Chromaticity characteristics of binary and ternary molybdenum(vi) complexes with o,o’-Dihydroxyazo and heterocyclic azo compounds

The chromaticity characteristics of molybdenum(VI) complexes with o.o’-dihydroxyazo compounds (Lyumogallion IREA and Magnezon IREA) and heterocyclic azo compounds [4-(2-pyridylazo)resorcinol and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol] were studied in the presence and in the absence of the third component, hydroxylamine. It was demonstrated that chromaticity characteristics can be used for analyzing samples with low molybdenum concentrations. The calibration graph equations for the color characteristics of complexes both in solution and in the immobilized exhibit sensitivity coefficients more than an order of magnitude higher than for absorbance and the Kubelka-Munk function     

Azo compounds as reagents for the voltammetric determination of molybdenum(VI)

Linear sweep voltammograms of Lumogallion IREA (pH 2), Magneson IREA (pH 2), 4-(2-pyridylazo)resorcinol (pH 4.8), and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (pH 4.8) in the presence of molybdenum(VI) exhibit peaks at potentials more negative than the potentials of reduction peaks of the reagents by approximately 0.1 V. In all of the above cases, the heights of these peaks linearly increased with an increase in the concentration of molybdenum(VI) in the range from 5 x 10^-7 to 2.5 x 10^-6 M; thus, these peaks can be used for the determination of molybdenum. The simultaneous proportional decrease in the heights of the cathodic peaks of the reagents can be used for indirect determination of molybdenum(VI). The limits of detection without preliminary accumulation at a dropping mercury electrode with a drop time of 5 s are (1.5-3.9) x 10^-7 M, depending on the nature of the reagent and the technique used for determining the concentration.     

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.     

Complexation of aluminium, yttrium, lanthanum and lanthanides with 4-(2-pyridylazo)resorcinol (par)

The sensitive reactions between 4-(2-pyridylazo)resorcinol (PAR) and yttrium, lanthanum and the lanthanides can be used for the spectrophotometric determination of these elements. The method has no advantage over other methods for the determination of aluminium and lanthanum. Only M(PAR)H and M(PAR) complexes are formed in solutions where the molarity of the metal ion is greater than or nearly equal to the molarity of the ligand at pH < 7-5. If there is molar excess of PAR, 1:2 complexes may be formed but this is certain only for the yttrium-PAR system. Errors in analysis may result from the simultaneous occurrence of optically different complexes; close control of pH and reagent concentration is essential. Optical and equilibrium data are given for the systems investigated.     

Color Reactions of Niobium and Tantalum with Bromine-Substituted Reagents of the PAR–PAN Group

Color reactions of niobium and tantalum with some heterocyclic azo reagents of the PAR–PAN group (2-(2-pyridylazo)-5-aminophenol, 2-(3,5-dibromo-2-pyridylazo)-5-aminophenol, and 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol) were studied. Quantitative characteristics of the reactions were determined, and conditions were found for the determination of small and large amounts of niobium and tantalum in the presence of each other using the 3,5-dibromo-PADAP reagent.     

The speciation of trace amounts of organometallics in marine organisms by gel-permeation high-pressure liquid chromatography with PAR derivatization

A high-pressure liquid chromatograph equipped with an off-column calorimetric reactor was used for the determination of metallorganic compounds such as metallothioneins. The stainless-steel gel-permeation column used was first tested with ultraviolet detection of a standard protein mixture. The metallothioneins were determined by absorbance measurements at 520 nm after an off-column reaction of the metal-containing eluates with a buffered 4-(2-pyridylazo)resorcinol (PAR) solution. The eluates were also tested by flame and electrothermal atomic-absorption spectrometry; a correlation between AAS and ICP results and the peak areas of the calorimetric detection was also made. A zinc-inhibiting reagent was also added to the PAR solution in order to find the calorimetric error due to the presence of other metals such as copper or cadmium.     

