The use of ethyl cellulose film lifts to collect particle traces from exposed adhesive on the edges of duct tape

Abstract

Environmentally acquired particles (EAP), trapped along the edges of duct tape in the exposed adhesive, are a possible source of information regarding prior exposures of the tape and a possible means to associate duct tape rolls to segments of duct tape that are collected as traces during the investigation of criminal activity. The recovery and separation of EAP is complicated by (1) the need to separate the particles from the adhesive, and (2) the presence of adhesive filler and pigment particles that are part of adhesive formulations. Approaches such as cutting the tape edge, followed by solvent extraction, or swabbing of the duct tape edges using solvents, result in thousands of adhesive filler/pigment particles, overwhelming much smaller numbers of EAP. A recovery method has been developed employing a 10% solution of ethylcellulose (EC) in ethanol. Duct tape segments are pressed onto a glass plate and a bead of the viscous EC solution is pipetted along the edge. After drying, the EC forms a robust film that is peeled away from the tape edge, lifting the EAP along with only very small amounts of adhesive. The film lift (containing EC, duct tape adhesive and EAP) can be examined directly by steromicroscopy and particles of interest can be removed by softening the film using locally applied ethanol. Particles can be examined in situ by transmitted light microscopy using glycerol as a mounting medium to match the EC film. Batch recovery of particles from the film can be achieved by dissolution of the film lift in xylene and washing to remove adhesive residues. Xylene is then removed by washing with ethanol, leaving an ethanol suspension of EAP along with the duct tape filler/pigment particles. Larger particles can be separated by sieving and smaller particles can be recovered by filtration. This method was found to efficiently collect EAP found trapped along the edges of duct tape in the exposed adhesive, as well as for the preparation of these particles for microscopical and instrumental analysis. Limitations, not fully evaluated, include the loss or alteration of some particle types by dissolution, agitation and filtration steps. Further development of this method is expected to provide a means to recover trace particles from the edges of other types of tape and from related adhesive products such as stamps and labels.