Kiril Blazhev Gavazov

• PhD
• Professor (Full) at Medical University Plovdiv

A chromogenic solvent extraction system for Fe(III) based on 4-nitrocatechol (4NC) and xylometazoline hydrochloride (XMH) was investigated. The optimum conditions for extraction spectrophotometric determination of iron were found. Under these conditions, the formula of the extracted complex was (XMH⁺)3[Fe(4NC)3] and the apparent molar absorption co...

A novel chromogenic system for the liquid-liquid extraction and determination of trace amounts of tungsten(VI) was investigated. The system comprises 4-nitrocatechol (4NC) as a chromogenic reagent, sulfuric acid as a complexing medium, and benzalkonium chloride (BAC) as a source of bulky cations (BA+), which readily form chloroform-extractable ion-...

The hydrophobic reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) was investigated as part of a cloud-point extraction (CPE) system for the spectrophotometric determination of Zn(II). In the system, complexes with different stoichiometries, including 1:1 and 2:2 (Zn:HTAR), are formed. Their ground-state equilibrium geometries were optimized at th...

The hydrophobic reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) was investigated as part of a cloud point extraction (CPE) system for the spectrophotometric determination of Zn(II). In the system, complexes with different stoichiometries, including 1:1 and 2:2 (Zn:HTAR), are formed. Their ground-state equilibrium geometries were optimized at th...

Zeolites of natural origin are materials exhibiting many positive effects on the human body. Silver-modified zeolites have already been introduced as bactericidal agents, although studies dealing with their toxicity are insufficient. This work describes the synthesis of activated and silver-loaded Bulgarian zeolite using a simple wet impregnation m...

Most chemistry textbooks claim that oxygen was discovered almost simultaneously by Carl Scheele and Joseph Priestley about 250 years ago. Priestley obtained oxygen by heating mercuric oxide (1774), and Scheele -by heating NaNO 3 , as well as by dissolving pyrolusite in sulfuric acid (1772). The name “oxygen” was given a few years later (1779) by An...

Two new vanadium (V) complexes involving 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) and tetrazolium cation were studied. The following commercially available tetrazolium salts were used as the cation source: tetrazolium red (2,3,5-triphenyltetrazol-2-ium;chloride, TTC) and neotetrazolium chloride (2-[4-[4-(3,5-diphenyltetrazol-2-ium-2-yl)phenyl]ph...

Four azo dyes known to form anionic complexes with V(V) were investigated as potential liquid–liquid extraction–spectrophotometric reagents for the antihistamine medication hydroxyzine hydrochloride (HZH). A stable ion-association complex suitable for analytical purposes was obtained with 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). The molar absor...

The hydrophobic azo dye 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied as part of a system for the centrifuge-less cloud point extraction (CL-CPE) and spectrophotometric determination of traces of cobalt. The extracted 1:2 (Co:HTAR) complex, [CoIII(HL⁻)(L²⁻)]⁰, shows an absorption maximum at 553 nm and contains HTAR in two different a...

A new liquid—liquid extraction system for molybdenum(VI) was studied. It contains 4-nitrocatechol (4NC) as a complexing chromogenic reagent and benzalkonium chloride (BZC) as a source of heavy cations (BZ⁺), which are prone to form chloroform-extractable ion-association complexes. The optimum conditions for the determination of trace molybdenum(VI)...

A simple, cheap, and environmentally friendly centrifuge-less cloud point extraction procedure was developed for the preconcentration of traces of Cu(II) before its spectrophotometric determination. It is based on a complexation reaction with the hydrophobic azo reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR), in which a complex with a stoichio...

A simple, low-cost, and green cloud point extraction (CPE) procedure was developed for the preconcentration of traces of vanadium as a preliminary step for its spectrophotometric determination. Vanadium(V) was complexed with H2O2 and a novel commercially available reagent, 6-hexyl-4-(2-thiazolylazo)-resorcinol (HTAR), which was preliminary investig...

The interaction between CoII and 5-methyl-4-(2-thiazolylazo)-resorcinol (MTAR) was studied in a water-chloroform system, in the presence or absence of benzalkonium chloride (BZC) as a cationic ion-association reagent. The optimum pH, concentration of the reagents and extraction time for the extraction of Co were found. In the presence of BZC, the e...

A water-isobutanol extraction-chromogenic system for NiII, based on the azo dye 5-methyl-4-(2-thiazolylazo)resorcinol (MTAR; H2L) and the ionic liquid Aliquat 336 (A336), was studied. Under the optimal conditions (cMTAR = 2.0 × 10–4 mol dm–3, cA336 = 5.6 × 10–3 mol dm–3, pH 8.5 and extraction time t = 1 min), NiII is extracted as a ternary complex...

