Electrochemical Characterization and Voltammetric Determination of Methylisothiazolinone on a Boron-Doped Diamond Electrode

At a Glance

Metadata	Details
Publication Date	2022-12-17
Journal	Molecules
Authors	Magdalena Jakubczyk, Sławomir Michałkiewicz, Agata Skorupa, Kinga Krajcarz
Institutions	Jan Kochanowski University, Holy Cross University
Analysis	Full AI Review Included

Technical Documentation & Analysis: Voltammetric Determination of Methylisothiazolinone on Boron-Doped Diamond Electrodes

This document analyzes the research detailing the use of Boron-Doped Diamond Electrodes (BDDE) for the determination of Methylisothiazolinone (MIT) via Differential Pulse Voltammetry (DPV). This application highlights the superior electrochemical stability and sensitivity of 6CCVD’s diamond materials for advanced sensing and quality control applications.

Executive Summary

Novel Application: Developed a new, highly accurate voltammetric method for determining Methylisothiazolinone (MIT), a critical preservative/biocide, in complex matrices like household products.
Material Superiority: The Boron-Doped Diamond Electrode (BDDE) demonstrated significantly better performance (best-shaped, symmetrical peaks, lowest residual currents) compared to traditional electrodes (Gold, Platinum, Glassy Carbon).
High Sensitivity: Achieved a low Limit of Detection (LOD) of 0.24 mg L^-1, which is below regulatory limits for MIT in cosmetics (0.0015% or 15 mg L^-1).
Robust Performance: The method exhibited excellent precision (Intra-day Relative Standard Deviation (RSD) of 0.6%) and high accuracy (Recovery 99.0-99.5%) in real-world samples.
Electrochemical Mechanism: The anodic oxidation of MIT on BDDE is an irreversible, diffusion-controlled process involving a two-electron exchange, optimally performed in a citrate-phosphate buffer (pH 5.6).
Green Chemistry Compliance: The procedure simplifies sample preparation, requiring only dissolution, thus reducing analysis time and reagent consumption compared to prevailing chromatographic methods (HPLC/UHPLC).

Technical Specifications

Parameter	Value	Unit	Context
Working Electrode Material	Boron-Doped Diamond (BDDE)	N/A	Selected for optimal performance
Electrode Diameter	3	mm	Used for all DPV/CV measurements
Optimal Buffer Solution	Citrate-Phosphate (C-PB)	N/A	McIlvaine buffer selected at optimal pH
Optimal pH	5.6	N/A	Guarantees maximum peak current (I_p)
Anodic Peak Potential (E_p)	1.535 ± 0.005	V vs. Ag/AgCl	Potential of irreversible MIT oxidation
Linear Concentration Range	0.7 to 18.7	mg L^-1	Wide range with high correlation (r = 0.9999)
Limit of Detection (LOD)	0.24	mg L^-1	Achieved using Differential Pulse Voltammetry (DPV)
DPV Amplitude (dE)	50	mV	Optimized for high sensitivity
DPV Pulse Width	80	ms	Optimized parameter
Oxidation Mechanism	Irreversible, Diffusion-Controlled	N/A	Two-electron exchange (n=2), no proton exchange
Intra-day Repeatability (RSD)	0.6	%	Excellent precision (n=10)
Inter-day Precision (RSD)	1.1	%	Measured over 5 consecutive days

Key Methodologies

The successful determination of MIT relies on precise control of the BDDE surface and electrochemical parameters:

Electrode Surface Preparation: The BDDE surface was mechanically polished using 0.01 µm alumina powder slurry, followed by sonication in distilled water.
Electrode Activation: Daily cathodic activation was performed in 1 mol L^-1 H₂SO₄ at a potential of -2.4 V for 5 minutes to ensure the highest surface activity and reproducibility.
Buffer Optimization: Various buffer systems (Britton-Robinson, acetate, phosphate, citrate, and citrate-phosphate) were tested. The McIlvaine (C-PB) buffer at pH 5.6 yielded the best-shaped curves and highest current intensity.
Voltammetric Optimization: Differential Pulse Voltammetry (DPV) parameters were optimized to maximize signal resolution and peak current, selecting an amplitude of 50 mV, a potential step of 5 mV, and a pulse width of 80 ms.
Mechanism Confirmation: Cyclic Voltammetry (CV) confirmed the process was diffusion-controlled (linear relationship between I_p and v^1/2) and irreversible (absence of cathodic peak and E_p shift with scan rate).
Reproducibility Restoration: Between successive scans, the electrode activity was restored by applying cathodic polarization at the hydrogen evolution potential (-1.2 V for 30 s).

