Sensitive spectrophotometric determination of gallium with bromopyrogallol red in the presence of surfactants

Gallium in the presence of surfactants (NTGE and CTA) forms with BPR a violet ternary complexes with λ_max at 615 and 625 nm, respectively, with molar absorptivities of 7.0 × 10⁴ and 1.3 × 10⁵ liters mol^?1 cm^?1. These complexes can be advantageously used for the determination of gallium. The molar ratio of gallium to BPR, which is 1:1 in the binary complex, increases to 1:3 in the ternary complex. The presence of surfactants changes the number of BPR molecules bonded to gallium. This is the main factor in the increase in color intensity. Numerous metals interfere. Gallium can be separated by extraction of gallium from 7 M hydrochloric acid with diisopropyl ether.     

Spectrophotometric and solvent extraction study of o-hydroxybenzaldehyde isonicotinoyl hydrazone complexes with gallium and indium

Complex formation of o-hydroxybenzaldehyde isonicotinoyl hydrazone with Ga^III, In^III and Tl^III has been studied. The thallium complex is unstable. The composition and the instability constants of gallium and indium complexes were determined. Molar absorptivity of gallium complex at 390 nm is 3.40 × 10⁴ and that of indium at 380 nm is 3.20 × 10⁴ l mole^?1 cm^?1. Both complexes were found to be rapidly and quantitatively transfered into 1-pentanol. The corresponding aluminum complex is not extracted. Possible analytical application for separation and spectrophotometric determination of these elements is also examined.     

Selektivitätssteigerung katalytischer bestimmungsverfahren—extraktionskataly-metrische molybdänbestimmung

To increase the selectivity of catalytic methods, a solvent extraction and catalytic determination have been combined. By means of the determination of molybdenum based on the catalytic oxidation of 1-naphthylamine by bromate, it is shown that by selection of a suitable extraction system the catalyst can be determined directly in the organic extract. The catalytic activity of different complexes of molybdenum was tested and for an analytical application the extraction of molybdenum as oxinate was chosen. The method enables molybdenum to be determined down to 2.7 × 10^?9M. The relative error of the determinations is 10%. 10^?4M V, 2 × 10^?4M Cr, 5 × 10^?5M W and 10^?2M Mn, Ni, Cu, Co, Fe, Mg, Zn, Cd, Al and Pb cause no interference. The method has been used for the determination of molybdenum in sea-water.     

Propriétés des oxinates d'aluminium,de gallium et d'Indium.: Séparation du gallium par extraction par le chloroforme

A study has been made of the solubility in water as a function of pH of oxine and of the oxinatus of aluminium, gallium and indium, as well as their solubility in chloroform.The curves showing the partition between chloroform and water as a function of pu have been established.Gallium can be separated, from aluminium by extraction of the oxinate al pH₂O. It is possible by this means to separate one part of gallium from 10¹ parts of aluminium. The formation of the oxinates serves as a basis of an acidimetric determination of the ions Al⁺³, Ga⁺³ and In⁺³.     

Spectrophotometric determination of aluminum with bromopyrogallol red in the presence of surfactants

Spectrophotometric methods are described for the determination of microgram amounts of aluminum based on the formation of a ternary complex between the metal, bromopyrogallol red, and cetyltrimethylammonium bromide or nonylphenol tetradecaethylene glycol ether. The complexes have absorbance maxima at 627 and 612 nm, respectively, with molar absorptivities of 5.0 × 10⁴ and 2.2 × 10⁴ liter mol^?1 cm^?1. Numerous metals interfere. Aluminum can be easily separated by extraction of interfering ions with cupferron.     

