Comparison of Voltammetric Techniques for Ammonia Sensing in Ionic Liquids

Abstract

In electroanalytical chemistry, it is often observed that square wave voltammetry (SWV) and differential pulse voltammetry (DPV) are more sensitive techniques compared to linear sweep voltammetry (LSV), due to their method of sampling which minimises the charging current (non-faradaic processes). In this work, a comparison of the three techniques (LSV, DPV and SWV) is performed for ammonia (NH 3 ) gas oxidation (a chemically and electrochemically irreversible redox process) in an ionic liquid over a concentration range of 10-100 ppm. Four different platinum electrodes are employed: a screen-printed electrode (SPE), a thin-film electrode (TFE), a microarray thin-film electrode (MATFE) and a Pt microdisk electrode (m-disk). Calibration plots (current vs concentration) for all three different electrochemical techniques on all four surfaces showed excellent linearity with increased concentrations of NH 3 gas and relatively low limits of detection (LODs). On the larger mm-sized surfaces (SPE and TFE), the current responses for LSV and SWV were quite similar, but DPV gave the lowest currents. Whereas for the smaller micron sized electrodes (MATFE and m-disk), currents were of the order LSV > SWV > DPV, with LSV being far superior to the pulse techniques. These findings suggest that the pulse techniques of SWV and DPV may not be the optimum methods, particularly on microelectrodes, for the detection of analytes such as ammonia in RTILs.

The Use of Electrochemical Voltammetric Techniques and High-Pressure Liquid Chromatography to Evaluate Conjugation Efficiency of Multiple Sclerosis Peptide-Carrier Conjugates

“…DPV is a more sensitive approach compared to CV and hence, has been extensively used as a more sensitive method for the detection of molecules in low concentration [ 38 ]. In Figure 5 , the DPVs are recorded for the bare film electrode, as well as for each part that constitutes the final structure of OM-(KG) 5 -MOG 35-55 conjugate on the Graphite/SiO 2 working electrode.…”

“…As such, mannan was used as a carrier and conjugated to immunodominant MS peptides including MBP 83-99 , PLP 139-141 , and MOG 35-55 or their analogues, and were shown in animal models to tolerize T cells or switch Th1 cells to Th2 cells, depending on the peptide analogue used and showed stimulation of Th2 cells in peripheral blood mononuclear cells from patients with MS [ 17 , 21 , 33 , 34 , 35 ]. The conjugation of mannan, in its oxidized form (OM), to MOG 35-55 peptide (MOG 35-55 was used as an example in this study) via a (Lys-Gly) 5 linker [(KG) 5 ] was used and evaluated (OM-(KG) 5 -MOG 35-55 conjugate) using voltammetric techniques [ 1 , 2 , 3 , 4 , 36 , 37 , 38 ]. The conjugation between OM and peptide (MOG 35-55 ) occurs via formation of Schiff bases between the free amines of the linker (KG) 5 and aldehydes of OM.…”

New innovations in ionic liquid–based miniaturised amperometric gas sensors

“…Electrode materials made purely of metals give much more stable responses compared to screen-printed electrodes that are complicated by the presence of binders. Thin-film electrodes (TFEs), microarray thinfilm electrodes (MATFEs), and interdigitated electrodes (IDEs) have all been explored as new sensor surfaces in RTILs for the detection of ammonia [31,32] and oxygen [33] gases. The design of a commercially-available MATFE form MicruX is shown in Figure 3a; the WE consists of 90 recessed microdisk electrodes, in close proximity with the RE and CE.…”

Ionic Liquid‐based Microchannels for Highly Sensitive and Fast Amperometric Detection of Toxic Gases

“…LODs of 6.2 ppm and 6.8 ppm, and sensitivities of 1.80 3 10 À9 A/ppm and 6.84 3 [41]. They pointed out that the LSV technique presents the best sensitivity among LSV, DPV (differential pulse voltammetry) and SWV (square wave voltammetry) for NH 3 sensing.…”

“…Compared with the results obtained by LSV, it is suggested that the LSV technique is more suitable and sensitive for lower concentrations of NH 3 with a higher sensitivity and a lower LODs. Similar behavior was reported by Hussain et al who studied voltammetric techniques comparison for NH 3 sensing in [C 2 mim][NTf 2 ] [41]. They pointed out that the LSV technique presents the best sensitivity among LSV, DPV (differential pulse voltammetry) and SWV (square wave voltammetry) for NH 3 sensing.…”