Mass spectra of some bivalent transition-metal ion chelates with pyridylazo phenols and naphthols

The mass spectra of 2- and 4-(2-pyridylazo)phenol, 2-(2-pyridylazo)-1- and 1-(2-pyridylazo)-2-naphthol and several chelates of these compounds with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) are discussed. Comparisons are made with the results of solution studies of complex formation of the same chelates.     

Xerogels modified with l-(2-Pyridylazo)-2-naphthol and dimethylglyoxime: Indicator tubes for determining nickel

A simple and rapid sol-gel method was proposed for preparing xerogels modified with l-(2-pyrilylazo)-2-naphthol and dimethylglyoxime. Reactions between nickel and xerogels modified with l-(2-pyrilylazo)-2-naphthol and dimethylglyoxime were studied by solid-phase spectrophotometry, and the optimal conditions were found. Procedures for determining nickel in solution by solid-phase spectrophotometry and tests based on indicator tubes containing powdered xerogel modified with l-(2-pyrilylazo)-2-naphthol were developed. The analytical ranges for nickel in the above methods were 0.1–2 and 0.2–30 mg/L, respectively. The interference from cobalt(II) was eliminated by its adsorption on hydrophobic C₁₆ and C_phenyl silica gels modified with l-(2-pyrilylazo)-2-naphthol. The interference of copper(II) and iron(III) was eliminated by the addition of a mixture of Na₂S₂O₃ and NH₄F.     

Test determination of aniline in solutions based on azo coupling with analytical reagents incorporated into silicic acid xerogels

Silicic acid xerogels modified with 1-naphthol, 2-naphthol, 8-hydroxyquinoline, 2,7-dihydroxynaphthalene,N-(l-napthyl)ethylenediamine andp-hydroxydiphenyl were synthesized. It was shown that the immobilized reagents can participate in reactions of azo coupling with products of aniline diazotization. The best (among the studied) immobilized reagent for determining aniline was 1-naphthol. Xerogel modified with 1-naphthol was used for determining aniline in solutions by solid-phase spectrophotometry and with visual detection. The analytical ranges for aniline at the optimal conditions were 0.005-10 mg/L using solid-phase spectrophotometry and 0.05-15 ng/L with visual detection. The results were verified in the analysis of synthetic mixtures.     

Analytical Properties of Gaize- and Silicate Glue-Based Xerogels with Immobilized Chrome Azurol S

A method is proposed for the synthesis of silicic acid xerogels based on opoka aluminosilicate (gaize) and silicate glue. The physicochemical properties of xerogels were studied. The complexation of Be(II) with immobilized Chrome Azurol S was studied by electronic absorption and diffuse-reflection spectrometry and solid-phase spectrophotometry. Test procedures were developed for determining Be(II) and Al(III) in waters and soils.     

Indicator Tubes and Indicator Powders for Determining Fluoride and Chloride Ions

Noncovalent immobilization of Arsenazo I, Alizarin Red, Xylenol Orange, and diphenylcarbazone by incorporation into silicic acid xerogels and modification of silica gels was studied, and procedures for determining fluoride and chloride ions by solid-phase spectrophotometry and test methods were developed. Reactions of immobilized reagents with aluminum(III), zirconium(IV), and mercury(II) were studied. The possibility of using immobilized reagent–metal ion–halide ion systems for the determination of halide ions was assessed. Indicator powders were proposed for determining 0.5–10 mg/L fluoride ions and 1–30 mg/L chloride ions, and indicator tubes were developed for determining 20–200 mg/L chloride ions. The determination of fluoride and chloride ions is based on exchange complexation reactions proceeding in the systems immobilized Xylenol Orange–zirconium(IV) and immobilized diphenylcarbazone–mercury(II), respectively. Performance characteristics of the developed procedures were estimated. The procedures were verified by determining halide ions in Narzan mineral water.     

