Development of a Paper-based Analytical Strip for Rapid On-site Colorimetric Detection of Homovanillic Acid in Urine Samples

A BSTRACT Objective: Accurate detection of homovanillic acid (HVA) in urine is crucial for diagnosing and monitoring neurological conditions such as Parkinson’s disease, schizophrenia, and mood disorders. Traditional methods such as spectrophotometry and high-performance liquid chromatography, while precise, are costly and require specialized equipment, making them impractical for on-site analysis. Materials and Methods: This study investigates the use of paper-based analytical devices (PADs) as a cost-effective and portable alternative for HVA detection in urine. PADs are increasingly popular in various fields, including chemical detection and environmental monitoring. We evaluated different Whatman filter papers (No. 1, No. 2, and No. 4) and chromatography paper as substrates for PADs using a colorimetric reaction with potassium ferrocyanide and ferric chloride. Results: Our results show successful HVA detection across these substrates, with optimal results obtained after immersion times of 30 min to 3 h, followed by a 30-min drying period at room temperature. The developed strips showed a color shift from green to blue in the presence of HVA, with a detection limit of 1 mg/ml, and performed comparably to ultraviolet spectroscopy methods. Conclusion: Notably, Whatman CF6 paper showed significant variations in detection efficiency, underscoring the importance of substrate selection in PAD development.