Desarrollo de un sistema para la determinación de mercurio basado en resonancia plasmónica de superficies

Abstract

The species of mercury are toxic compounds that can be present in the waters reservoirs and other environmental samples. Generally, mercury is present as Hg [II], which can be combined as much with organic and inorganic ligands and can be methylated that is the most toxic specie. The maximum concentration level of Hg accepted by environmental protection agency is 2 ng/mL. For this reason, it is important to have highly sensible instruments for its determination. Atomic absorption with cold vapor, atomic fluorescence with cold vapor, inductively coupled plasma with mass spectrometry and recently, the surface plasmonic resonance (SPR) are the commonly used technique for Hg determination in water. They exhibit great sensitivity for the mercury detection in elementary state. In the present work a continuous flow system for mercury determination in water was developed based on SPR with images detection via CCD. Dissolved ionic mercury in waters is reduced to elemental HG using sodium borohydride in inorganic acid media. Hg can be easily transported to the gold surface due its low superficial tension and it is adsorbed changing the refractive index in the surface and modifying the surface plasmonic resonance signal. The instrument presented limits of detection lower than 0.5 ng, comparable to those obtained with atomic absorption spectrometer. Also, It was studied the limit of saturation that it approximately 1014 atoms/cm2.