No description available.

Forensic investigation television shows such as police procedurals, rooted in both fact and fiction, have become an ever-popular staple of modern television in the last 20 years. The popularity of these shows has been blamed for generating higher expectations for forensic evidence by juries across America and may also have had the effect of inspiring criminals attempt to cover up their crimes by destroying potential evidence, particularly bloodstains. Luminol is a popular blood detection technique because it can be sprayed throughout an area in a dark room and will chemiluminesce when it interacts with hemoglobin. This chemiluminescence is a signal to investigators that latent blood may be located in that spot. Luminol’s specificity and sensitivity have long been studied. Luminol is a stable molecule that becomes oxidized when it comes in contact with an oxidant such as hydrogen peroxide and a catalyst. In this excited state, the molecule is unstable and forms 3-aminophthalate. This molecule produces light, and the luminescence slowly dies out as the molecule returns to its ground state. Chemicals that disrupt the luminol reaction can be considered interferents. These include cleaning agents, biological agents, foods, and drinks, among others. Compounds such as sodium hypochlorite, sodium percarbonate, and hydrogen peroxide are commonly used as primary cleaning products or as components in popular brands of household cleaners. Such multisurface cleaners, extra strength detergents or other chemicals are readily accessible to someone attempting to clean up a crime scene. Sodium hypochlorite, also known as bleach, has previously been found to cross react with luminol, generating a chemiluminescent reaction whether heme is present or not. Sodium percarbonate is also known as active oxygen and is used in detergents to improve their stain removing capabilities. It can affect the luminol and Bluestar® Forensic tests by causing a negative result, even in the presence of blood. Hydrogen peroxide is a common disinfectant and a necessary component of most presumptive blood tests, however, bulk quantities of it in the luminol reaction stop the reaction from proceeding. Antioxidants, found in many foods and drinks, can inhibit luminescence by preventing heme from being degraded, an important step in order for the luminol reaction to proceed. The purpose of this investigation is to evaluate the effectiveness of common cleaning agents for removing detectable traces of blood based on published studies. Additionally, an attempt was made to determine if cleaning agents completely remove blood or if they disrupt the luminol reaction when a negative luminol result is obtained. To supplement the literature, a limited experiment was carried out and preliminary data was obtained. This investigation finds that some cleaners interfere with the luminol reaction by altering one or more components in a way that prevents the reaction from fully proceeding, even when blood is still present.

No description available.

One of the main problems encountered in chemical analysis operations in the field is collecting sufficient sample from the source and transferring that sample to the measurement instrument for fast separation and identification. I have been involved in developing a field-portable gas chromatography-mass spectrometry (GC-MS) system with solid phase microextraction (SPME) sampling for point detection of chemical agents. The objective is to minimize the analysis time between sampling and detection of a potential chemical threat. SPME offers a convenient means for sampling gaseous and liquid samples, concentrating the analytes, and transferring the analytes to the injection port of a GC system for separation and identification. GC-MS has advantages of high efficiency, speed, and applicability for field analysis. Work was done to optimize the SPME fiber coating, capillary column dimensions, and GC operating conditions to provide complete analysis within 3 minutes. Since isothermal operation of the GC was a prior requirement, many components in the chromatograms were unresolved. Therefore, a peak de-convolution algorithm was applied to allow for identification and quantitation of poorly resolved and often completely obscured trace components. Details of the instrumentation and optimization of operating conditions are described in this thesis.