Elemental Analysis of Adhesive Tapes by Laser-Based Methods

Authors

Claudia Martinez LopezFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Jose R. Almirall

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Shekhar Bhansali

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Yong Cai

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Kevin O’Shea

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Kathleen Rein

Fifth Advisor's Committee Title

Committee member

Keywords

LA-ICP-MS, laser ablation, adhesive tapes, elemental analysis, forensic, chemistry

Date of Defense

10-29-2018

Abstract

Adhesive tapes are a common type of evidence involved in violent crimes and national security threats. This research evaluated the utility of LA-ICP-MS and LIBS for the characterization of the trace elemental signature in adhesive tapes for forensic comparisons. LA-ICP-MS and LIBS methods were developed, for the first time, for the qualitative and quantitative analysis of adhesive tapes.

The backings of 90 black electrical tapes, previously characterized by conventional techniques (physical examination, IR, Py-GC-MS, and SEM-EDS), were analyzed by LA-ICP-MS to evaluate the ability of the technique to discriminate samples originating from different sources and to associate pieces of tapes originating from the same roll. The discrimination for the LA-ICP-MS analysis of the 90 samples was found to be 93.9%, greater than the discrimination found using SEM-EDS (87.3%). Moreover, 100% correct association resulted for the control samples evaluated in this study.

The analysis of tapes by LIBS allowed to separate pairs of tapes that were not previously distinguished by LA-ICP-MS by detecting differences in lithium, calcium, and potassium.

The potential of normalization strategies was evaluated for LIBS spectral and statistical comparisons.

Two quantitative analysis methods were developed for the analysis of tapes and other polymers. These quantitative methods can help in creating and populating databases that can lead to the use of likelihood ratios and the development of standard methods of analysis and interpretation for tape evidence.

Two interlaboratory trials including 7 operational and research laboratories were completed as part of this study. SEM-EDS resulted in 16.7% and 12.5% false positive rates for interlaboratory tests #1 and #2, respectively. Up to 7 and 8 elements were detected by SEM-EDS for interlaboratory test #1 and #2, respectively. LIBS and LA-ICP-MS resulted in no false positives or false negatives. In addition, increased characterization of the samples was obtained by detecting up to 17 elements by LIBS and 32 elements by LA-ICP-MS. The increased sensitivity and selectivity of LIBS and LA-ICP-MS methods has been shown to distinguish tapes originating from different sources, and to correctly associate tapes belonging to the same rolls in different laboratories and by different analysts.

Identifier

FIDC007041

Recommended Citation

Martinez Lopez, Claudia, "Elemental Analysis of Adhesive Tapes by Laser-Based Methods" (2018). FIU Electronic Theses and Dissertations. 3862.
https://digitalcommons.fiu.edu/etd/3862