A highly sensitive sensor for quantification of uric acid (UA) directly in body fluids (saliva and sweat) is reported, working at a potential as low as 0.0 V vs Ag/AgCl. New mixed hydroxide materials exhibiting stable electrocatalytic responses from alkaline to acidic media were prepared, their structure was thoroughly characterized, and the electrochemical properties of the modified FTO (fluorine-doped tin oxide) electrodes were evaluated for UA determination by cyclic voltammetry, chronoamperometry, and batch injection analysis. A very low limit of detection (2.3 × 10-8 mol L-1) with good repeatability (RSD = 3.2% for 30 successive analyses) was achieved based on a fast and simple BIA procedure. Finally, α-Ni0.75Zn0.25(OH)2 screen-printed electrodes (SPE) were developed for the measurement of UA directly in real saliva and sweat samples, without interference of ascorbic acid, acetaminophen, lactate, and glucose at their typical concentrations present in those body fluids, revealing high potential for application as disposable sensors in biological systems. Graphical abstract.
Keywords: Batch injection analysis; Biofluids; Nanocatalysts; Nickel double hydroxide; Screen-printed electrodes; Uric acid.