Complexation of Lanthanum(III) and Terbium(III) with 5-Br-PAAP in the Presence of Surfactants

The complexation of lanthanum(III) and terbium(III) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PAAP) in the presence of surfactants was studied by spectrophotometry. Optimal conditions of interaction and chemical and analytical characteristics of the resulting complexes were determined. Molar absorptivities are 7.8 × 10⁴ (La) and 8.7 × 10⁴ (Tb). The effect of the ionic strength of the solution and concentration of the organic solvent on the conditions of complexation in the presence of surfactants was considered. Correlation equations relating all chromaticity characteristics to the concentration of lanthanum, terbium, and erbium in the range 5–25 g per 25 mL were deduced. It was demonstrated tat the use of the most sensitive chromaticity functions (yellowness, chromaticity coordinates, color saturation, etc.) increases the sensitivity of the determination by a factor of 25–100 in comparison with the photometric method.     

Improved spectrophotometric determination of osmium(VIII) with 4-(2-pyridylazo) resorcinol in mixed surfactants

The colour development between 4-(2-pyridylazo)-resorcinol(PAR) and osmium(VIII) in the presence of cationic and nonionic surfactants in a weakly acidic medium was more stable and reproducible than in the absence of surfactant (PAR-alone method). An improved spectrophotometric determination of osmium(VIII) with PAR was investigated in the presence of mixed surfactants of N-hexadecyltrimethylammonium chloride (HTAC) and Brij 58 [poly(oxyethylene)lauryl ether] as cationic and nonionic surfactants at pH 6.0-7.2. The calibration graph was linear in the range 0-110 microg/10 ml osmium(VIII), and the apparent molar absorptivity was 2.4 x 10(4) l.mole(-1).cm(-1) with a Sandell sensitivity of 0.0079 microg/cm(2) osmium(VIII).     

RP-HPLC study of redox equilibria in vanadium-PAR binary and ternary systems: Direct determination of vanadium in steel

The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C₁₈ column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H₂O₂-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH₂OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH₂OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel.     

The reaction of uranyl ions with 4-(2-pyridylazo)resorcinol

The uranyl ion and 4-(2-pyridylazo)resorcinol (PAR) form only 1:1 chelates in solutions of pH < 8.5, UO(2),(PAR)H(+) being formed at pH > 3 and UO(2),(PAR) at pH > 5.5. Equilibrium constants and spectrophotometric data for both chelates are given. Solid, non-stoichiometric crystalline species in which the mole ratio of PAR to uranium is more than 1:1 are precipitated up to pH 6. The medium of 0.1-0.2M triethanolamine at pH 8 recommended by other workers proved satisfactory for the sensitive spectrophotometric determination of uranium, as did pH 3.6 in the presence of < 0.1M formate or 20-30% v/v dimethylformamide.     

Determination of Serum Iron and Iron Binding Capacity Using 4-(2-Pyridylazo) Resorcinol (Par)

Abstract

Procedures are described for the determination of serum iron and iron binding capacity using the chromogenic reagent 4-(2-pyridylazo) resorcinol (PAR). The high molar absorptivity of the iron (II) PAR complex makes possible an approximate two fold increase in sensitivity over previous methods. The described procedures have few interferences, and give linear results for samples containing 0 – 750 μg/dl of iron.     

Anionic Lead Complexes on the Solid Phase of Fibrous Filled Materials in the Reaction with 4(2-Pyridylazo)resorcinol

The influence of the nature of anions (iodide, bromide, thiosulfate, pyrophosphate, tartrate, and acetate) in the anionic lead complex adsorbed on a solid phase of a fibrous sorbent filled with the AV-17 anion exchanger on the color reaction between lead and 4-(2-pyridylazo)resorcinol (PAR) was studied by diffuse reflectance spectrometry. The influence of anions on the complexation of lead with PAR on the solid phase was discussed for different types of the color reaction. It was demonstrated that the reactions with iodide at pH 5–10 and with thiosulfate at pH 10 are significant in the determination of lead as three-component complexes on the support. In the presence of other anions, lead ions do not react with PAR on the AV-17 solid phase.     

