Towards faster FT-IR imaging by reducing noise

Fourier transform infrared (FT-IR) imaging is a powerful technique that can be used to obtain spatially resolved chemical information from a large sam ple area in a relatively short time. However, temporal resolution of fast F T-IR imaging is limited by rapid degradation of data quality (due to increa sed noise) with faster image acquisition. We present various coaddition sch emes to reduce noise and improve the quality of images acquired from such s ystems. The application of the proposed schemes allows for improved signal- to-noise ratio (SNR) characteristics in the resulting data. These schemes a re tested by monitoring the dissolution of a polymer film [poly(alpha-methy l styrene)] by a low-molecular-weight solvent [methyl isobutyl ketone (MIBK )]. Pseudo coaddition improved the SNR by similar to 45%, while the SNR for sampling coaddition was found to scale as similar to N-0.5 where N is the number of coadded pixels. A total acquisition time of about 100 s was achie ved, allowing the dissolution process to be monitored by using image acquis itions separated by 3 min. Low noise concentration profiles, linear solvent penetration rate, and polymer dissolution rate were measured. Detection li mits of similar to 5% and quantification limits of similar to 20% were achi eved by using optimal coaddition strategies. This result represents an orde r of magnitude improvement over untreated data.