Electrochemical Detection of Explosive Compounds in an Ionic Liquid in Mixed Environments: Influence of Oxygen, Moisture, and Other Nitroaromatics on the Sensing Response

2019 ◽  
Vol 72 (2) ◽  
pp. 122 ◽  
Author(s):  
Junqiao Lee ◽  
Debbie S. Silvester

From a security point of view, detecting and quantifying explosives in mixed environments is required to identify potentially concealed explosives. Electrochemistry offers a viable method to detect nitroaromatic explosive compounds owing to the presence of easily reducible nitro groups that give rise to a current signal. However, their reduction potentials can overlap with interfering species, making it difficult to distinguish particular compounds. We have therefore examined the effect of oxygen, moisture, and other nitroaromatic species on the cyclic voltammetry and square wave voltammetry of nitroaromatic compounds of a range of mixed environments, focussing on 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) as model analytes, and using the hydrophobic room-temperature ionic liquid (RTIL) [P14,6,6,6][NTf2] as the solvent. Oxygen (0–20% vol.) minimally affected the current of the first reduction peak of TNT in [P14,6,6,6][NTf2], but significantly affects the current for DNT. The impact of water (0 to 86% relative humidity), however, was much more dramatic – even in the hydrophobic RTIL, water significantly affected the currents of the analyte peaks for TNT and DNT, and gave rise to additional reduction features, further contributing to the current. Additionally, the voltammetry of other related di- and tri-nitro compounds (2,6-dinitrotoluene, 1,3-dinitrobenzene, 2,4,6-trinitrotoluene, 1,3,5-trinitrobenzene, and musk xylene) was also studied to understand how different substituents on the aromatic ring may affect the reduction potentials. A 50:50 mixture of TNT and DNT revealed that both analytes could be separately identified and quantified using square wave voltammetry. Overall, this information is useful in determining the effect of other species on the current signals of electrochemical explosive sensors, and reveals that it may be necessary to dry the aprotic RTIL electrolyte when used in humid environments.

2009 ◽  
Vol 21 (21) ◽  
pp. 2297-2302 ◽  
Author(s):  
Joaquín A. Ortuño ◽  
Carmen Serna ◽  
Angela Molina ◽  
Encarnación Torralba

2006 ◽  
Vol 31 (1) ◽  
pp. 31-38 ◽  
Author(s):  
M. A. G. Trindade ◽  
P. A. C. Cunha ◽  
T. A. de Araújo ◽  
G. M. da Silva ◽  
V. S. Ferreira

This work presents an electroanalytical method for the determination of moxifloxacin (MOXI) in tablets by its interaction with Cu(II) ion and subsequent electrochemical reduction at hanging mercury drop electrode (HMDE). A well-defined reduction peak at -0.21 V vs. Ag/AgCl in Phosphate buffer 0.04 mol L-1 pH 8.0 was observed for the complex reduction MOXI-Cu(II), using square-wave voltammetry (SWV). Using a 10 s of accumulation time at -0.40 V was found a limit detection of 3.60x10-8 mol l-1. The obtained results have shown good agreement with those obtained by spectrophotometric method.


2016 ◽  
Vol 190 ◽  
pp. 339-349 ◽  
Author(s):  
Chao Huang ◽  
Xiaolong Liu ◽  
Yuan Gao ◽  
Shizhe Liu ◽  
Bing Li

In this paper, cyclic voltammetry and square wave voltammetry are applied to characterize the cathode processes of neodymium ions on a W electrode in LiF–NdF3 melts with or without the metal Nd. The results indicate that neodymium ions in the LiF–NdF3 (2 wt%) melt are reduced in two steps, i.e. Nd3+ → Nd2+ and Nd2+ → Nd0, corresponding to starting reduction potentials of 0.35 V vs. Li+/Li and 0.1 V vs. Li+/Li, respectively. The Nd3+ → Nd2+ process is controlled by mass transfer and the Nd2+ → Nd0 process is controlled by both an interfacial step and mass transfer. But in the LiF–NdF3 melt with excess metal Nd equilibrium, the kinetics of the above two processes are controlled by mass transfer. After potentiostatic electrolysis at 0.35 V in the LiF–NdF3–Nd2O3 melt NdF2 is formed on the Mo cathode, and metallic Nd is obtained by potentiostatic electrolysis at 0.1 V in the LiF–NdF3–Nd2O3–Nd melt, which validates the above electrochemical reduction results.


2010 ◽  
Vol 64 (3) ◽  
Author(s):  
Semiha Çakir ◽  
Emine Arslan

AbstractElectrochemical behavior of resazurin on HMDE in Britton-Robinson (B-R) buffers (pH 2.0–10.0) was studied using the square-wave voltammetry (SWV), square-wave adsorptive stripping voltammetry (SWAdSV), and cyclic voltammetry (CV) techniques. The voltammogram of resazurin in B-R buffer at pH < 4.0 exhibited two cathodic reduction peaks. The voltammetric peaks were obtained at −0.144 V (reversible) and −1.250 V (irreversible) at pH 3.2, and correspond to the reduction of resorufin to dihydroresorufin and to the catalytic hydrogen wave, respectively. At pH > 4.0, a new irreversible cathodic reduction peak, assigned to the protonation of N-oxide on the phenoxazin ring, was observed. Electrochemical parameters (I p/E p, I p/v, I p/pH, I p/t acc) of the compound were determined. From the voltammetric data, electrochemical reduction mechanisms for all peaks have been suggested. Maximum peak current for the reversible peak was obtained at pH 4.1. A linear relationship between the current and concentration was determined, and also the lowest detection limit was found as 3.25 × 10−8 mol L−1 and 1.98 × 10−10 mol L−1 for SWV and SWAdSV, respectively.


2020 ◽  
Vol 16 (3) ◽  
pp. 341-348
Author(s):  
Surinya Traipop ◽  
Suchada Chuanuwatanakul ◽  
Orawon Chailapakul ◽  
Eakkasit Punrat

Background: Recently, Derris scandens, a Thai herbal medicine with anti-inflammatory activity, is widely used as beverage and supplementary food. When the traditional medicine is a choice for health therapy, the simple and reliable equipment is required to control the suitable consuming amount of the active component. Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation. Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5×1.0 cm. Only 50 µL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry. Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt( II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 µM and the detection limit was 1.5 µM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results. Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.


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