A comparative study of the complexation of Am(III) and Eu(III) with TODGA in room temperature ionic liquid

On the growing awareness of the environmental impact associated with the use of volatile organic diluents, room temperature ionic liquid gained world-wild acceptance as environmentally benign diluents for actinide partitioning. The observed unusual behavior of less extraction efficiency of Eu with TODGA in RTIL in comparison with that of Am-TODGA was addressed in this paper. The stoichiometry of Am-TODGA complex was found to be 1:2 while that of Eu-TODGA was 1:1. More the ligand molecules associated in the metal ligand complex, the organophilicity of the complex will be more and the solubility of the metal–ligand complex in RTIL will be more which reflects in the higher distribution ratio for Am. In RTIL both Am and Eu showed slower kinetics of extraction with TODGA which can be attributed to the high viscosity coefficient of RTIL compared to the molecular diluents. The observed slower kinetics of extraction was quantified and found to follow first order kinetics with the rate constant of 5.5 × 10^?4 s^?1. The formation constant of Am-TODGA complex was found to be more (4.18 × 10⁸ M^?1) than Eu-TODGA complex (3.31 × 10⁸ M^?1) in RTIL. The parameters viz. diffusion coefficient, activation energy for Eu(III)/Eu(II) were determined and found to be 3.08 × 10^?8/cm² s^?1 (at 303 K) and 39.34 kJ mol^?1 respectively. The thermodynamic parameters ΔG, ΔH and ΔS for the reaction were evaluated using the linear regression of the plot of E ^0* versus T. The redox reaction was found to be exothermic with decrease in entropy value.     

A highly sensitive spectrophotometric determination of gallium with chromal blue G in the presence of cetyltrimethylammonium chloride

A new spectrophotometric method for the determination of gallium with chromal blue G in the presence of cetyltrimethylammonium chloride is described. The sensitivity of color reaction between gallium and chromal blue G is greatly increased by the sensitizing action of cetyltrimethylammonium chloride. The gallium complex has maximal absorbance at 662 nm and pH 6.2–6.8. Beer's law is obeyed over the range 0.04–0.6 ppm of gallium. The molar absorptivity of the complex is 1.44 × 10⁵ liters mol^?1 cm^?1 at 662 nm, and the spectrophotometric sensitivity is 4.8 × 10^?4 μg Ga cm^?2. The mole ratio of gallium and chromal blue G in the complex is estimated to be 1:4. The formation constant and effect of interfering ions are described.     

Precipitation of copper(II) by formation of a complex with 2,4-dioxo-4-(4-hydroxy-6-methyl-2-pyrone-3-yl) butyric acid ethyl ester

Mononuclear copper(II) complex with 2,4-dioxo-4-(4-hydroxy-6-methyl-2-pyrone-3-yl) butyric acid ethyl ester is readily precipitated in ethanolic medium. The metal to ligand ratio in the crystalline species was found to be 1:2. On the basis of the spectroscopic data collected so far, the site of coordination could not be identified. The detection limit of the precipitation of the binuclear complex in aqueous buffer, pH 7.00, solution is at a 2 × 10^?5 mol dm^?3 copper(II) concentration. By radiometric measurements with ⁶⁴Cu isotope, the time neccessary for a quantitative precipitation, the amount of copper(II) in the precipitate and in the solution, the amount of ligand needed for the optimal precipitation yield, and the solubility product of the complex were determined.The precipitate separated from the supernatant can be dissolved in ethanol and copper(II) determined by absorbance measurement at 374 nm. The sensitivity of this procedure lies at the detection limit of the complex precipitation. The calibration diagram, a straight line (b = 0.00677; s_b = 0.00003; s² = 0.00146), confirms the validity of Beer's law in the range of 2 × 10^?5? 4 × 10^?4 mol dm^?3 copper(II) concentrations, with a systematic error of 7 × 10^?6 mol dm^?3 arising from solubility loss of the precipitate remaining constant.Concentrations exceeding 10^?6 mol dm^?3 of nickel(II) cause too high values and those exceeding 10^?5 mol dm^?3 of aluminium, zinc, iron(II), thorium(IV), or vanadium(V) too low values in copper determinations.     

