A Sensitive Voltammetric Approach Employing a Bare Boron-Doped Diamond Electrode as a Sensor for the Determination of Hydroxocobalamin

At a Glance

Metadata	Details
Publication Date	2023-09-25
Authors	Lenka Janíková, Renáta Šelešovská, Iveta Stýblová, Jaromíra Chýlková
Institutions	University of Pardubice
Citations	1
Analysis	Full AI Review Included

Executive Summary

This research details the development of a highly sensitive voltammetric sensor utilizing a bare Boron-Doped Diamond Electrode (BDDE) for the determination of Hydroxocobalamin (OH-CBL, Vitamin B12).

Sensor Material: Bare BDDE was employed due to its wide potential window, high stability, and low background current, proving effective without surface pretreatment for the primary analytical signal.
Analytical Technique: Differential Pulse Voltammetry (DPV) was optimized, focusing on the well-developed anodic peak (Peak 1) observed in acidic media.
Optimal Conditions: The highest response for OH-CBL oxidation was achieved using 0.1 mol/L H₂SO₄ as the supporting electrolyte.
High Sensitivity: The developed DPV method achieved a low Limit of Detection (LD) of 13.2 nmol/L, positioning it as a sensitive tool for trace analysis.
Electrochemical Mechanism: Analysis of the scan rate dependence indicated that the analytical anodic process (Peak 1) is influenced by both diffusion and kinetic control, while the cathodic reduction process is primarily diffusion-controlled.
Practical Application: The method was successfully validated for the quantification of OH-CBL in commercial vitamin preparations using the standard addition method, showing good agreement with declared values.

Technical Specifications

Parameter	Value	Unit	Context
Working Electrode Material	Bare Boron-Doped Diamond	N/A	High stability, wide potential window
Electrode Surface Area	7.07	mm²	Working electrode specification
Supporting Electrolyte	0.1	mol/L	H₂SO₄ (Optimal for anodic signal 1)
Analytical Signal (Anodic Peak 1)	+412	mV	vs. Ag/AgCl
Limit of Detection (LD)	13.2	nmol/L	Calculated for anodic peak 1
Limit of Quantification (LQ)	43.9	nmol/L	Calculated for anodic peak 1
Linear Dynamic Range (LDR)	2.00 x 10^-8 to 8.25 x 10^-7	mol/L	Concentration range for anodic peak 1
DPV Scan Rate (Oxidation)	30	mV/s	Optimized parameter for anodic peak 1
DPV Pulse Height (Oxidation)	65	mV	Optimized parameter for anodic peak 1
DPV Pulse Width (Oxidation)	20	ms	Optimized parameter for anodic peak 1
Method Repeatability (RSD)	1.26	%	Relative standard deviation for 11 repeated CV measurements (Anodic Peak 1)
Anodic Process Control Slope	0.384	N/A	log(I_p) vs. log(ν) slope, indicating mixed diffusion/kinetic control

Key Methodologies

The analytical approach involved systematic optimization using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) on the bare BDDE sensor.

Electrolyte Selection (CV pH Study):
- A wide range of supporting electrolytes (BRB, BB, AB, HNO₃, H₂SO₄) were tested to determine the influence of pH on OH-CBL behavior.
- Four anodic signals (1-4) were observed in acidic media (pH less than 3), and only one signal (Peak 3) was detected in alkaline media (pH 8-11).
- The highest, most well-developed, and easily evaluable signal (Anodic Peak 1) was achieved in 0.1 mol/L H₂SO₄, which was selected for all subsequent experiments.
Scan Rate Analysis (CV):
- The dependence of peak current (I_p) on scan rate (ν) was examined from 10 to 500 mV/s.
- A linear relationship was found between I_p and ν^1/2 for both anodic (Peak 1) and cathodic (RED) responses, suggesting diffusion control.
- Logarithmic analysis (log(I_p) vs. log(ν)) confirmed that the cathodic reaction was diffusion-controlled (slope 0.453), while the anodic reaction was influenced by mixed diffusion and kinetics (slope 0.384).
Surface Pretreatment Optimization:
- Anodic (+2000 mV) and cathodic (-2000 mV) pretreatment procedures were tested to enhance sensitivity and repeatability.
- For the analytical anodic signal (Peak 1), the omission of any pretreatment provided the best stability and repeatability (RSD_M(11) = 1.26%), leveraging the inherent stability of the bare BDDE surface.
- For the cathodic signal (RED), a combination of anodic and cathodic pretreatment (20 potential jumps between +2000 mV and -1500 mV) was necessary to achieve a stable response (RSD_M(11) = 1.45%).
DPV Optimization and Validation:
- DPV parameters (E_in, E_fin, ν, pulse height, pulse width) were optimized for the anodic signal 1 (see Technical Specifications table).
- The method was validated using model solutions, confirming linearity (R² = 0.9982) and high recovery (99.6%-103.0%).
- Real samples (liquid and tablet vitamin preparations) were analyzed using the standard addition method, confirming the method’s applicability for quality control.

Commercial Applications

The use of Boron-Doped Diamond Electrodes (BDDE) in this study highlights their utility in advanced electrochemical sensing, particularly in areas requiring high stability and resistance to fouling.

Industry/Sector	Application Area	Relevance to BDDE Technology
Pharmaceutical & Nutraceutical QC	Quality control and trace analysis of vitamin preparations (e.g., Vitamin B12 derivatives like OH-CBL).	BDDE offers high sensitivity (nmol/L detection limits) and stability for routine analysis in complex matrices.
Clinical Diagnostics	Monitoring of cobalamin levels in biological fluids (e.g., blood plasma) due to the low detection limit achieved.	The wide potential window minimizes interference from biological components, and the robust surface resists fouling.
Environmental Monitoring	Sensing of trace organic pollutants or pharmaceuticals in water systems.	BDDE’s resistance to deactivation and high chemical inertness make it ideal for harsh or complex environmental samples.
Advanced Electrochemistry	Fundamental studies of complex redox reactions (like those of cobalamins) where a stable, reproducible, and inert electrode surface is critical.	The low and stable background current allows for accurate measurement of subtle electrochemical events.
Electrochemical Sensor Manufacturing	Development of robust, long-lifetime sensors for industrial process control and portable analytical devices.	BDDE materials, often sourced from specialized suppliers like 6ccvd.com, provide the necessary material quality (e.g., specific doping levels) for high-performance electrochemical applications.

View Original Abstract

The voltammetric behavior of hydroxocobalamin (OH-CBL) was firstly studied by employing a bare boron-doped diamond electrode as a working electrode. It was found that OH-CBL provided four anodic signals on BDDE in acidic supporting electrolytes and one cathodic signal. The anodic peak situated at +412 mV (vs. Ag|AgCl|KCl (sat.) recorded in 0.1 mol/L H2SO4) was found to be suitable for analytical purposes due to its position and shape. A novel voltammetric approach based on differential pulse voltammetry was developed and it was found as a sensitive analytical tool, with low limit of detection (LD = 13.2 nmol/L), applicable in analysis of vitamin preparations.

Tech Support

Original Source

DOI: https://doi.org/10.3390/csac2023-14894

References

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2016 - Electroanalytical approach for vitamin B12 quantification based on its oxidation at boron doped diamond electrode [Crossref]
2020 - A novel electrochemical strategy for determination of vitamin B12 by Co (I/II) redox pair monitoring with boron-doped diamond electrode [Crossref]
2013 - Silver solid amalgam electrode as a tool for monitoring the electrochemical reduction of hydroxocobalamin [Crossref]
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