Reaction of mercury(II) and xylenol orange-III: determination of microamounts of mercury

Xylenol Orange and mercury(II) react in the presence of various bases, such as hexamine, pyridine and ammonia, to form ternary complexes, which conform to Beer's law. The 1:1:1 Hg(II)/XO/ base complex at pH 6.1 has an absorption maximum at 590 nm and a molar absorptivity of 2.2 x 10(5) l.mole(-1).cm(-1). In the absence of the base the Hg(II)(XO)(2) complex at pH 7.5 and 580 nm has a molar absorptivity of 1.7 x 10(5) l.mole(-1).cm(-1). Interferences are discussed.     

Determination of mercury in the presence of chloride by means of the ternary complex Hg(II)/xylenol orange/amberlite La-2 in non-aqueous media

The system Hg(II)/Xylenol Orange/Amberlite LA-2 dissolved in 1:1 v v 3-methylbutan-1-ol/chloroform medium has been studied. A 3:2:2 complex is formed, which is suitable for analytical measurements at temperatures <18 degrees . This complex allows the determination of mercury in the range 0.19-5.5 ppm with a molar absorptivity of 2.12 x 10(4).mole(-1).cm(-1) at 600 nm and extraction pH of 7.4 (standard deviation 0.065 ppm). The proposed method has been applied to the determination of mercury in contaminated water with a high chloride content.     

Absorption characteristics of xylenol orange

Absorption characteristics of Xylenol Orange have been reinvestigated for the purpose of its spectrophotometric estimation. The molar absorption coefficient of Xylenol Orange at 580 nm and pH 10.0 is 3.12 x 10(4) l.mole(-1), cm(-1).     

Spectrophotometric study of the mercury(II)-Xylenol Orange chelate

The reaction between mercury(II) and Xylenol Orange has been studied in aqueous hexamine medium. The chelate is 1:1 and has an apparent stability constant of 2.4 (+/-0.6) x 10(6) at pH 7 (2.9 M hexamine). Beer's law is obeyed over the concentration range 0.5-2.0 x 10(-5)M mercury(II) when the hexamine concentration is 2.9 M.     

Purification of xylenol orange by preparative paper chromatography, and examination of its zirconium complex

Preparative paper chromatography is proposed as a suitable method for purification of Xylenol Orange (XO). The last three dissociation constants of pure XO have been determined with the aid of the program SPEKTFOT, the values found being pK(9) = 12.34; pK(8) = 10.66; pK(7) = 6.69 (0.1M KNO(3), 20 +/- 0.5 degrees ). The complexation of zirconium with the purified reagent has been studied and the co-existence of ML and M(2) L complexes proved by use of the program DALSFEK. The following conditional stability constants of the complexes and their molar absorptivities were computed: log beta'(ml) 4.58; log beta'(M(2)L) 11.59; (ML) 2.00 x 10(4); (M(2)L) 9.40x 10(4) l.mole(-1).cm(-1) at 550 nm.     

Extraction and spectrophotometric determination of mercury(II) with Xylenol Orange in the presence of diphenylguanidine as a synergistic agent

The system Hg(II)/XO/DPG extracted into several alcohols and mixtures alcohol/chloroform (as depressing of the solubility of the alcohol in water) is studied. A ternary complex 1:1:1 Hg(II)/XO/DPG is observed when the mixture 1:1 ($\text{V}\text{V}$) iso-amyl alcohol/chloroform is considered. This complex shows a molar absorptivity 2.3 × 10⁴ liter mol^?1 cm^?1 at 590 nm, pH_ex 8.0, and T ? 18 °C. This complex allows to determine Hg(II) in the concentration range 0.25-5.8 ppm. According to the experimental results a reaction mechanism in which the alcohol and DPG take part in the coordination sphere of Hg(II) ion is suggested. The optimal extraction conditions of XO and its mercury complex are discussed, as well as the study of the interferences.     

Spectrophotometric determination of chromium with xylenol orange and methylthymol blue

A new simple and sensitive method for determining traces of chromium is described. Xylenol Orange and chromium(III) form a red complex at pH 3 on heating in boiling water for 20 min. The molar absorptivity is 19.0 x 10(3). No catalytic action of the bicarbonate ion, carbon dioxide, or chromium(II) generated by metallic zinc was observed. Methylthymol Blue is a less sensitive reagent for chromium, the molar absorptivity being 11.5 x 10(3).     

