Thiazolylazo Resorcinol Research Articles

Multielement Solid Phase Preconcentration Using a Chelating Resin of Styrene Divinylbenzene Copolymer and Application for the Analysis of Seawater and Fish Otoliths by Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

A new chelating resin was synthesized by immobilizing 4–(2–thiazolylazo) resorcinol (TAR) on to a styrene divinylbenzene copolymer. This material was examined for on-line solid phase extraction/preconcentration of Cd, Co, Cu, Ni, Pb, and Zn in seawater and fish otoliths for determination by inductively plasma mass spectrometry (ICP-MS). A volume of 5.0 mL sample solution was loaded on to a mini-column of the resin at 2.0 mL min−1 via a sequential injection system. The optimum pH for multielement preconcentration was around pH 5.5. Recoveries were better than 96% in artificial seawater. Elution was achieved with 1.0 mL of 0.75 mol L−1 HNO3. The resin possesses a large sorption capacity ranging from 82.0 µmol g−1 for Pb to 319 µmol g−1 for Cu. The detection limits (3σ) varied between 0.0016 µg L−1 (Cd) and 0.015 µg L−1 (Zn) for preconcentration of 5.0 mL blank solutions (pH 5.5). Relative standard deviation for three replicate runs was between 0.3% (Cd) and 6% (Zn) at the 1.0 µg L−1 level. The procedure was validated by analysis of a nearshore seawater and a fish otoliths certified reference material, and employed for coastal seawater and estuarine water samples.

Synthesis, Characterization, and Applications of a New Chelating Resin Containing 4-2-(Thiazolylazo) Resorcinol (TAR)

A new phenol–formaldehyde based chelating resin containing 4-(2-thiazolylazo) resorcinol (TAR) functional groups has been synthesized and characterized by Fourier transform infrared spectroscopy and elemental analysis. Its adsorption behavior for Cu(II), Pb(II), Ni(II), Co(II), Cd(II), and Mn(II) has been investigated by batch and column experiments. The chelating resin is highly selective for Cu(II) in the pH range 2 ∼ 3, whereas alkali metal and alkaline earth metal ions such as Na(I), Mg(II), and Ca(II) are not adsorbed even at pH 6. Quantitative recovery of most metal ions studied in this work except Co(II) is achieved by elution with 2M HNO3 at a flow rate of 0.2 mL min−1. A similar trend is observed for distribution coefficient values. The quantitative separations achieved on a mini-column of chelating resin include Cd(II) – Cu(II), Mn(II) – Pb(II), Co(II) – Cu(II), Mn(II) – Ni(II), and Mn(II) – Co(II) – Cu(II). The recovery of copper(II) is quantitative (98.0–99.0%) from test solutions (10–50 mg/L) by 1 mol/L HNO3-0.01 mol/L EDTA. The chelating resin is stable in acidic solutions below 2.5 M HNO3 or HCl as well as in alkaline solution below pH 11. The adsorption behavior of the resin towards Cu(II) was found to follow Langmuir isotherm and second order rate.

PHYSICOCHEMICAL STUDIES OF NICKEL AND COPPER COMPLEXES WITH TAR AND SIMULTANEOUS DETERMINATION OF THE METAL IONS IN MIXTURES BY DERIVATIVE SPECTROPHOTOMETRY

Nickel(II) and Copper(II) chelates of 4-(2̀–thiazolylazo)resorcinol (TAR) were reported. The dissociation constants of the ligand and the stability constants of the metal complexes were calculated pH-metrically and spectrophotometrically at 25 ◦C, in 50% (v/v) ethanol and 0.1 M ionic strength. The effects of an acid or a base on the visible absorption behaviour of the ligand and complexes has been investigated. Nickel and copper react with 4-(2̀–thiazolylazo)resorcinol (TAR) to form a binary complexes. The equilibria occurring in solution were established and the basic characteristics of the complexes formed were determined. The complexation reaction in the systems investigated were demonstrated and characterized using graphical logarithmic analysis of the absorbance versus pH graph. The composition of the formed complexes with the reagent have been determined. The molar absorptivity of the binary system is investigated. The binary systems obeyed beer's law up to 0.23 and 0.25 µg/ml for Ni2+ and Cu2+ respectively. A simple and highly sensitive procedure for spectrophotometric determination of Ni2+ and Cu2+ has been developed. A method for the simultaneous determination of nickel and copper in mixtures by first-derivative spectrophotometry is described. Zero-crossing measurement technique is found suitable for the simultaneous determination of the metal ions. The method has been applied to direct determination of copper and nickel in dome synthetic mixtures without any separation.

