Carbon Fiber Paper Sensor for Determination of Trimethoprim Antibiotic in Fish Samples

At a Glance

Metadata	Details
Publication Date	2023-03-29
Journal	Sensors
Authors	Álvaro Torrinha, Miguel Tavares, Vitória Dibo, Cristina Delerue‐Matos, Simone Morais
Institutions	Rede de Química e Tecnologia, Polytechnic Institute of Porto
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced Electrochemistry

Executive Summary

This documentation analyzes the application of an unmodified Carbon Paper Sensor (CPS) for the determination of Trimethoprim (TMP) antibiotic in complex fish samples via Square Wave Voltammetry (SWV). The findings provide a direct comparative opportunity for 6CCVD’s superior Boron-Doped Diamond (BDD) electrode technology.

Application Focus: Quantitative determination of the emerging contaminant Trimethoprim (TMP) in complex solid food matrices (fish).
Analytical Performance: Achieved high sensitivity (48.8 µA µM⁻¹ cm⁻²) and a competitive Limit of Detection (LOD) of 0.065 µM using a simple, unmodified carbon paper transducer.
Methodology: Utilized optimized SWV parameters (0.02 V amplitude, 50 Hz frequency, 60 s deposition time) combined with QuEChERS solid-phase extraction for sample cleanup.
Validation Success: Demonstrated excellent recovery (105.9 ± 1.8% RSD 1.8%) in spiked fish samples, validating the method for challenging environmental analysis.
Competitive Advantage: The paper explicitly notes that the CPS performance is comparable to or better than more expensive, nanostructured Glassy Carbon Electrodes (GCE) and Boron-Doped Diamond (BDD) electrodes, highlighting a key market entry point for 6CCVD to demonstrate the superior stability and wider potential window of BDD.
Material Limitation: The CPS exhibited a loss of performance upon reuse, necessitating disposal after a single measurement, a critical drawback that 6CCVD’s BDD materials overcome.

Technical Specifications

The following optimized parameters and performance metrics were achieved using the Carbon Paper Sensor (CPS) for Trimethoprim detection:

Parameter	Value	Unit	Context
Electrode Material	Carbon Fiber Paper (Toray TGP-H-60)	N/A	Unmodified, untreated
Electrode Area (Geometric)	0.63	cm²	Immersed area
Detection Technique	Square Wave Voltammetry (SWV)	N/A	Optimized method
Optimum Electrolyte	Britton-Robinson Buffer (BRB) pH 7	0.1 M	Selected for maximum peak height
SWV Amplitude	0.02	V	Optimized parameter
SWV Frequency	50	Hz	Optimized parameter
SWV Step Potential	0.015	V	Optimized parameter
Deposition Potential	+0.7	V	Optimized parameter
Deposition Time	60	s	Optimized parameter
Linear Range	0.05 to 2	µM	Trimethoprim concentration
Sensitivity	48.8 ± 3.2	µA µM⁻¹ cm⁻²	Mean sensitivity (n=3)
Limit of Detection (LOD)	0.065	µM	Calculated from blank response
Repeatability (RSD)	6	%	Seven measurements (0.5 µM TMP)
Reproducibility (RSD)	9	%	Five different CPS (0.5 µM TMP)
Recovery in Fish Samples	105.9 ± 1.8	%	Standard addition method (0.25 µM spike)

Key Methodologies

The experiment focused on optimizing electrochemical parameters and utilizing robust sample preparation techniques to handle the complex fish matrix.

1. Sensor Fabrication and Setup

Working Electrode: Carbon Paper (Toray TGP-H-60) was cut to 2.5 x 0.7 cm² (0.19 mm thickness).
Connection: One end was covered with aluminum foil for connection via a crocodile clip.
Electrochemical Cell: Standard three-electrode format was used: Ag/AgCl (KCl, 3 M) reference electrode, Platinum counter electrode, and the CPS working electrode.

2. Analytical Optimization (SWV)

pH Optimization: Britton-Robinson Buffer (0.1 M) pH was varied from 3 to 12. Optimum performance was achieved at pH 7, near the pK_a (6.6) of trimethoprim.
Voltammetry Parameters: SWV amplitude (0.02 V), frequency (50 Hz), and step potential (0.015 V) were optimized to maximize signal and reproducibility.
Electrodeposition: Deposition potential (+0.7 V) and time (60 s) were optimized to enhance the TMP signal prior to the SWV measurement.

3. Real Sample Preparation (Fish)

Matrix: Edible meat of Merluccius capensis (Hake) was used, spiked with Trimethoprim (0.25 µM).
Extraction: A modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure was employed.
- Sample was mixed with water and acetonitrile, followed by the addition of QuEChERS salts (4 g magnesium sulfate, 1 g sodium chloride).
- Dispersive Solid-Phase Extraction (SPE) cleanup was performed using a kit containing C18 and magnesium sulfate to remove interfering compounds (fats, proteins, etc.).
Final Analysis: The evaporated residue was redissolved in 30:70 acetonitrile:buffer (v/v) and analyzed using the Standard Addition Method to compensate for matrix effects.

