Raman identification of drug of abuse particles collected with colored and transparent tapes.

Raman microscopy is a useful tool for the analysis of drug particles collected with adhesive tapes. In this work, first, the spectra of thirty drugs of abuse, degradation products, metabolites, and common cutting agent standards were recorded and the Raman bands observed were summarized providing the forensic analyst useful information for the identification of drug evidence. Then, the collection of different drug particles by a fingerprint lifting tape commonly used to remove and store fingerprints and fibers, and a white and green packaging tape, followed by the subsequent identification of the drugs by confocal Raman spectroscopy was performed. The particles were analyzed on top of the tapes, trapped between glass slides and the tapes, trapped in the tape folded over itself in the case of the transparent tape, and after folding and unfolding the tape in the case of the colored tape. The results obtained by the different approaches show that both tapes did not compromise the drugs spectra. However, the use of transparent tape is preferred because this tape allows the previous visual detection of the particles. Finally, several drug and sugar particles were spread over a clean table and inside a pocket, and the particles were collected with transparent tape and then properly identified. Although good results were obtained in both cases, the amount of fibers and other substances present in the collection area made the previous detection of the particles difficult and increases the analysis time.

Study of the suitability of DUO plastic bags for the storage of dynamites.

A comparative study on the retentiveness of two plastic bags (DUO and Royal Pack) has been carried out by gas chromatography with mass spectrometry detection. Two types of dynamites were packed in both plastic bags. The bags were placed into glass jars and headspace analyses were performed over 11 weeks to detect whether the volatile constituents of the dynamites were released from the bags. DUO plastic bags showed much better retentiveness than Royal Pack plastic bags. Ethylene glycol dinitrate (EGDN) was quickly detected in the headspace of the glass jars containing Royal Pack plastic bags after 1 week of storage. On the contrary, only a weak signal of EGDN, which was not detectable in the total ion chromatogram, was detected after 11 weeks of storage. Moreover, DUO plastic bags have shown less background signals than the Royal Pack bags, being the former bags much more suitable for the storage of dynamites.

Why is methenamine detected in Goma-2 dynamites originally methenamine free? An interpretation of relevant forensic results.

After the train bombing in Madrid (Spain) on 11 March 2004, methenamine was detected in some of the specimens of Goma-2 ECO dynamite submitted to the forensic laboratories when analyzed by gas chromatography coupled with mass spectrometry detection (GC-MS). Methenamine is synthesized from formaldehyde and ammonia through a condensation reaction. However, neither methenamine nor any of these compounds were used to manufacture Goma-2 ECO dynamite. Four different experiments were designed in order to explain the presence of methenamine detected in the dynamite samples analyzed. In the first one, GC-MS was used to analyze the individual components of Goma-2 ECO provided by the manufacturer and the components mixed in a raw paste. Methenamine was detected in the manufacturer's ammonium nitrate and in the raw paste. The other experiments were designed to find the precursors sources for methenamine generation in Goma-2 ECO. Results revealed that these sources could be ammonium nitrate for ammonia and sawdust for formaldehyde. Under heating conditions, dynamite could produce these precursors, which could condense in the injection port of the GC-MS system and generate methenamine. However, methenamine was not always detected in these dynamites. This was explained by the existence of two opposite effects: (a) dynamite stability makes difficult that ammonium nitrate releases ammonia and (b) there is a gradual loss of formaldehyde in sawdust along the time. Both effects can prevent the formation of an amount of methenamine large enough to be detected.

Study of losses of volatile compounds from dynamites. Investigation of cross-contamination between dynamites stored in polyethylene bags.

The purpose of this work was to study the appropriateness of polyethylene bags for the preservation of explosive specimens. To this end, specimens of two types of dynamites, Goma-2 EC, containing nitroglycol (EGDN) and dinitrotoluene (DNT), and Goma-2 ECO, containing only EGDN, were placed individually inside bags and introduced into hermetically sealed glass jars, which were stored for a period of time. Losses of volatile compounds were studied by headspace analysis using gas chromatography coupled to mass spectrometry (GC-MS). The cross-contamination between dynamites was studied by using high performance liquid chromatography with mass spectrometry (HPLC-MS) to analyse the extracts obtained after a sequential solvent extraction of these specimens. Polyethylene bags permit the loss of volatile compounds since EGDN and DNT were detected in the headspaces of the jars. Moreover, cross-contamination between dynamites was also demonstrated since DNT content decreased in the dynamite containing this compound and increased in the dynamite that had not contained it.