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).     

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.     

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.     

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.     

Locating the more acidic hydroxyl group on dihydroxy compounds o,o'-dihydroxyazo-dye metal-ion indicators

In o,o'-dihydroxyazo-dye metal-ion indicators, one hydroxyl group is 10(4) times more acidic than the other. The location of the more acidic group has been a mystery. By methylation of the acidic group, reduction of the monomethylated compound, isolation and characterization of the split methoxyamine and hydroxyamine, the location of the acidic group has been established. Indicators examined include Calmagite, Eriochrome Black T, Eriochrome Blue Black R and 4-(2-pyridylazo)resorcinol (PAR).     

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.     

Solochrome Black P.V. as a new reagent in chelatometry

Summary Solochrome Black P.V. has proved to be a suitable metallochromic indicator in direct titrations of Mg, Zn, Cd and Mn^II with EDTA or in back titrating Pb, M and Co at p_H 10. By its aid together with the application of masking agents as potassium cyanide and ammonium fluoride and the mercuric nitrate procedure, fifteen binary mixtures were analysed using simple procedures which gave precise, reproducible and highly accurate results. It can be used as a substitute for Eriochrome Black T in determining micro and milligram amounts of the above mentioned cations.Part I: Khalifa, H., and S. W. Bishra: Z. analyt. Chem. 183, 108 (1961).     

Determination of magnesium in blood serum using a flow-injection system with a potential-scanning electrochemical detector equipped with a thin-film deaerator

Batch and flow-injection determination of magnesium in blood serum, based on the adsorptive reduction current peak of the Eriochrome Black T—magnesium complex, is described. A potential-scanning electrochemical detector, equipped with a novel thin-film deaerator, allows the successful adaptation of the batch method to a flow-injection system. Using a simple flow system, up to 35 samples h^?1 can be processed. The results obtained agree well with those obtained by atomic absorption spectrometry.     

Automatic determination of calcium and magnesium in water

Magnesium and calcium may each be determined in water by an automatic spectrophotometric method. At 571 nm with an excess of Eriochrome Black T as metallochromic agent, the variation m absorbance is proportional to the magnesium concentration regardless of the calcium concentration. By addition of MgEDTA to displace the calcium from its CaEBT complex, this element may be determined at the same wavelength. For 3-25 ppm of magnesium and 5-40 ppm calcium, the standard deviation was about 4%. The apparatus is described.     

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.     

依来铬蓝黑B-镁配合物的极谱研究

依来铬蓝黑B是一种金属指示剂^[1],在pH1.95～12.20的Britton-Robinson缓冲溶液中产生一良好的还原波^[2]。在氨性缓冲溶液中,当溶液的pH在9.5～11.3时,依来铬蓝黑B也产生一明晰波。     

Use of hydroxylamine hydrochloride in the titrimetric determination of manganese in pyrolusite

A procedure is described for the determination of total manganese in pyrolusite. The sample is decomposed with hydroxylamine hydrochloride solution. The residue left after filtration is fused with sodium carbonate and extracted again with hydroxylamine hydrochloride solution. A suitable aliquot is titrated with EDTA at pH 10, with Eriochrome Black T as indicator, after masking of interfering elements.     

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 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.     

Surface-enhanced Raman scattering and DFT investigation of Eriochrome Black T metal chelating compound

The surface-enhanced Raman scattering (SERS) spectra of Eriochrome Black T (EBT) and its Cu(II), Fe(III), Mn(II) and Pb(II) complexes were recorded using a hydroxylamine reduced silver colloid. Molecular geometry optimization, molecular electrostatic potential (MEP) distribution and vibrational frequencies calculation were performed at B3LYP/6-31G(d) level of theory for the EBT molecule and its Cu(EBT), Fe(EBT) and Mn(EBT) metal complexes. Differentiation between EBT complexes of Cu(II), Fe(III), Mn(II) and Pb(II) is shown by the SERS spectral features of each 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.     

Chelatometrische bestimmung von zink-, cadmium- und bleiionen in anwesenheit von variaminblau als redoxindikator

A direct chelatometric method for the determination of zinc, cadmium and lead ions was developed. Using the redox systems potassium ferrocyanide-potassium ferricyanide and Variamine Blue as redox indicator, the determination could be carried out at pH 5 with sufficient accuracy Magnesium, barium, strontium and calcium do not disturb the determination. In solutions containing zinc, lead or cadmium ions, magnesium can also be determined when Eriochrome Black T is used as the indicator.     

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.     

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     

Paper chromatography of some sulfonated azo-dyes used as metallochromic reagents in liquid-liquid anion exchange systems

Summary Chromatographic behaviour of 11 sulfonated azo-dyes used as metallochromic reagents in chloride systems was investigated by paper extraction chromatography and the moist paper technique. It was found that the affinity of reagents to the cellulose treated with liquid anion exchangers decrease in the following order: Titan Yellow, Stilbazo, Zincon, Eriochrome Black T>Magneson II >SPADNS and Arsenazo IArsenazo III>Thoron. The results suggest that the retention of the reagents in extraction chromatography is caused not only by anion exchange process but also by adsorption phenomena. It was found that in acidic media only the sulfonic groups of the reagents form ion-pairs with alkylammmonium cations.