Sulphonated Azo Dye Research Articles

Batchwise separation of gallium by an anion exchange resin loaded with a sulphonated azo dye

Gallium(III) is sorbed by a strong base anion exchange resin loaded with a sulphonated azo-dye, T-azo-R [1-(tetrazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid], which is able to complex it in aqueous solution. As sorption takes place at acidities at which the hydrolysis of gallium is not negligible, it must be considered as conconmitant equilibrium. The distribution equilibria depend on the amount of ligand sorbed, and on the volume, acidity and ionic composition of the aqueous solution, according to the Gibbs-Donnan model. The thermodynamic complexation constant in the resin phase can be calculated from the experimental distribution coefficients; the value of log K = −1.24(0.20) is in acceptable agreement with that in aqueous solution [log K = −0.75(0.33)] which was also determined in the present investigation. Two equations deriving from the Gibbs-Donnan model are used for predicting the conditions for sorption and elution of gallium by a batch procedure, and for separating it from aluminium.

Interaction of serum albumin with a sulphonated azo dye in acidic solution

The uptake of the sulphonated azo dye [1-(tetrazolylazo)-2-hydroxynaphthalene 3,6-disulphonic acid, or T-azo-R] by bovine serum albumin (BSA) in the pH range 1–4 was investigated by a spectrophotometric method, based on the fact that the absorption spectra of the free and bound dye are different. The effect of increasing concentration of sodium chloride and sodium perchlorate was considered, as well as the influence of the BSA on the protonation equilibria of the dye. The Scatchard model, which has been widely used previously to describe the interaction between small substances and proteins, was not helpful in the treatment of data obtained in the acidity range considered here. Instead a phase distribution model allowed a good quantitative treatment of the experimental findings. The distribution constant of the monoprotonated T-azo-R between aqueous solution and the albumin microphase was found to be log K d(HL)/γ′HL = 6.3, while the biprotonated form does not bind to BSA. As a consequence, the protonation constant of T-azo-R is decreased in the presence of BSA, particularly at low salt concentrations in aqueous solution. An equation relating the observed protonation constant to the protonation constant of the dye in solution and to the ionic strength is proposed. It has been found that the effect of salts on the uptake of T-azo-R by BSA can be explained simply by considering the variation of the activity coefficients of the ionic species involved in aqueous solution.

The Analysis of Some Sulphonated Azo Dyes by Mixed Mode HPLC

Abstract A mixed mode (anion exchange/reverse phase) column for the analysis of some commercial sulphonated azo dyes was investigated as an alternative to simple reverse phase columns which require the use of either somewhat aggressive acidic elution solvents or the inclusion of ion pair reagents. Good separations of structural isomers were obtained using isocratic elution with solvents containing acetonitrile and near neutral phosphate buffers. A pattern of pH dependence for the retention times distinguished dyes according to the number of sulphonate groups present in their structure. Low levels of impurities in the commercial dyes could be observed by using a methanol/water solvent which did not elute the principal component.

Separation of trace amounts of aluminium on a strong anion-exchange resin loaded with a sulphonated azo dye

The sulphonated azo dye Chromotrope 2B is sorbed quantitatively by the strong anion exchanger AG 1-X8. A chelating resin is obtained, which is able to sorb aluminium from aqueous solutions selectively. The distribution equilibria were investigated under different conditions and interpreted on the basis of a Donnan equilibrium based model for the resin. A separation and pre-concentration method for aluminium in natural waters is proposed, based on the use of the modified resin in a column at ambient pressure. The selectivity with respect to other metal ions was good; this was to be expected because Chromotrope 2B in solution is also selective for aluminium. Recoveries of 100 ± 1% were obtained, with a pre-concentration factor of 50, at a total aluminium concentration of 2 × 10–6 mol kg–1.