Complex formation between Ga(III) and 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied in a water-chloroform medium, in the presence or absence of xylometazoline hydrochloride (XMH). Optimum conditions for the extraction of Ga(III) were found. In the presence of XMH, the extracted ion-associate has the formula (XMH⁺)[GaIIIL2], where HTA...

Liquid-liquid extraction-chromogenic systems for vanadium(V) based on xylometazoline hydrochloride (XMZ) and azo derivatives of resorcinol (ADRs) were studied. The following ADRs were used: 4-(2-thiazolylazo)resorcinol (TAR), 5-methyl-4-(2-thiazolylazo)resorcinol (MTAR), and 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). Concentration of the reagents...

A cloud point extraction-chromogenic system for vanadium determination containing 4-(2-thiazolylazo)resorcinol (TAR), H2O2, H2SO4, and Triton X-100 was investigated. Optimal conditions for the formation and extraction of a 1:2:1 (VV:O2²⁻:TAR) ternary complex with an absorption maximum at 569 nm were found: concentration of TAR (4 × 10⁻⁵ mol dm⁻³),...

In the presence of semicarbazide hydrochloride (SCH) and traces of AgI, the tetrazolium salt 2,5-diphenyl-3-(1-naphmyl)-2H-tetrazolium chloride (Tetrazolium violet, TV) is reduced in alkaline medium to intensely colored chloroform-extractable 3,5-diphenyl-1-(1-naphthyl)formazan (Tetrazolium violet formazan, TVF). The following experimental paramete...

The azo dye 4-(2-thiazolylazo)orcinol (TAO) and the cationic ion-pair reagent 2,3,5-triphenyl-2 H -tetrazolium chloride (TTC) were examined as constituents of a water-chloroform extraction-chromogenic system for vanadium(IV). The effects of TAO concentration, TTC concentration, pH and extraction time were examined. Under the optimum conditions the...

Miniaturized extraction techniques are well established in analytical protocols following the guidelines of green chemistry. In spite of this, analytical chemistry researchers continue to look for alternatives and modifications that minimize or solve problems associated with the application of microextraction techniques. This manuscript goes over t...

The current short review is devoted to cloud point extraction (CPE). It provides information about history, present status and future trends in the development of this method. After a brief overview of the review papers on CPE, the attention is focused on applications of nanoparticles (NPs) in CPE procedures. Two main directions are discussed: (i)...

The quaternary ammonium salt Aliquat 336 (A336; R 4 N ⁺ Cl ⁻ ) and the azo dye 4-(2-thiazolylazo)orcinol (ТАО) were examined as constituents of a water-isobutanol extraction-chromogenic system for vanadium(V). Under the optimum conditions (c TAO = 1.6×10 –3 mol dm –3 , c A336 = 1.3×10 –2 mol dm –3 and pH 5.0), vanadium(V) is extracted as a ternary...

A cloud point extraction-chromogenic system, containing Cu II , 1-(2-thiazolylazo)-2-naphthol (TAN), and Triton X-100 (TX) was investigated. The optimum conditions for Cu II extraction and spectrophotometric determination were found: absorption maximum (565 nm), concentration of TAN (4  10-5 M), mass fraction of TX (2.5%), pH (6.0), and incubation...

Liquid-liquid extraction systems for VIV/V containing 2,3-dihydroxynaphtahlene (DN) and 3-(4,5-dimethylthi-azol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (thiazolyl blue, MTT) were studied. The optimum conditions for VIV and VV extraction were found. VIV is extracted in chloroform as a 1:2:2 complex (V:DN:MTT) with λmax = 570 nm and ε570 = 2.9 × 10...

A cloud-point extraction-chromogenic system containing vanadium(V), 1-(2-thiazolylazo)-2-naphthol (TAN), H2O2 and Triton X-100 was investigated. The optimum conditions for vanadium extraction and spectrophotometric determination were found to be: concentrations of TAN and H2O2 (5 × 10− 5 and 3.0 × 10− 4 mol L− 1, respectively), mass fraction of Tri...

For the first time an optical probe is proposed as the microdrop holder and simultaneously the measuring cell in a direct immersion single-drop microextraction (DI-SDME) procedure. This approach enables the analytical signal (absorbance of organic phase) to be monitored and recorded online during the extraction process. Based on the suggested appro...

A novel, sensitive and selective method for the spectrophotometric determination of the basic inorganic iodine species was developed based on the vortex-assisted liquid–liquid microextraction (VALLME) of an ion pair formed between colorless tetrabutylammonium cation (TBA) and triiodide anion (I3⁻). Molecular iodine was determined spectrophotometric...

