Dynamite packaging and portable capillary electrophoresis in forensics

Abstract

Evidence storage is a serious concern in forensic laboratories. If evidential items are not properly packaged and stored, important information can be lost. Specifically, packaging for evidence with volatile compounds is a sore point, since those components tend to volatilize, to leave the evidential item, and to escape from the container. There are many types of containers for evidence with volatile compounds, and all of them have advantages and disadvantages. During the development of this thesis, two types of plastic bags have been studied in order to analyze their suitability for the storage of dynamites, which are explosives with volatile compounds such as ethylene glycol dinitrate or dinitrotoluene. Firstly, an extraction method to recover ethylene glycol dinitrate from dynamites was developed. Then, high performance liquid chromatography was used for the determination of ethylene glycol dinitrate in the extract. The analytical method was developed and optimized for the separations of seven compounds that may be present in dynamites and was the method also validated. Finally, the EGDN content of a sample of the Goma-2 ECO dynamite was determined obtaining a concentration of 30.29%, which was in accordance with the manufacturer’s specifications for this dynamite (25.7% - 31.4%). The same high performance liquid chromatography but using mass spectrometry detection, which was 2 orders of magnitude more sensitive than diode array detection, was subsequently applied, together with gas chromatography analyses, in a new study on the suitability of polyethylene bags for the storage of dynamites. The results proved that those polyethylene bags were not really appropriate for the storage of dynamites since they allowed the rapid escape of volatile compounds as ethylene glycol dinitrate and dinitrotoluene from the bags. Moreover, it was demonstrated that the bags allowed the cross-contamination between dynamites of different compositions. In a following study, the polyethylene bags were compared to a multilayer nylon/polyethylene bag, which have been designed to show high retentiveness for volatile compounds. The ethylene glycol dinitrate released from dynamites stored in the bags was followed by gas chromatography analysis in a comparative study over eleven weeks of storage. The results showed that the new bags were much more suitable for the storage of dynamites, since only a weak signal for ethylene glycol dinitrate was detected out of the new bags after eleven weeks, instead of the first week needed to be released from the polyethylene bags. Furthermore, the use of portable analytical instrumentation has attracted attention in recent years due to its benefits. Portable analytical instrumentation allows in situ analyses, permitting the obtention of results and to make decisions directly at the place of sample collection, usually reducing the number of analyses needed, and reducing the chances of occurrence of sample degradation, alteration, misplacement or loss during its transportation and storage. A new portable capillary electrophoresis with automated injection and contactless conductivity detection was developed. The system, of about 8 kg and able to operate continuously for 9 h in the batterypowered mode, relied on pressurized air for solution delivery and a micromembrane pump for sample aspiration. The injection system allowed easy optimization for high separation efficiency, for fast separations, or for low limits of detection. Another portable capillary electrophoresis, allowing to deliver up to four different solutions, was also built. The system was applied to the determination of degradation products of nitrogen mustards in different water samples, taken from a well and from three different rivers. The capillary was coated to avoid analyte-wall interactions and the coating procedure was optimized to get the best repeatability of the analyte migration times. The electrophoretic method was successfully applied to the determination of nitrogen mustards degradation products in the spiked water samples, without matrix interferences. Finally, the same portable capillary electrophoresis was applied to the determination of scopolamine in different samples. Scopolamine has been commonly used in recent years for predatory and recreational uses. In fact, there are several cases in which people have died, have been raped and robbed, due to the abuse of this drug. The different evidential items analyzed were a infusion of Datura stramonium L., a spiked moisturizing cream, and six spiked beverages, since they have recently been used in different criminal actions or used with fatal consequences. An effort was made to develop easy and fast sample treatments which can be readily carried out at the place of sample collection. The developed electrophoretic method was applied to the determination of the drug in the three above-cited evidential items, without sample interferences.