Dangers of dynamite storage: Cross-contamination of evidence bags from Madrid train bombings

DNT

Bombs in bags

The devastating Madrid train bombings in March 2004 killed almost 200 people and injured nearly 2000 and, despite the best efforts of the authorities, the attacks remain unattributed. The type of explosive used for this attack seems to point to the Basque terrorist organisation ETA, although Al-Qaeda is thought to have claimed responsibility.

The forensic teams identified traces of nitroglycerin and dinitrotoluene (DNT) in the explosion debris. These are components of the explosive known as Titadyn, a dynamite which has been used in many Spanish terrorist bomb attacks.

The debris from the Madrid train bombings was collected in polyethylene bags and sealed before transportation to a lab where it was stored for three years before analysis. This type of bag was considered the best available option to avoid losses of vapours from the bags compared with metal paint cans and glass jars.

However, recent studies have suggested that volatile components can escape from polyethylene bags, compromising the evidence in forensic cases. The bags from the train bombings were kept alongside further plastic bags containing Titadyn and other types of dynamite from different cases, raising the possibility of cross-contamination between the different samples.

These concerns have now been addressed by Spanish scientists who have undertaken a study of the Goma-2 EC and Goma-2 ECO dynamites, two common dynamites that are manufactured in Spain. Goma-2 EC contains DNT, nitrocellulose and ethyleneglycol dinitrate (EGDN) whereas Goma-2 ECO has no dinitrotoluene, in line with recent European legislation on toxic nitrotoluenes.

Their results were reported by senior reporter Carmen Garcia-Ruiz and colleagues from the Police Sciences University Research Institute at the University of Alcala, and the Criminalistics Service of Guardia Civil in Madrid.

 

Leaks require tweaks

In the first instance, the researchers examined losses of EGDN from Goma-2 ECO which was stored in an official polyethylene carrier bag fitted with a rubber seal designed to prevent the transfer of volatile compounds in either direction, in or out of the bag.

Following storage under varying conditions in glass jars, the compositions of the jar headspaces were measured by GC/MS and the concentrations of EGDN remaining in the dynamites were measured after solvent extraction by HPLC with mass spectrometric detection.

For LC/MS, the analytes were separated on a silica gel column with a gradient of methanol in water. The eluting compounds were analysed by atmospheric pressure chemical ionisation in negative-ion mode. LC/MS was preferred to HPLC-DAD, due to a better detection limit for 2,6-DNT: of 3 ng/mL compared with 300 ng/mL.

Both EGDN and DNT were lost over time, the rate increasing with rising temperature. About 30 and 66% of the total EGDN was lost within one and two months of storage at room temperature, respectively, altering the composition of the sample, which could have serious consequences when the samples are evidence in a criminal case.

However, the effects on evidence could be two-fold. If volatile components can escape from the bags, then it is possible that other volatiles can infiltrate them.

In a second set of experiments, the researchers stored pairs of polyethylene bags containing either Goma-2EC or Goma-2 ECO within a closed glass jar. The jars were separated by a piece of paper to avoid direct contact and the levels of EGDN and DNT were determined by LC/MS.

The Goma-2 ECO dynamite was expected to contain no DNT, but traces were detected straightaway. These were attributed to contamination during manufacture because the same reactors were used to make both Goma-2 EC (which does contain DNT) and Goma-2 ECO.

However, the levels of DNT in the “DNT-free” dynamite increased over time during storage. This increase correlated with a decrease from Goma-2 EC, until a steady state appeared to be reached, strongly implicating transfer between the two bags.

So, not only do volatiles escape from the plastic bags containing the explosives, they also permeate into neighbouring bags, providing measurable levels of cross-contamination within just one week. The official plastic bags are not fit for purpose and alternatives should be sought immediately.

These same polyethylene bags were used for explosive evidence from the Madrid train bombings, which must raise doubts as to the validity of the evidence. Losses of volatiles could have occurred during transport and further losses and cross-contamination is a strong possibility while they were stored alongside other explosive-containing plastic bags.

Source: separationsNOW.com

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