Field-Flow Fractionation−Inductively Coupled Plasma Mass Spectrometry:  An Alternative Approach to Investigate Metal−Humic Substances Interaction

Abstract

Interaction between metal ions and humic matter was investigated using a hyphenated technique, field-flow fractionation-inductively coupled plasma mass spectrometry (FFF-ICP-MS). Aggregation of a metal-spiked commercial Aldrich humic acid in an aqueous solution of calcium ion or in seawater was examined over time intervals of 0-4320 min. The aggregation was demonstrated by shifts in peak maximum of humic matter from smaller size (2.9 nm) to larger size (5.1 or 5.8 nm in Ca2+ solution or in seawater, respectively) and also by the broadening of size distribution profiles. With FFF, size distribution of humic aggregate was characterized. Further, dominant particle size (2.9 nm), mean particle size (3.8 nm), and diffusion coefficient (1.51 x 10(-6) cm2/s) of humic acid solution were determined. With FFF-ICP-MS, associations of Cd, Cu, and Pb with humic aggregates were examined. The mean diameters of Cd-, Cu-, and Pb-bound humic aggregates in the metal-spiked humic acid were 4.1, 4.5, and 5.8 nm, respectively. These diameters were shifted to 6.0, 6.0, and 6.9 nm, respectively, in the humic acid incubated with calcium solution, whereas they were shifted to 6.5, 5.7, and 7.4 nm, respectively, in the humic acid incubated with seawater for three days. Humic aggregate of small size showed more affinity for Cu than Cd and Pb, whereas the large aggregate showed more affinity for Pb than Cd and Cu, respectively.

Selective incorporation of dissolved organic matter (DOM) during sea ice formation

“…However, earlier studies concerning the freeze fractionation of inorganic ions have suggested that freezing rejects preferably smaller ions with larger diffusion coefficients (e.g., 2 × 10 −9 m 2 s −1 for K + ) than larger ions with smaller diffusion coefficients (e.g., 0.5 × 10 −9 m 2 s −1 for SO 4 2− ; Granskog et al, 2004;Maus et al, 2011). The diffusion coefficients of humic-like DOM, shown in our analyses, can range over four-fold like those of major inorganic ions in seawater (Hassellöv, 2005;Siripinyanond et al, 2005). If diffusion plays a major role in the process of selective rejection of DOM as suggested for inorganic ions, we should have observed a shift towards larger molecules in the samples collected from ice in our LC-SEC measurements.…”

Separation Technology as a Powerful Tool for Unfolding Molecular Complexity of Natural Organic Matter and Humic Substances

“…Another technique widely used for size separation of humic materials is fi eld -fl ow fractionation (FFF) (e.g., Baalousha et al, 2006 ;Boehme and Wells, 2006 ;Geckeis et al, 2003 ;Hassil ' ov et al, 2007;Siripinyanond et al, 2005 ;Suteerapataranon et al, 2006 ;Zanardi -Lamardo et al, 2002 ). This technique was developed and introduced in 1966 by Giddings (1966) as a method for the separation and characterization of materials ranging in size from macromolecules to particulates.…”

“…Size characteristics were reported by several authors (Baalousha et al, 2006 ;Boehme and Wells, 2006 ;Geckeis et al, 2003 ;Siripinyanond et al, 2005 ;Suteerapataranon et al, 2006 ;Zanardi -Lamardo et al, 2002 ). Over the past decade, about 20 papers were published on FlFFF fractionation of humic materials.…”

Pyridoxal Based Fluorescent Chemosensor for Detection of Copper(II) in Solution With Moderate Selectivity and Live Cell Imaging

“…Therefore, in environment as well as health monitoring, the detection of Cu 2+ is undoubtedly important. As a result, various analytical techniques for Cu 2+ detection have been developed such as by atomic absorption/emission spectroscopy [8], inductively coupled plasma mass spectrometry (ICP-MS) [9], and capillary electrophoresis [10]. However, all of these methods require expensive and sophisticated instruments combined with complicated sample pretreatment and therefore impractical for a real-time experiment.…”