Development of a simple extraction cell with bi-directional continuous flow coupled on-line to ICP-MS for assessment of elemental associations in solid samples

Abstract

A continuous-flow system comprising a novel, custom-built extraction module and hyphenated with inductively coupled plasma-mass spectrometric (ICP-MS) detection is proposed for assessing metal mobilities and geochemical associations in soil compartments as based on using the three step BCR (now the Measurements and Testing Programme of the European Commission) sequential extraction scheme. Employing a peristaltic pump as liquid driver, alternate directional flows of the extractants are used to overcome compression of the solid particles within the extraction unit to ensure a steady partitioning flow rate and thus to maintain constant operationally defined extraction conditions. The proposed flow set-up is proven to allow for trouble-free handling of soil samples up to 1 g and flow rates < or =10 mL min(-1). The miniaturized extraction system was coupled to ICP-MS through a flow injection interface in order to discretely introduce appropriate extract volumes to the detector at a given time and with a given dilution factor. The proposed hyphenated method demonstrates excellent performance for on-line monitoring of major and trace elements (Ca, Mn, Fe, Ni, Pb, Zn and Cd) released when applying the various extracting reagents as addressed in the BCR scheme, that is, 0.11 M CH(3)COOH, 0.1 NH(2)OH.HCl and 30% H(2)O(2), even when a well recognized matrix-sensitive detector, such as ICP-MS, is used. As a result of the enhanced temporal resolution of the ongoing extraction, insights into the breaking down of phases and into the kinetics of the metal release are obtained. With the simultaneous multielement detection capability of ICP-MS, the dynamic fractionation system presents itself as an efficient front-end for evaluation of actual elemental association by interelement comparison of metals leached concurrently during the extraction time. Thus, the intimate elemental association between Cd and Zn in contaminated soils could be assessed.

A Review of the Different Methods Applied in Environmental Geochemistry For Single and Sequential Extraction of Trace Elements in Soils and Related Materials

“…Some of the useful references in this area are Buanuam et al 2006;Nakazato et al 2006;Tongtavee et al 2005;Sun et al 2004Sun et al , 2005Vaeisaenen and Kiljunen 2005;Chomchoei et al 2004Chomchoei et al , 2005Jimoh et al 2005;Katasonova et al 2005;KrasnodebskaOstrega et al 2003;Davidson and Delevoye 2001.…”

Dynamic flow-through sequential extraction for assessment of fractional transformation and inter-element associations of arsenic in stabilized soil and sludge

“…A solid sample known to have an accurate weight of 0.25 g was placed in a flow-through extraction column described in detail elsewhere [29]. The assembled extraction unit was connected to the extractant reservoir and the fraction collector vial using Tygon ® tubing.…”

“…formation of channels, strong differences in particle size, long extraction times, different dynamic (flow-based) extraction systems have been developed. These extraction approaches [23][24][25][26][27][28][29][30] are mostly based on the continuous introduction of fresh portions of extracting reagents through small containers containing the solid sample under investigation. This approach offers enhanced information on the fractionation procedure with regard to the kinetics of the ongoing leaching process, elemental associations and size of element pools available under environmentally changing scenarios.…”

Fractionation of Sb and As in soil and sludge samples using different continuous-flow extraction techniques

“…A particulate solid sample (about 300 mg) was placed into the microcolumn, which is schematically illustrated and described in our previous works [17,24]. The extraction MC unit is made of polyoxymethylene that can tolerate the extractants used.…”