Reactions of palladium(II) and rhodium(III) with pyridylazo-2-naphthol and dithizone on PANV–KU-2 and PANV–AV-17 fibrous materials

Reactions of palladium(II) and rhodium(III) with dithizone (DT) on polyacrylonitrile fiber filled with an AV-17 anion exchanger (PANV–AV-17) and 1-(2-pyridylazo)-2-naphthol (PAN) immobilized on polyacrylonitrile fiber filled with a KU-2 cation exchanger (PANV–KU-2–PAN) are studied by diffuse reflection spectroscopy. Conditions of rhodium complexation on PANV–KU-2–PAN (ascorbic acid concentration, pH of solution in adsorption, and the duration of heating samples) and palladium complexation with DT after adsorption from a 0.1 M NaCl solution (pH 2) on PANV–AV-17 in the dynamic mode are found. The limits of detection for rhodium and palladium are 10 and 5 ng/mL, respectively. At 640 nm, the calibration graphs are linear in the ranges of palladium and rhodium concentrations 0.008–0.06 µg/mL and 0.02–0.2 µg/mL, respectively. The mutual influence of rhodium and palladium is studied. It is shown that the determination of palladium with DT on a PANV–AV-17 solid phase is not affected by the presence of a 5-fold amount of rhodium, and rhodium can be determined on PANV–KU-2–PAN at 590 nm in the presence of 2-fold amounts of palladium.     

Complex formation of thiocyanate ions with iron(III) on the solid phase of fibrous ion exchangers

Characteristics of complex formation of SCN^–-ions with iron(III) on fibrous materials filled with an AV-17 anion exchanger (PANV–AV-17) and a KU-2 cation exchanger (PANV–KU-2) are studied by diffuse reflection spectroscopy. Sorption conditions of thiocyanate ions on PANV–AV-17 in the dynamic mode and the influence of concentrations of Cl^–, SO ₄ ^2- and NO ₃ ^- on the sorption and analytical signals of thiocyanate complexes are studied. Sorption conditions of iron(III) on PANV–KU-2 and the conditions of formation of thiocyanate complexes are studied. Systems for the sorption–spectroscopic determination of 0.1–0.7 μg/mL of SCN^–-ions in aqueous solutions of pH 5 ± 1 on PANV–AV-17 and test-determination of 5–30 μg of SCN^–-ions on PANV–KU-2 are proposed.     

Adsorption-luminescence determination of copper concentration using silica gel chemically modified with <Emphasis Type="Italic">N</Emphasis>-(1,3,4-thiadiazol-2-thiol)-<Emphasis Type="Italic">N</Emphasis>′-propylurea groups

Silica gel chemically modified with 1,3,4-thiadiazol-2-thiol groups recovered 99% of the copper(II) from solutions of pH 4–6; the adsorption equilibrium was attained in no more than 5 minutes. During irradiation with ultraviolet light, a yellow-orange luminescence (λ_max = 575 nm) of surface copper complexes appeared in the phase of adsorbent cooled to 77 K; it was used as an analytical signal in the procedure for the low-temperature adsorption-luminescence determination of copper concentration. The detection limit was 0.3 μ g/0.1 g adsorbent. The calibration graph was linear up to 50 μg/0.1 g adsorbent. The determination of copper concentration is not affected by 10000-fold amounts of Zn(II), Cd(II), Mn(II), Co(II), Ca(II), Mg(II), and Al(III) and 300-fold amounts of Fe(III). The procedure was used to determine copper concentration in natural and technogenic waters.     

Sequential determination of nickel(II) and zirconium(IV) with dimethylglyoxime and arsenazo III after adsoprtion on one substrate disc

The possibility of the sequential determination of nickel with dimethylglyoxime and zirconium with arsenazo III from a single aliquot portion using polyacrylonitrile fiber as a solid phase impregnated with a KU-2 cation exchanger is studied. Conditions for the simultaneous adsorption of nickel and zirconium in the dynamic mode from 0.01 M HNO₃ are found as along with the ones for their sequential determination on one disc. The calibration functions are linear in the range 5–50 ng/mL, the detection limits for both elements are 2 ng/mL. In their simultaneous presence, the determination of nickel and zirconium is not affected by 10-fold weight amounts of Fe(III), Cu(II), Co(II), Al, Mn(II), Pb, Zn, Cd, Cr(VI), Mo(VI), and V(V). A method is proposed for determining nickel and zirconium from a single aliquot portion on a single substrate disc at their ratios from 1: 1 to a 5-fold excess of each element.     

