Sequential determination, of arsenic

Andreae [683] described a sequential volatilisation method for the sequential determination of arsenate, arsenite, mono-, di- and trimethylarsine, monomethylarsonic and dimethylarsinic acid, and... 

Andreae described a method for the sequential determination of arsenate, arsenite, mono-, di- and trimethyl arsine, MMAA, DMAA and trimethylarsine oxide in natural waters with detection limits of several ng/1. The arsines are volatilized from the sample by gas stripping the other species are then selectively reduced to the corresponding arsines and volatilized. The arsines are collected in a cold trap cooled with liquid nitrogen. They are then separated by slow warming of the trap or by gas chromatography, and measured with atomic absorption, electron capture and/or flame ionization detectors. He found that these four arsenic species all occurred in natural water samples. 

Fiorina JA, Jones JW, Capar SG. 1976. Sequential determination of arsenic, selenium, antimony and tellurium in foods via rapid hydride evolution and atomic absorption spectrometry. Anal Chem 48 120-125. 

Menegario, A. A., and Gine, M. E (2000). Rapid sequential determination of arsenic and selenium in waters and plant digests by hydride generation inductively coupled plasma-mass spectrometry. Spectrochim. Acta, Part B 55(4), 355—362. 

Huggins, F.E., Huffman, G.P., Kolker, A. et al. (2002) Combined application of XAFS spectroscopy and sequential leaching for determination of arsenic speciation in coal. Energy and Fuels, 16(5), 1167-172. 

Ultrasonic nebulizers have also been employed in continuous flow systems as interfaces between sample preparation steps in the analytical process and detection by virtue of their suitability for operating in a continuous mode. Thus, preconcentration devices have commonly been coupled to atomic spectrometers in order to increase the sensitivity of some analytical methods. An enhancement factor of 100 (10 due to USNn and 10 due to preconcentration) was obtained in the determination of platinum in water using a column packed with polyurethane foam loaded with thiocyanate to form a platinum-thiocyanate complex [51]. An enhancement factor of 216 (12 with USNn and 18 with preconcentration) was obtained in the determination of low cadmium concentrations in wine by sorption of metallic complexes with pyridylazo reagents on the inner walls of a PTFE knotted reactor [52]. One special example is the sequential determination of As(lll) and As(V) in water by coupling a preconcentration system to an ICP-AES instrument equipped with a USN. For this purpose, two columns packed with two different resins selective for each arsenic species were connected via a 16-port valve in order to concentrate them for their subsequent sequential elution to the spectrometer [53]. 

The aim of this work was to investigate the arsenic mobilization from the tailings material (200 - 500 pg/g As) into the seepage water (up to 3.5 mg/L As) and the process of seepage water effluent forming an immobilized precipitate (up to 8 % As) in the creek. Different analytical methods for the determination of total concentrations and different sequential extraction methods as well as hyphenated techniques for speciation analysis were applied to follow the way of the arsenic in this environment. 

The functions of the reagents used in the reduction of arsenic compounds, such as Zn, HCl, NiCla, SnCh, and KI are discussed below in connection with the Gutzeit method. Sodium borohydride also has been proposed as the reducing agent [39-42]. Sequential spectrophotometric determination of As(III) and As(V) is possible by using borohydride [40]. Hydrogen sulphide, which interferes in the reaction, is separated from arsine on cotton wool impregnated with lead acetate. 

Figure 3.40 Schematic of an LC-HGAAS system (Reprinted from Analytica Chimica Acta, Niedzielski, P. The new concept of hyphenated analytical system Simultaneous determination of inorganic arsenic(lll), arsenic(V), selenium(IV) and selenium(VI) by high performance liquid chromatography-hydride generation-(fast sequential) atomic absorption spectrometry during single analysis, 55 (1-2), 199-206 T Copyright 2005 with permission from Elsevier).

Anthemidis, A. N., E. I. Daftsis, and N. O. Kalogiouri. 2014. A sequential lab-on-valve (SIA-LOV) platform for hydride generation atomic absorption spectrometry (HG-AAS) On-line determination of inorganic arsenic. Anal. Methods 6 2745-2750. 

Ivaska, A. Kubiakb, W.W. (1997). Application of sequential injection analysis to anodic stripping voltammetry. Talanta. Vol. 44, pp. 713-723 Kopanica, M. Novotny, L. (1998). Determination of traces of arsenic (III) by anodic stripping voltammetry in solutions, naturals waters and biological material. Analytica Chimica Acta. V ol. 38, pp. 211-218... 

The coating chamber was equipped with a set of independently controlled stainless steel boats and a shutter system to enable the fabrication of multilayer structures. Pure selenium pellets were loaded into one boat and As Sei alloys into another. The two sources were evaporated sequentially (without breaking the vacuum) at boat temperatures of about 450 K. Typical coating rates were l j,m/min. After evaporation, they were allowed to anneal over several weeks in the dark at room temperature. During this period, due to structural bulk relaxation, most physical properties of the photoconductor film become stabilized. The compositions of the deposited films were determined by electron probe microanalysis, and the compositions quoted (0 < X < 0.20) are accurate to within 0.5 at.%. By shuttering the beginning and the end of the evaporation, a uniform arsenic composition across the film thickness can be obtained. In all experiments, a transparent gold electrode ( 300 jm thick) was used as the top contact. 

Locatelli, C. (2004) Heavy metals in matrices of food interest sequential voltammetric determination at trace and ultratrace level of copper, lead, cadmium, zinc, arsenic, selenium, manganese an iron in meals. Electroanalysis, 16,1478-1486. 

---