title: Detection limits for blood on four fabric types using infrared diffuse reflection spectroscopy in mid- and near-infrared spectral windows.
abstract: Detection limits (DL) for blood on four fabric types were estimated for calibrations derived using partial least squares regression applied to infrared (IR) diffuse reflection spectra. Samples were prepared by dip-coating acrylic, cotton, nylon, and polyester fabrics from solutions of diluted rat blood. While DLs often appear in terms of dilution factor in the forensic community, mass percentage, coverage (mass per unit area), or film thickness are often more relevant when comparing experimental methods. These alternate DL units are related to one another and presented here. The best IR diffuse reflection DLs for blood on acrylic and cotton fabrics were in the mid-IR spectral window corresponding to the protein Amide I/II absorption bands. These DLs were dilution by a factor of 2300 (0.019% w/w blood solids) for acrylic and a factor of 610 (0.055% w/w blood solids) for cotton. The best DL for blood on polyester was found in the mid-IR spectral window corresponding to the protein Amide A absorption band at dilution by a factor of 900 (0.034% w/w blood solids). Because of the similarity between the IR spectra of blood solids and nylon fabrics, no satisfactory IR DLs were determined for the calibration of blood on nylon. We compare our values to DLs reported for blood detection using the standard luminol method. The most commonly reported luminol DLs are of the order of 1000-fold dilution, which we estimate are a factor of 2-7 lower than our reported IR DLs on a coverage basis.
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: DeJong
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Brianna M
authors.initials: BM
authors.lastname: Cassidy
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Wayne L
authors.initials: WL
authors.lastname: O'Brien
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Morgan
authors.affiliation: Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Myrick
mesh_terms: D000179:Acrylates / Q000737:chemistry; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D032561:Cotton Fiber; D057230:Limit of Detection; D015999:Multivariate Analysis; D011091:Polyesters / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013784:Textiles
chemical_list: D000179:Acrylates; D011091:Polyesters; C036658:acrylic acid