Single-Pot Extraction-Analysis of Dyed Wool Fibers with Ionic Liquids

Abstract

Analytical capabilities to identify dyes associated with structurally robust wool fibers would critically assist crime-scene and explosion-scene forensics. Nondestructive separation of dyes from wool, removal of contaminants, and dye analysis by MALDI- or ESI-MS, were achieved in a single-pot, ionic liquid-based method. Ionic liquids (ILs) that readily denature the wool α-keratin structure have been identified and are conducive to small volume, high-throughput analysis for accelerated threat-response times. Wool dyed with commercial or natural, plant-based dyes have unique signatures that allow classification and matching of samples and identification of dyestuffs. Wool released 0.005 mg of dye per mg of dyed wool into the IL, allowing for analysis of single-thread sample sizes. The IL + dye mixture promotes sufficient ionization in MALDI-MS: addition of common MALDI matrices does not improve analysis of anionic wool dyes. An inexpensive, commercially available tetrabutylphosponium chloride IL was discovered to be capable of denaturing wool and was determined to be the most effective for this readily fieldable method.