Managing Spectral Intensity Variations With In‐Line Fiber‐Optic High‐Volume Noncontact Raman Probes: A Strategy Exploration

Noncontact fiber‐optic Raman probes are increasingly deployed in industrial environments, where variations in laser power and working distance can compromise quantitative performance. We investigated the stability of partial least squares regression under combined changes in laser power (200–450 mW) and working distance (5–30 cm), comparing intensity‐correction strategies that preserve absolute intensity related to absolute concentration with approaches that suppress it. The effect was discussed in terms of absolute fat concentration measurements and compared with the relative concentration measurement of fatty acid (FA) 18:1 expressed as % of fat. Overall, both correction strategies yielded comparable slope and variance errors, with bias emerging as the primary distinction. Laser power fluctuations were effectively corrected using sapphire‐based normalization or other methods suppressing intensity variations ( and ). Working distance effects were nonlinear and required dedicated compensation. We demonstrated the potential of using nitrogen signals from the air for working distance corrections in bulk fat measurements (). For FA 18:1, accurate quantification depended on explicit removal of instrument and air background, and only an extended multiplicative scatter correction (EMSC) including both background components as separate interferents achieved acceptable bias, providing , compared with for MSC. These results outline practical strategies for maintaining quantitative robustness in noncontact Raman measurements under realistic industrial variability.