Adsorptive stripping voltammetric behaviour of uranium chelates of some azo compounds

Summary The adsorptive stripping voltammetric behaviour of Arsenazo III, Eriochrome Black T, 4-(2-pyridylazo) resorcinol, Mordante Blue 9 and their uranyl complexes has been investigated in detail. All compounds and complexes adsorb on the static mercury drop electrode. Results are presented and the limitations of the methods are discussed.     

An electrochemical sensing platform for trace analysis of Eriochrome Black T using multi-walled carbon nanotube modified glassy carbon electrode by adsorptive stripping linear sweep voltammetry

ABSTRACT

A highly sensitive electrochemical sensing platform was proposed for trace analysis of Eriochrome Black T in aqueous solutions by adsorptive stripping linear sweep voltammetry based on the open-circuit accumulation of Eriochrome Black T onto the fabricated multi-walled carbon nanotubes modified glassy carbon electrode surface. The proposed methodology was quite linear between 0.1 and 10 µM of Eriochrome Black T concentration with a correlation coefficient of 0.9981. The precision of the technique was acceptable with the relative standard deviations of lower than 13.4% for inter-day assays. In addition, the sensitivity properties of the proposed method were compared with those of the spectrophotometric method, which is frequently used in the literature for Eriochrome Black T analysis. The results showed that the proposed electrochemical sensing platform would be a more sensitive alternative to the existing spectrophotometric techniques. Finally, the methodology was successfully applied to the determination of Eriochrome Black T in a well water spiked at different concentration levels.     

Adsorption-Bonded Azo Reagents in Chemical Tests Based on the Principles of Precipitation Paper Chromatography

The possibility of using three groups of azo compounds in chemical tests based on the principles of precipitation paper chromatography is considered. The first group consists of the reagents showing the highest affinity to cellulose (Congo Red, Brilliant Yellow, Stilbazo, Cadion IREA, Sulfarsazen, and Titan Yellow). These reagents are immobilized on paper and are not washed out of it in acidic, alkaline, and neutral solutions. The immobilization of the reagents results in a bathochromic shift of their absorption bands with respect to their solutions and enhances the acidic properties of the reagents. The second group comprises compounds that are immobilized on paper only in acidic solutions (mono- and bisazo derivatives of chromotropic acid: Arsenazo II, Arsenazo III, Orthanilic K, Sulfochlorophenol S, Chlorophosphonazo III, and Carboxyarsenazo). Their immobilization on paper does not lead to a shift in the absorption spectra and acidic properties. The third group consists of compounds that are immobilized on paper either in acidic or in alkaline solutions (Acid Chrome Dark Blue, Eriochrome Black T, Magneson KhS, and Eriochrome Blue Black R). They are absorbed by cellulose as free acids in acidic solutions and as sodium salts in alkaline solutions. Test procedures have been developed for the determination of acids; alkalis (0.1–100 mM); the total alkalinity of water (0.2–35 mM); the total acidity of water (0.2–20 mM); Cd, Al, and Pb (1–200 mg/L); Al, Th, U, and Zr (0.5–200 mg/L); and the total hardness of water (0.05–40 mM). The length of the colored zone in test strips laminated into a polymer film and contacting the test solution through a narrow edge is the analytical signal. The relative standard deviation does not exceed 30%; the analysis time is 10–15 min.     

A examination of the EDTA titration of manganese(II) taking into consideration formation of 1:1 and 1:2 complexes with Eriochrome Black T indicator

In the EDTA titration of manganese(II) with Eriochrome Black T as indicator, the effect of formation of 1:1 and 1:2 manganese(II)—indicator complexes must be taken into consideration. The titration error can be reduced to less than 0.1%. For comparison purpose the titration of zinc(II) has also been studied.     

Extraction of catechol violet, chrome azurol S and eriochrome cyanine R with chloroform solutions of liquid anion-exchangers

The extraction of Catechol Violet, Chrome Azurol S and Eriochrome Cyanine R with chloroform solutions of tri-n-octylamine (TOA), TOA hydrochloride and Aliquat 336 has been investigated. From the extraction isotherms, absorption spectra of the organic phases and dependence of the extraction coefficients on extractant concentration, it was found that the singly-charged anions HL(-) are extracted preferentially, but acidic groups other than sulphonate can also form ion-pairs with alkylammonium cations at higher pH values of the aqueous phase, and at high acidity these dyes can be extracted other than by an anion-exchange reaction. The three dyes (especially Eriochrome Cyanine R and Chrome Azurol S) were strongly extracted with the liquid anion-exchanger used and Aliquat 336 was a better extractant than TOA or TOA hydrochloride. The absorption spectra for the organic phases containing Chrome Azurol S and Eriochrome Cyanine R depended on the extractant used.     