Spectrophotometric determination of acidity constants of 4-(2′–thiazolylazo)- resorcinol (TAR) in water–organic mixtures

The acidity constants of TAR in different water–organic solvent binary mixtures at 25 °C have been determined spectrophotometrically. DATa ANalysis (DATAN) program was used for calculations of the acidity constants and pure spectra of all formed species and their concentration distribution diagram in applied pH interval. Results show that there are a fairly inverse relationship between acidity constants and the mole fraction of the organic solvent in the binary mixtures. Effects of solvent composition on the p K as and pure spectrum of each component are also discussed.

Spectrophotometric determination of chromium in steel with 4-(2- thiazolylazo)-resorcinol (TAR) using microwave radiation

A spectrophometric method for the determination of Cr(III) with 4-(2- thiazolylazo)-resorcinol was developed. Cr(III) slowly forms a red complex with TAR at pH 5.7. Irradiating the reacting mixture with microwave energy can accelerate the complex formation. The absorbance reached its maximum with 5 min of irradiation and remained stable, at least, for 24 h. N-cetyl-N,N,N-trimethylammonium bromide (CTAB) was used for increasing the sensitivity and solubility of the system. The method allowed the determination of chromium ranging from 0.050 to 3.0 mg mL-1 (9.62 x 10-7 to 5.77 x 10-5 mol L-1) with a molar absorptivity of 2.73x104 L-1 mol-1 cm-1 and a detection limit of 17 ng mL-1 (3.3 x 10-7 mol L-1) at 545 nm. The selectivity was improved by using EDTA and citrate as masking agents. Fe(III) interferes and must be extracted previously, if present in the sample. The proposed method has been successfully applied to the determination of chromium in steel. The precision (R.S.D. < 2%) and accuracy were satisfactory.

Determination of the thermodynamic parameters of hexaoxoiodate(VII) hydrates of the type M 2HIO 6· nH 2O, where M II = Ni, Cu, Zn and Cd, by solubility measurements in water at various temperatures

The solubilities of metal hexaoxoiodate(VII) hydrates of the type M 2HIO 2 · nH 2O (M II = Ni, Cu, Zn, Cd; n = 3, 2, 1.25, 1.25) in water have been measured at several temperatures with the aid of 4-(2'-thiazolylazo)-resorcinol (TAR) reagent using a Beckman DU-2 spectrophotometer. Mean activity coefficients are determined. The thermodynamic parameters of these salts, e.g., Δ H o, Δ G o and Δ S o, have been computed. A retrograde solubility phenomenon has been observed over the temperature range 298.5–328 K.

4-(4, 5-Dimethyl-2-thiazolylazo) Resorcinol as a Metallochromic Indicator for Cu (II)

Abstract The dissociation constants of 4- (4,5 -dimethyl -2-thiazolylazo) resorcinol (DMTAR) and formation constant of its complexes with Cu (II) were measured spectrophotometrically. The utility of DMTAR as the metallochromic indicator for Cu (II) in EDTA titrations is comparable to 4 - (2 -thiazolylazo) resorcinol (TAR).

Metal complexes of 4-(2'-thiazolylazo)-resorcinol: A comparative study with 4-(2'-pyridylazo)-resorcinol

The acid dissociation constants of 4-(2'-thiazolylazo)-resorcinol (TAR) and the formation constants of the metal complexes formed by this reagent with Cu(II), Ni(II), Co(II), Zn(II) and Mn(II) have been determined potentiometrically at 25° in 50% v/v mixtures of dioxane and water. The values obtained for TAR and the metal complexes are contrasted with similar values for the reagent 4-(2'-pyridylazo)-resorcinol (PAR). Differences and similarities between the co-ordinating tendencies of these two reagents are revealed in terms of the proton displacement constant and the acid dissociation constants of the metal complexes. Evidence is presented which suggests that both TAR and PAR may act as terdentate ligands toward some bivalent metal ions.