Evaluation of the catalyzed photo-cold vapour generation for determination of mercury by AAS

Abstract

Nanopartículas de Ag suportadas em TiO 2 (Ag-TiO 2 ) foram usadas como catalisador na geração de vapor frio induzida por radiação UV com ácido fórmico, acoplado à absorção atômica para determinação do mercúrio total em amostras analíticas. A atividade redutora de Ag-TiO 2 foi comparada com dois catalisadores semicondutores: TiO 2 não modificado e ZnO. O efeito do tipo de catalisador, sua concentração na amostra analisada, pH da amostra, concentração do ácido fórmico e tempo de irradiação ultravioleta foi investigado. Na presença de ácido fórmico, Ag-TiO 2 foi o mais eficiente na redução de mercúrio. Nas condições experimentais otimizadas, a recuperação de mercúrio em quatro materiais de referência contendo 0,20-1,99 µg g -1 Hg foi de 95-99% dos valores certificados. O desvio padrão relativo para amostras foi igual ou melhor do que 11%. A análise de materiais de referência certificados (correspondentes a amostras ambientais e biológicas) mostrou a potencialidade do método Ag-TiO 2 -UV-CVGAAS na determinação de mercúrio em amostras analíticas no nível de ultra-traço.Nano-Ag particles loaded on TiO 2 (Ag-TiO 2 ) were used as catalyst for the UV-induced cold vapour generation with formic acid coupled to atomic absorption for determination of total mercury in analytical samples. The reducing activity of Ag-TiO 2 was compared with two semiconductor catalysts: unmodified TiO 2 and ZnO. The effect of catalyst type, its concentration in the analyzed sample, sample pH, formic acid concentration and ultraviolet irradiation time have been investigated. In the presence of formic acid, most effective in the reduction of mercury was Ag-TiO 2 . Under the optimized experimental conditions recovery of mercury in four reference materials containing 0.20-1.99 µg g -1 Hg was 95-99% of certificate values. The relative standard deviation for samples was equal to or better than 11%. Certified reference materials (corresponding to biological and environmental samples) analysis using the Ag-TiO 2 -UV-CVGAAS method revealed that it is promising for mercury determination in analytical samples at ultratrace level.

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