A new sensitive method for the spectrophotometric determination of molybdenum using 3-hydroxy-2-(2'-thienyl)-4H-chromen-4-one

A spectrophotometric method has been developed for the determination of Molybdenum (VI) using 3-hydroxy-2-(2'-thienyl)-4H-chromen-4-one as a complexing agent. The complex formed was dissolved in water in the presence of Triton X-100 and exhibits an absorption maximum at 410 nm. A large number of metal ions like Co(II), Ni(II), Mn(II), Cr(III), Zn(II), Cu(II), Hg(II), Bi(III), Fe(II), Fe(III), Zr(IV), V(V) can be tolerated at an appreciable concentrations. Molar absorptivity and Sandell's sensitivity of the method is 2.80 x 10(5) l mol-1cm-1 and 3.42 x 10(-4) micrograms cm-2, respectively. Beer's law is obeyed in the concentration range of 0.01-0.4 ppm Mo(VI). Aliquots containing 0.2 ppm of Mo(VI) give a mean absorbance of 0.56 with a relative standard deviation of 1.3%.     

Spectrophotometric study of the reaction of bismuth(III) with Xylenol Orange

The reaction between bismuth(III) and Xylenol Orange (XO) has been investigated by spectrophotometry. It has been established that bismuth(III) and Xylenol Orange form complex compounds with compositions Bi(III):XO = 1:1 (up to pH 1) and Bi(III):XO = 1:2 (above pH 1) which have absorption maxima at 550 and 500 nm respectively. The formula of the 1:1 complex is [Bi(H(3)R)] whereas the 1:2 complex can take one of the following forms: [Bi(H(4)R)(2)](1-), [Bi(H(4)R)(H(3)R)](2-) and [Bi(H(3)R)(2)](3-). If the values for pK(Bi(H(3)R)) and pK(Bi(H(3)R)(2)) respectively are 9.80 +/- 0.03 and 15.53 +/- 0.03 at a constant ionic strength of 1.0.     

Analysis of mixtures of hafnium and zirconium by the methylthymol blue-hydrogen peroxide method

The reaction of hydrogen peroxide with the zirconium(IV) and hafnium(IV) Methylthymol Blue complexes (MeMTB) has been investigated. The conditional stability constants of the Zr(IV) and Hf(IV) complexes with hydrogen peroxide [K'(Me(H(2)O(2)))] were determined spectrophotometrically. The K'(Me(H(2)O(2))) values found, which depend on the acidity, are 3.91 x 10(2) 3.24 x 10(2), 2.63 x 10(2) at [HCl] = 0.2, 0.3, 1.0M respectively for Me = Zr(IV) and 0.828, 0.523, 0.319 for Me = Hf(IV). The ratios of the conditional stability constants, K'(Me(H(2)O(2)))/ K'(MeMTB), are: 5.52 x 10(-4), 5.79 x 10(-4), 8.23 x 10(-4) for Me = Zr(IV) and 2.08 x 10(-6), 2.74 x 10(-6), 1.48 x 10 (-5) for Me = Hf(IV) at the three acidities. The maximum of the ratio of the relative conditional stability constants is obtained in 0.2M hydrochloric acid. The conditions which should be complied with for the determination of hafnium in the presence of zirconium are discussed. The results were compared with those obtained by the Xylenol Orange-hydrochloric acid method. They are superior for samples containing less than 20 mole% of hafnium in admixture with zirconium.     

Spectrophotometric determination of thorium with Xylenol Orange and cetyltrimethylammonium bromide

The thorium-Xylenol Orange reaction sensitized by cetyltrimethylammonium bromide ( = 5.51 x 10(4) l.mole(-1).cm(-1)) is accompanied by a bathochromic shift from 570 to 600 nm. The system is more selective than the binary system, because the reaction pH is lowered from 4.0 to 2.5; Beer's law is obeyed for 0.04-4.00 ppm of thorium.     