Spectrophotometric study and analytical applications of the complexes of copper(II) and zinc(II) with some sulphonated azo dyes

The complexing ability of some water-soluble azo dyes towards copper(II) and zinc(II) were studied in 0.1 M sodium perchlorate and perchloric acid solutions, at 25.0 °C. Solutions with CM≫CL, where CM is the concentration of metal and CL the concentration of ligand, and CL≫CM(CM up to 10–3M, CL up to 2 × 10–4M and pH up to the precipitation of metal hydroxides) were investigated spectrophotometrically.The ligands T-azo-C and 3,6-disulpho-TAN are able to complex both copper(II) and zinc(II), but amaranth only copper(II). Besides the usual complexes having 1:1 metal to ligand molar ratios, a 2:1 complex has been detected in the system copper(II)- T-azo-C. The results are compared with others obtained previously. The copper(II) complexes are much more stable than those of zinc(II) and those of many other metal ions. Therefore, a method is proposed for the spectrophotometric determination of copper(II), which is almost free from interferences.

Detection of 14C-carmoisine metabolites by high performance liquid chromatography.

14C-Carmoisine, a sulphonated azodye, 200 mg/kg b.w. (25 muCi), was administered to rats by gavage. Separation of radioactive compounds in faeces and urine of these animals was carried out by HPLC with a UV and a radioactivity detector. In addition to unmodified carmoisine, five radioactive compounds were present. The main peak showed both the retention time and the UV spectrum of naphtionic acid. Metabolic patterns similar to those observed "in vivo" were found by incubation of 14C-carmoisine under anaerobic conditions with a bacterial suspension isolated from human faeces and from the intestinal contents of rats. This procedure permits the preparation of amounts of unknown metabolites suitable for their identification.

Polarization microscopy and microspectrophotometry of Sirius Red, Picrosirius and Chlorantine Fast Red aggregates and of their complexes with collagen.

A detailed quantitative analysis of the anisotropic properties of Sirius Red F3B, Picrosirius, and Chlorantine Fast Red crystals, and of their complexes with a macromolecularly oriented protein either in a pure form or as part of a tissue structure was carried out. Collagen I was used as the protein model. Linear dichroism and dispersion of birefringence were investigated in dye aggregates, in stained filaments of collagen I and in collagen bundles in sections of tendon. A positive linear dichroism, the characteristics of which varied as a function of the dye type used, was demonstrated for the dye aggregates and stained substrates. However, even thin regions of the stained tendon collagen bundles showed very high absorbances, differing from the pattern reported previously for collagen stained with another sulphonated azo dye, Xylidine Ponceau. Consequently, not all these dyes enable protein concentration and orientation to be determined in collagen-containing structures. From the linear dichroism patterns it is assumed that the long axis of the molecules of these azo dyes is mostly parallel to that of filaments of pure collagen I and statistically parallel to the long axis of collagen bundles of tendon sections. The dye aggregates and, stained pure collagen I and tendon collagen bundles exhibited birefringent images with interference colours that varied as a function of thickness and packing state of the preparations, which is in agreement with reports in the literature. The optical retardations of the collagen bundles increased by a factor of 5-6 times after staining with Picrosirius. From data on form dichroism it is concluded that when studying the macromolecular orientation of collagen preparations stained with azo dyes, the choice of the mounting medium deserves consideration.

Reduction of sulphonated water-soluble azo dyes by micro-organisms from human faeces

The anaerobic reduction of four currently used sulphonated azo dyes, amaranth, sunset yellow, new coccine and tartrazine, has been studied by incubating bacterial suspensions isolated from human faeces and from the intestinal contents of rats with 50 μ m concentrations of the dyes in phosphate buffer, pH 7·4, using nitrogen as the gaseous phase. Human faecal flora from five male volunteers reduced the four dyes at mean rates of 38·4, 25·1, 18·2 and 6·5 nmol/mg protein/hr, respectively. For each dye, there was little difference in the reduction rates effected by the bacterial suspensions from the different individuals in spite of a considerable divergence in age, daily diets and living circumstances. These reductions proceeded at an approximately constant rate until the colours had faded almost completely. The rates of amaranth and sunset yellow reduction by rat-gut flora were four to five times higher than those by human faecal flora, but there was no significant difference between the two types of bacterial suspension in the reduction rates for new coccine and tartrazine.

The Absorption, Metabolism and Excretion of the Sulphonated Azo Dye, Acid Yellow, by Rats

The Absorption, Metabolism and Excretion of the Sulphonated Azo Dye, Acid Yellow, by Rats

REVERSAL OF SOLUBILITY CHARACTERISTICS OF 'LUXOL' DYE-PHOSPHOLIPID COMPLEXES.

