An inner filter effect based sensing system for the determination of caffeine in beverage samples

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Environmental Analysis

Background:

• Caffeine (CF) is a widely consumed stimulant found in various beverages.
• Accurate quantification of CF is essential for quality control and consumer safety.
• Existing methods may require complex sample preparation or lack sensitivity.

Purpose of the Study:

• To develop a novel, sensitive, and efficient method for caffeine determination in beverage samples.
• To utilize the inner filter effect (IFE) of caffeine on glibenclamide (GLB) fluorescence for quantitative analysis.
• To validate the method's performance and applicability to real-world samples.

Main Methods:

• Employing the inner filter effect (IFE) where caffeine absorbs glibenclamide's excitation light, causing a "turn-off" fluorescence response.
• Optimizing parameters including glibenclamide concentration, pH, and temperature for maximum sensitivity.
• Utilizing spectrofluorometry for fluorescence intensity measurements at specific excitation and emission wavelengths.

Main Results:

• The method demonstrated a linear response for caffeine detection in the range of 1.00–100.0 mg L⁻¹, with a low limit of detection (LOD) of 0.10 mg L⁻¹.
• High precision was achieved with relative standard deviation (RSD) values of 0.75% (intra-day) and 1.24% (inter-day).
• The method successfully quantified caffeine in untreated beverage samples, showing no significant difference compared to a reference method.

Conclusions:

• The IFE-based fluorescence quenching method provides a simple, rapid, and sensitive approach for caffeine determination.
• The developed method is suitable for the direct analysis of caffeine in complex matrices like beverages.
• This technique offers a viable alternative to conventional methods for routine caffeine analysis.