Sensitive Voltammetric Detection of Chloroquine Drug by Applying a Boron-Doped Diamond Electrode

At a Glance

Metadata	Details
Publication Date	2020-11-11
Journal	C – Journal of Carbon Research
Authors	Geiser Gabriel Oliveira, Déborah C. Azzi, Tiago Almeida Silva, Paulo Roberto de Oliveira, Orlando Fatibello‐Filho
Institutions	Universidade Federal de São Carlos, Universidade Federal do Tocantins
Citations	19
Analysis	Full AI Review Included

Technical Documentation & Analysis: Boron-Doped Diamond for High-Sensitivity Electroanalysis

This document analyzes the research detailing the use of Boron-Doped Diamond (BDD) electrodes for the sensitive voltammetric detection of chloroquine. The findings confirm BDD’s superior performance in electroanalysis, particularly when surface termination is optimized. 6CCVD is uniquely positioned to supply the high-quality, customized BDD material required to replicate and advance this research.

Executive Summary

Record Sensitivity Achieved: The study successfully utilized a cathodically pretreated Boron-Doped Diamond (CPT-BDD) electrode combined with Square-Wave Voltammetry (SWV) to achieve a Limit of Detection (LOD) of 2.0 nmol L^-1 for chloroquine, the lowest recorded LOD to date for this analyte.
Material Validation: BDD proved highly effective for the irreversible anodic oxidation of chloroquine, demonstrating excellent electron transfer kinetics (kº = 0.0056 cm s^-1).
Surface Termination Criticality: Cathodic pretreatment (hydrogen termination) was confirmed to yield a significantly better-defined anodic peak and higher current intensity compared to anodic pretreatment (oxygen termination).
Linear Range: The method provided a linear analytical curve in the submicromolar range (0.01 to 0.25 µmol L^-1), suitable for rigid control in pharmaceutical formulations.
Material Specification: The BDD film was synthesized via Hot Filament Chemical Vapour Deposition (HFCVD) with a high boron doping concentration of 8000 ppm on p-silicon wafers.
6CCVD Value Proposition: 6CCVD specializes in high-purity, custom-doped MPCVD BDD wafers, offering precise control over doping levels (e.g., 8000 ppm) and surface quality necessary for high-performance electroanalytical applications.

Technical Specifications

The following hard data points were extracted from the research paper, highlighting the performance and material characteristics of the BDD electrode used:

Parameter	Value	Unit	Context
Boron Doping Level	8000	ppm	Concentration in BDD film
Electrode Exposed Area	0.32	cm²	Working electrode size
Cathodic Pretreatment (CPT)	-0.5	A cm^-2	Applied current density (180 s duration)
Anodic Pretreatment (APT)	+0.5	A cm^-2	Applied current density (30 s duration)
Linear Range (Chloroquine)	0.01 to 0.25	µmol L^-1	SWV analytical curve
Limit of Detection (LOD)	2.0	nmol L^-1	Record low detection limit
Analytical Sensitivity	12.2	µA L µmol^-1	Slope of the analytical curve
Heterogeneous Electron Transfer Rate (kº)	0.0056	cm s^-1	Calculated using Nicholson’s method
Peak Potential Separation (∆E_p)	83	mV	For Fe³⁺/Fe²⁺ redox probe
Electrode Active Area	0.285	cm²	Calculated via Randles-Sevick equation

Key Methodologies

The experiment relied on precise material synthesis and electrochemical surface conditioning to achieve optimal performance.

BDD Synthesis:
- Method: Hot Filament Chemical Vapour Deposition (HFCVD).
- Substrate: p-silicon wafers.
- Doping: Boron content fixed at 8000 ppm.
Electrode Assembly:
- The as-received BDD plate was fixed onto a conductive copper support using silver ink and epoxy resin, resulting in a defined exposed area of 0.32 cm².
Electrochemical Pretreatment (Surface Termination Control):
- Cathodic Pretreatment (CPT-BDD): Applied -0.5 A cm^-2 for 180 s in 0.50 mol L^-1 H₂SO₄ solution, resulting in a predominantly hydrogen-terminated surface. This termination yielded the superior analytical signal.
- Anodic Pretreatment (APT-BDD): Applied +0.5 A cm^-2 for 30 s in 0.50 mol L^-1 H₂SO₄ solution, resulting in an oxygen-terminated surface.
Voltammetric Detection (SWV Optimization):
- Technique: Square-Wave Voltammetry (SWV).
- Supporting Electrolyte: 0.1 mol L^-1 Britton-Robson buffer (pH 6.0).
- Optimized SWV Parameters:
  - Frequency (f): 100 Hz
  - Amplitude (A): 50 mV
  - Potential Increment (∆E): 5 mV

6CCVD Solutions & Capabilities

The successful detection of chloroquine at nanomolar levels hinges on the quality and precise specification of the Boron-Doped Diamond electrode. 6CCVD’s advanced Microwave Plasma Chemical Vapour Deposition (MPCVD) capabilities provide the ideal platform for replicating and enhancing this research.

