Method Development and Validation of Comparative Finished Fiber Analysis Using Nano-Sampling Cryomicrotomy and Time-of-Flight Secondary Ion Mass Spectrometry.

摘要

The overall goal of the project is to provide an unprecedented, comprehensive, repeatable and reproducible analytical methodology for dyed and finished fibers that will have insignificant negative impact on evidence preservation, and that will enable reduction or even elimination of cross-contamination. This has been achieved via sub-micron level sample removal of fibers using cryomicrotomy followed by Time-Of-Flight Secondary Ion Mass Spectrometry (TOF SIMS) analysis of the surface and cross-section of dyed fibers. The data collected via TOF SIMS has been validated using High Performance Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry (LC-Q-TOF) following microextraction of dye from the dyed fibers under investigation. A cryomicrotome-based fiber cross-sectioning method has been developed and its utility has been compared to the Analytical Instrumentation Facilitys conventional microtome method for fiber cross-sectioning. The experiments to date have shown that the cryo-based method is key to obtaining consistent and effective cross-sectioning of the fibers. We have successfully employed the developed crymicrotome method to make cross sections of a single fiber for TOF SIMS analysis. A TOF SIMS method has been developed to analyze disperse dyes in polyester and acetate and acid dyes in nylon. A revised TOF SIMS method using C60 ion beam has been demonstrated to improve the detection limit for acid dyes in nylon cross sections. The new developed methodology using cryomicrotome and TOF SIMS has been validated via comparison of data with more conventional micro extraction LC-Q-TOF mass spectrometry. Extraction methods have been developed to extract dyes from polyester, acetate and nylon fibers. The isocratic and gradient elution methods developed for LC analysis of a series of disperse dyes and acid dyes have been demonstrated to have excellent repeatability for single dye analysis.