6CCVD Solutions & Capabilities

The research successfully demonstrated a low-cost sensor alternative. However, the paper explicitly notes the high cost and pre-treatment requirements of traditional Boron-Doped Diamond (BDD) electrodes, while simultaneously highlighting the critical limitation of the CPS: poor reusability (Page 9).

6CCVD specializes in high-performance MPCVD diamond, offering solutions that directly address the limitations of the CPS while providing the superior electrochemical properties required for next-generation environmental monitoring.

Applicable Materials: Boron-Doped Diamond (BDD)

To replicate or extend this research, 6CCVD strongly recommends utilizing our Heavy Boron-Doped Diamond (BDD) Wafers/Plates.

CPS Limitation	6CCVD BDD Solution	Technical Advantage
Poor Reusability (Discarded after one use)	BDD Stability	BDD offers unparalleled chemical inertness and stability, allowing for thousands of reproducible measurements without performance loss or complex regeneration.
Narrow Potential Window (Inferred)	Wide Potential Window	BDD provides the widest solvent potential window of any electrode material, enabling the detection of analytes like TMP (oxidation peak at +1.2 V) with minimal background interference.
Rough/Porous Surface (Micrometer fibers)	Polished Surface Options	6CCVD offers BDD with polishing down to Ra < 1nm (SCD) or Ra < 5nm (PCD), ensuring highly reproducible, low-noise measurements superior to the tortuous CPS surface.
Requires Complex Sample Prep (QuEChERS/SPE)	Reduced Fouling	The anti-fouling nature of BDD minimizes surface contamination from complex matrices (fats, proteins in fish), potentially simplifying or eliminating some extraction steps.

Customization Potential for Advanced Sensors

6CCVD provides full customization capabilities necessary to transition from laboratory-scale carbon paper prototypes to robust, integrated BDD sensors for in situ environmental applications.

Custom Dimensions: We supply BDD plates and wafers in custom dimensions and shapes, suitable for integration into microfluidic devices or sensor arrays, exceeding the simple 2.5 x 0.7 cm² cut used in this study.
Thickness Control: BDD layers can be grown from 0.1 µm to 500 µm, allowing engineers to optimize conductivity and cost for specific sensor designs.
Integrated Metalization: Unlike the CPS, which required an aluminum foil connection, 6CCVD offers in-house metalization services (Au, Pt, Ti, W, Cu) applied directly to the BDD surface, providing robust, low-resistance contacts for reliable device packaging.
Surface Finish: We offer highly polished BDD surfaces (Ra < 5nm for polycrystalline BDD) which are essential for achieving the lowest possible detection limits and highest signal-to-noise ratios in voltammetry.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science and electrochemical applications of diamond. We can assist researchers and engineers in selecting the optimal BDD doping level and surface finish required to maximize sensitivity and stability for similar environmental electroanalysis projects, ensuring a seamless transition from proof-of-concept to commercial deployment.

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

View Original Abstract

The increase in anthropogenic pollution raises serious concerns regarding contamination of water bodies and aquatic species with potential implications on human health. Pharmaceutical compounds are a type of contaminants of emerging concern that are increasingly consumed and, thus, being frequently found in the aquatic environment. In this sense, an electrochemical sensor based on an unmodified and untreated carbon fiber paper (CPS—carbon paper sensor) was simply employed for the analysis of trimethoprim antibiotic in fish samples. First, the analytical conditions were thoroughly optimized in order for the CPS to achieve maximum performance in trimethoprim determination. Therefore, an electrolyte (0.1 M Britton-Robinson buffer) pH of 7 was selected and for square wave voltammetry parameters, optimum values of amplitude, frequency and step potential corresponded to 0.02 V, 50 Hz, and 0.015 V, respectively, whereas the deposition of analyte occurred at +0.7 V for 60 s. In these optimum conditions, the obtained liner range (0.05 to 2 µM), sensitivity (48.8 µA µM−1 cm−2), and LOD (0.065 µM) competes favorably with the commonly used GCE-based sensors or BDD electrodes that employ nanostructuration or are more expensive. The CPS was then applied for trimethoprim determination in fish samples after employing a solid phase extraction procedure based on QuEChERS salts, resulting in recoveries of 105.9 ± 1.8% by the standard addition method.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s23073560

References

2017 - Pharmaceuticals and personal care products (PPCPs) in the freshwater aquatic environment [Crossref]
2018 - A review of the pharmaceutical exposome in aquatic fauna [Crossref]
2017 - Occurrences and removal of pharmaceuticals and personal care products (PPCPs) in drinking water and water/sewage treatment plants: A review [Crossref]
2012 - Emerging organic contaminants in groundwater in Spain: A review of sources, recent occurrence and fate in a European context [Crossref]
2019 - Pharmaceuticals in freshwater aquatic environments: A comparison of the African and European challenge [Crossref]
2022 - Pharmaceuticals in water as emerging pollutants for river health: A critical review under Indian conditions [Crossref]
2022 - Environmental contamination in a high-income country (France) by antibiotics, antibiotic-resistant bacteria, and antibiotic resistance genes: Status and possible causes [Crossref]