Determination of Caffeine in Energy Drinks Using a Composite Modified Sensor Based on Magnetic Nanoparticles

At a Glance

Metadata	Details
Publication Date	2025-05-20
Journal	Molecules
Authors	Katarzyna Tyszczuk‐Rotko, Aleksandra Liwak, Aleksy Keller
Institutions	Maria Curie-Skłodowska University
Analysis	Full AI Review Included

Executive Summary

The research details the fabrication and optimization of a highly sensitive voltammetric sensor for the determination of caffeine (CAF) in energy drinks.

Sensor Architecture: A composite modified boron-doped diamond electrode (BDDE) was developed, featuring a Nafion polymer layer embedding Fe₃O₄ magnetic nanoparticles, further enhanced by an in situ electrochemically deposited Bismuth Film (BiF) (BDDE/Nafion@Fe₃O₄/BiF).
Performance: The sensor achieved an ultra-low Limit of Detection (LOD) of 0.043 nM and a Limit of Quantification (LOQ) of 0.14 nM, significantly outperforming many established methods (Table 1).
Analytical Range: The method demonstrated a wide linear concentration range for CAF spanning from 0.5 nM up to 10,000 nM (10 µM).
Mechanism: The Fe₃O₄ nanoparticles and BiF modification collectively improved electron transfer kinetics (lowest xº value of 2.10) and increased the number of active sites for CAF adsorption, leading to enhanced differential-pulse adsorptive stripping voltammetric (DPAdSV) signals.
Robustness and Selectivity: The sensor exhibited satisfactory repeatability (RSD < 2.4%) and reproducibility (RSD 5.9%). It maintained accuracy even in the presence of 100-fold excesses of common energy drink excipients (glucose, vitamins, citric acid).
Practical Application: The optimized DPAdSV procedure was successfully validated for accurate CAF determination in commercial energy drink samples, yielding high recovery rates (up to 100.0%).

Technical Specifications

Parameter	Value	Unit	Context
Sensor Architecture	BDDE/Nafion@Fe₃O₄/BiF	N/A	Composite modified electrode
Limit of Detection (LOD)	0.043	nM	Calculated via 3 SD_a/b
Limit of Quantification (LOQ)	0.14	nM	Calculated via 10 SD_a/b
Linear Range (CAF)	0.5 to 10,000	nM	Wide analytical range (0.0005-10 µM)
Supporting Electrolyte	0.4	M	H₂SO₄ (Optimized concentration)
Bi(III) Concentration	5	µM	Used for in situ BiF deposition
Deposition/Accumulation Potential (E_dep)	-0.95	V	Optimal potential for BiF/CAF accumulation
Deposition/Accumulation Time (t_dep)	60	s	Optimized for fast analysis
DPAdSV Amplitude (ΔE_A)	150	mV	Optimized technique parameter
Scan Rate (v)	100	mV/s	Optimized technique parameter
Modulation Time (t_m)	6	ms	Optimized technique parameter
Electrode Reproducibility (RSD)	5.9	%	For 5 nM CAF (n=15 electrodes)
BDDE Doping Level	1000	ppm	Boron doping level
BDDE Resistivity	0.075	Ωm	Electrical resistivity
Fe₃O₄ Mass (Optimal)	0.5	mg	In 100 µL of 3% Nafion
Nafion Concentration (Optimal)	3	% (v/v)	Used in nanocomposite preparation
Nanocomposite Droplet Volume	0.5	µL	Applied onto BDDE surface
Energy Drink Recovery (Sample 2)	100.0	%	Accuracy test for 0.72 mM CAF sample

Key Methodologies

The BDDE/Nafion@Fe₃O₄/BiF sensor was prepared and utilized via the following steps:

BDDE Pre-treatment: The commercial boron-doped diamond electrode (BDDE, 3 mm diameter) was mechanically polished using 0.3 µm alumina slurry.
Nanocomposite Preparation: 0.5 mg of Fe₃O₄ nanoparticles (50-100 nm) were dispersed in 100 µL of 3% (v/v) Nafion (in ethanol) and subjected to ultrasonic treatment for 2 hours.
Electrode Coating: A small volume (0.5 µL) of the prepared nanocomposite was applied onto the polished BDDE surface and dried for 5 minutes at room temperature.
Electrolyte Selection: The optimized base electrolyte was determined to be 0.4 M H₂SO₄, which promotes the protonated form of CAF for effective adsorption in the cation-exchange Nafion layer.
In Situ Modification and Accumulation: The modified electrode was immersed in the electrolyte containing 5 µM Bi(III) and the CAF analyte. Bismuth film deposition and CAF accumulation were performed simultaneously at an optimized potential of -0.95 V for 60 seconds under stirring.
Voltammetric Measurement: Differential-Pulse Adsorptive Stripping Voltammetry (DPAdSV) was performed in the range of 0.25 to 1.85 V using optimized technique parameters (ΔE_A = 150 mV, v = 100 mV/s, t_m = 6 ms).
Sample Analysis: Commercial energy drinks were diluted 1:10 and analyzed using the standard addition method to confirm practical applicability.

Commercial Applications

The developed sensor technology, leveraging the stability of BDD and the enhanced performance of magnetic nanocomposites, is highly relevant for several industrial and analytical sectors:

Industry/Sector	Application Focus	Technology Advantage
Food and Beverage Quality Control	Rapid, high-throughput analysis of caffeine content in regulated products (energy drinks, supplements, coffee).	Ultra-low LOD allows for accurate measurement of trace contaminants or low-concentration ingredients; fast analysis time (60 s accumulation).
Pharmaceutical Manufacturing	Quality control and formulation testing for drugs containing caffeine (e.g., pain relievers), ensuring precise dosage and purity.	High selectivity against common excipients (vitamins, acids) ensures accurate CAF quantification in complex drug matrices.
Electrochemical Sensor Development	Fabrication of robust, high-performance sensors utilizing BDD substrates, which offer low background current and chemical inertness.	The composite modification (Nafion/Fe₃O₄/BiF) provides a blueprint for enhancing BDD electrodes for other organic molecule detection.
Portable and Field Analysis	Development of miniaturized, portable voltammetric devices (potentially using screen-printed BDD electrodes) for on-site testing of food safety and environmental pollutants.	Voltammetry is inherently suitable for low-cost, portable instrumentation compared to HPLC or GC/MS.

View Original Abstract

A new voltammetric sensor (BDDE/Nafion@Fe3O4/BiF) was fabricated by applying a nanocomposite drop of Fe3O4 magnetic nanoparticles in Nafion onto the polished boron-doped diamond electrode (BDDE) surface. Then, after drying (5 min at room temperature), the electrode was electrochemically modified with bismuth film (BiF) during in situ analysis. The Nafion@Fe3O4/BiF modification of the BDDE contributes to the acquisition of the highest differential-pulse adsorptive stripping voltammetric (DPAdSV) signals of caffeine (CAF) due to the improvement of electron transfer and the increase in the number of active sites on which CAF can be adsorbed. The DPAdSV signals exhibited a linearly varied oxidation peak with the CAF concentration range between 0.5 and 10,000 nM, leading to the 0.043 and 0.14 nM detection and quantification limits, respectively. The practical applicability of the DPAdSV procedure using the BDDE/Nafion@Fe3O4/BiF was positively confirmed with commercially available energy drinks.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules30102219

References

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