5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl}-3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl<Emphasis Type="Italic">o</Emphasis>-benzoquinone and related polymers. Synthesis and some properties

A norbornene-containing ortho-quinone, 5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl)-3,6-ditert-butyl-o-benzoquinone, was synthesized by the nucleophilic addition of 5-(hydroxymethyl)bicyclo[2.2.1] hept-2-ene to 3,6-di-tert-butyl-o-benzoquinone. The structure of the compound was established by the X-ray analysis. The monomer obtained undergoes metathesis polymerization in the presence of Grubbs catalyst of the third generation with the formation of polynorbornene containing quinone fragments in the side chains.     

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.     

Determination of trace vanadium in sea cucumbers by ultrasound-assisted cloud point extraction and graphite furnace atomic absorption spectrometry

An ultrasound-assisted cloud point extraction (CPE) procedure was used for preconcentration and determination of vanadium by graphite furnace atomic absorption spectrometry. The vanadyl(IV) complex with ascorbic acid form a hydrophobic complex with 4-(2-pyridylazo) resorcinol (PAR) in a micelle medium, which is stable under our working conditions, and followed by its extraction into Triton X-100 surfactant-rich phase. The main factors affecting CPE efficiency, such as pH, concentrations of PAR, ascorbic acid and Triton X-100, incubation temperature, frequency and equilibration time of ultrasonic bath were investigated in detail. Under the optimum conditions, preconcentration of 10 mL sample gave a preconcentration factor of 36.4 and a detection limit of 4.0 µg kg^?1. The proposed method was successfully applied to determination of vanadium in sea cucumbers with satisfactory results.     

Sensitive determination of glyoxal, methylglyoxal and hydroxyacetaldehyde in environmental water samples by using dansylacetamidooxyamine derivatization and liquid chromatography/fluorescence

In this study we improved the dansylacetamidooxyamine (DNSAOA)-LC-fluorescence method for the determination of aqueous-phase glyoxal (GL), methylglyoxal (MG) and hydroxyacetaldehyde (HA). As derivatization of dicarbonyls can potentially lead to complex mixtures, a thorough study of the reaction patterns of GL and MG with DNSAOA was carried out. Derivatization of GL and MG was shown to follow the kinetics of successive reactions, yielding predominantly doubly derivatized compounds. We verified that the bis-DNSAOA structure of these adducts exerted only minor influence on their fluorescence properties. Contrary to observations made with formaldehyde, derivatization of GL, MG and, to a lesser extent of HA, was shown to be faster in acidic (H(2)SO(4)) medium with a maximum of efficiency for acid concentrations of ca. 2.5 mM. Concomitant separation of GL, MG, HA and of single carbonyls was achieved within 20 min by using C(18) chromatography and a gradient of CH(3)CN in water. Detection limits of 0.27, 0.17 and 0.12 nM were determined for GL, MG and HA, respectively. Consequently, low sample volumes are sufficient and, unlike numerous published methods, neither preconcentration nor large injection volumes are necessary to monitor trace-level samples. The method shows relative measurement uncertainties better than ±15% at the 95% level of confidence and good dynamic ranges (R(2)>0.99) from 0.01 to 1.5 μM for all carbonyls. GL, MG and HA were identified for the first time in polar snow samples, but also in saline frost flowers for which unexpected levels of 0.1-0.6 μM were measured. Concentrations in the 0.02-2.3 μM range were also measured in cloud water. In most samples, a predominance of HA over GL and MG was observed.     

