The effect of pesticides on Byssus formation in the common mussel, Mytilus edulis

Seed mussels (Mytilus edulis) were exposed to a range of pesticides and PCBs, several of which caused a reduction in byssal attachment at higher concentrations. In queen scallops (Chlamys opercularis) byssus formation was similarly affected although this species was more sensitive than M. edulis. The sensitivity of mussels was greater at higher temperatures and decreased with increase in size. Of the compounds tested Endosulfan (organochlorine) was the most toxic, causing a 50% reduction in byssal attachment after 24 h at 0•45 mg/l. Trichlorphon (organophosphate) was the least toxic and did not affect byssal attachment at concentrations up to 30 mg/l. The probable cause of decreased byssal attachment is a reduction in pedal activity, although it is possible that direct interference with the synthesis or combination of byssus components may be involved. It is suggested that byssogenesis tests offer a rapid and convenient technique for the routine screening of potential marine pollutants.

NMR analysis of Nile Blue (C I Basic Blue 12) and Thionine (C I 52000) in solution

The dyes Nile Blue (C I Basic Blue 12) and Thionine (C I 52000) were examined in both ionic and neutral forms in different solvents using NMR and UV-visible spectroscopy to firmly establish the structures of the molecules and to assess the nature and extent of their aggregation H-1 and C-13 NMR assignments and chemical shift data were used together with nuclear Overhauser effect information to propose a self-assembly structure These data were supplemented with variable temperature dilution and diffusion-based experimental results using H-1 NMR spectroscopy thereby enabling extended aggregate structures to be assessed in terms of the relative strength of self-association and the extent to which extended aggregates could form (C) 2010 Elsevier Ltd All rights reserved

Effect of alkali on methylene blue (CI Basic Blue 9) and other thiazine dyes

A detailed study of the action of alkali on methylene blue (Cl. Basic Blue 9) and other thiazine dyes was carried out through a combination of UV/visible spectroscopy, thin layer chromatography, mass and NMR spectrometry and computational methods. In 0.1 M aq alkali solution, methylene blue forms a highly coloured, lipophilic species that is mainly Bernthsen's methylene violet i.e. a hydrolysis decomposition product, this being contrary to the report of a red N-hydroxy methylene blue adduct. The nature of the heterocyclic nitrogen atom in C.I. Basic Blue 9 is discussed and it is concluded there is no basis for the proposal of nucleophile addition at this site of the dye. In contrast, other thiazine dyes are deprotonated by alkali to form their neutral, highly coloured, lipophilic conjugate base forms. (C) 2010 Elsevier Ltd. All rights reserved.

A novel reversible relative-humidity indicator ink based on methylene blue and urea

A new relative-humidity sensitive ink based on methylene blue and urea is described which can utilise the deliquescent nature of urea.

Blue bottle light: lecture demonstrations of homogeneous and heterogeneous photo-induced electron transfer reactions

The classic, non-photochemical blue bottle experiment involves the reaction of methylene blue (MB) with deprotonated glucose, to form a bleached form of the dye, leuco-methylene blue (LMB), and subsequent colour recovery by shaking with air. This reaction is a popular demonstrator of key principles in kinetics and reaction mechanisms. Here it is modified so as to highlight features of homogenous and heterogeneous photoinduced electron transfer (PET) (Pure Appl. Chem., 2007, 79, 293-465) reactions, i.e. blue bottle light experiments. The homogeneous blue bottle light experiment uses methylene blue, MB, as the photo-sensitizer and triethanolamine as the sacrificial electron donor. Visible light irradiation of this system leads to its rapid bleaching, followed by the ready restoration of its original colour upon shaking away from the light source. The heterogeneous blue bottle light experiment uses titania as the photo-sensitizer, MB as a redox indicator and glucose as the sacrificial electron donor. UVA light irradiation of this system leads to the rapid bleaching of the MB and the gradual restoration of its original colour with shaking and standing. The latter 'dark' step can be made facile and more demonstrator-friendly by using platinised titania particles. These two photochemical versions of the blue bottle experiment are used to explore the factors which underpin homogeneous and heterogeneous PET reactions and provide useful demonstrations of homogeneous and heterogeneous photochemistry.

Novel photochemistry of leuco-Methylene Blue

leuco-Methylene Blue has a previously unrecognized, very reactive, UV-driven triplet state photochemistry and, in particular, undergoes photo-oxidative quenching with dissolved oxygen.

Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media

The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq)

Photobleaching of methylene blue sensitised by TiO2: an ambiguous system?

The photobleaching of methylene blue MB, sensitised by TiO2, in an aqueous solution is studied in the absence and presence of oxygen, in the absence of oxygen and in the presence of a sacrificial electron acceptor (SED), MB is photoreduced to its colourless leuco form, LMB, by the TiO2 photocatalyst. This same photoreduction process is observed even if an SED is not present, indicating that MB itself can act as an SED. The oxidation of LMB by oxygen to regenerate MB is significantly slower if the aqueous solution is acidified (0.01 mol dm(-3) HClO4) and, at low partial pressures, the rate of reaction depends directly upon the concentration of dissolved oxygen. The TiO2-sensitised photobleaching of MB is irreversible in an oxygen-saturated aqueous solution, as expected, since the bleaching was due to an oxidative process. However, in an acidified solution (0.01 mol dm(-3) HClO4), the photobleaching process, in an oxygen-saturated solution, generates LMB initially. The latter situation arises because, under acidic conditions, LMB reacts only very slowly with oxygen to form MB. The significance of these findings with respect to the popular use of photobleaching of MB as a demonstration of semiconductor photomineralisation is discussed. (C) 1999 Elsevier Science S.A. All rights reserved.