Kinetic determination of Hg(II) in different materials, based on its inhibitory effect on a catalysed process

A new kinetic method for the determination of Hg(II) based on its inhibitory effect on the Pd(II)-catalysed reaction between Co(III)-EDTA and hypophosphite is proposed. The reaction is followed spectrophotometrically at 540 nm by measuring the induction period. Both the influence of the reaction variables and the interference of many ions have been studied. A mechanism for the inhibition process is also proposed. Under the selected experimental conditions of 2.7 x 10(-1)M Co(III)-EDTA, pH-3.2 Britton-Robinson buffer, 0.3M H(2)PO(-)(2), 0.35 mug/ml Pd(II), and temperature 18 +/- 0.2 degrees , Hg(II) was determined in the range 13-120 ng/ml. The method was applied to the determination of Hg(II) in sphalerites and pharmaceuticals.     

Kinetic determination of microamounts of some sulphur-containing ligands

Some sulphur-containing ligands have been shown to inhibit the Hg(II)-catalysed substitution of p-nitrosodiphenylamine (p-NDA) for cyanide in hexacyanoferrate(II), by binding the mercury(II). This effect is used for determination of microamounts of cysteine, thioglycollic acid and thiosulphate. The reactions are followed spectrophotometrically at 640 nm (lambda(max) of [Fe(CN)(5).p-NDA](3-)). The determination range depends on the amount of mercury(II) added and the stability of the Hg(II)-ligand complex. Under specified conditions, the detection limits are: thioglycollic acid 1 x 10(-7)M, cysteine 1 x 10(-6)M and thiosulphate 4 x 10(-7)M.     

Ternary Complex Nickel(II)/3-(4′,5′-Dimethyl-2′-Thiazolylazo)-2,6-Dihydroxybenzoic Acid/Cyanide. Spectrophotometric Determination of Nickel

Abstract

A spectrophotometric method for nickel has been developed based on the formation of a ternary complex in the system Ni(II)/3-(4′,5′-dimethyl-2′-thiazolylazo)-2,6-dihydroxybenzoic acid/cyanide at pH 9.2 (borate buffer), which allows the determination of 0.05–0.47ppm of nickel (ε = 3.53×10⁴ 1.mol^?1. cm^?1) at 538nm. Interferences have been studied and the method applied to the determination of nickel in low alloy steels.     

Formation constants of zinc(II) complexes with Semi-Xylenol Orange

A potentiometric and spectrophotometric investigation on the formation of zinc(II) complexes with Semi-Xylenol Orange (SXO or H(4)L) is reported. In an aqueous solution (mu = 0.1), three 1:1 complex species, MH(2)L, MHL(-), ML(2-), and a 1:2 complex, ML(6-)(2), seem to exist. In a strongly alkaline medium (above pH 12.5) the complexes may dissociate to give zinc hydroxide and L(4-). The formation of a hydroxy complex is not observed. The absorption maxima are at 445 nm (MH(2)L), 466 nm (MHL(-)) and 561 nm (ML(2-)), the molar absorptivities being 2.34 x 10(4), 2.42 x 10(4) and 3.14 x 10(4) 1.mole(-1) .cm(-1) respectively. The formation constants are (at 25 +/- 0.1 degrees ) log K(M)(ML) = 11.84, log K(M)(MHL) = 7.13, log K(M)(MH(2)L) = 2.70, log K(M)(ML(2)) = 16.60.     

Furoin thiosemicarbazone as an analytical reagent for nickel(II), palladium(II) and copper(II)

Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported.     

Facile synthesis of water-soluble and size-homogeneous cadmium selenide nanoparticles and their application as a long-wavelength fluorescent probe for detection of Hg(II) in aqueous solution

Highly luminescent uncoated water-soluble and mono-disperse CdSe nanoparticles (NPs) have been prepared facilely. Uncoated CdSe core NPs possessing a good size distribution was accompanied with long wavelength of fluorescence emission. It is interesting to note that these functionalized NPs are soluble in water medium stably for more than 1 month, and no significant changes were found in the optical characteristics in comparison with fresh CdSe NPs prepared. The functionalized CdSe NPs exhibited strong specific affinity for mercury(II) through their surface functional groups. Based on the significant quenching of fluorescence emission of functionalized CdSe NPs with a long-wavelength 630nm, a simple, rapid and specific detection for Hg(II) was proposed. Under optimum conditions, the response of linearly proportional to the concentration of Hg(II) is between 0mol/L and 1.25x10(-6)mol/L, and the limit of detection is 4.50x10(-9)mol/L. The relative standard deviation (R.S.D.) of six replicate measurements is 2.0% for 2.0x10(-7)mol/L of Hg(II). In terms of fluorescence quenching at 630nm of CdSe NPs, no obvious wavelength shift or no new emission band in presence of Hg(II) at pH 7.50 of phosphate buffer solution were found; furthermore, a significant reduction in absorbance at 230nm of CdSe NPs was first observed in our work. We could speculate that Hg(II) as an effective quencher (even at low concentration) for functionalized CdSe NPs emission suggests that it is capable of directly intercepting one of the charge carriers, thus disrupting the recombination process.     

