Electrooxidation of thiourea and its square-wave voltammetric determination using pencil graphite electrode

Abstract

The electrochemical properties of thiourea (TU) were investigated in pH range 2.0 -12.0 by cyclic and square-wave voltammetry. The compound was irreversibly oxidized at a pencil graphite electrode in one or two oxidation steps which are pH-dependent. Based on the voltammetric peak for the second oxidation process of TU in phosphate buffer at pH 12.0, a square-wave voltammetric method was proposed for the determination of the compound in the range 6.3 -30 µ m , with a detection limit of 1.29 µ m . The applicability to direct assays of wastewaters was also tested.

Electrocatalytic oxidation of thiourea on graphene nanosheets–Ag nanoparticles hybrid ionic liquid electrode

“…The oxidation potential of TU at the surface of this electrode was much less than those reported in previous works [1,8,[21][22][23]44]. A renewable electrode surface could be easily obtained using the proposed sensor.…”

“…Boron-doped diamond electrode [8] 4-4000 -1.10 HMDE [19] 0.13-78.83 0.06 -Graphite electrode [22] 2.60-66 -0.60 Pencil graphite electrode [21] 6.3-30 1.29 0.95 Rotating silver disk electrode [44] 0.1-10 -−0.095 Copper oxide-copper electrode [1] 1000-8000 -0.625 Alumina modified Pt [23] 25-7000 4.8 0.345 Hanging mercury drop electrode [24] Up to 3.94 3.28 × 10 −5 -This work 1-3000 0.7 −0.20 Precipitated in alkaline medium a Can be removed by purging air through acidic solutions [46]. b Can be removed by adding 0.035% mercuric nitrate [2].…”

“…Several analytical methods have been reported for determination of TU such as titrimetry [13], piezoelectric method [14], high performance liquid chromatography (HPLC) [15], Fourier transform infrared (FT-IR) spectrometry [16], chemiluminescence [10], flow injection methods [11], UV-vis spectrophotometry [17,18] and electrochemical methods [1,8,[19][20][21][22][23][24]. Compared with other methods, electrochemical techniques have some advantages including simplicity, rapidity, high selectivity and sensitivity.…”

“…The direct electro-oxidation of TU at different carbon based electrodes such as conductive diamond [8], graphite [22] and pencil graphite electrodes [21] has been investigated and large overpotentials have been reported. To the best of our knowledge, this is the first report on TU determination using carbon nanocomposite electrodes based on graphene supported metal nanoparticles.…”

Ultra Sensitive Quantification of Thiourea at Nanomolar Level by Catalytic‐Kinetic Differential Pulse Voltammetry

“…However, chromatography, mainly HPLC methods, are expensive techniques and spectrophotometry can be used if combined with a preconcentration step. At this time a few electrochemical methods are reported for the determination of thiourea such as amperometry 11, 22, voltammetry 23, 24, 32 and potentiometric methods 35. Stripping voltammetry, especially differential pulse voltammetry (DP), if combined with a catalytic reaction, may be as a simple, inexpensive, ultra‐sensitive and selective technique to analysis the organic or inorganic material 25.…”