Control of the composition of lanthanum gallium silicate by laser ablation inductively coupled plasma mass spectrometry

The possibilities of determining the impurities and basic components of lanthanum gallium silicate using laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) were shown. A procedure for the determination of 54 impurity elements with the limits of determination from n × 10^?5 wt % for Mg, Ti, V, Cr, Mn, Ni, Cu, and Zn to 2 × 10^?7 wt % for U and also a procedure for the determination of a ratio between basic components were developed. It was found that the concentration ratios between gallium and lanthanum and silicon and lanthanum in the crystals of lanthanum gallium silicate remained constant upon consecutive melting operations with the addition of a charge mixture to the crucible.     

Simultaneous Analysis of Sugars and Polyphenols in Tobacco by CZE with Amperometric Detection Based on a Cu2O/MWCNT-COOH Composite Electrode

A composite electrode was fabricated from Cu₂O powder, carboxyl-functionalized multi-wall carbon nanotubes (MWCNT-COOH), and paraffin oil in the proportions 51:17:32 (w/w). This composite electrode was used for amperometric detection (CZE–AD) in simultaneous capillary zone electrophoretic analysis of chlorogenic acid, rutin, sucrose, glucose, mannose, and fructose in tobacco samples. Under the optimum conditions, the six analytes could be separated in 100 mmol L^?1 NaOH buffer within 30 min. Good linearity was achieved in the range 1 × 10^?7–1 × 10^?4 mol L^?1 for the two polyphenols and 5 × 10^?6–1 × 10^?3 mol L^?1 for the four sugars. The detection limits (S/N = 3) for the polyphenols and sugars were as low as 10^?8 mol L^?1 and 10^?6 mol L^?1, respectively.     

The electrochemical stripping determination of bismuth in aqueous and nonaqueous media after its extraction

The cyclic voltammetry of bismuth in aqueous media and electrochemical stripping determination of bismuth in aqueous and nonaqueous media after its extraction using a rotating disc electrode of glassy carbon was studied. To raise the conductivity of the organic medium and for the preparation of a convenients medium for the determination of bismuth, an alcoholic (methanol) solution of NH₄SCN+HClO₄ was employed. In non-aqueous medium bismuth can be determined down to concentrations 10^?8M by anodic stripping voltammetry and to 5×10^?8M by anodic stripping chronopotentiometry. The selectivity of the determination of bismuth after its extraction was studied. Electrochemical determination of 10^?6M Bi³⁺ with error ±3–4% was not interfered with by these elements: Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, As³⁺ in the concentration 8×10^?3M, Fe³⁺, In³⁺, Sn²⁺ and Sn⁴⁺ (5× 10^?3M), Cu²⁺ (10^?3M), Sb³⁺ (1.5×10^?4M) and Hg²⁺ (2×10^?5M). The reproducibility of the electrochemical determination of bismuth according to the recommended procedure is very good.     

Simultaneous Quantitation of Quinolone Residues in Biological Fluid by CE Combined with Electrogenerated-Chemiluminescent Detection

A simple, rapid and sensitive method has been proposed for simultaneous electrogenerated-chemiluminescent detection of quinolone residues in biological fluid after effective separation by capillary electrophoresis. Enrofloxacin, levofloxacin and ciprofloxacin can be assayed in the range of 3.0 × 10^?8–5.0 × 10^?6 g mL^?1 within 10 min. The relative standard deviations of the signal intensity and the migration time were less than 4.9 and 2.4% for a standard sample containing 1.0 × 10^?7 g mL^?1 of each quinolone (n = 5), respectively. The presented method has been successfully applied to determine the amounts of quinolones in pig urine after clean-up by C₁₈ solid phase extraction column.     

Molecular imprinting polymer electrosensor based on gold nanoparticles for theophylline recognition and determination

An electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold nanoparticles using a potentiostatic method. The effects of pH, ratio between template molecule and monomer, number of cycles for electropolymerization, and of the solution for extraction were optimized. The current of the electro-active model system hexacyanoferrate(III) and hexacyanoferrate(IV) decreased linearly with successive addition of ThPh in the concentration range between 4.0?×?10^?7?~?1.5?×?10^?5 mol·L^?1 and 2.4?×?10^?4?~?3.4?×?10^?3 mol·L^?1, with a detection limit of 1.0?×?10^?7 mol·L^?1. The sensor has an excellent recognition capability for ThPh compared to structurally related molecules, can be regenerated and is stable.

