendly graphical interface (GUI) and built-in tools, including objective smoothness metrics and a principal component analysis (PCA) module, to facilitate parameter selection and intuitively evaluate correction quality. Furthermore, we offer practical recommendations for data acquisition strategies tailored for effective atmospheric correction. VaporFit, the user guide, and sample data sets are freely available at https://zenodo.org/records/15411176 and https://github.com/piobruzdpg/VaporFit/releases/tag/v1.0.