Preconcentration of Uranium in Seawater with Heterocyclic Azo Dyes Supported on Silica Gel

Abstract

The chelating adsorbents, heterocyclic azo dyes supported on silica gel, were prepared and their adsorption behaviors of metal ions were investigated. The 1-(2-pyridylazo)-2-naphthol(PAN)-SG and 2-(2-thiazolylazo)-p-cresol(TAC)-SG show greater affinity for UO₂(II) and ZrO(II), compared with the other metal ions like Cu, Cd, Fe and alkaline earths. Trace uranyl can be quantitatively retained on the column of the gels at neutral pH region and flow-rate 3–4 ml/min. The uranyl retained is easily eluted from the column bed with a mixture of acetone and nitric acid(9:1 v/v) and determined by spectrophotometry using Arsenazo-III. Matrix components in seawater do not interfere and the spiked recovery of uranyl in artificial seawater was found to be average 98.6 %, with the relative standard deviation of 1.08 %. Both gels were applied to the determination of uranium in seawater with satisfactory results.     

Some new heterocyclic compounds as analytical reagents

A survey of the metal-complexing reactions, as determined by reactions on chromatography paper, of 44 compounds with a substituted or modified 4-(2-pyridylazo)-resorcinol (PAR) or 1-(2-pyridylazo)-2-naphthol (PAN) structure is reported.     

Analytical properties of 1-(2-pyridylazo)-2-naphthol immobilized on a polymethacrylate matrix

The adsorption of 1-(2-pyridylazo)-2-naphthol (PAN) with a polymethacrylate matrix from a water-ethanol solution is studied. It is shown that PAN immobilized on a polymethacrylate matrix retains its analytical properties.     

Determination of Manganese (II) in Foodstuffs by β-Cyclodextrin Polymer Phase Spectrophotometry with 1-(2-Pyridylazo)-2-naphthol

The chromogenic agent, 1-(2-pyridylazo)-2-naphthol (PAN) was included in g -Cyclodextrin polymer ( g -CDP) and the modified polymer of inclusion of PAN ( g -CDP-PAN) was obtained. Based on the fact that g -CDP-PAN can adsorb Mn (II) in solution to form Mn (II)-PAN complex, a sensitive and selective solid phase spectrophotometric method for the determination of trace amounts of Mn (II) has been developed. The maximum absorbance of Mn (II)-PAN complex in g -CDP was at 514 nm. The working range of the calibration graph was 2-12 w g of Mn (II). The interference of molybdenum, lead, cobalt, chromium, iron, nickel, zinc, tin, cadmium, and copper that form colored species with PAN in the polymer phase was investigated. The method was applied to the determination of Mn (II) in black rice and tea samples. A new method for the determination of trace amounts of manganese by polymer phase spectrophotometry is described. Manganese reacted with 1-(2-pyridylazo)-2-naphthol (PAN) that was included in a g -cyclodextrin polymer. The absorbance of the colored polymer, packed into a 5 mm quartz cell, was determined directly at 514 nm. The proposed method was applied to the determination of manganese in black rice and tea samples.     

Xerogels Modified with 4-(2-Pyridylazo)-Resorcinol and Cetylpyridinium Chloride: Determination of Zinc in Solutions by Solid-Phase Spectrophotometry

Silicon dioxide-based xerogels modified with 4-(2-pyridylazo)-resorcinol (PAR) and cetylpyridinium chloride (CP) were synthesized. The concentration of PAR and CP in the hydrolyzed mixture in the ranges (0.6–3.10) × 10^–3 and (5–12) × 10^–3 M, respectively, does not affect the rate of gel formation as well as the specific surface area and average pore diameter of xerogels obtained upon drying in a microwave oven with a power of 600 Wt. It was found that the retention of PAR can be significantly improved in the presence of CP. Reactions of zinc with modified xerogels were studied by solid-phase spectrophotometry at different concentrations of PAR and CP, pH of the solution, and equilibrium time. A procedure was developed for determining 0.1–4.5 mg/L zinc in solutions by solid-phase spectrophotometry. Results of determining zinc in acid soil extracts and milk ash are given.     

