The Development of Novel Micro Paper-based Analytical Devices for the Detection of Explosives
- Publication Type:
- Thesis
- Issue Date:
- 2022
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Colourimetric detection, a technique where explosives, constituent functional groups, and taggants may be identified by a change in colour of the reagent, is a rapid and accurate detection method of explosives in-field. However, this approach is presumptive, subjective and inherently relies on the user’s ability to distinguish colour changes. Paper-based analytical devices (PADs), using traditional colourimetric detection has overcome some of the limitations of using colourimetric detection alone, and a desirable technique for further development and application in-field.
This thesis presents a method for the improved detection of explosives utilising a ‘universal’ paper-based analytical device by using traditional colourimetric detection with concomitant fluorescence quenching; where fluorescent chromophore emissions were diminished in the presence of nitro-containing compounds due to complex formation between the compound and fluorophore. In-situ and microfluidic PADs (µPADs), were designed and optimised to incorporate both colourimetric and fluorescence quenching reagents, used both independently or combined. In-situ and µPADs were designed with two viewing wells per µPAD, and quantitative detection was achieved via a novel transmittance detector under both a white and a 310 nm LED light sources; referred throughout as the eBeagle v.3 detector.
Pyrene and pyrene with sodium dodecyl sulphate (SDS) formulations were found to have superior detection selectivity ranges of nitro-containing explosives compared to other tested fluorophores, detecting between 8 – 9 of the 16 nitro-containing explosives. The eBeagle v.3 detector compared had a detection range of 0.09 ± 0.05 mg – 5.29 ± 2.55 mg using pyrene and 0.22 ± 0.27 mg – 0.75 ± 0.17 mg using pyrene with SDS, respectively.
Five out of nine tested traditional and unconventional colourimetric reagents for the detection of organic and inorganic explosives were feasible using in-situ or microfluidic PADs and were further optimised with pyrene. A ‘universal’ two well µPAD using two concomitantly colourimetric detection reagents was developed; 1) a pyrene-KOH mixture for the detection of eight nitro-containing explosives, and sub-classification of some tertiary nitro-aromatic explosives (tetryl, trinitrotoluene (TNT), and trinitrobenzene (TNB)), and 2) an ammonium titanyl oxalate and a variant of Griess reagent performed sequentially to determine the presence of hydrogen peroxide and nitrite-based explosives, respectively. This approach had an instrumental minimum detectable amount (MDA) range of 0.97 ± 0.85 mg – 1.66 ± 1.39 under white lighting conditions and 0.25 ± 0.12 mg – 0.83 ± 0.55 mg under UV lighting conditions.
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