Synthesis, structural characterization, and electrophosphorescent properties of rhenium(I) complexes containing carrier-transporting groups

Two novel diimine rhenium(I) carbonyl complexes with the formula [Re(CO)(3)(L)Br], where L = 1-(4-5'-phenyl-1,3,4-oxadiazolylbenzyl)-2-pyridinylbenzoimidazole (1) and 1-(4-carbazolylbutyl)-2-pyridinylbenzoimidazole (2), have been successfully synthesized and characterized by elemental analysis, (1)H NMR, and IR spectra. Their electrochemical, photophysical, and electroluminescent behaviors, along with the X-ray crystal structure analysis of 2, are also described. White electrophosphorescent devices were fabricated using 1 and 2 as emitters. The devices based on carbazole-containing (hole-transporting group) 2 with the structure ITO/m-MTDATA (30 nm)/NPB (20 nm)/2:CBP (8%, 30 nm)/Bphen (20 nm)/Alq(3) (20 nm)/LiF (0.8 nm)/Al (200 nm) exhibit Commission Internationale de L'Eclairage coordinates of x = 0.34, y = 0.33 with a maximum brightness of 2300 cd/m(2) at 580 mA/cm(2). When a brightness of 1500 cd/m(2) appears at 230 mA/cm(2), the devices based on 10 wt % 2 still possess 56% of the maximum efficiency which appeared at 2.7 mA/cm(2). These performances are among the best reported for devices using Re(I) complexes as emitters. By comparison of the electroluminescent properties of the devices based on 1 and 2, we conclude that the introduction of the carbazole group into the ligand improves the performance of 1-doped devices.     

Highly sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using benzildithiosemicarbazone.

A simple and highly sensitive method was developed for the extractive-spectrophotometric determination of palladium with benzilidithiosemicarbazone. The metal ion formed a reddish brown complex with benzildithiosemicarbazone in a potassium chloride-hydrochloric acid buffer of pH 2.5, which was easily extractable into methyl isobutyl ketone. The 1:1 complex showed the maximum absorbance at 395 nm with a Beer's law range of 0.25-3.5 ppm. The molar absorptivity and Sandell's sensitivity were found to be 3.018 x 10(4) dm3 mol(-1) cm(-1) and 0.0035 microg cm(-2), respectively. The correlation coefficient of the Pd(II)-BDTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) (n = 10), which was 0.46%. The instability constant of the complex calculated from Edmond and Birnbaum's method was 2.41 x 10(-5), that of Asmus' method is 2.53 x 10(-5) at room temperature. The interfering effects of various cations and anions were studied. The proposed method was successfully applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The validity of the method was tested by comparing the results with those obtained using an atomic absorption spectrophotometer.     

Use of 1-(2-thiazolylazo) 2-naphthol in rapid determination of iron in geological matrices

The present work describes the use of 1-(2-thiazolylazo)-2-naphthol (TAN) as a spectrophotomeric reagent for iron determination. TAN reacts with iron(II) forming a brown complex with absorption maximum at 575 and 787 nm. The following parameters were studied: complex stability, pH effect, amount of the TAN, buffer selection, amount of acetate buffer, reductor effect, order of addition of reagents and adherence to Beer's Law. The results demonstrated that iron can be determined with TAN in a pH range of 4.0-6.2 with an apparent molar absorptivity of 1.83 x 10(4) 1 . mol(-1) . cm(-1) (at 787 nm) and 1.41 x 10(4) 1 . mol(-1) . cm(-1) (at 575 nm). Beer's Law is obeyed for at least 3.00 microg/ml. The TAN reacts with other cations, but at 787 nm only the iron(II)-TAN complex absorbs. So, iron can be determined selectively in the presence of several cations. A procedure based on the direct mixture of the sample and a chromogenic solution is proposed, where iron can be determined rapidly and easily. Such procedures were used for the determination of iron in several geological matrices. No significant differences were obtained for TAN method and certificate results.