Organocation speciation. II. Methylene blue photosensitization as a model for speciation and toxicity of herbicides

Abstract

Can. J. Chem. 58.555 (1980). A chemical model that employs the photosensitization properties of methylene blue to mimic herbicide toxicity is used to test size separation as a method of chemical speciation. A spectrophotometric study of the dye interactions with the humic colloid indicated that the dye -humic acid complex has a weaker absorption spectrum than the free dye. The absorption spectra suggested that the binding sites on the humic acid are sufficiently isolated to prevent dye-dye interactions on the colloid su~-fxe. The dye photosensitization of tryptophan degradation indicated that only the free methylene blue was active in the presence of humic acid. clay. and polystyrene sulphonic acid. The model suggests that if the pollutant must be in true solution to be biologically active then a size separation by dialysis would be a satisfactory speciation procedure.ROBERT D. GUY et DEORAJ R, NARINE. Can. J. Chem. 58,555 (1980). On a utilisk un modeie chimique qui fait appel aux proprietes photosensibilisatrices du bleu de methylkne dans ia toxicit6 de I'herbicide mimique, pour verifier la separation dimensionnelle comme une methode de determination de i'esptces chimique. Une etude spectrophotornetrique des interactions entre le colorant et le colloide humique icdique que le complexe colorant -acide humique a un spectre d'absorption plus faible que le colorant B l'ltat libre. Les spectres d'absorption suggkrent que les sites de liaison dans l'acide humique sont suffisamment isoles pour prevenir les interactions colorant-colorant a L a surface du colloide. La degradation du tryptophane phoiosensibilisee par le colorant indique que seu! le bleu de methyl&ne est actif en presence d'acide humique, d'argile et de l'acide polystyrene sulfonique. Le modele suggere que si le polluant doib se trouver rkellement en solution pour itre biologiquement actif la separation par dialyse peut &re satisfaisante commr mcthode de determination de I'espece.[Traduit par le journal]

Methylene blue adsorption by the waste of Abu-Tartour phosphate rock

“…Moreover, an increase in the adsorption capacity occurs three pH units above the PZC. These facts point to the existence of hydrophobic interactions which have been suggested by different authors to have a role in the interaction of methylene blue with different kinds of surfaces [31][32][33][34][35].…”

Determination of equilibrium and rate constants for binding of a polychlorinated biphenyl congener by dissolved humic substances

“…The system represented by reactions 1 and 2 can be described mathematically. At equilibrium, reaction 2 is described by eq 1, which may also be expressed as Kb -k\2l/kl2 (4) The total concentration of the test compound in (CT) at any time is solution cT = cb + Caq (5) The rate expressions for Cb, Caq, CT, and Cg are dCb/dt = k21 Caq -kl2Ch (6) dCaq/df = ki2C^-(k21 + k23)Ca(l (7) 638 Environ. Sel.…”

“…Several laboratory studies have provided evidence for binding of hydrophobic organic compounds by dissolved or colloidal macromolecules in water. Experimental approaches have included solubility enhancement (1)(2)(3)(4), gel permeation chromotography (5), dialysis (6,7), ultrafiltration (8), sorption inhibition (9), and decrease in volatilization (10). Potential environmental consequences of binding of hydrophobic compounds include effects on aqueous solubility (1)(2)(3)(4), adsorption (9), volatility (10), photolysis (11), hydrolysis (12), and bioaccumulation (13).…”

Tryptophan Photo-Oxidation by Clay-Adsorbed Sensitizers

“…The photo-oxidation of TRP by MB adsorbed on bentonite has been investigated by Guy & Narine (1980) who concluded that only free or dialysable MB can be held responsible for TRP degradation. The clay quenched the production of 10 2.…”