For both fiber surface analysis and, with the aid of cryomicrotomy, fiber cross-section analysis, this research project used time-of-flight-secondary ion mass spectrometric (TOF-SIMS) to identify various dyes in finished textile fibers.
A minimally destructive technique for the determination of dyes in finished fibers provides an important tool for crime scene and other forensic investigations. The analytical power and the minimal sample consumption of time-of-flight-secondary ion mass spectrometric (TOF-SIMS) analysis provides the ability to obtain definitive molecular and elemental information relevant to fiber identification, including identification of dyes from a small volume of sample. In the current study, the analysis of C.I. Acid Blue 25 in nylon is presented as a representative example. The molecular ion of C.I. Acid Blue 25 with lower than 3 percent on weight-of-fiber (owf) dye loading cannot be identified on dyed nylon surfaces by TOF-SIMS using a Bi3+ primary ion beam. Sputtering with C60+ provided the ability to remove surface contamination, as well as at least partially remove Bi-induced damage, resulting in a greatly improved signal-to-noise ratio for the Acid Blue 25 molecular ion. The use of C60+ for damage removal in a cyclic manner, along with Bi for data acquisition, provided the ability to unambiguously identify Acid Blue 25 via its molecular ion at a concentration of 0.1 percent owf from both fiber surfaces and cross sections. (publisher abstract modified)