6CCVD Solutions & Capabilities

The research demonstrates the critical role of high-quality Boron-Doped Diamond (BDD) in achieving sensitive and reliable electrochemical detection of biocides. 6CCVD is uniquely positioned to supply the necessary materials and customization required to replicate and advance this research.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Material: High-Performance Boron-Doped Diamond (BDDE)	Heavy Boron Doped PCD/SCD: 6CCVD specializes in MPCVD growth of highly conductive BDD wafers and plates, ensuring the widest potential window and lowest residual currents necessary for trace analysis.	Our BDD materials guarantee the superior electrochemical stability and sensitivity required to achieve the reported low LOD (0.24 mg L^-1) for MIT determination.
Dimensions: 3 mm diameter electrode	Custom Fabrication & Sizing: We provide custom laser cutting and shaping services. We can supply BDD electrodes in precise diameters (e.g., 3 mm) or as large plates up to 125 mm (PCD/BDD) for multi-sensor arrays.	Enables seamless integration into existing laboratory setups or high-throughput industrial quality control systems.
Surface Finish: Ultra-smooth, low-noise surface	Precision Polishing (Ra < 5 nm): 6CCVD offers standard polishing to Ra < 5 nm for inch-size PCD/BDD, minimizing background noise and maximizing signal-to-noise ratio.	Ensures the excellent repeatability (RSD < 1.1%) and high resolution observed in the DPV measurements.
Electrode Activation: Need for specific H₂SO₄ activation	Custom Surface Termination: We offer specific surface terminations (e.g., hydrogen-terminated or oxygen-terminated) to optimize the diamond surface for specific electrochemical reactions, potentially reducing or simplifying the required pre-treatment steps.	Accelerates research timelines and improves long-term electrode stability by providing tailored surface chemistry.
Future Integration: Need for contact pads (e.g., Au, Pt)	In-House Metalization Services: 6CCVD provides internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu, for creating robust electrical contacts or integrated reference electrodes directly on the BDD substrate.	Delivers ready-to-use, fully integrated diamond sensor chips, simplifying device assembly for commercial or research applications.

Engineering Support

6CCVD’s in-house PhD team offers expert consultation on material selection, doping levels, and surface preparation techniques for electrochemical sensing projects, particularly those involving the detection of biocides, pharmaceuticals, or environmental contaminants. We can assist engineers and scientists in optimizing the BDD properties to match the specific requirements of their voltammetric determination projects.

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

View Original Abstract

The electrochemical properties of methylisothiazolinone (MIT), the most widely used preservative, were investigated by cyclic (CV) and differential pulse voltammetry (DPV) to develop a new method for its determination. To our knowledge, this is the first demonstration of a voltammetric procedure for the determination of MIT on a boron-doped diamond electrode (BDDE) in a citrate-phosphate buffer (C-PB) environment. The anodic oxidation process of methylisothiazolinone, which is the basis of this method, proved to be diffusion-controlled and proceeded with an irreversible two-electron exchange. The radical cations, as unstable primary products, were converted in subsequent chemical reactions to sulfoxides and sulfones, and finally to more stable final products. Performed determinations were based on the DPV technique. A linear calibration curve was obtained in the concentration range from 0.7 to 18.7 mg L−1, with a correlation coefficient of 0.9999. The proposed procedure was accurate and precise, allowing the detection of MIT at a concentration level of 0.24 mg L−1. It successfully demonstrated its suitability for the determination of methylisothiazolinone in household products without the need for any separation steps. The proposed method can serve as an alternative to the prevailing chromatographic determinations of MIT in real samples.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules27249013

References

2015 - Determination of methylisothiazolinone and methylchloroisothiazolinone in cosmetic products by ultra high performance liquid chromatography with tandem mass spectrometry [Crossref]
2017 - Fast and Sensitive Liquid Chromatography Method for Simultaneous Determination of Methylisothiazolinone, Salicylic Acid and Parabens in Cosmetic Products [Crossref]
2012 - Determination of isothiazolinone preservatives in cosmetics and household products by matrix solid-phase dispersion followed by high-performance liquid chromatography-tandem mass spectrometry [Crossref]
2019 - Isothiazolinone Content of US Consumer Adhesives: Ultrahigh-Performance Liquid Chromatographic Mass Spectrometry Analysis [Crossref]
2014 - Emission of isothiazolinones from water-based paints [Crossref]
2015 - Biocides in hydraulic fracturing fluids: A critical review of their usage, mobility, degradation, and toxicity [Crossref]
2014 - Patch testing with serial dilutions of various isothiazolinones in patients hypersensitive to methylchloroisothiazolinone/methylisothiazolinone [Crossref]
2009 - The efficacy of biocides and other chemical additives in cooling water systems in the control of amoebae [Crossref]
2010 - Analysis of isothiazolinone biocides in paper for food packaging by ultra-high-performance liquid chromatography-tandem mass spectrometry [Crossref]