Influence of microwave radiation on the growth of gold nanoparticles and microporous zincophosphates in a reverse micellar system

The water core of reverse micelles has been extensively used as the site for synthesis of a variety of materials. However, water-in-oil reverse micelles have a limited range of temperatures over which they are stable as a single phase. Directing heat to the water cores, the usual site of synthesis without heating the bulk provides added opportunities for synthesis. Microwave radiation is a method for superheating the water cores. In this study, we use an H2O-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-heptane reverse micelle system for the synthesis of Au particles by hydrazine reduction of HAuCl4 in the presence and absence of microwave radiation. The duration of the microwave radiation was limited to a 2-min duration at a power of 300 W, thereby ensuring that the reverse micelle phase is maintained during the synthesis. At all hydrazine concentrations studied (0.5-2 M), the presence of microwave radiation led to an increase in the particle size of Au. The second system examined was the growth of microporous zincophosphate-X (ZnPO-X, an analogue of the faujasite structure) synthesized from H2O-dioctyldimethylammonium chloride (DODMAC)-heptane reverse micelle system. Microwave radiation was applied for 1 min at 150 W at various stages of the nucleation and growth process, and did not disrupt the reverse micelle system. Product analysis after 48 h of reaction showed that the 1-min microwave pulse, if applied during the nucleation stage (the first 4 h), promoted the formation of NaZnPO4.H2O over ZnPO-X. The effect of the microwave pulse at the growth stage was to promote the formation of ZnPO-X. Absorption of the microwave radiation by the water core and surrounding polar surfactant molecules leads to a rapid rise in local temperature (predicted to be approximately 150 degrees C/min for the AOT system), increasing the rates of intramicellar reactions.     

Spectrophotometric determination of traces of cobalt in water after preconcentration on reagent-loaded polyurethane foams

Open-cell Polyurethane foam loaded with 1-(2-pyridylazo)-2-naphthol (PAN) is used for the preconcentration of traces of cobalt from water at the ppb level with a preconcentration tration factor of 1000 or more. Cobalt is retained quantitatively from thiocyanate solution on the loaded foam placed in a column, at flow rates up to 100 ml min^-1, and then recovered completely from the foam by elution with acetone. Cobalt is determined spectrophotometrically with 4-(2-pyridylazo)-resorcinol at 510 nm, after the removal of interfering ions with a Dowex 1-X8 column. The amount of PAN leached by the water percolating through the column is too low to affect quantitative retention of traces of cobalt.     

Chemical analysis of mixtures of some heavy metals by means of differential reaction rates of ligand substitution reactions

The simultaneous determination of some heavy metals in their mixtures is described. The method is based on the differential reaction rate of ligand substitution reactions involving ethyleneglycol bis(2-aminoethylether)N,N,N',N'-tetraacetic acid (EGTA) and 4-(2-pyridylazo)-resorcinol (PAR). Various combinations at the 10^-6M level of heavy metal ions such as manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), mercury(II) and lead(II) can be determined photometrically.     

Integrated reaction/spectrophotometric detection in unsegmented flow systems

The use of ion-exchangers located in the flow cell of an unsegmented flow system is proposed and applied to the determination f copper(II) based on the formation of a colored chelate with 1-(2-pyridylazo)-2-naphthol retained on Dowex 50W resin. The sample solution can be injected in the normal way or pumped into the system over an interval of time dependent on the analyte concentration (preconcentration method for very dilute samples). Kinetic measurements are made along the retention curve. Copper(II) is eluted with thioglycollic acid, which makes the system reversible. The determination limit achieved is 1 ng ml^-1 and the calibration curves have good features. Depending on the conditions chosen, the sampling frequency is 10–110 h^?1.     

