Electrochemical detection explosives

Lloyd JBF. 1983. High-performance liquid chromatography of organic explosives components with electrochemical detection at a pendant mercury drop electrode. J Chromatogr 257 227-236. 

Bratin, K., P. T. Kissinger, R. Briner, and C. Bruntlett. Determination of nitro aromatic, nitramine, and nitrate ester explosive compounds in explosives mixtures and gunshot residue by liquid-chromatography and reductive electrochemical detection. Anal. Chim. Acta 130, 295-311 (1981). 

K. Bratin, P. T. Kissinger, R. C. Briner, and C. S. Bruntlett, Determination of Nitro Aromatic, Nitramine and Nitrate Ester Explosive Compounds in Explosive Mixtures and Gunshot Residue by Liquid Chromatography and Reductive Electrochemical Detection, Analytica Chimica Acta 130, no. 2 (1981) 295. 

J. B. F. Lloyd, High-Performance Liquid Chromatography of Organic Explosives Components with Electrochemical Detection at a Pendant Mercury Drop Electrode, Journal of Chromatography 257 (1983) 227. 

J. B. F. Lloyd, Liquid Chromatography with Electrochemical Detection of Explosives and Firearms Propellant Traces, Analytical Proceedings (London) 24 (1987) 239. 

Krull IS, Ding XD, Selavka C, et al. 1984. Explosives and other nitro compounds determined by liquid chromatography with photolysis-electrochemical detection. Methodological Surveys in Biochemistry and Analysis 14 365-366. 

Lloyd JBF. 1983a. Clean-up procedures for the examination of swabs for explosive traces by high-performance liquid chromatography with electrochemical detection at a pendent mercury drop electrode. J Chromatogr 261 391-406. 

Selavka CM, Krull IS. 1986. Liquid chromatography with photolysis - electrochemical detection for nitro-based high explosives and water gel formulation sensitizers. J Energetic Material 4 273- 303. 

Finally, HPLC is used for the analyses of explosives and in some forensic laboratories it is being introduced as a routine procedure. Chromatographic separation of explosives can be achieved by reversed-phase chromatography on alkyl-bonded silicas but a major problem has been in finding a technique capable of detecting nanogram quantities of materials. To date, the most sensitive method has been reductive electrochemical detection and provided fairly extensive operational precautions are taken (in particular the exclusion of oxygen), the required detection levels can be achieved. 

Antibody-based, fully automated immunosensors for small molecules have been used to detect explosives (see Refs. [11,12]) and biological warfare agents (see Refs. [13,14]), and can be used to analyse drinking water and extracts at hazardous waste sites (for examples, see Refs. [15-17]). In the following section, we will discuss how the addition of electrochemical detection has broadened the capabilities of such devices. 

Key words Nitroaromatic explosives, electrochemical detection, voltammetry, sensors, microchips. 

The examples described in this chapter illustrate the power and versatility of modem electrochemical devices for detecting explosives. These developments would allow field testing for major explosives to be performed more rapidly, sensitively, inexpensively, and reliably, should greatly facilitate the realization of in-situ detection of explosive compounds. The resulting real-time monitoring capability should thus have a major impact on the way explosive materials are monitored and upon the prevention of terrorist activity. 

Many explosives pyrolyze to produce NO2. Since electrochemical sensors have been used for quite some time to reliably monitor NO2 they are a logical choice for detecting explosives. However, sensitivity in the low ppb to ppt range is essential for this application. Preconcentration is usually employed and the explosive vapours must be released from the trap in a pulse which passes through and over the sensor in 2-3 seconds. The sensor has little time to respond before the NO2 spike is flushed from the system with clean air. The following work describes the variety of techniques employed to achieve an acceptable response at such low explosive vapour concentrations. 

Liquid chromatographic electrochemical detection has been widely used for metabolite studies in complex matrices and has general applicability in many helds, for example, the pharmaceutical industry, forensic science, medicine, the explosives industry, and agriculture. 

Guo CX, Lei Y, Li CM. Porphyrin functionalized graphene for sensitive electrochemical detection of ultratrace explosives. Electroanalysis 2011 23 885-93. 

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