Inductively Coupled Plasma Mass Spectrometry with On-Line Leaching:  A Method To Assess the Mobility and Fractionation of Elements

Abstract

A new technique has been developed to assess the mobility and site of specific elements in complex natural materials such as rocks. Concentration profiles during leaching were obtained by pumping reagents (water, 1% HNO3, 10% HNO3, 30% HNO3), either continuously or with flow injection, through a microcolumn of sample while continuously monitoring analyte signals by inductively coupled plasma mass spectrometry (ICPMS). Compared to batch extraction procedures normally used, the approach involves minimal sample preparation and reduced contamination since the leaching is performed in a closed system. Continuous on-line monitoring also allows a greater resolution of the various phases reacting with given reagent. Compared to continuous leaching, flow injection increased the resolution of the various phases using discrete injections of reagents while reducing reagent consumption and minimizing etching of the MS interface. Furthermore, sensitivity was preserved by injecting into air instead of an aqueous carrier. Whether in the continuous or flow injection modes, the proposed approach provides real-time data on what phases are breaking down and what metals are released. It can therefore be used to design effective leaching strategies and to trace isotopic compositions. However, the resulting spectra are complex and the correct determination of some elements requires high-resolution ICPMS.

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

“…The main assets of dynamic fractionation are as follows: (1) accurate monitoring of the ongoing leaching of trace and major elements; (2) simplification of the overall procedure (from days to hours); (3) minimization of risks of sample contamination and straightforward manipulation of leaching agents; and (4) evaluation of the efficiency and selectivity of the extractants as well as the maximum pool of available fractions [9]. Among the dynamic approaches suited for the fractionation of trace elements in environmental substrates, the so-called rotating coiled column (RCC) extraction [10], microcolumn (MC) extraction [11][12][13], and stirred flow cell extraction [14,15] should be mentioned. In RCC, the particulate sample (usually 500 mg) is retained by centrifugal forces, whereas different eluents are continuously pumped through.…”

Fluidized-bed column method for automatic dynamic extraction and determination of trace element bioaccessibility in highly heterogeneous solid wastes

“…Intensive research in the field of dynamic extraction has been over the past few years devoted to the design of low to moderate pressure flow setups capitalized on the different generations of flow analysis, that is, continuous-flow analysis, flow injection analysis and sequential injection analysis, wherein the amount of solid sample usually loaded into the flow-through container ranged from 5 to 300 mg [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] to prevent excessive backpressure in the flow network. In continuous-flow rotating column-based fractionation assays, larger sample masses have been partitioned, yet the particle size distribution should be carefully controlled (samples are frequently sieved down to 250 m) because of the narrow tubing of the column, usually 1.5 mm i.d.…”

A multisyringe flow-through sequential extraction system for on-line monitoring of orthophosphate in soils and sediments

“…Several attempts have been made on the characterization and evaluation of dynamic (non steady-state) partitioning methods, mostly exploiting continuous-flow or flow injection systems, where fresh portions of leaching agents are continuously provided to small containers or columns containing the solid material [7][8][9][10][11][12][13][14][15][16][17][18]. Dynamic approaches should be regarded as appealing avenues for fractionation assays not only because they alleviate the shortcomings of batch procedures including analyte re-adsorption and limited information on the size of actual available pools, but at the same time result also in improved precision and sample throughput.…”

“…As a consequence of the development of flow-based extraction approaches, on-line leachate measurements are readily applicable, as deduced from current trends in the field [9, 12-14, 16, 18, 19]. However, most of the works capitalize on hyphenated analytical methods based on coupling of the miniaturizated column extraction manifold to continuously operating atomic spectrometers, such as flame atomic absorption spectrometry, inductively coupled plasma-mass spectrometry or inductively coupled plasma-atomic emission spectrometry, whereby the on-line generated extracts are directly injected into the detection system without any further treatment [9,13,14,16,18,19].…”