Electrochemical Sensor for Caffeine Based on a Glassy Carbon Electrode Modified with an Attapulgite/Nafion Film

Abstract

In the present work, a simple and economic analytical method based on attapulgite/nafion coated glassy carbon electrode (AT/Naf/GCE) has been developped for the electrochemical determination of caffeine. Prior to its use, the ionic exchange properties and conductivity of AT/Naf/GCE were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Caffeine gave an irreversible oxidation peak around +1.41 V (vs Ag/AgCl reference electrode) in 0.1 M H2SO4 at pH 1.5. The peak current varied linearly with the square root of the scan rate, showing that the transfer process is controlled by diffusion. The heterogeneous rate constant, the transfer coefficient and the number of electrons involved were calculated. Upon optimization of key analytical parameters involved in the electroanalysis of caffeine by DPV, the recorded oxidation peak current varied linearly with caffeine concentration in the range from 0.1 to 4 μm, leading to a detection limit of 4.57×10−8 M (S/N=3). The developed electrode exhibited good stability and was easily regenerated. The effect of some important potential interfering compounds (ascorbic acid, dopamine, uric acid, sulphite ions and glucose) on the signal of caffeine was also examined. The obtained electrode was successfully employed in the determination of caffeine content in a commercial drug.

Montmorillonite clay-modified disposable ink-jet-printed graphene electrode as a sensitive voltammetric sensor for the determination of cadmium(II) and lead(II)

“…These results are consistent with previous data on this clay mineral [49]. Some crystalline impurities associated with montmorillonite revealed by XRD data were quartz and anorthite that were eliminated by wet sedimentation during the collection of the clay fraction with particle size ≤ 2 µm [9,24,25]. The inset in Fig.…”

“…Thus, chemically modified electrodes (CMEs) represent one of the main areas of electrochemistry research with many applications including analytical chemistry [13,14], solar energy conversion [15,16], electrochromic display devices [17] and molecular electronic devices [18]. In the analytical field, different types of conductive materials were used to develop CMEs: polymers [19,20], mesoporous silicate films [21,22], nanoparticles [23] and clay minerals [9,[24][25][26][27]. Clay-modified electrodes have distinct advantages over conventional electrodes in many areas of application, such as electrocatalysis, electrochemical sensors and preconcentration electroanalysis.…”

“…For their development, different modification techniques are used to increase the sensitivity of electrochemical sensors. They include drop casting, spin coating and drop coating [9,24,25]. Montmorillonite is a natural and inexpensive clay material found in many parts of the world and composed of layers of silicates stacked on top of each other.…”

Fullerene/MWCNT/Nafion Modified Glassy Carbon Electrode for the Electrochemical Determination of Caffeine

“…of its original activity for CAF, indicating the electrode was very stable. Graphene oxide-Nafion/GCE 2.0 0.20 [22] MWCNT-Nafion/GCE 4.1 0.51 [43] Nafion/GCE 1.0 0.79 [23] Nafion/MWCNT/GCE 2.0 0.23 [21] Attapulgite/Nafion/GCE 1.5 0.045 [26] 4-Cu II TAPc/SAM/GCE 4.0 0.0304 [44] ZnO/MWCNT/GCE 1.0 0.0097 [45] Pt-GR/GCE / 0.1129 [46] GORG/CPE/SDS 1.0 0.153 [47] GrRAC-70% / 2.94 [48] NCOM/CPE/SDS 0.75 0.016 [49] 3D-printed cell-on-a-chip / 2.84 [50] GCE / 20 [51] Nafion/PDDA-MWCNT/GCE 1.5 0.05 [52] Fullerene/MWCNT/Naf/GCE…”

“…It is a perfluorinated sulfonated cation exchanger polymer widely used in electrochemistry to modify electrodes because it possesses many excellent properties such as chemical inertness, thermal stability, capacity, mechanical strength, huge cation exchange and antifouling properties [20]. Several nafion-based composite electrodes were used for the quantification of caffeine, that include nafion/modified boron-doped diamond [21], nafion/carbon nanotube [22], nafion/graphene modified electrode [23], nafion modified carbon electrode [24], nafion/graphite nanoplatelets [25], nafion/attapulgite [26] and nafion-ruthenium oxide pyrochlore modified glassy carbon electrode [27].…”