‘LUXOL’ fast blue G (Du Pont), the diarylguanidine salt of a sulphonated azo dye, forms complexes stoichiometrically with phospholipids1. These complexes have been found to be insoluble in a varying pattern in the lower alcohols. For this study phospholipid-dye complexes were prepared with the same dye and phosphatidyl choline, phosphatidyl serine, phosphatidyl ethanolamine, phosphatidyl inositol, or sphingomyelin. The complexes were produced by bringing together the dye and phospholipid in pyridine solution. After evaporation of the solvent, excess uncomplexed dye or phospholipid could be removed by the alcohol in which the complex was insoluble. The solubility of the complexes in methanol, ethanol, isopropanol and isobutanol was determined. The results are summarized in Table 1. It was found that the complexes were soluble to the extent of at least 0.1 per cent or else were completely insoluble in the alcohols used. When alcoholic solutions of dye and phospholipid were mixed, precipitates were formed in those alcohols in which the particular complex had been found to be insoluble. The absorption maximum for the dye alone in the alcohols used is 597 mµ. When alcoholic solutions of the dye and phospholipid were mixed, the absorption maximum dropped to 570 mµ, before precipitation took place. If the precipitate was then centrifuged and the deposit redissolved in methanol or an alcohol in which it is soluble the absorption maximum was found to return to 597 mµ. This can be taken as evidence of dissociation where complexes are marked soluble in Table 1.

A quantitative histochemical method for estimating phospholipids.

THE affinity of the ‘Luxol’ solvent dyes for phospholipids has been investigated. One of these dyes, ‘Luxol’ fast blue MBS, was introduced by Kluver and Barrera1 as a myelin stain. It is a diarylguanidine salt of a sulphonated copper phthalocyanine dye. The dyes used in this investigation are diarylguanidine salts of sulphonated azo dyes. ‘Luxol’ fast blue G, ‘Luxol’ fast blue ARN, and ‘Luxol’ fast black L, have been found to form complexes with phosphotidyl, choline, phosphotidyl ethanolamine, and phosphotidyl serine. Pearse2 has already noted that ‘Luxol’ fast blue MBS forms precipitates with certain phospholipids in in vitro tests. He believed it was possibly an acid base reaction and that the base of the phospholipid replaced the base of the dye. He found his precipitates confined to the choline containing phospholipids. I have found that the dyes ‘Luxol’ fast blue G and ARN, and the phospholipids, phosphotidyl choline and phosphotidyl serine, form complexes stoichiometrically. Furthermore, there is a reversal of their common solubility in absolute ethanol (Table 1).

Dyeing Chrome‐tanned Leather with the Aid of Ethylene Oxide Levelling Agents

A brief description is given of the properties of leather, with particular reference to the application of dyes in presence of non-ionic, anionic, and cationic auxiliary agents. Fixation of chrome complex, vegetable, and synthetic tanning agents is described. The dyeing of suede leather is considered in detail, and the effect of two “non-ionic” polyoxvethylene derivatives on the absorption spectra of six sulphonated azo dyes is studied. It is concluded that, to obtain satisfactory dyeings on chrome-tanned suede leather, the dyes used must have similar affinity, any differences in affinity must be minimised by addition of a suitable auxiliary agent, and the agent must have similar effects on the absorption spectra of all the dyes used.

The excretion of some azo dyes in rat bile.

Abstract A quantitative comparison of the biliary excretion of sixteen water soluble sulphonated azo dyes has been made to ascertain if any relation between the excretion pattern and molecular structure exists

Adsorption at Organic Surfaces IV—Adsorption of Sulphonated Azo Dyes by Chitin from Aqueous Solution

Lobster‐shell chitin has been used in quantitative adsorption studies with sulphonated azo dyes in aqueous solutions, mainly under acid conditions. The extent of adsorption has been correlated with the dye structures.The mechanism of adsorption appears to be largely one of physical association between the aromatic residues of the dye and the molecular chains of the chitin, hydrogen bonding in acid solutions being unimportant. When inorganic acid is present, one sulphonate group in the dye anion takes part in ion exchange with inorganic anions at the cationic centres in chitin. Additional sulphonate groups appear to remain uncombined with the substrate and to reduce the affinity of the dye.