Covalent Attachment of Some Phenol Derivatives to the Silica Surface by Use of Single-stage Aminomethylation

The reaction conditions and component ratios were established for the attachment of 4-(2-pyridylazo)resorcinol (PAR), 1-(2-pyridylazo)-2-naphthol (PAN) and 8-hydroxyquinoline (8-HQ) to the silica surface by means of a single-stage Mannich reaction. The modified sorbents that were synthesized were characterized by an adsorption method, and DRIFT and UV spectroscopies. The concentrations of PAR, PAN and 8-HQ grafted to the silica surface that were attained were 2.8×10⁻⁵, 8.5×10⁻⁵ and 2.7×10⁻⁴ mol g⁻¹, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

The preparation of 2H-1,2,3-benzothiadiazine-1,1-dioxides, 11H-11a-dihydrobenzimidazo[1,2-b] [1,2] benzisothiazole-5,5-dioxides, 6H-dibenzo[c,g] [1,2,5] thiadiazocine-5,5-dioxides and 5H-Dibenzo[c,g] [1,2,6] thiadiazocine-6,6-dioxides

o-Benzoylbenzenesulfonyl chlorides (I) were prepared conveniently from aminobenzophenones by diazotization followed by reaction with sulphur dioxide in the presence of Cu⁺, according to the general method of Meerwein. Reaction of the sulfonyl chlorides with hydrazine led to 4-phenyl-2H-1,2,3-benzothiadiazine-1,1-dioxides (II). The latter compounds could be methylated and acetylated readily in the 2-position. The 2-methyl derivative (III) could be prepared also by reaction of the sulfonyl chloride (Ia) with methylhydrazine. Catalytic hydrogenation of 6-chloro-4-phenyl-2H-1,2,3-benzothiadiazine-1,1-dioxide (IIa) gave the 3,4-dihydro derivative (V). Reaction of the sulfonyl chlorides (I) with o-phenylenediamine followed by cyclodehydration led to 11H-11,11a-dihydrobenzimidazo[1,2-b] [1,2]benzisothiazole-5,5-dioxides (VII). One of the latter compounds (VIIa) in sodium hydroxide solution in the presence of methyl iodide or benzyl chloride was transformed into 6-methyl- and 6-benzyl-5H-dibenzo[c,g] [1,2,6]thiadiazocine-5,5-dioxides (VIII), respectively. 5H-Dibenzo[c,g] [1,2,6] thiadiazocine-6,6-dioxides (XIV) were prepared also by cyclodehydration of 2-amino-2′-benzoylbenzenesulfonanilides (XIII).     

Heterocycles from Pyrazoloylhydroximoyl Chloride: Synthesis of Certain Quinoxaline,Benzothiadiazine, Benzoxadiazine,Quinazolinone, Imidazo[1,2-a]pyridine,Imidazo[1,2-a]pyrimidine,Isoxazole, Pyrazolo[3,4-d]pyridazine and Pyrrolidino[3,4-d]isoxazolin-4,6-dione Derivatives

3-Ethoxycarbonyl-5-methyl-1-(4-methylphenyl)-4-pyrazoloylhydroximoyl chloride (1) reacted with o-phenylenediamine, o-aminothiophenol, o-aminophenol and methyl anthranilate to afford 3-nitrosoquinoxaline, benzothiadiazine, benzoxadiazine, and 3-hydroxyquinazoline, respectively. Imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine and isoxazole derivatives were obtained via the reaction of 1 with 2-aminopyridine, 2-aminopyrimidine and the appropriate active methylene compounds, respectively. Pyrazolo[3,4-d]pyridazines, and pyrrolidino[3,4-d]isoxazolines derivatives were also synthesized. The structures of the newly synthesized compounds were established on the basis of spectral data and alternate synthesis whenever possible.     

Spectrophotometric determination of calcium with a flow injection system

The indirect spectrophotometric determination of 0.8–7.2 ppm calcium in the presence of magnesium, phosphate and sulphate by flow injection analysis (f.i.a.) is described. The method is based on the exchange reaction between the calcium and the zinc complex of ethylene glycol-bis(2-aminoethylether)tetraacetic acid (EGTA) in the presence of 4-(2-pyridylazo)resorcinol (PAR): Ca + Zn(EGTA) + 2 PAR ? Zn(PAR)₂ + Ca(EGTA). A home-made and a commercial flow injection system with a sampling rate of 80 h^?1, are compared. Results for water samples are in good agreement with those obtained by atomic absorption spectrometry.