Acid-base titration using a microfluidic thread-based analytical device (TAD)

This work presents the development and application of a novel analytical approach for the determination of acid and base concentrations by titration using a microfluidic thread-based analytical device (mu TAD). This approach proved to be a simple to fabricate and to use, high precision, and cost-efficient means of acid-base quantification. The mu TAD was fabricated by immobilizing the untreated cotton threads onto a wood frame, followed by pre-coating with an indicator (20 mu L) and a primary standard solution (3 mu L), and was tested using real samples including drug, food, and household products where 3 mu L of each sample was dropped onto the center of a thread. Afterward, the distance of color change on the thread, easily observed and measured using the naked eye and a ruler, was used for analysis. The analysis using the mu TAD, completed within 2 minutes and validated by the conventional titration, showed high accuracy and precision (RSD < 12.9%), good linearity ranges and low limit of quantification. The fabricated mu TAD also remained stable for an extended period of time (>2 weeks under various storage conditions).