Ion-chromatography of metals with post-column ion displacement

A post-column reagent mixture of Eriochrome Black T and magnesium-EDTA complex is added to the eluent from an ion-chromatograph. Eluted metal cations displace the magnesium, which then forms a complex with the Eriochrome Black T. The absorbance of this complex is measured at 520 nm. Detection limits for several cations are in the mug/ml range.     

Adsorptive stripping voltammetry of trace manganese in the presence of 2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)

Trace levels of manganese can be determined by voltammetry after controlled adsorptive accumulation of the manganese-2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complex on a hanging mercury drop electrode. Optimal conditions include an ammonia buffer solution (pH 8.8) containing 1 x 10(-5)M 5-Br-PADAP and an accumulation potential of -1.20 V. The technique offers enhanced sensitivity over analogous measurements of the manganese-Eriochrome Black T chelate. The detection limit is 0.2 mug/1 with 1 min accumulation. The new adsorptive approach is characterized with new selectivity dimensions (compared to the Eriochrome Black T scheme), and is not affected by large excess of commonly coexisting calcium and magnesium cations (which severely interfere in the Eriochrome Black T procedure).     

Osmium assay in fixatives and stained rat tissues by means of acid and <Emphasis Type="Italic">o,o</Emphasis>′-dihydroxo substituted monoazo dyes and some flavonoids

New simple, rapid and accurate spectrophotometric techniques for osmium assays in fixatives and stained tissues have been elaborated using acid (Tropaeolin O, Tropaeolin OOO-I, Tropaeolin OOO-II, Orange G), o,o′-dihydroxo substituted azo dyes (Eriochrome Blue Black R, Acid Chrome Dark-Blue, Eriochrome Black T) and flavonoids (morin, quercetin, luteolin). Methods are based on sensitive osmium(IV) reactions with reagents and the formation of stable coloured compounds. Tolerance ratios of main matrix components of histological specimens during Os(IV) spectrophotometric determination with reagents has been established. Results of osmium determination in fixatives and fixed tissues, obtained by means of different reagents, appeared to be sufficiently similar, although effects of matrix components differ. The accuracy of spectrophotometric osmium assay in fixatives with azo dyes has been confirmed with voltammetric investigations. Results obtained from osmium uptake by rat gum tissues are valuable for clinical testing of dental drugs, indicating the influence of drug treatment on the gums.      

Eriochrome black a as an indicator for chelatometric titrations

The use of Eriochrome Black A for the EDTA titrations of Zn, Mn, Ni, Pb and Cu ions is described. Spot tests for the determination of the sensitivity limits of detection have been made     

Determination of 2,3-dimercaptopropanol-l (BAL) by titration with zinc, with eriochrome black T as indicator

A method is proposed for the titrimetric determination of BAL with zinc solution and Eriochrome Black T (EBT) as indicator. It is based on the difference of the stabilities of the Zn(BAL)a and Zn-EBT complexes. The accuracy of the method is very good and the interference of diverse mercaptans is limited to those compounds forming zinc complexes more stable than the Zn-EBT complex.     

Complexometric determination of magnesium in nodular cast iron and alloyed cast iron roll samples

A complexometric method for the determination of magnesium in nodular cast iron, alloyed cast iron and roll samples has been developed. The bulk of the iron is removed by ether extraction and the phosphate as zirconium phosphate. The other elements are removed by extraction with dithiocarbamate into chloroform. Magnesium is then titrated with EDTA at pH 10, with Eriochrome Black T as indicator. Calcium interferes, but is very rarely present in such cast iron samples.     

Spectrophotometric determination of magnesium in aluminium alloys

The determination of magnesium in aluminium alloys by a differential spectrophotometric method is describcd. Magnesium is separated and the absorbance of its coloured complex with Eriochrome Black T measured.     

Crystalline calmagite and a study of sulphonation effects on azo dye metal-ion indicators

Calmagite was introduced in 1960 as a stable substitute for Eriochrome Black T in EDTA titrations of calcium plus magnesium. The colour changes were the same but somewhat sharper. Indicator stock solutions were stable indefinitely. The new indicator was designed as an indicator and not as a wool dye. Azo dye impurities which may be present in some commercial supplies tend to lengthen the end-points. A simple means of removing these impurities to yield crystalline indicator has been developed. The effects of sulphonation on the performance of azo dyes as indicators have been studied.     

