Highly sensitive colour change system within slight differences in metal ion concentrations based on homo–binuclear complex formation equilibrium for visual threshold detection of trace metal ions

A new technique of expressing slight differences in metal ion concentrations by clear difference in colour was established for visual threshold detection of trace metal ions. The proposed method is based on rapid change of the mole fraction of the homo–binuclear complex (M 2L) about a ligand in a na...

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Vydáno v:Analytica chimica acta Ročník 527; číslo 2; s. 131 - 138
Hlavní autoři: Mizuguchi, Hitoshi, Atsumi, Hiroshi, Hashimoto, Keigo, Shimada, Yasuhiro, Kudo, Yuki, Endo, Masatoshi, Yokota, Fumihiko, Shida, Junichi, Yotsuyanagi, Takao
Médium: Journal Article
Jazyk:angličtina
Vydáno: Amsterdam Elsevier B.V 06.12.2004
Elsevier
Témata:
Analytical chemistry
Chemistry
Exact sciences and technology
Highly sensitive colour change
Homo–binuclear complex
Slight differences in metal ion concentrations
Spectrometric and optical methods
Visual threshold detection
XO analogues
Highly sensitive colour change
Homo–binuclear complex
Slight differences in metal ion concentrations
XO analogues
Visual threshold detection
Trace analysis
Water
Complexation
Homo-binuclear complex
Triarylmethane dye
Metal ion
Colorimetry
Xylenol orange
Flame spectrometry
Iron III
Gallium III
Simulation
Indium III
Aluminium III
River water
Methylthymol blue
Ultraviolet visible spectrometry
Atomic absorption spectrometry
ISSN:0003-2670, 1873-4324
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Shrnutí:A new technique of expressing slight differences in metal ion concentrations by clear difference in colour was established for visual threshold detection of trace metal ions. The proposed method is based on rapid change of the mole fraction of the homo–binuclear complex (M 2L) about a ligand in a narrow range of the total metal ion concentration ( M T) in a small excess, in case the second metal ion is bound to the reagent molecule which can bind two metal ions. Theoretical simulations showed that the highly sensitive colour change within slight differences in metal ion concentrations would be realized under the following conditions: (i) both of the stepwise formation constants of complex species are sufficiently large; (ii) the stepwise formation constant of the 1:1 complex (ML) is larger than that of M 2L; and (iii) the absorption spectrum of M 2L is far apart from the other species in the visible region. Furthermore, the boundary of the colour region in M T would be readily controlled by the total ligand concentration ( L T). Based on this theory, the proposed model was verified with the 3,3′-bis[bis(carboxymethyl)amino]methyl derivatives of sulphonephthalein dyes such as xylenol orange (XO), methylthymol blue (MTB), and methylxylenol blue (MXB), which can bind two metal ions at both ends of a π-electron conjugated system. The above-mentioned model was proved with the iron(III)–XO system at pH 2. In addition, MTB and MXB were suitable reagents for the visual threshold detection of trivalent metal ions such as iron(III), aluminium(III), gallium(III) and indium(III) ion in slightly acidic media. The proposed method has been applied successfully as a screening test for aluminium(III) ion in river water sampled at the downstream area of an old mine.
ISSN:0003-2670
1873-4324
DOI:10.1016/j.aca.2004.09.080