Anodic stripping voltammetry of tungsten at graphite electrodes

Abstract

Trace levels of tungsten can be determined at a graphite electrode using anodic stripping voltammetry. Tungsten is concentrated at the electrode surface after reduction to Wv as a insoluble ternary complex in the presence of rhodanide ions and antipyrine (ANT) or 4-dimethyl-aminoantipyrine (pyramidon, PYR). The optimal conditions of this determination are: electrolyte 1 M H2S04 containing 0.078 M NH4SCN + 0.04M ANT or 0.02M PYR; deposition potential -0.5OV; sweep from -0.4 to -0.05V using differential pulse stripping technique. Detection limit is 1 x 10-9M (0.2 pg/L) for a 180 s accumulation time (with a relative standard deviation of 15%). Results obtained for waste waters, steel and olive leaves are reported.

A Lead Film Electrode for Adsorptive Stripping Voltammetric Analysis of Ultratrace Tungsten(VI) in Acidic Medium

“…The graphite electrodes were also applied to the determination of tungsten by anodic stripping voltammetry. The detection limits obtained at these electrodesere equal to 10 −7 mol L −1 11, 10 −8 mol L −1 12, 10 −9 mol L −1 13.…”

Modified carbon-containing electrodes in stripping voltammetry of metals. Part II. Composite and microelectrodes

“…IGE are modified by metals (Hg, Au, Cu, Tl, Jr) [97,[98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114], polymer films fixing the modifier and capable of the ion exchange [115], and Mo (IV) oxocomplexes [116,117]. The IGE surface has good adsorbability and, hence, is readily modified by reagents specific for determined ions [118][119][120][121][122][123][124][125][126][127][128][129]. The IGE surface is modified most frequently, but examples of the IGE bulk modification can be found too [118,119].…”

Ultrasensitive determination of tungsten(VI) on pikomolar level in voltammetric catalytic adsorptive catechol-chlorate(V) system

“…A drawback of these polarographic methods is their low selectivity, a fact which makes it necessary to separate tungsten from the sample matrix by extraction techniques [21,23,26,27,30,31]. In the group of voltammetry the stripping methods such as anodic stripping voltammetry on graphite electrodes with the detection limit of 10 À8 M [32] 10 À7 M [33] and 10 À9 M [34] could be obtain but these methods required a long preconcentration time and characterizes of poor precision. Very sensitive adsorptive stripping voltammetry witch catalytic effect with different complexing agents, such as 8-hydroxyquinoline and 3-methoxy-4-hydroxymandelic acid [35] with the detection limit of 10 À11 M) or chloranilic acid [36] with the detection limit of 10 À10 M were successfully used.…”