Colour changes of chemical indicators-VI: metallochromic indicators for direct chelometric titrations of zinc

Eriochrome Blue SE, Eriochrome Red B, Naphthylazoxine 6S, SNAZOXS, and Zincon have been studied in order to find optimum conditions for their use as metallochromic indicators in direct visual chelometric titrations of zinc. The sharpness of the indicator transitions has been investigated by means of photometric titrations and the colour quality has been specified with the aid of the C.I.E. chromaticity systems. Zincon and Eriochrome Blue SE have been found to be the most convenient for visual titrations of zinc.     

Spectral study of Eriochrome Blue Black R in different cationic surfactant solutions

Interactions of anionic dye Eriochrome Blue Black R (EBBR) with various cationic micelles of surfactants n-alkyltrimethylammonium CnTAB (n=12; 14; 16 and 18) have been investigated spectrophotometrically at 25°C in premicellar and postmicellar region. The results have shown that with increasing the alkyl chain length of surfactants, the maximum absorbance of EBBR shifted to a higher wavelength and the binding constants of EBBR to cationic micelles (Kb) increases. This confirms that the surfactant micelle, which has a longer alkyl hydrocarbon chain, enables greater solubilization of dye. Thus, the hydrophobic interaction of the dye with micelles increases in the order: C12TAB相似文献   

Reactions of eriochrome Blue Black R

The reactions of Eriochrome Blue Black R with approximately 25 metals are tabulated. Photometric titrations of molybdenum and uranium are described, and a new method of titrating thulium with EDTA is presented.     

An improved selective determination of mercury(II) by complexometric titration

A simple and accurate method has been developed for selective determination of mercury in alkaline solution. It involves the addition of an excess of EDTA to the mercury solution, titration of unreacted EDTA with a standard zinc solution, and then addition of N-allylthiourea solution at pH ? 9. By heating, the mercury-EDTA chelate is decomposed selectively, mercury sulfide is precipitated, and the EDTA freed is again titrated with standard zinc solution. Eriochrome Black T is used as indicator. Interference of some cations is discussed.     

The determination of fluoride by titration with calcium chloride

A new method for the determination of fluoride ions is described. Precipitation is effected with an excess of standard calcium chloride and, after standing overnight, the unconsumed calcium ions are back-titrated with ethylenediamine tetra-acetic acid (EDTA) using Eriochrome Black T as indicator. Halides, sulphate, phosphate and arsenate do not interfere under the recommended conditions. The method is applicable over the range 5-65 mg of fluoride ion.     

A spectral study of tautomerism in 4-arylamino-1,2-naphthoquinones

The tautomerism of 4-arylamino-1,2-naphthoquinones in aqueous solutions has been investigated by UV-visible absorption spectroscopy. It has been demonstrated that in strongly acidic solutions (Ph 0·8), protonation of the 2-keto group leads to 2-hydroxy-1,4-naphthoquinone-4-arylimine as the more stable tautomer. However, weakly acidic or alkaline solutions (Ph 4–13) contain 4-arylamino-1,2-naphthoquinone as the more stable tautomer.     

Sensitive microdetermination of scandium,yttrium, and lanthanides using Eriochrome azurol B in the presence of a micelle-forming cationic surfactant

The chelation reactions of Sc³⁺, Y³⁺, and some lanthanides with Eriochrome azurol B in the presence and absence of cetyltrimethylammonium bromide has been studied in detail. The complexes show a marked bathochromic shift in their λ_max at pH 6.0. The composition of the complexes in the absence and presence of cetyltrimethylammonium bromide was found to be 1:2 (Metal:ligand). The values of the conditional formation constants have also been evaluated. The studies were further extended to the analytical aspects of the complex equilibria and a suitable procedure has been recommended for the spectrophotometric microdetermiantion of Sc³⁺, Y³⁺, and some lanthanides under study using Eriochrome azurol B in the presence of cetyltrimethylammonium bromide which considerably increases the sensitivity of the color reaction. The use of Eriochrome azurol B in the presence of cetyltrimethylammonium bromide as a complexometric indicator has also been reported.The effect of surfactant concentration and the effect of mineral salts on the absorption spectra of Eriochrome azurol B at pH 11.6 and 6.0 have also been reported.