Color reactions of vanadium(V) with 8-hydroxyquinoline-5-sulfonic acid and ascorbic acid on PANV–AV-17 disks

The adsorption of vanadium(V) and 8-hydroxyquinoline-5-sulfonic acid (HQS) on polyacrylonitrile fiber disks filled with an AV-17 (PANV–AV-17) anion exchanger is studied by diffuse reflection spectroscopy. Vanadium(V) at pH 5?7 is adsorbed on PANV–AV-17; when a HQS solution is applied to the disk, a yellowish green complex compound formed, which changed color to almost black after the treatment of the disk with a HCl solution. The presence of sulfo groups in the HQS molecule ensures the preconcentration of the reagent on PANV–AV-17 disks with the registration of an analytical signal after the treatment of the disk with NaVO₃ and 0.1 M HCl solutions. A linear dependence of the analytical signal is observed in the HQS concentration range of 1?10 μg/mL. The presence of 20-fold amounts (by weight) of 8-hydroxyquinoline (HOQ) does not interfere with the determination. When ascorbic acid is applied to the disk with a vanadium(V)?HQS?HCl complex, the color changes from black to green. A test method for the determination of ascorbic acid is proposed. 8-Hydroxyquinoline can be determined by the intrinsic color of the adsorbate on PANV–KU-2 in the range of concentrations of HOQ solution in two drops 5?100 μg.     

Indirect determination of ampicillin sodium with sodium nitrate-ammonium thiocyanate-water system by extraction-flotation of cuprous thiocyanate

A novel method for indirect determination of ampicillin sodium by the extraction-flotation is proposed in this paper. It is indicated that the degradation of ampicillin sodium took place in the presence of 0.30 M sodium hydroxide in boiling water for 20 min. At pH 4.0, in the presence of ammonium thiocyanate, the thiol group of the degradation product of ampicillin sodium could reduce copper(II) to copper(I) due to the formation of the emulsion cuprous thiocyanate precipitation. By determining the residual amount of copper(II) in the solution and calculating the flotation yield of cuprous thiocyanate, the indirect determination of ampicillin sodium can be performed. When the concentration of cooper(II) was 5.0 μg/mL, a good linear relationship was obtained between the flotation yield of cuprous thiocyanate and the amount of ampicillin sodium in the range of 0.40～9.6 μg/mL. The linear equation is E = 4.1469 + 3.7949c with the correlation coefficient r = 0.9992, and the detection limit (3σ/K) of 0.37 μg/mL. Each parameter has been optimized and the reaction mechanism has been studied. The method has been successfully applied to the determination of ampicillin sodium in pharmaceutical, human plasma and urine samples. Analytical results obtained are satisfactory.     

Solid-phase extraction of antimony using chemically modified SiO2-PAN nanoparticles

A new analytical method using 1-(2-pyridylazo)-2-naphthol (PAN)-modified SiO2 nanoparticles as solid-phase extractant has been developed for the preconcentration of trace amounts of Sb(III) in different water samples. Conditions of the analysis such as preconcentration factor, effect of pH, sample volume, shaking time, elution conditions, and effects of interfering ions for the recovery of the analyte were investigated. The adsorption capacity of nanometer SiO2-PAN was found to be 186.25 micromol/g at optimum pH and the LOD (3sigma) was 0.60 microg/L. The extractant showed rapid kinetic sorption. The adsorption equilibrium of Sb(III) on nanometer SiO2-PAN was achieved in 10 min. Adsorbed Sb(III) was easily eluted with 4 mL 2 M hydrochloric acid. The maximum preconcentration factor was 62.20. The method was applied for the determination of trace amounts of Sb(III) in various water samples (tap, mineral water, and industrial effluents).     

Sorption-spectroscopy determination of zirconium on a PANV-KU-2 fibrous ion exchanger using Arsenazo III

The sorption and complexation of zirconium with Arsenazo III have been studied on a polyacry-lonitrile fibrous material filled with strongly acidic KU-2 cation exchanger in strongly acidic media. The optimal conditions have been chosen for the sorption-spectrophotometric and test determination of zirconium by diffuse reflection spectroscopy or visual testing. The limit of zirconium detection is 0.02 ??g/mL. The procedure was tested in the analysis of model solutions of ammonium molybdate and vanadate and copper chloride using the standard addition method.     

Electrothermal Atomic Absorption Spectrometric Determination of Cobalt,Copper and Nickel in Fresh Water After Their Preconcentration by Precipitate Flotation

Abstract

A method is developed for simultaneous separation and determination of μg/L levels of Co(II), Cu(II) and Ni(II) in fresh water by precipitate flotation. The optimal conditions of the experimental procedure with hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate as collectors were investigated. The pH interval of the working medium, within which Co(II), Cu(II) and Ni(II) can be successfully separated, was determined from the aspect of collectors and surfactant stability. The amounts of the elements investigated were determined by electrothermal atomic absorption spectrometry. The detection limit of the method is 0.15 μg/L for cobalt, 0.03 μg/L for copper and 0.79 μg/L for nickel.     

