A collaborative study on Raman spectroscopy was carried out by members of the ENFSI (European Network of Forensic Science Institutes) European Fibres Group (EFG) on three dyed fibers: two red acrylics and one red wool. Raman instruments from six different manufacturers were tested as well as nine different laser wavelengths ranging from blue (λ = 458 nm) to near infrared-NIR (λ = 1064 nm). This represents the largest comparison study of Raman analytical parameters carried out on identical fiber samples. For the chosen fiber and dye samples, red lasers (λ = 633 and 685 nm) gave the poorest spectral quality whereas blue (458 nm), green (514 nm) and near infrared lasers (785, 830 and 1064 nm) provided average results. Blue (488 nm) and green lasers (532 nm) globally gave the best quality spectra. Fluorescence problems were often encountered with some of the excitation wavelengths and therefore a flexible Raman instrument equipped with different lasers can be recommended to measure forensic fiber samples. The instrument should also be equipped with a Raman microscope in order to be able to focus on a single fiber. This study shows that Raman spectroscopy usually enables the identification of the main dye present in a colored fiber; however, minor dye components are much more difficult to detect. SERRS (Surface Enhanced Resonance Raman Scattering) techniques give an improvement of the dye's spectral intensity but no spectral improvement was observed for the two red acrylic and red wool fibers tested.

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Spectrophotometers are used for estimating sperm concentrations from raw ejaculates in semen processing laboratories. Unfortunately, these instruments have a limited detection spectrum and do not permit accurate quantification of sperm numbers in highly diluted or concentrated samples. The objectives of this study were to validate a DNA assay for quantification of sperm numbers in extended or undiluted semen samples and to determine precision of the assay. The principle of the assay is based upon a fluorescent dye that binds to adenine-thymine base pairs in double-stranded DNA. Semen samples and calf thymus DNA standards were sonicated in 2 M NaCl buffer with 1 mM EDTA. The DNA content of samples was compared to standards of calf thymus DNA using fluorometry. Sensitivity of the assay was determined to be 1.4 x 10(5) sperm cells. Concentrations of sperm estimated from DNA assay values did not differ from flow cytometric cell counts. Assays were performed in three different laboratories, using different equipment, to assess the assay's repeatability. Estimates of sperm concentrations determined by the DNA assay were similar, regardless of location and source of equipment used to perform the assays. This assay fulfills statistical criteria for being sensitive, accurate, and repeatable, and it can be employed in laboratories processing semen for artificial insemination as a tool for spectrophotometer calibration, a check for straw filling accuracy, or to quantify sperm numbers in extended, packaged semen.