ABSTRACT
RESUMO A pesquisa descreve a reação espectrofotométrica do complexo Cu(II)-PAN (1-(2-piridilazo)-2-naftol) e determina a concentração de cobre (II) em aguardente de mandioca (Tiquira). Para isso, dimensionamos a reação para os estudos de absorção do complexo, pH, estabilidade, proporção estequiométrica, interferentes, correlação e recuperação. Após essa etapa, determinamos a concentração de cobre(II) em cinco amostras de bebidas destiladas artesanalmente de cinco municípios do Estado do Maranhão. O resultados mostram que o complexo absorve em 548 nm em pH 6, é estável em um tempo de 7 horas em proporções estequiométrica mínima de 1:1 do ligante e metal, possui limite de detecção em 3,3 X 10-2 mg L-1, faixa de linearidade de 1 X 10-6 a 1 X 10-5 mol L-1, correlação (R2= 0,9990), desvio padrão=0,0035 e recuperação em 104,54 ± 7,01 e os principais íons interferentes são o ferro (III) e o cobalto (II). Na aguardente, constatamos que o teor de cobre está acima do permitido pela legislação brasileira.
SUMMARY The search describes the spectrophotometric reaction of the Cu (II)-PAN (1-(2-pyridilazo) -2-naphthol) complex and determines the concentration of copper (II) in manioc spirit (Tiquira). For this, we dimensioned the reaction for the studies of complex absorption, pH, stability, stoichiometric ratio, interferences, correlation, and recovery. After this step, we determined the concentration of copper (II) in five samples of beverages distilled artisanal from five municipalities of the State of Maranhão. The results show that the complex absorbs at 548 nm at pH 6, is stable at a time of 7 hours in minimum 1:1 stoichiometric proportions of the binder and metal, has a detection limit in 3.3 X 10-2 mg L-1, range (R2= 0.9990), standard deviation= 0.0035 and recovery at 104.54 ± 7.0, and the main interfering ions are iron (III) and cobalt (II). In the brandy, we find that the copper content is above that allowed by Brazilian legislation.
ABSTRACT
Objective To develop a new method for the determination of trace manganese in water by flame atomic absorption after cloud point extraction. Methods The effect of experimental conditions such as pH value and concentration of reagents and equilibration temperature on cloud point extraction and determination sensitivity was discussed. The chemical variables affecting the separation phase and extraction recovery were optimized. Results Under the optimum conditions, pre-concentration of only 50 ml of sample in the presence of 0.05% Triton X-114 presented a detection limit of 0.28 ?g/L(3?) for manganese. The enhancement factor was 65 for manganese. The relative standard deviation was 2.17%. The calibration graph using the pre-concentration system for manganese was linear with a correlation coefficient of 0.999 at levels near the detection limits up to at least 120 ?g/L. The recovery rates were 98.0%-101.5%. Conclusion The method is rapid, accurate, simple and is suitable for determination of trace manganese in water samples.