A Review of FTIR Spectroscopy for Molecular Monitoring From Static Characterization to Dynamic Trends

Fourier Transform Infrared (FTIR) spectroscopy has evolved into an indispensable analytical platform for molecular monitoring, spanning static compositional characterization to real‐time dynamic trend analysis across environmental, industrial, and biomedical domains. This review provides a unified synthesis of FTIR applications, systematically examining how its synergy with chemometric algorithms—including principal component analysis, partial least squares regression, and artificial neural networks—transforms raw vibrational spectra into actionable quantitative and qualitative information. A central theme addressed is the dual role of water in FTIR: its strong midinfrared absorption represents a dominant interference in industrial waste monitoring yet simultaneously serves as an intrinsic probe of hydrogen‐bonding environments and hydration states, offering an underexploited diagnostic potential. The review critically evaluates FTIR‐based strategies for simultaneous multicomponent quantification in gaseous emissions, wastewater, and solid residues, alongside contactless remote sensing across ground‐based, airborne, and orbital platforms. In the biomedical sphere, label‐free FTIR diagnostics and high‐resolution chemical imaging are assessed for disease screening, therapeutic monitoring, and single‐cell histopathology. Cross‐cutting challenges—including matrix interference, model transferability, and sensitivity–portability trade‐offs—are discussed, and a forward‐looking roadmap is proposed that prioritizes interpretable machine learning, harmonized spectral libraries, and closed‐loop process control. By distilling common bottlenecks and synergistic opportunities from fragmented literature, this review articulates a trajectory in which FTIR, augmented by intelligent data analytics and standardization, matures into a regulatory‐grade, autonomous molecular monitoring technology for the next generation of environmental surveillance and precision diagnostics.