Applicable Materials

To replicate the high-sensitivity electroanalysis demonstrated in this paper, 6CCVD recommends the following material specifications:

Material: Heavy Boron-Doped Diamond (BDD) Wafers.
Doping Precision: 6CCVD offers precise control over boron concentration. We can supply BDD wafers doped specifically at 8000 ppm (or customized ranges from 100 ppm up to 10,000 ppm) to ensure optimal conductivity and electrochemical activity.
Substrate Options: While the paper used p-silicon, 6CCVD can supply BDD films on various substrates (e.g., Si, Quartz, or freestanding BDD plates) depending on the final device integration requirements.
Surface Quality: Our standard polishing achieves a surface roughness of Ra < 5 nm for inch-size PCD/BDD, ensuring the uniform pyramidal structure and high electrochemical quality required for reliable CPT/APT procedures.

Customization Potential

The research utilized a manually assembled electrode (silver ink/epoxy). 6CCVD can streamline the manufacturing process for scalable research and commercial applications:

Research Requirement	6CCVD Customization Service	Technical Advantage
Custom Area (0.32 cm²)	Custom Dimensions & Laser Cutting: We supply plates/wafers up to 125mm and offer precision laser cutting to exact geometric specifications (e.g., 0.32 cm² discs or custom microelectrode arrays).	Ensures high repeatability and eliminates manual cutting variability.
Electrode Assembly	Integrated Metalization: We offer in-house metalization services (Au, Pt, Ti, W, Cu) directly onto the BDD surface.	Eliminates the need for silver ink/epoxy assembly, providing superior electrical contact, stability, and robustness for harsh chemical pretreatments.
Thickness Control	Precise Thickness: We offer BDD films from 0.1 µm up to 500 µm, allowing researchers to optimize film thickness for specific charge transfer kinetics or mechanical stability.	Enables optimization beyond the standard HFCVD film used in the study.

Engineering Support

The success of this voltammetric method relies heavily on the precise control of the BDD surface termination (hydrogen vs. oxygen). 6CCVD’s in-house PhD team specializes in diamond surface chemistry and electrochemistry.

Surface Optimization: We provide consultation on material selection and surface preparation protocols (e.g., CPT/APT parameters) to ensure optimal hydrogen termination for similar electroanalytical projects, such as drug detection, environmental sensing, or pharmaceutical quality control.
MPCVD Advantage: While the paper used HFCVD, 6CCVD utilizes advanced MPCVD, which offers superior control over film uniformity, purity, and crystal quality, leading to more reproducible electrochemical performance across large wafer sizes.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

In this research, a boron-doped diamond (BDD) electrode has been explored to detect the chloroquine drug. The electrochemical performance of BDD electrode towards the irreversible anodic response of chloroquine was investigated by subjecting this electrode to the cathodic (−0.5 A cm−2 by 180 s, generating a predominantly hydrogen-terminated surface) and anodic (+0.5 A cm−2 by 30 s, oxygen-terminated surface) pretreatments. The cathodically pretreated BDD electrode ensured a better-defined anodic peak and higher current intensity. Thus, by applying the cathodically pretreated BDD electrode and square-wave voltammetry (SWV), the analytical curve was linear from 0.01 to 0.25 µmol L−1 (correlation coefficient of 0.994), with sensitivity and limit of detection of 12.2 µA L µmol−1 and 2.0 nmol−1, respectively. This nanomolar limit of detection is the lowest recorded so far with modified and unmodified electrodes.

Tech Support

Original Source

DOI: https://doi.org/10.3390/c6040075

References

2020 - Mechanisms of action of hydroxychloroquine and chloroquine: Implications for rheumatology [Crossref]
2015 - Chloroquine analogues in drug discovery: New directions of uses, mechanisms of actions and toxic manifestations from malaria to multifarious diseases [Crossref]
2017 - Increased incidence of gastrointestinal side effects in patients taking hydroxychloroquine: A brand-related issue? [Crossref]
2016 - Recommendations on Screening for Chloroquine and Hydroxychloroquine Retinopathy (2016 Revision) [Crossref]
2020 - Of chloroquine and COVID-19 [Crossref]
2020 - A systematic review on the efficacy and safety of chloroquine for the treatment of COVID-19 [Crossref]
2019 - Disposable and flexible electrochemical sensor made by recyclable material and low cost conductive ink [Crossref]
2011 - Factorial design and response surface: Voltammetric method optimization for the determination of ag(i) employing a carbon nanotubes paste electrode