Dyed Hair and Swimming\nPools: The Influence of Chlorinated\nand Nonchlorinated Agitated Water on Surface-Enhanced Raman Spectroscopic\nAnalysis of Artificial Dyes on Hair

Chlorine, commonly found in pools and tap water, presents\nan intriguing\nconcern in forensic hair analysis due to its sources and composition.\nCurrent forensic analysis involves optical microscopy which is subjected\nto advanced training where even multiple experts can deliver opposing\nconclusions for the same hair sample. Despite challenges in traditional\nanalysis methods, emerging techniques like surface-enhanced Raman\nspectroscopy (SERS) offer promising solutions, showcasing success\neven in harsh environments like prolonged sunlight or stagnant water\nimmersion. This study employs partial least-squares discriminant analysis\n(PLS-DA) to evaluate SERS efficacy in identifying dyes on hair immersed\nin chlorinated and distilled moving water for up to eight weeks. Our\nresults demonstrated that one semipermanent colorant overwhelmingly\ninfluenced Raman signals in dyed hair exposed to both chlorinated\nand nonchlorinated water over an eight-week period, masking other\ncolorants’ spectral signatures. Despite one colorant’s\ndominance, PLS-DA identified underlying colorants and their exposure\nconditions, suggesting persistent, unique interactions between original\ncolorants and the environment. This study demonstrates the high potential\nfor PLS-DA-based identifications of dyes on hair using SERS.