Determination of trace elements in gallium arsenide by graphite-furnace atomic absorption spectrometry after pretreatment in gas streams

Atomic absorption spectrometry (AAS) with a resistively-heated graphite furnace is used for the determination of chromium (0.3–1 atom/10⁶ atom) in chromium-doped gallium arsenide after pretreatment in a separate furnace in a stream of argon to remove arsenic, and of manganese and silver (0.03 and 0.04 atom/10⁶ atoms, respectively) by a similar procedure after pretreatment with argon and chlorine, the latter to remove both gallium and arsenic as volatile chlorides. Results for chromium were in agreement with those obtained by furnace AAS after dissolution and by spark-source mass spectrometry (SSMS) but AAS after dissolution is more precise. Results for manganese and silver obtained by both gas pretreatments were in good agreement, but were higher than those obtained for presparked material by SSMS, indicating that surface contamination of gallium arsenide was not completely removed by the etching methods used. The procedures established that the concentrations of bismuth, indium and lead in the gallium arsenide sample were below the limits of detection of 3 × 10^?3, 10 × 10^?3 and 1 × 10^?3 atom/10⁶ atoms, respectively. In all cases, calibration graphs were constructed from data obtained with aqueous solutions of appropriate salts.     

Untersuchungen über (1:1)-Chelate des Curcumins mit Borsäure und Phenylborsäuren

The existence of 1∶1 boron-curcumin chelates in solution has been proved by the straight-line method of Asmus. The compounds with boric resp. phenylboronic acid propably exist as diacetato-resp. phenylacetato-boron chelates of curcumin. The dissociation constants of the 1∶1 complexes of curcumin and boron are K _D =4×10^?5 with boric acid in acetic acid and 3×10^?4 in dioxan, 1×10^?3 with phenylboronic acid in dioxan and 1×10^?4 when stabilized with phenol, 7×10^?5 with diphenylborinic acid in dioxan solution. All boron-curcumin chelates are formed from the quinonoid protonized form of curcumin, which can be stabilized by phenol.     

Determination of Anionic Surfactant in Fresh Water and in Sea Water

Ion pairs formed from suitable cationic dye and anionic surfactant in water were separated by solvent extraction. The extracts were used subsequently for spectrophotometric determinations. The extraction of ion pairs with various combinations is described. Of the dyes and solvents examined, ethyl violet and p-xylene are the most useful combination as the cationic dye and extraction solvent. The extracts are determined spectrophotometrically at 611.5 nm; the molar absorptivity is 1, 01 × 10⁵ M^?1 cm^?1. The detection limit is 1.4 ppb in water. The method is simple, rapid and sensitive. It can also be applied to the determination of anionic surfactants in sea water.     

Kinetics of enantioselective liquid-liquid extraction of phenylglycine enantiomers using a BINAP-copper complex as chiral selector

Kinetic study of reactive extraction of phenylglycine (PhgH) racemate with S-BINAP ((S)-(?)-2,2′-bis(diphenylphosphino)-1,1′-binaphthalene)-copper complex (BINAP-Cu) as the chiral selector was performed in a modified Lewis cell. The theory of extraction accompanied by a chemical reaction was applied to achieve insightful understanding of the extraction process. The effects of agitation speed, interface area, pH value of the aqueous phase, initial concentration of PhgH racemate, and initial concentration of BINAP-Cu on the specific rate of extraction were investigated. An extraction course was simulated based on the rate equations. The forward rate constants of 3.14 × 10^?5 m^3.4 mol^?0.7 s^?1 for R-PhgH and 4.03 × 10^?5 m^3.4 mol^?0.7 s^?1 for S-PhgH, respectively, were found. The modeled extraction course was in good agreement with the experimental one.     

