Electrochemical detection of folic acid: Sensitivity and selectivity trends across carbon-based, metal-based, and other modified electrodes

Folic acid (FA), the synthetic form of vitamin B9, is an essential micronutrient required for various cellular processes. It’s deficiency and excessive intake have been linked to health complications, including neural tube defects, anaemia, cardiovascular diseases, and certain cancers. As folate cannot be synthesised endogenously by human, adequate intake must be obtained through diet and fortified foods in accordance with the Recommended Dietary Intake (RDI). This makes continuous FA monitoring in foods, pharmaceuticals, and clinical samples essential. Analytical methods such as chromatography and spectrophotometry have been widely used, though effective, are expensive, labour-intensive, and often require highly skilled personnel. In contrast, electrochemical detection methods, an increasingly attractive alternatives due to their sensitivity, specificity, cost-effectiveness, and suitability to complex sample matrices. This narrative review critically examines the evolution and application of electrochemical techniques for FA detection, with particular focus on electrode type and nanomaterial-based modifications for enhanced sensor performance. Using a systematic literature search with the SPIDER framework, 116 relevant experimental studies were selected from an initial 5531 articles. Extracted data were synthesised to show detection trends, linear ranges, electrodes, techniques and real-sample applicability. Across studies, carbon-based electrodes, particularly nanostructured and surface-modified variants, dominate FA detection due to strong electron-transfer kinetics, stability, and wide linear ranges. Metal-based systems achieve superior sensitivity and lower detection limits but are limited by practicality and stability. Differential pulse voltammetry (DPV) is the most applied technique, while Molecularly Imprinted Polymer (MIP) and ionic liquid-modified interfaces improve selectivity. However, issues persist in reproducibility, standardisation, and real-sample validation. These findings highlight the prominence of carbon-based electrodes and nanostructured modifiers in advancing next-generation FA sensors.