Combinação da Voltametria de Micropartículas Imobilizadas e filme de quitosana reticulada à base de carbon black para a análise quantitativa de hidroquinona em creme dermatológico.

Hydroquinone (HQ) has been widely applied in the field of cosmetics as it isa strong depigmentation agenthaving the main function of inhibiting melanin production [1,2]. New progress in the application of Voltammetry of Immobilized Microparticles (VIM) technique in electroanalytical chemistry is reported in this work. The designed electrode was based on glassy carbon substrate modified with crosslinked chitosan film containing carbon black nanoparticles and hydroquinone standard or dermatologic creamim mobilized. Electrochemical experiments were performed using a Potentiostat/Galvanostat Autolab PGSTAT204 (Metrohm-Autolab, Utrecht, Netherlands) controlled by NOVA 2.0 software (Eco Chemie) fitted with an electrochemical cell containing three electrodes (15 mL): Ag/AgCl (3.0 mol L−1 KCl) reference electrode, Pt foilas the counter electrode and GCE modified with a crosslinked chitosan film containing immobilized carbon blackparticles and the hydroquinone standard or sample as the working electrode. The influence of supporting electrolyte (KCl, acetate and phosphate buffer solution), pH(4-10), ionic strength(0.1, 0.2 and 0.4 mol L-1) and parametersof theDifferential Pulse Voltammetry (DPV)aswell, scan rate(2.5-10mV s-1), amplitude(10-100 mV)and modulation time(10-40 ms)were optimized.DPV measurements were performed in 0.2 mol L−1phosphate buffer solution (pH = 5.0). The experimental conditions were: Estart:-0.1 V, Eend: 0.35 V, scan rate: 5 mV s−1, modulationamplitude:80 mV and modulation time: 35 ms. The analytical curve was linear(R2=0.997)by concentration range between 2.7 and 43 ng, with detection and quantification limits of 0.045 ng and 0.15 ng, respectively. Two commercial dermatologic cream samples (A1 and A2) were successfully immobilized and analysed using the proposed VIM procedure, showed results similar to those recorded by a spectrophotometric comparative procedure (USP) and results with agreement ranging from 96 to 105%by labelled value. The samples (A1 and A2) showed concentrations ranging 3.84 and 4.2%, respectively. Moreover, the effect of major substances were also investigated (fluocinolone acetonide and tretinoin), not affecting voltammetric determination. Our set of results represents a unique and exciting advance in the scenario of electroanalytical chemistry for future applications.