Development of a new flow-through bulk optode for the determination of manganese(III)

A flow-through bulk optode based on the use of 1-(2-pyridylazo)-2-naphthol (PAN) immobilized in a plasticized poly(vinyl chloride) membrane entrapped in a cellulose support, in conjuntion with the flow injection analysis technique, is proposed for the determination of manganese(II). The calibration graph obtained at 570 nm was linear in the range 0.27-27.5 mg L(-1) (5 x 10(-6)-5 x 10(-4) M) Mn(II) with a detection limit of 0.18 mg L(-1). The coefficients of variation of the sensor response for 5.5 mg L(-1) of Mn(II) were +/-0.22% for consecutive measurements (n = 10), +/-0.48% between days (n = 5) and +/-0.38% between different membranes (n = 6). The sensor was readily regenerated with the carrier acetic acid/acetate buffer of pH 4.5. The method was applied to the determination of manganese in steels, waters and lemon tree leaves.     

Silaned glass beads for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol

Silaned glass beads are applied for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol (PADAP). Traces of cobalt are collected as the coloured PADAP complex on a column of the beads, and the complex is then eluted with a small volume of ethanol-hydrochloric acid mixture and the absorbance of the eluate is measured at 575 nm. The cobalt can easily be concentrated by a factor of 50-500 in this way, and 0.1-2 mug of cobalt in 100 ml of sample solution can be determined reproducibly. High concentrations of Fe(III), Cr(III), Pb, Zn, Cu(II), Mn(II), Cd, Al, Ca and Mg can be tolerated but Pd(II) interferes.     

Microwave-immobilized polybutadiene stationary phase for reversed-phase high-performance liquid chromatography

Polybutadiene (PBD) has been immobilized on high-performance liquid chromatography (HPLC) silica by microwave radiation at various power levels (52-663 W) and actuation times (3-60 min). Columns prepared from these reversed-phase HPLC materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (%C) and infrared spectroscopy. A microwave irradiation of 20 min at 663 W gives a layer of immobilized PBD that presented good performance. Longer irradiation times give thicker immobilized layers having less favorable chromatographic properties.     

Flame atomic absorption determination of manganese(II) in natural water after cloud point extraction

The possibility to use 4-(2-pyridylazo)resorcinol (PAR) and 1-(2-pyridylazo)-2-naphthol (PAN) for manganese(II) concentrating by the micellar extraction at cloud point (CP) temperature and subsequent atomic absorption spectrometry (AAS) determination was investigated. Under the optimum conditions, preconcentration of 100 ml of water sample in the presence of 1% non-ionic surfactant (NS) OP-7, 1×10⁻⁴ M 1-(2-pyridylazo)-2-naphthol permitted the detection 5 μg l⁻¹ manganese. The proposed method has been applied to the AAS determination of manganese in water samples after cloud point extraction.     

Inkjet-printed disposable metal complexing indicator-displacement assay for sulphide determination in water

A sulphide selective colorimetric metal complexing indicator-displacement assay has been developed using an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphthol printed by inkjetting on a nylon support. The change in colour measured from the image of the disposable membrane acquired by a digital camera using the H coordinate of the HSV colour space as the analytical parameter is able to sense sulphide in aqueous solution at pH 7.4 with a dynamic range up to 145 μM, a detection limit of 0.10 μM and a precision between 2 and 11%.     

Silica-based xerogels modified with cobalt(III): Determination of naphthols in solutions by solid-phase spectrophotometry

Silica-based xerogels modified with various concentrations of cobalt ions were prepared. The redox and complexing properties of immobilized cobalt ions were studied. Modified xerogels were used for determining naphthols in solutions by solid-phase spectrophotometry after their nitrosation. The effects of various factors on the absorbance of xerogels were studied. These factors are the average pore diameter in powdered xerogels, the concentration of cobalt(III), the pH of the test solution, and the concentration of CH₃COOH and NaNO₂ at the stage of nitrosation. The best conditions for determining naphthols were found. The developed procedure was used in the analysis of various samples.