Development of a turnkey analytical system for the forensic comparison and identification of fiber dyes on casework-sized fibers

At present, forensic fiber dye analysis is performed by empirical comparison methods that are not supported by chemical identification of the dyestuffs present on the fibers. The research and development project proposed here is intended to utilize the simple and inexpensive technique of TLC to separate the dyes, followed by microchemical methods to isolate and identify the separated dye spots using a dyestuff database containing infrared, solution, fluorescence and SERS spectra of at least 300 commercially important dyestuffs. Case-work experience has shown that dyes can be extracted and separated by TLC from fibers as short as 5 mm. Existing microchemical techniques for extracting these dyes from the separated spots will optimized so the crystalline residue of the extract can be analyzed by micro-FTIR spectroscopy and solution Spectrophotometry by uv-vis microspectrophotometry (MSP). Both of these analytical instruments are already found in virtually every laboratory in the U.S. that performs fiber comparisons. Surface enhanced Raman spectroscopy (SERS) spectra collected from the dyes in situ on the TLC plate will also be obtained as this simple method is likely to gain traction as increasing numbers of laboratories obtain Raman spectrometers. The analytical data from these instruments lifts TLC from a method of separation and comparison to a method of separation and identification. The analytical data obtained from these instruments would, at present however, be of little practical value since no database of infrared, Raman or solution spectrophotometry exists. One major aspect of this project is; therefore, the preparation of a spectral database of 300 authentic dyestuffs to which this data can be compared and identified. Our in-house collection of over 5,500 dyes with accompanying C.I. designations -- many of which consist of the same dye produced by known manufacturers will be characterized to build this database. In addition, we will use our reference collection of dyed fibers from manufacturers' shade cards (fabrics and yarns of all the major man-made fibers as well as wool and cotton dyed by the fiber manufacturers or according to their exact specifications) to develop and test the dye extraction, TLC separation, recovery and analysis techniques. The final products will include: 1. A comprehensive final "Guide to Identification of Dyes in Fibers" that summarizes all of the experimental data collected, the optimized techniques, and the scientific basis for these methods. The methods and validation will be provided in a format that conforms to ISO 17025 guidelines, to encourage adaptation by laboratories. 2. A comprehensive final report that summarizes all of the experimental data collected, all of the techniques designed and perfected and lays the scientific foundation for the procedure that will be presented. 3. The most extensive database of dyes ever created for forensic purposes consisting of FTIR, MSP, and SERS data collected from 300 dyes of traceable origin identified by chemical name. ca/ncf