Desenvolvimento e otimização de metodologia para análise de nitrito e nitrato em amostras de soro lácteo por eletroforese capilar

Abstract

The whey is the aqueous portion of the coagulum liberated during cheese making and is considered both a residual effluent as a byproduct of high biological value. Its reuse is studied and suggested for improve the economic efficiency of dairy and minimize environmental impacts. However, the addition of NaNO3 or KNO3 at the milk for cheese production (except fresh) has specialists concerned, since it can be ingested NO3- reduced to NO2- in the human organism can both bind to form amides and amines, and N-nitroso compounds such as nitrosamines that under certain exposure conditions, are potentially mutagenic, carcinogenic and teratogenic agents as binding to hemoglobin and cause methemoglobinemia. As, on average, 70% of the NO3- added to milk is dragged by whey and this is used as raw material in the dairy industry, the determination of these ions is of paramount importance. Nevertheless, the official method generally used, has some disadvantages such as low analytical frequency (2 samples per hour), need to employ columns of cadmium and its regeneration, disposal of waste resulting from regeneration, pre-treatment of samples and addition to being a laborious method requires the use of various reagents and exposes the analyst to potential health risks. So an alternative method for the simultaneous determination of nitrite and nitrate by capillary zone electrophoresis (CZE), with indirect UV detection at 210 nm analysis time of about 3 minutes is proposed. The optimized electrolyte consists of 100 mmol L-1 TRIS, 50 mmol L-1 HCl and 0.150 mmol L-1 of CTAB at pH 8.2. The results achieved were satisfactory, indicating that the optimized CZE method can be used for simultaneous determination of nitrite and nitrate ions in samples of whey, presenting advantages: shorter time of analysis, simple sample preparation and low cost.