A novel approach to cold vapor generation for the determination of mercury in biological samples

Abstract

Propõe-se uma nova maneira de gerar vapor de mercúrio em altos valores de pH pela adição de NaOH ou de outra base a uma solução contendo íons de mercúrio, sem utilizar redutor, como NaBH 4 ou SnCl 2 . Após dissolução total da amostra em sistema de microondas fechado, empregando HNO 3 e H 2 O 2 , o pH da solução da amostra é elevado para 13 com NaOH. Após 90 min de repouso, o vapor frio é transportado até o plasma por um fluxo de gás argônio. O Hg é determinado em 253,652 nm em um espectrômetro de emissão óptica com plasma indutivamente acoplado com configuração axial. O procedimento foi aplicado a cinco amostras biológicas certificadas obtendose um limite de detecção (3s, n = 10) de 0,04 g g -1 para uma massa da amostra de 0,5 g em um volume final de 50 mL. A calibração foi realizada com soluções padrão aquosas em NaOH 0,1 mol L -1 . O procedimento foi eficiente, com recuperações dos valores certificados entre 85 e 113%, demonstrando concordância entre o valor encontrado e o certificado para um nível de 95% de confiança (teste-t). A precisão apresentou resultados aceitáveis com desvios padrão relativos de 7 a 9%. Mercúrio a partir de espécies orgânicas em solução, não foi detectado; somente Hg 2+ em solução produz sinal. O procedimento é novo, simples, pode permitir estudos de especiação e serve para demonstrar liberação de vapor de mercúrio de soluções aquosas em altos valores de pH.A novel approach to the generation of mercury vapor at high pH by the simple addition of NaOH or other base to a solution containing mercury ions is described. Subsequent addition of another reducing agent, such as NaBH 4 or SnCl 2 , is unnecessary. Following total dissolution of sample using HNO 3 and H 2 O 2 in a closed microwave vessel, the pH of the sample solution is increased to 13 by the addition of NaOH. After standing for 90 min in a closed vessel, the Hg 0 is directed to the plasma by a flow of argon. Emission from mercury is measured at 253.652 nm by an axial view inductively coupled plasma optical emission spectrometer (ICP OES). The procedure was applied to five certified biological samples, yielding a detection limit (3s, n = 10) of 0.04 g g -1based on a nominal sample mass of 0.5 g in a final volume of 50 mL. Calibration was achieved using simple aqueous standard solutions containing 0.1 mol L -1 NaOH. The procedure was efficient, with determined values lying in the range of 85-113 % of the certified values, showing good agreement at the 95% confidence level (t-test). The precision was fit for purpose, with relative standard deviations ranging from 7 to 9%. Organomercury species in solution were not detected; only Hg 2+ in solution produces a signal. This new procedure provides for a simple approach to quantitation (and potentially speciation).

Analytical chemistry in Brazil: healthy and growing

“…25 According to the proposed procedure mercury vapor can be generated at pH 13 in a medium containing sodium hydroxide or other base without any further addition of another reducing agent, such as sodium borohydride and stannous chloride. The simple and innovative procedure seems also applicable for speciation because only Hg 2+ in solution generated a signal and organomercury species were not detected.…”

Removal of traces of mercury from a carrier gas for analytical purpose

“…The impact of mercury in the environment concerning its toxicity, mobility, bioaccumulation, and biomagnification is responsible for a continuous interest to investigate the fate of this metal (Santos et al 2008;Stergarsek et al 2013;Emili et al 2012). The development of analytical methods and lower limits of quantification have allowed increasing the understanding of biogeochemical processes involving mercury and other metals.…”

“…The development of analytical methods and lower limits of quantification have allowed increasing the understanding of biogeochemical processes involving mercury and other metals. Among the most popular analytical methods to analyze mercury is the cold vapor atomic fluorescence spectrometry (CVAFS) (Santos et al 2008;Leermakers et al 2005), whose main advantage is separation of the analyte from the matrix by purging the volatile mercury with an inert gas to the detector, with a net result of high sensitivity and selectivity and lower limit of quantification. However, the success of the determination by CVAFS is closely related to the quality of the gas used to purge the analyte, since it is often necessary to make determinations of a few picograms of mercury (Liang et al 1996).…”

Determination of some inorganic species of Fe, Mn and Cr by chemical vapor generation hyphenated with inductively coupled plasma atomic emission spectrometry

“…Similarly, Peña-Vázquez and co-workers, 3 during their interference study on Ag, Au, Cd, Cu and Ni vapor generation at the one optimized condition (HNO 3 + THB + 8-hydroxyquinoline), obtained volatile species of Fe and Cr. Dos Santos et al 14 investigated a novel approach to the generation of Hg vapor and additionally tested applicability of this procedure to vapor generation of other metals (including Cr, Fe, Mn). Feng et al 6 were the only ones who mentioned the existence of volatile Mn species generated from Mn 2+ in the reaction of HNO 3 with THB.…”