Synthesis of rhodanine-bonded silica gel and its application in the preconcentration and separation of noble metals

A silica gel based sorbent containing rhodanine as functional group (RDSG) was prepared. Its adsorption and separation characteristics for Ag(I), Au(III) and Pd(II) were studied by flow-injection (FI) on-line preconcentration. Influence of different experimental parameters such as acidity, eluent, co-existing ions were investigated. Trace amounts of Ag, Au and Pd could be efficiently adsorbed by rhodanine-bonded silica gel from acidic solution and eluted with thiourea solution. Common co-existing ions exhibited virtually no interference to the preconcentration and determination. The adsorption capacity of RDSG was 0.0352, 0.107 and 0.122 mmol/g for Ag, Au and Pd, respectively. Detection limits of 0.004, 0.022 and 0.019 μg/mL for Ag, Au and Pd, respectively, were achieved with a sampling time of 60 s at a flow rate of 5.0 mL/min. The relative standard deviation were 0.5%, 0.9% and 1.7% for 0.040 μg/mL Ag, 0.200 μg/mL Au and 0.300 μg/¶mL Pd. The sorption property did not change after 1000 cycles of sorption-desorption. The contents of Ag and Au in three national certified ore samples and Pd in a secondary nickel alloy, an anode slime and a CoCl₂ electrolytic solution were determined. The results showed good agreement with the certified values.     

Determination of thiosulfate ions by the complexation of lead thiosulfate with 4-(2-pyridylazo)-resorcinol on the PANF-AV-17 solid phase

A procedure was developed for determining thiosulfate ions; the procedure involved their adsorption as a complex with lead ions at pH 4 on disks of polyacrylonitrile fiber filled with an AB-17 anion exchanger and determination by the reaction with 4-(2-pyridylazo)-resorcinol at pH 10. The analytical range was (0.2–0.8) × 10^?4; the detection limit was 2 μg/mL. The determination did not interfere with metal cations at the level of the maximum permissible concentrations for potable water, as well as 2–15-fold amounts of sulfites, sulfides, and iodides; 100–200-fold amounts of sulfates, pyrosulfates, and bromides; and 1000-fold amounts of chlorides. The developed procedure was used in the analysis of tap water by the “added-found” method (RSD < 20%).     

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.     

Selective spectrophotometric determination of uranium

Uranium(VI) (10–100 μg) is extracted with 2% dibenzoylmethane in benzene at pH 6–7 while other cations are masked with CDTA (maximum of 8 μg/100 ml). Shaking with 6 M hydrochloric acid reintroduces uranium(VI) into the aqueous phase, where after evaporation and complexation with Arsenazo III in 0.02 M hydrochloric acid the final measurement of absorbance at 650 nm is performed. Iron(III), copper(II), aluminum, and zinc do not interfere even if present in amounts of 15–19 mmol.     

Separation and determination of trace amounts of aluminium(III), vanadium(V), iron(III), copper(II) and nickel(II) with CALKS and PAR by RP-HPLC.

An RP-HPLC method for the separation and determination of aluminium(III), vanadium(V), iron(III), copper(II) and nickel(II) with CALKS (Chromazol KS) and PAR ([4-(2-pyridylazo)resorcinol]) chelating on a YWG-ODS column was developed. A mixture of methanol-tetrahydrofuran(THF)-water (60:5:35 v/v) containing 0.2 mol/L LiCl, 5 x 10(-5) mol/L CALKS, 5 x 10(-5) mol/L PAR and acetate buffer solution (pH 4.9) was selected as mobile phase. The method has high sensitivity, with the detection limits being 6 ng/mL for aluminium(III), 3.5 ng/mL for vanadium(V), 10.4 ng/mL for iron(III), 6.3 ng/mL for copper(II) and 8.7 ng/mL for nickel(II). It also has good selectivity, so that most foreign metal ions do not interfere under the optimum conditions. The method can be applied to the simultaneous determination of trace amounts of aluminium, vanadium, iron, copper and nickel in rice and flour samples.     

