APPLICATION OF FT-IR STEP-SCAN PHOTOACOUSTIC PHASE MODULATION METHODSTO KERATIN FIBERS

Step-scan FT-IR/PAS is shown to be a powerful tool for the nondestruct ive analysis of keratin fibers. Depth profiling studies were performed either by varying the optical velocity of the interferometer (scannin g FT-IR/PAS depth profiling) or by a phase modulation method, utilizin g a lock-in amplifier to separate the surface and bulk components of t he signal phase. Both methods were shown to be capable of distinguishi ng spectroscopically between the cuticle and cortex of wool and hair f ibers, the different spectral features being consistent with the diffe rences in protein composition between these components. Phase-modulate d spectra exhibited improved signal-to-noise ratios, with relatively l ittle interference from saturation effects, compared with scanning FT- IR/PAS depth profile spectra.