Highly sensitive electrochemical detection of riboflavin in biological samples using a phthalic acid–doped polyaniline-modified pencil graphite electrode

The development of electrochemical sensor for riboflavin detection is important for assessing health status, pharmaceutical efficacy, and nutritional content in food samples. This study describes a novel electrochemical sensor based on a pencil graphite electrode (PGE) modified with a phthalic acid-doped polyaniline film. Following polymer deposition, the electrode was subjected to a controlled overoxidation process. Overoxidation of polyaniline generates a chemically reactive and functionally modified surface. Incorporation phthalic acid into the polyaniline matrix enhances surface roughness and interfacial properties. The modification enhances electron transfer kinetics and increases electrochemically active surface area. As a result, the modified electrode demonstrates a significantly enhanced response toward riboflavin compared to the bare electrode. The sensor displays a linear response over the concentration range of 1 × 10⁻³ M up to 5 × 10^⁻9 M. The calibration curve shows excellent linearity (R² = 0.9957). The limit of detection (LOD) and limit of quantitation (LOQ) were calculated as 1.14 × 10⁻ ⁹ M and 3.80 × 10⁻⁹ M, respectively. The proposed sensor exhibits high selectivity toward in the presence of common interfering species such as ascorbic acid, uric acid, dopamine, glucose, sucrose, and pyridoxine. The sensor demonstrates good repeatability with a relative standard deviation (RSD) of 2.57%. Furthermore, the RSD for independently prepared electrodes were found to be 2.7%. In addition, the sensor maintains its electrochemical activity over multiple uses. To evaluate practical applicability, the sensor was tested in human blood serum and urine samples. Recovery values ranged from 95.6% to 105.5%.