Sorption and complexation of uranium(VI) and thorium(IV) with reagents Arsenazo III and Arsenazo M on fibrous filled sorbents

The possibility of the highly sensitive sorption-spectrometric determination of Th(IV) and U(VI) in the presence of each other on the solid phase of fibrous anion-exchange materials with Arsenazo M and Arsenazo III was examined. Polyacrylonitrile fiber filled with an exchanger AN-31, ANKB-50, or EDE-10p was used as the solid phase. It was demonstrated that the studied systems allow the selective determination of thorium in the presence of one-to twofold amounts of uranium. On PANV-EDE-10p with immobilized Arsenazo III, the detection limit of thorium in 2–10 M HCl is 0.002 μg/mL, and in 10 M HCl the presence of up to twofold amounts of uranium is permissible. A high sensitivity of the determination of uranium in 2–7 M HCl of 0.005 μg/mL, which has not been reported before, was attained. The time of the analysis of five or six samples is no longer than 20 min.     

A simple potentiometric method for the determination of reducing substances in urine with a copper-selective electrode

A potentiometric method for the determination of reducing substances in urine is described. Samples are treated with Stanley—Benedict reagent and the unused copper(II) is determined with a copper(II)-selective electrode by the standard addition technique. Glucose in the range 25–200 μg in 0.1ml samples can be determined with an average error of about 2%. The recovery of added glucose for six samples was 96–107% (average 100.5%). Comparison with the conventional titrimetric method shows good agreement. The effect of other non-glucose reducing substances present in urine is reported.     

2‐Aminocyclopentene‐1‐Dithiocarboxylic Acid‐Naphthalene Adsorbent for the Preconcentration and Determination of a Trace Copper in Real Samples by Spectrophotometric Method

A solid uncharged complex produced from 2‐aminocyclopentene‐1‐dithiocarboxylic acid (synthetic reagent) on naphthalene provides a very sensitive, selective and economical method for the preconcentration and determination of trace amounts of copper in drug and alloy samples. The 2‐aminocyclopentene‐1‐dithiocarboxylate of copper is retained quantitatively on microcrystalline naphthalene in the pH range 2.8–3.3. After filtration the solid mass consisting of copper complex‐naphthalene is dissolved with 4 mL of dimethylformamide (DMF). The absorbance is measured at 462 nm with a spectrophotometer against the reagent blank and molar absorptivity found to be 2.8 × 10⁵ liter mol^?1 cm^?1. Beer's law is obeyed over the concentration range of 0.1–16.0 μg of copper in 4 mL of the dimethylformamide solution. Detection limit is 3 ng mL^?1 [signal to noise ratio = 2]. Ten replicate determinations on a sample containing 1 μg of copper gave a relative standard deviation of 0.76%. The interference of a large number of anions and cations have been studied and the optimized conditions developed were utilized for determination of copper in various real samples.     

Sorption-spectrometric determination of thorium(IV) and uranium(VI) with the reagent Arsenazo III on the solid phase of a fibrous material filled with a cation exchanger

The possibility of the use of organic reagents of the Arsenazo III group for the sorption-spectrometric determination of elements on fibrous cation-exchange materials was examined. The conditions of the sorption of Arsenazo III with the use of diphenylguanidinium chloride on the strongly acidic fibrous cation exchanger PANV-KU-2 were found. Procedures for the determination on the solid phase were developed for thorium in 7 M HNO₃ in the presence of 30-fold amounts of uranium with the detection limit of thorium of 0.005 μg/mL and for uranium in 0.05 M HCl in the presence of fivefold amounts of thorium with a detection limit of uranium of 0.05 μg/mL. The conditions were found for the selective preconcentration of thorium and uranium in the presence of each other, and a procedure was developed for their separate sorption-spectrometric determination.     

SPE coupled with dispersive liquid–liquid microextraction followed by GC with flame ionization detection for the determination of ultra‐trace amounts of benzodiazepines

SPE combined with dispersive liquid–liquid microextration was used for the extraction of ultra‐trace amounts of benzodiazepines (BZPs) including, diazepam, midazolam, and alprazolam, from ultra‐pure water, tap water, fruit juices, and urine samples. The analytes were adsorbed from large volume samples (60 mL) onto octadecyl silica SPE columns. After the elution of the desired compounds from sorbents with 2.0 mL acetone, 0.5 mL of eluent containing 40.0 μL chloroform was injected rapidly into 4.5 mL pure water. After extraction and centrifugation, 2 μL of the sedimented phase was injected into a GC equipped with a flame ionization detector. Several parameters affecting this process were investigated and optimized. Under the optimal conditions, LODs ranged from 0.02 to 0.05 μg/L, a linear dynamic range of 0.1–100 μg/L and relative SDs in the range of 4.4–10.7% were attained. Very high preconcentration factors ranging from 3895–7222 were achieved. The applicability of the method for the extraction of BZPs from different types of complicated matrices, such as tap water, fruit juices, and urine samples, was studied. The obtained results reveal that the proposed method is a good technique for the extraction and determination of BZPs in complex matrices.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food.