Evidence for arsenic-driven redox chemistry in a wetland system: a field voltammetric study

2010 ◽  
Vol 7 (4) ◽  
pp. 386 ◽  
Author(s):  
L. Haffert ◽  
S. G. Sander ◽  
K. A. Hunter ◽  
D. Craw
Keyword(s):  
Arsenic Speciation ◽  
Stripping Voltammetry ◽  
Redox Couple ◽  
Chemical System ◽  
Chemical Components ◽  
Cathodic Stripping Voltammetry ◽  
System A ◽  
Aqueous Environments ◽  
Major Chemical ◽  
Natural Laboratory

Environmental context.The speciation of the toxic element arsenic directly controls its environmental mobility and toxicity. The current study took place on site in an historic mine processing environment that is extremely arsenic-rich and comparatively sulfur-deficient. When arsenic is one of the major chemical components, redox state and pH of the chemical system are closely linked to arsenic speciation. Abstract.This study investigates the chemistry of the AsIII–AsV redox couple in association with As-rich processing residues (up to 40 wt%) from a historic gold mine in New Zealand. The site provides a unique natural laboratory of a sulfide-free chemical system driven by arsenolite dissolution. Field based cathodic stripping voltammetry, which circumvents post-sampling preservation issues, was successfully applied to analyse the AsIII to the microgram level. The AsIII–AsV redox couple, in particular the oxidation of AsIII, was found to have a noticeable influence on system pH and EH. The As redox pair itself is controlled by a range of processes, which were identified for the varying aqueous environments present on the studied site.

Arsenic Speciation: Reduction of Arsenic(V) to Arsenic(III) by Fulvic Acid

2006 ◽  
Vol 3 (2) ◽  
pp. 137 ◽  
Author(s):  
Tsanangurayi Tongesayi ◽  
Ronald B. Smart
Keyword(s):  
Fulvic Acid ◽  
Arsenic Removal ◽  
Research Effort ◽  
Arsenic Speciation ◽  
Inorganic Arsenic ◽  
Stripping Voltammetry ◽  
Reduction Reaction ◽  
Cathodic Stripping Voltammetry ◽  
Suwannee River Fulvic Acid ◽  
Removal Technologies

Environmental Context.Most technologies for arsenic removal from water are based on the oxidation of the more toxic and more mobile arsenic(iii) to the less toxic and less mobile arsenic(v). As a result, research effort has been focussed on the oxidation of arsenic(iii) to arsenic(v). It is equally important to explore environmental factors that enhance the reduction of arsenic(v) to arsenic(iii). An understanding of the redox cycling of arsenic could result in the development of cheaper and more efficient arsenic removal technologies, especially for impoverished communities severely threatened by arsenic contamination. Abstract.The objective of this study was to investigate the reduction of inorganic arsenic(v) with Suwannee River fulvic acid (FA) in aqueous solutions where pH, [FA], [As(v)], [As(iii)], and [Fe(iii)] were independently varied. Samples of inorganic As(v) were incubated with FA in both light and dark at constant temperature. Sterilisation techniques were employed to ensure abiotic conditions. Aliquots from the incubated samples were taken at various time intervals and analysed for As(iii) using square-wave cathodic-stripping voltammetry at a hanging mercury drop electrode. The study demonstrated the following important aspects of As speciation: (1) FA can significantly reduce As(v) to As(iii); (2) reduction of As(v) to As(iii) is a function of time; (3) both dark and light conditions promote reduction of As(v) to As(iii); (4) Fe(iii) speeds up the reduction reaction; and (5) oxidation of As(iii) to As(v) is promoted at pH 2 more than at pH 6.

Arsenic speciation in natural waters by cathodic stripping voltammetry

2010 ◽  
Vol 662 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Kristoff Gibbon-Walsh ◽  
Pascal Salaün ◽  
Constant M.G. van den Berg
Keyword(s):  
Natural Waters ◽  
Arsenic Speciation ◽  
Stripping Voltammetry ◽  
Cathodic Stripping Voltammetry ◽  
Cathodic Stripping

Isolation and HPLC Determination of the Chemical Components of Gentianella acuta (Michx.) Hulten

2018 ◽  
Vol 15 (1) ◽  
pp. 21-33
Author(s):  
Ying Wei ◽  
Yongqiao Liu ◽  
Yifan Hele ◽  
Weiwei Sun ◽  
Yang Wang ◽  
...  
Keyword(s):  
Medicinal Plant ◽  
High Speed ◽  
Chemical Constituents ◽  
Folk Medicine ◽  
Gradient Elution ◽  
Chemical Components ◽  
Isolation And Characterization ◽  
Major Chemical ◽  
Main Components ◽  
First Time

Background: Gentianella acuta (Michx.) Hulten is an important type of medicinal plant found in several Chinese provinces. It has been widely used in folk medicine to treat various illnesses. However, there is not enough detailed information about the chemical constituents of this plant or methods for their content determination. Objective: The focus of this work is the isolation and characterization of the major chemical constituents of Gentianella acuta, and developing an analytical method for their determination. Methods: The components of Gentianella acuta were isolated using (1) ethanol extraction and adsorption on macroporous resin. (2) and ethyl acetate extraction and high speed countercurrent chromatography. A HPLC-DAD method was developed using a C18 column and water-acetonitrile as the mobile phase. Based on compound polarities, both isocratic and gradient elution methods were developed. Results: A total of 29 compounds were isolated from this plant, of which 17 compounds were isolated from this genus for the first time. The main components in this plant were found to be xanthones. The HPLC-DAD method was developed and validated for their determination, and found to show good sensitivity and reliability. Conclusion: The results of this work add to the limited body of work available on this important medicinal plant. The findings will be useful for further investigation and development of Gentianella acuta for its valuable medicinal properties.

Determination of trace amounts of lead by adsorptive cathodic stripping voltammetry with L-3-(3,4-Dihydroxyphenyl)alanine

2009 ◽  
Vol 74 (4) ◽  
pp. 599-610 ◽  
Author(s):  
Mohammad Bagher Gholivand ◽  
Alireza Pourhossein ◽  
Mohsen Shahlaei
Keyword(s):  
Lead Concentration ◽  
Stripping Voltammetry ◽  
Optimum Conditions ◽  
Lead In Blood ◽  
Accumulation Time ◽  
Cathodic Stripping Voltammetry ◽  
Voltammetric Measurement ◽  
Adsorbed Complex ◽  
Reduction Current

A sensitive and selective procedure is presented for the voltammetric determination of lead. The procedure involves an adsorptive accumulation of lead L-3-(3,4-dihydroxyphenyl)alanine (LDOPA) on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of an adsorbed complex at –0.15 V (vs Ag|AgCl). Optimum conditions for lead analysis include pH 8.5, 80 μM LDOPA and accumulation potential –0.15 V (vs Ag|AgCl). The peak currents are proportional to the lead concentration 1–300 nmol l–1 with a detection limit of 0.6 nmol l–1 and accumulation time 60 s. The method was used for the determination of lead in blood, dry tea and also in waters.

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