Desenvolvimento de sensor eletroquímico de pasta de carbono modificado com biocarvão de murumuru para determinação de ácido nicotínico em multivitamínicos e medicamento

Abstract

Nicotinic acid (NA) is the main constituent of vitamin B3, acting directly in the metabolism of macronutrients and synthesis of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). The deficiency of NA in the body can affect the digestive, nervous and skin systems. However, the excess of NA can cause hepatotoxicity and other severe complications. Therefore, it’s necessary to develop analytical methods to monitor this substance in pharmaceutical products, such as medicines and multivitamins. The development of methods using voltammetric techniques, such as differential pulse voltammetry (DPV), becomes viable, since these techniques have a low cost and short analysis time. The development of modified electrodes with carbonaceous materials, such as murumuru biochar, can improve the sensitivity of voltammetric methods. This happens due to interaction between the electrode and the analyte which is improved due to the physicochemical properties of this modifier. Thus, the aim of this work was to develop an electrochemical sensor made of carbon paste modified with murmuru biochar for determining AN in samples of medicines and multivitamins. The proportion of carbon paste was optimized through mixture design, resulting in a proportion of: 31.7% graphite, 31.7% BCM and 36.6% binder. HClO4 at pH 2 with KCl (0.1 mol L-1) was selected as supporting electrolyte. In studies carried out using cyclic voltammetry, a reduction in AN was observed with irreversible charge transfer and diffusion-controlled mass transport. Furthermore, the AN reduction mechanism was also evaluated. For analyzes performed by DPV, the technique parameters were optimized resulting in a step of 5 mV, pulse amplitude of 100 mV, time modulation of 2 ms and time interval of 75 ms. The analytical curve showed a determination coefficient (R2) of 0.999, in a linear range of 4 μmol L-1 to 100 μmol L-1. The detection limit of 0.359 μmol L-1 and quantification limit of 1.196 μmol L-1. From the analytical curve obtained, AN was quantified in children's multivitamins (syrup), multivitamin tablets and medication, which resulted in AN mass of 3.51 mg, 70.42 mg and 507.51 mg, respectively. The masses found using the developed method were close to the nominal values for each of the samples. Therefore, the developed method can be applied to quantify AN in drug and multivitamin samples.