Highly Sensitive Adsorptive Stripping Voltammetric Method for Sitagliptin Determination on Renewable Amalgam Film Electrode

Highly sensitive voltammetric method for sitagliptin (STG) determination was developed. As working electrode cyclic renewable amalgam film electrode Hg(Ag)FE was used (surface area 10.4 mm(2)). Application of Hg(Ag)FE allowed to improve sensitivity of the method in comparison with HMDE. Instrumental parameters were optimized and were as follow: waiting and sampling time t(w)= t(p)= 10 ms, step potential E-s= 5 mV and pulse amplitude Delta E = 50 mV. Preconcentration step was carried out at the potential equal to -600 mV for 15 s. Supporting electrolyte was optimized: 0.025 M ammonium buffer (pH 8.2). Conducted calibration allowed to determine linear range: 20-140 nM and limit of detection LOD: 2.6 nM (1.3 ng ml(-1)) (20 s preconcentration time). Based on linear sweep voltammetry (LSV) measurements the possible mechanism of sitagliptin reduction has been proposed. The applicability of the method was confirmed by analysis of commercially available pharmaceutical product containing sitagliptin. Obtained results were in a good agreement with producer's declaration. Calculated recoveries (102%-107%) proved the accuracy of the method. Signal repeatability expressed as RSD was equal to 3.2% (STG concentration 0.1 mu M, n = 5).