Simple and reliable novel methods for the determination of uric acid (UA) are proposed and validated. For quantitative determination of UA, two matrices were used: the Bray-Liebhafsky (BL) oscillatory reaction in a stable non-equilibrium stationary state close to the bifurcation point (method A) as well as, the BL non-oscillating subsystem (mixture KIO3 and H2SO4), i.e., Dushman reaction (DR) in a steady state (method B). The proposed methods are optimized in a continuously fed well stirred tank reactor (CSTR) and applied with excellent results in the determination of UA in human urine samples. The linear relationship between maximal potential shift ΔEm, and both the logarithm of the UA concentration (procedure A) and UA concentration (procedure B) is obtained in the concentration range 2.98 × 10- 5-2.68 × 10- 4 mol L- 1 and 2.98 × 10- 5-3.58 × 10- 4 mol L- 1, respectively. The methods have an excellent sample throughput of 30 samples h- 1 (method A) and 7 samples h- 1 (method B) with the sensitivity determined to be 1.1 × 10- 5 mol L- 1 (method A) and 8.9 × 10- 6 mol L- 1 (method B) as well as the precision RSD < 3.4% for both methods. Some aspects of the possible mechanism of UA action on the BL oscillating and Duschman non-oscillating reaction systems are discussed in detail.
uric acid; perturbation technique; Bray-Liebhafsky oscillatory reaction; Dushman reaction; urine