Kinetic study on reactive extraction for chiral separation of phenylsuccinic acid enantiomers

The kinetics of the extraction of phenylsuccinic acid (PSA) enantiomers by hydroxypropyl-β-cyclodextrin (HP-β-CD) in a modified Lewis cell was studied, in which HP-β-CD dissolved in 0.1 mol L^?1 NaH₂PO₄/H₃PO₄ buffer solution (pH = 2.5) was selected as the chiral extractant. PSA enantiomers were extracted from organic phase to aqueous phase in the extraction module. The theory of extraction accompanied by a chemical reaction has been used to obtain the intrinsic kinetics of this extraction module. The different parameters affecting the extraction rate such as agitation speed, interfacial area, initial concentration of PSA enantiomers in organic phase as well as HP-β-CD concentration in aqueous phase were separately studied. The experimental results demonstrate that the extraction reactions are fast. The reactions were found to be first order with respect to PSA and second order with respect to HP-β-CD with forward rate constants of 3.4 × 10^?2 m⁶ mol^?2 s^?1 for R-PSA and 9.96 × 10^?3 m⁶ mol^?2 s^?1 for S-PSA. These data will be useful in the design of extraction processes.     

Electrochemical Responses and Sensitivities of Films Based on Multi-Walled Carbon Nanotubes in Aqueous Solutions

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of chemical vapor deposition with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene as catalyst. The electrochemical responses of MWCNT-based films towards the ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple were probed by means of cyclic voltammetry and electrochemical impedance spectroscopy at 25.0?±?0.5?°C. Both MWCNT-based films exhibit Nernstian response towards [Fe(CN)₆]^3?/4? with some slight kinetic differences. Namely, heterogeneous electron transfer rate constants lying in ranges of 2.69?×?10^?2?C1.7?×?10^?3 and 9.0?×?10^?3?C2.6?×?10^?3?cm·s^?1 were obtained at v?=?0.05?V·s^?1 for MWCNT_ACN and MWCNT_BZ, respectively. The detection limit of MWCNT_ACN, estimated to be about 4.70?×?10^?7?mol·L^?1 at v?=?0.05?V·s^?1, tends to become slightly poorer with the increase of the scan rate, namely at v?=?0.10?V·s^?1 the detection limit of 1.70?×?10^?6?mol·L^?1 was determined. Slightly poorer response ability was exhibited by MWCNT_BZ; specifically the detection limits of 1.57?×?10^?6 and 4.35?×?10^?6?mol·L^?1 were determined at v?=?0.05 and v?=?0.10?V·s^?1, respectively. The sensitivities of MWCNT_ACN and MWCNT_BZ towards [Fe(CN)₆]^3?/4? were determined as 1.60?×?10^?7 and 1.51?×?10^?7?A·L·mol^?1·cm^?2, respectively. The excellent electrochemical performance of MWCNT_ACN is attributed to the presence of incorporated nitrogen in the nanotube??s structure.     

A multivariate calibration procedure for the tensammetric determination of detergents

A multivariate calibration procedure based on singular value decomposition (SVD) and the Ho-Kashyap algorithm is used for the tensammetric determination of the cationic detergents Hyamine 1622, benzalkonium chloride (BACl), N-cetyl-N,N,N-trimethylammonium bromide (CTABr) and mixtures of CTABr and BACl. The sensitivity and accuracy depend strongly on the nature of the detergent. Acceptable accuracy is obtained with a two-step calculation procedure in which calibration constants for the total concentration range of interest are used to guide the choice of a more specific set of calibration constants which are valid for a much smaller concentration span. For Hyamine 1622, concentrations in the range 5 × 10^?6?2 × 10^?4 M could be determined with an accuracy of ± 10^?6 M. For CTABr, these numbers were 3 × 10^?6?2 × 10^?4 M and ± 5 × 10^?7 M; for BACl, they were 2 × 10^?3?9 × 10^?2 g l^?1 and ± 1 × 10^?3 g l^?1. In the mixtures of CTABr and BACl, the accuracies were ± 3 × 10^?6 M and × 1 × 10^?3 g l^?1, respectively.