Development of a 3D disposable device for the electrochemical determination of diclofenac in different matrices

In this work, the development of a disposable electrochemical device (US$ 0.02 per electrode) using a 3D printed support (3Ds) of acrylonitrile butadiene styrene (ABS) insulating filament with a composite material (CM) based on graphite and nail polish, immobilized on the support surface, was described for the electrochemical determination of diclofenac (DCF). The device was compared to the commercial glassy carbon electrode (GCE) and showed superior electroanalytical performance with approximately 1.8-fold higher current density. Additionally, an amperometric method for DCF determination in tap water, synthetic urine, and pharmaceutical formulation samples with the proposed electrode, using a flow injection analysis (FIA-AD) system, was developed. The optimized method presented excellent detectability (LOD = 0.47 µmol L^-1), with excellent precision and accuracy (relative standard deviation < 5.6%) and percent recovery from spiked samples ranging from 89 to 106%. In addition, the sensor showed optimal analytical frequency with approximately 108 injections per hour, which demonstrates the potential of this system using the proposed disposable electrode for implementation in routine analysis and quality control with good selectivity and sensitivity.

Design of an electrochemical platform for the determination of diclofenac sodium utilizing a graphenized pencil graphite electrode modified with a Cu–Al layered double hydroxide/chicken feet yellow membrane

A novel electrochemical sensor based on a Cu–Al layered double hydroxide (Cu–Al LDH)/chicken feet yellow membrane (CFYM) modified graphenized pencil graphite electrode (GPGE) was designed.

Boron Doped Diamond Electrodes in Flow-Based Systems

Boron-doped diamond (BDD) electrodes present several notable properties, such as the largest potential window of all electrode materials (especially in anodic potentials), low background and capacitive currents, reduced fouling compared to other electrodes, mechanical robustness, and good stability over time. On the other hand, flow-based systems are known as well-established approaches to minimize reagent consumption and waste generation and with good compromise between sample throughput and analytical performance (mechanization of chemical assays). This review focuses on the use of BDD electrodes for electrochemical detection in flow systems, such as flow injection analysis (FIA), batch injection analysis (BIA), high performance liquid chromatography (HPLC), and capillary electrophoresis (CE). The discussion deals with the historical evolution of BDD, types of electrochemical pre-treatments (cathodically/H-terminated or anodically/O-terminated), cell configurations, and analytical performance. Articles are discussed in chronological order and subdivided according to the type of flow system: FIA, BIA, HPLC, and CE.

3D printing for electroanalysis: From multiuse electrochemical cells to sensors

This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the 3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and $ 6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of $ 1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 μmol L^-1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k₀) for the redox probe Ru(NH₃)₆⁺³ revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.

Low cost microfluidic device based on cotton threads for electroanalytical application

Microfluidic devices are an interesting alternative for performing analytical assays, due to the speed of analyses, reduced sample, reagent and solvent consumption and less waste generation. However, the high manufacturing costs still prevent the massive use of these devices worldwide. Here, we present the construction of a low cost microfluidic thread-based electroanalytical device (μTED), employing extremely cheap materials and a manufacturing process free of equipment. The microfluidic channels were built with cotton threads and the estimated cost per device was only $0.39. The flow of solutions (1.12 μL s(-1)) is generated spontaneously due to the capillary forces, eliminating the use of any pumping system. To demonstrate the analytical performance of the μTED, a simultaneous determination of acetaminophen (ACT) and diclofenac (DCF) was performed by multiple pulse amperometry (MPA). A linear dynamic range (LDR) of 10 to 320 μmol L(-1) for both species, a limit of detection (LOD) and a limit of quantitation (LOQ) of 1.4 and 4.7 μmol L(-1) and 2.5 and 8.3 μmol L(-1) for ACT and DCF, respectively, as well as an analytical frequency of 45 injections per hour were reached. Thus, the proposed device has shown potential to extend the use of microfluidic analytical devices, due to its simplicity, low cost and good analytical performance.

Diclofenac on boron-doped diamond electrode: from electroanalytical determination to prediction of the electrooxidation mechanism with HPLC-ESI/HRMS and computational simulations

Using square-wave voltammetry coupled to the boron-doped diamond electrode (BDDE), it was possible to develop an analytical methodology for identification and quantification of diclofenac (DCL) in tablets and synthetic urine. The electroanalytical procedure was validated, with results being statistically equal to those obtained by chromatographic standard method, showing linear range of 4.94 × 10(-7) to 4.43 × 10(-6) mol L(-1), detection limit of 1.15 × 10(-7) mol L(-1), quantification limit of 3.85 × 10(-7) mol L(-1), repeatability of 3.05% (n = 10), and reproducibility of 1.27% (n = 5). The association of electrochemical techniques with UV-vis spectroscopy, computational simulations and HPLC-ESI/HRMS led us to conclude that the electrooxidation of DCL on the BDDE involved two electrons and two protons, where the products are colorful and easily hydrolyzable dimers. Density functional theory calculations allowed to evaluate the stability of dimers A, B, and C, suggesting dimer C was more stable than the other two proposed structures, ca. 4 kcal mol(-1). The comparison of the dimers stabilities with the stabilities of the molecular ions observed in the MS, the compounds that showed retention time (RT) of 15.53, 21.44, and 22.39 min were identified as the dimers B, C, and A, respectively. Corroborating the observed chromatographic profile, dimer B had a dipole moment almost twice higher than that of dimers A and C. As expected, dimer B has really shorter RT than dimers A and C. The majority dimer was the A (71%) and the C (19.8%) should be the minority dimer. However, the minority was the dimer B, which was formed in the proportion of 9.2%. This inversion between the formation proportion of dimer B and dimer C can be explained by preferential conformation of the intermediaries (cation-radicals) on the surface.

Two new electrochemical methods for fast and simultaneous determination of codeine and diclofenac

In this paper, we present two new electrochemical methods for fast and simultaneous determination of codeine (CO) and diclofenac (DCF). The first one is based on batch injection analysis with amperometric detection (BIA-MPA) and the second one is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D). The proposed BIA-MPA method is highly-precise (RSD of 1.1% and 0.9% for DCF and CO, respectively; n=10), fast (300 injections h(-1)) and has low detection limits (1.1 and 1.0 µmol L(-1) for DCF and CO, respectively). The proposed CE-C(4)D method allows the determination of CO and DFC in less than 1 min with high precision (RSD of 0.3% and 0.7% for DCF and CO, respectively; n=10) and low detection limits (11 and 21 µmol L(-1) for DCF and CO, respectively). Both proposed methods were applied to the determination of CO and DCF in pharmaceutical samples with similar results to those achieved by high-performance liquid chromatography (HPLC) at a 95% confidence level.