Adsorptive stripping square-wave voltammetry of creatine

An adsorptive stripping square-wave voltammetric method for quantitative determination of creatine is developed. The basic redox properties of creatine are investigated by means of square-wave and cyclic staircase voltammetry. Creatine undergoes an irreversible reduction in neutral and acidic medium at a hanging mercury drop electrode. The square-wave voltammetric response of creatine depends on the parameters of the SW excitation signal as well as on the concentration and type of the supporting electrolyte, the accumulation time and the potential and pH of the medium. The optimal experimental conditions for quantitative determination of creatine are as follows: supporting electrolyte 0.1 mol/L KNO3 buffered with 0.1 mol/L, acetate buffer to pH = 4 and accumulation potential -1.2 V. The optimal SW parameters found are: frequency f = 120 Hz, amplitude E-SW = 30 mV, and scan increment dE = 4 mV. A detection limit of 6.6 x 10(-8) mol/L creatine was obtained after 30 s preconcentration period at accumulation potential -1.2 V. The correlation coefficients of the calibration curves at concentration levels of 10(-7) to 10(-5) mol/L creatine are greater than 0.99. The results of recovery tests range from 92.18 % to 102.51 %.