Adsorption stripping voltammetry of phenol at Nafion-modified glassy carbon electrode in the presence of surfactants

Electrochemical determination of phenol using CTAB-functionalized montmorillonite electrode

Montmorillonite calcium (MMT) was modified with cetyltrimethylammonium bromide (CTAB) via replacement of its inorganic exchangeable cations. The resulting CTAB-modified MMT (CTAB/MMT) was used to modify the carbon paste electrode (CPE). The electrochemical behaviours of phenol at the unmodified CPE, MMT-modified CPE and CTAB/MMT-modified CPE were examined. It was found that the oxidation signal of phenol was remarkably improved at the CTAB/MMT-modified CPE, which was attributed to the higher accumulation efficiency of CTAB/MMT. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of phenol. The effect of supporting electrolyte on the oxidation of phenol was examined, and 0.1 mol l(-1) NaOH was finally employed. In addition, the influences of mass content of CTAB/MMT and accumulation time were also investigated. The optimal mass content of CTAB/MMT is 25%, and the accumulation time is 3 min. Under the optimized conditions, the oxidation peak current of phenol is proportional to its concentration over the range from 1.0 x 10(-7) to 3.0 x 10(-5) mol l(-1), and the limit of detection is estimated to be 6.0 x 10(-8) mol l(-1). Finally, the CTAB/MMT-modified CPE was successfully applied to determine phenol in water samples.

Direct electrochemistry of catalase at multiwalled carbon nanotubes-nafion in presence of needle shaped DDAB for H2O2 sensor

The direct electrochemistry of catalase (CAT) at didodecyldimethylammonium bromide (DDAB) present on nafion dispersed multiwalled carbon nanotubes (MWCNTs-NF) modified glassy carbon electrode (GCE) has been reported. The presence of DDAB in MWCNTs-NF-CAT film enhances the surface coverage concentration of CAT (Fe(III/II)) to 48%. Similarly, in presence of DDAB, there is a 57% enhancement in electron transfer rate (ks) with 66% increase in CAT stability. (Fe(III/II)) redox couple exhibits linear dependence with the pH variation (-51 mV pH(-1)). The UV-vis absorption spectroscopy study reveals the entrapped CAT in DDAB film retains its native structure at MWCNTs-NF modified electrodes. Similarly, electrochemical impedance spectroscopy results confirm the co-existence of CAT and DDAB in the modified film. Further, scanning electron microscopy results reveal the structural morphological difference between various components in MWCNTs-NF-(DDAB/CAT) film. The cyclic voltammetry (CV) and amperometry (i-t curve) have been used for the measurement of electroanalytical properties of H2O2 by means of various film modified GCEs. The sensitivity values of MWCNTs-NF-(DDAB/CAT) film for H2O2 using CV (35.62 microA mM(-1)cm2) are higher than the values which are obtained for MWCNTs-NF-CAT film (2.74 mmicroA mM(-1)cm2). Similarly, the sensitivity values using i-t curve are 101.74 microA mM(-1)cm2 for MWCNTs-NF-(DDAB/CAT) and 74.69 microA mM(-1)cm2 for MWCNTs-NF-CAT film. Finally, the diffusion coefficient of H2O2 at MWCNTs-NF-(DDAB/CAT) film (3.4 x 10(-10) cm2 s(-1)) has been calculated using rotating disc electrode studies.

Electrochemical behaviors of adrenaline at acetylene black electrode in the presence of sodium dodecyl sulfate

The electrochemical behaviors of adrenaline at the acetylene black electrode in the presence of sodium dodecyl sulfate (SDS) were investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results indicated that the electrochemical responses of adrenaline were apparently improved by SDS, due to the enhanced accumulation of protonated adrenaline via electrostatic interaction with negatively charged SDS at the hydrophobic electrode surface. This was verified by the influences of different kinds of surfactants on the electrochemical signals of adrenaline. The electrochemical parameters of the adrenaline oxidation were explored by chronocoulometry. Under optimal working conditions, the oxidation peak current at 0.57 V was proportional to adrenaline concentration in the range of 5.0x10(-8) to 7.0x10(-6) mol/L, with a low detection limit of 1.0x10(-8)mol/L for 70s accumulation by differential pulse voltammetry (DPV). This method was applied to determine adrenaline in the hydrochloride injection sample. The results are satisfying compared with that by the standardized method of high performance liquid chromatography (HPLC).

Beneficial role of surfactants in electrochemistry and in the modification of electrodes

This review deals with the beneficial use of surfactants in various fields of electrochemistry, in general and in the modification of electrodes with immobilized electroactive species, in particular. Special emphasis is laid on the modification of electrodes with metal hexacyanoferrates (MHCFs). After an introduction and brief notes on fundamentals of surfactants, and their applications in electrochemistry, covering some of the very important works in the past two decades involving beneficial use of surfactants, the article gives a brief account on metal hexacyanoferrate modified electrodes and the salient features of our published results on the beneficial role of cetyltrimethylammonium bromide (CTAB), a cationic surfactant, in the modification of electrodes with MHCFs and their derivatized oxides, and with titanium dioxide.

The influence of cetyltrimethyl ammonium bromide on electrochemical properties of thyroxine reduction at carbon nanotubes modified electrode

The effect of cetyltrimethyl ammonium bromide (CTAB) on the electrochemical behaviors of thyroxine at a glassy carbon electrode (GCE) modified with single-walled carbon nanotubes (SWNTs) was investigated. At the SWNTs film-coated GCE, a well-defined oxidation peak of thyroxine at 0.78 V was obtained, but the reduction peak of thyroxine was indiscernible. When trace CTAB was added to the working solution, the reduction current could be greatly enhanced and the oxidation current remained stable. The reaction mechanisms for the reduction of thyroxine were explored by chronocoulometry. Thyroxine might form particular ion complex with CTAB via the interaction between iodine atoms on thyroxine and bromide ions in CTAB, which made the concentration of thyroxine at the surface of the modified electrode increased and the electron transfer rate enhanced. The proper mechanisms for the enhanced reduction of thyroxine in the present of CTAB were explored by several electrochemical techniques including cycle voltammetry linear sweep voltammetry and others. It was concluded that the special interactions between the thyroxine CTAB and SWNTs resulted in the increase of the reduction peak current. All results indicated that two iodine atoms on the thyroxine and four electrons were involved the reduction process which was irreversible and two iodine ions produced. In this system, the sensitive reduction peak of thyroxine at 0.3 V was employed to determine thyroxine and a low detection limit of 2x10(-8) mol/L was obtained for 2 min accumulation at 0.9 V. The SWNTs coated GCE had good stability and reproducibility.

Effects of EDTA on signal stability during electrochemical detection of acetaminophen

The use of EDTA in the medium to avoid the passivation of a solid electrode during electrochemical analysis of acetaminophen is presented in this work. The performance of this system was investigated with respect to pH, applied potential and supporting electrolyte concentration. The major advantage in using EDTA in the supporting electrolyte is the significant increase in sensitivity, precision and stability of the measurements, when compared to the system in absence of the chelating agent. The sensitivity increases 5.5 times (21.5 and 3.9 mA l mol(-1) in the presence and the absence of EDTA, respectively), the repeatability (n=20) is 3.5 times better, expressed by within-run-precision of 4.0% for 6.0 x 10(-5) mol l(-1) acetaminophen in the presence of EDTA while, in its absence, the within-run-precision was higher than 14%. Moreover, the system showed excellent stability, allowing more than 120 measurements with no significant changes.