There is a great problem in forensic science to rescue of body fluid for its identification. For the identification of the fluid like blood, semen, saliva and sweat number of methods have been developed. Short time ago Lednev and Virkler profile have published on considerable evaluation on the methods which are well established for body fluid analysis in the forensic science. There is no much more research on the sweat identification because it has no specific marks. Sweat is a dilute substance therefore it is tough to detect sweat marks by using ALS (alternating light source). Usually the human sweat analysis is used to identify the contamination it may be drugs or may its metabolites. In unknown sample the appearance of lactic acid may possible that sweat is percent. However, lactic acid may also present in semen and saliva and to differentiate either sweat or semen is present, complementary test are made. Recent studies have shown that dermcidin, an antibiotic peptide which is secreted by sweat glands of human and may prospect biological marker of sweat. For the identification of sweat a newly method dermcidin-specific monoclonal antibody is used.
Especially non-destructive methods are advantageous because for forensic analysis uncovered evidences needs to be preserved in which DNA extraction are also include. Nondestructive and confirmatory test for the analysis of stains of sweat is Raman micro spectroscopy. It is based upon the scattering of laser light between the interaction with vibrating molecules of liquid, solid and gas. It may tell about the structure of the substance. There is no preparation of sample and chemical reagent is required. Recent last year’s Raman spectroscopy may use in the forensic identification of drugs, lipsticks, inks, paints and fibers. For the identification of human saliva, blood and semen multidimensional Raman spectroscopy have been developed. Each Raman spectroscopy signature has unique characters and may vary from one donor to another donor.
Here is the discussion of Raman multidimensional signatures of sweat of human. To minimize the false positive with other body fluid, statistical analysis was performed by taken the variation of Raman spectra. To collect Raman spectra from different marks of dried sample of sweat, automatic mapping is used. As a result unique multidimensional spectra are obtained. It may also noticed that multi-dimensional Raman spectra have revealed that body fluid like semen, saliva and sweat may have minor variation which means that body fluid compositions are almost same with small variation. But sweat composition may vary from donor to donor. Because sweat composition may depend upon the condition in which it is released like in normal condition that in environmental condition and in in stress condition. Experimental data and florescent background data are made subtracted by using an automatic correction baseline, as a result two sets of data were made. After baseline correction the Raman spectra may come in first set of data. And second set of data may contain fluorescent background. Examination of these two set of data are made separately for the purpose of spectroscopic components. This may allow us to separate Raman and fluorescent contribution. After complete observation it is indicated that Raman spectroscopy has powerful consideration in forensic for the analysis of traces of sweat.
In another study about the observation of concentration on the skin mainly two methods are used one of which is ex vivo method and another method is in vivo method. Ex vivo method may be invasive because cell layer is removed from the sternum corneum with the help of tape which is adhesive in nature. But in vivo method is not invasive. Mainly Raman spectroscopy is used for in vivo method. In Raman spectroscopy the sample which is to be observed is passed through the monochromatic laser light. The molecules present in the sample and photons of light interact with each other, after interaction scattering of light occur. As a result energy is transferred and excitation of vibrational mode takes place. Vibrational motion depends upon the bond between the molecules and the masses of atoms.
When sweat comes on the skin of donor, it is collected with the help of pipette then it is instantly frozen at -20oC for later use. Seven samples are collected from Lee Bio solution, Inc. and then these are tested for HCV, HbsAg, syphilis, HIV -1 & 2 and HIV-1 antigen by using FDA approved method.
Spectra were gotten utilizing a Renishaw inVia confocal Raman spectrometer furnished with an exploration grade Leica magnifying lens, 50× long-extend objective (numerical gap of 0.35). The programmed mapping was performed at the lower plate of a Renishaw earlier programmed stage framework, and estimations were taken utilizing Wire 3.2 programming. A 785 nm laser light was used for excitation. A 10µL drop of each sweat test was set on a microscopy slide, which was secured with aluminum foil and permitted to dry totally. Aluminum foil was utilized to diminish solid fluorescence from glass. The laser control on the dried examples was around 115 mW, and the spot size of the excitation shaft was 5µm utilizing the standard confocal mode. The spectral resolution was approximately 1 cm-1. For the purpose of calibration, standard of silicon was used. We utilized a Raman spectroscopic mapping strategy, in view of the successive spectra acquisition of adjoining districts of an example. The programmed mapping was performed for three territories of 60 µm × 40 µm (32 points each) on each example, with three 10s aggregations at each point. In this manner, three sets comprising of 32 spectra were gotten from each example, where every range in set speaks to a specific spot from the examined zone of the stain. The programmed mapping was performed for the remainder of the tests with same way.