Graphene and carbon nanotubes as solid phase extraction sorbents for the speciation of chromium: A review.

In this work magnetic cellulose xanthate was prepared with two different routes, i.e., fabrication of Fe3O4@cellulose followed by preparation of xanthate, and a one step approach by adding iron source to cellulose xanthate solution. The cellulose acts as both as reducing agent to convert Fe3+ ions to Fe2+ and template for growth of Fe3O4. The prepared composites were characterized by SEM, XRD, VSM, EDS, TGA, and FT-IR techniques. Magnetic sorbents were applied for adsorption of silver from acidic medium, and results revealed that the one step prepared composite has better performance in comparison with Fe3O4@cellulose xanthate, as the maximum adsorption capacity within 5 min extraction time was 166 and 15.6 mg g–1, respectively. The relative selectivity factor (αr) of Ag+ with respect to other cations, such as Zn2+, Cr3+, Co2+, Ni2+, Pb2+, and Pd2+, is 252, 74.8, 2543, 924, 3837, and 26.6, respectively. Moreover, the reusability of the sorbent was investigated by elution the adsorbed ions with 3.0 mL of 0...

Synthesis, Characterization, and Silver Adsorption Property of Magnetic Cellulose Xanthate from Acidic Solution: Prepared by One Step and Biogenic Approach

Study on column SPE with synthesized graphene oxide and FAAS for determination of trace amount of Co(II) and Ni(II) ions in real samples.

This is the eighth Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2014. This ASU review deals with all aspects of the analytical atomic spectrometry speciation methods developed for: the determination of oxidation states; organometallic compounds; coordination compounds; metal and heteroatom-containing biomolecules, including metalloproteins, proteins, peptides and amino acids; and the use of metal-tagging to facilitate detection via atomic spectrometry. The review does not cover fractionation, which is sometimes termed operationally defined speciation. As with all ASU reviews the focus of the research reviewed includes those methods that incorporate atomic spectrometry as the measurement technique. However, because speciation analysis is inherently focused on the relationship between the metal(loid) atom and the organic moiety it is bound to, or incorporated within, atomic spectrometry alone cannot be the sole analytical approach of interest. For this reason molecular detection techniques are also included where they have provided a complementary approach to speciation analysis. As in previous years, As and Se speciation continues to dominate the current literature and there has also been an increase in the number of publications concerning solid state speciation. This is presumably due to the increase in the number of synchrotron facilities available and a greater awareness of their potential for speciation studies.

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Atomic Spectrometry Update: review of advances in elemental speciation

The toxicity of elements largely depends on their chemical forms. Therefore, the elemental speciation analysis is of great importance and a hot topic in environmental science and engineering, food science, and biology. The use of nanomaterials in spectrometric detection provides a convenient, versatile, and sensitive technique for elemental speciation analysis. In this concise review, we aim to provide a brief overview of the versatility of nanomaterials in spectrometric elemental speciation analysis with focus on four elements: mercury, arsenic, chromium, and selenium. Various types of nanomaterials, together with their roles in the speciation analysis developed with prevailing spectrometric techniques, are discussed. We also offer an insight into the research trend of the application of nanomaterials for chemical speciation analysis.

Nanomaterials in speciation analysis of mercury, arsenic, selenium, and chromium by analytical atomic/molecular spectrometry

Using multi-walled carbon nanotubes (MWCNTs) as an adsorbent has been established for the on-line separation and preconcentration Cr(III) and chromium speciation. The surface functional groups and negative charges of MWCNTs are beneficial to the adsorption of Cr(III). At pH 3.0 - 6.0, a discrimination of Cr(III) and Cr(VI) is achieved on the MWCNTs surface. Cr(III) ions are adsorbed onto the oxidized MWCNTs surface, while Cr(VI) has no affinity for the MWCNTs. The adsorbed Cr(III) is quantitatively eluted by 10% (v/v) nitric acid with detection by flame atomic absorption spectrometry. By loading a 6.0-ml sample solution, an enrichment factor of 22, a detection limit (3σ) of 1.15 μg l(-1) and a precision of 1.7% RSD at the 30 μg l(-1) level (n = 7) are achieved for Cr(III) within a linear range of 5 - 200 μg l(-1) (r = 0.9994). After Cr(VI) has been reduced to Cr(III) with hydroxylamine hydrochloride, the total amount of chromium is obtained, and the content of Cr(VI) is given by subtraction. The procedure is validated by analyzing chromium in a certified reference material, and is further applied for the speciation of chromium in electroplating wastewater samples with satisfactory results.

http://www.jstage.jst.go.jp/article/analsci/28/12/28_1219/_pdf

Study on multi-walled carbon nanotubes on-line separation/preconcentration of chromium(III) and chromium speciation.

A novel flow injection system incorporating a micro-column packed with carbon nanotubes (CNTs) as an adsorbent has been applied to the on-line preconcentration of trace silver with detection by flame atomic absorption spectrometry. Silver is first chelated by dithizone (H2Dz), then retained on the CNTs surface and afterward quantitatively eluted by methanol. Influencing parameters, including the concentration of reaction reagent, enrichment variables, and elution variables were investigated. The adsorption mechanisms of Ag-H2Dz chelate retained onto the CNTs surface have also been studied. By loading 6.9 mL sample solution, a linear calibration graph is obtained within the range of 3–120 µg L−1 with R of 0.9996, and a detection limit (3σ) of 0.8 µg L−1 is achieved, along with a precision of 1.6% R.S.D. at the 30 µg L−1 level (n = 7). The dynamic sorption capacity of CNTs for silver is 122 mg g−1. The procedure is demonstrated by measurement of spike recovery in a series of water samples, giving rise to sp...

Determination of Silver with On-Line Preconcentration Using Dithiozone Chelate and Carbon Nanotubes for Preconcentration with Detection by Flame Atomic Absorption Spectrometry

Xiuhui Zhu

Papers

Study on multi-walled carbon nanotubes on-line separation/preconcentration of chromium(III) and chromium speciation.

Determination of Silver with On-Line Preconcentration Using Dithiozone Chelate and Carbon Nanotubes for Preconcentration with Detection by Flame Atomic Absorption Spectrometry