Optimum conditions for flotation-spectrophotometric determination of iron with 4-(2-pyridylazo)resorcinol (PAR) based on a 1:2 Fe II-PAR complex were found to be as follows: flotation solvent (chloroform), shaking time (2 min), pH (4.50.5), concentration of PAR (2.0×10 –4 mol L –1), reducing agent (hydroxylamine hydrochloride), solvent for the flo...

A liquid-liquid extraction-chromogenic system for vanadium(IV, V) containing 2,3-dihydroxynaphtahlene (DN), 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), water and chloroform was studied in detail. When the vanadium is in the oxidation state of IV, the extracted species are aggregates containing three 1:2:1 (V:DN:TTC) ion-pair units composed of tr...

The complex formation in the vanadium(V) / 4-(2-thiazolylazo)orcinol (TAO) / 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) liquid-liquid extraction-chromogenic system was studied. The chloroform-extracted complex has a composition of 2:2:2 under the optimum conditions (pH 4.8-5.2, extraction time 3 min, concentration of TAO 3.4 × 10-4 mol dm-3, and...

A liquid-liquid extraction-chromogenic system containing Fe(III), 4-(2-thiazolylazo)resorcinol (TAR), [3,3’-(3,3’-dimetoxy-4,4’-biphenylene)bis[2,5-di(4-nitrophenyl)-2H-tetrazolium] chloride (tetranitro-tetrazolium blue chloride, TNBT), water, and chloroform was studied and compared with similar systems containing such ditetrazolium salts (DTS), as...

The complex formation and solvent extraction were studied in a system containing iron(II), 4- nitrocatechol (4NC), 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), water, and chloroform. Under the optimum conditions, the extracted complex has a composition of 1: 1: 2 (Fe-4NC-TTC) and could be represented with the formula (TT+)2[FeII(4NC2-)(OH)2]. The...

Liquid-liquid extraction systems containing FeIII, 4-(2-thiazolylazo)resorcinol (TAR), and a ditetrazolium salt (DTS: Neotetrazolium chlortide, Blue Tetrazolium chloride, or Nitro Blue Tetrazolium chloride), water and chloroform were investigated. The optimum conditions for iron extraction, some equilibrium constants (association constants, distrib...

Complex formation and liquid-liquid extraction were studied in systems containing iron(III), 4-nitrocatechol (4NC),tetrazolium salt (TZS), water and organic solvent. Three different TZS were used: 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 3-(2-naphtyl)-2,5- diphenyl-2H-tetrazolium chloride (Tetrazolium violet, TV) and 2-...

Liquid–liquid extraction (LLE) and cloud point extraction (CPE) of vanadium(V) ternary complexes with 4-(2-pyridylazo)resorcinol (PAR) and 2,3,5-triphenyl-2H-tetrazolum chloride (TTC) were investigated. The optimal conditions for vanadium extraction and spectrophotometric determination were identified. The composition (V : PAR : TTC) of the extract...

29 liquid-liquid extraction-chromogenic systems containing M(V) (M=Nb or Ta), thiocatecholic compounds (TCs) and hydrophobic amines (HAs) were studied. The following TCs were used: 2,4-dihydroxythiophenol (DHTP), 2-hydroxythiophenol (HTP), 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP), and 2-hydroxy-5-iodothiophenol (HBIP)...

Ion-associates between cations originating from ditetrazolium salts [DT: Neotetrazolium chloride (NT), Blue Tetrazolium chloride (BT), Nitro Blue Tetrazolium chloride (NBT), and Tetranitro Blue Tetrazolium chloride (TNBT)] and anions originating from azo compounds [AC: 4-(2-pyridylazo)resorcinol (H2PAR) and 4-(2-thiazolylazo)resorcinol (H2TAR)] wer...

We performed a theoretical and experimental study of the (photo)stability of 3,5-dinitrocatechol (DNC) and its complexes with W(VI) and V(V). The investigation showed that irradiation of DNC is accompanied by a parallel proton migration from the hydroxy group to the neighboring NO2 group, which results in a large Stokes shift of the absorption and...

Complex formation and liquid-liquid extraction (LLE) were studied in systems containing vanadium( V), 5-methyl-4-(2-thiazolylazo)resorcinol (TAO), tetrazolium salt (TZS), water and chloroform. The following three TZSs were used: 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride...

27 liquid-liquid extraction-chromogenic systems containing Mo(VI), o-hydroxythiophenol derivative {HTPDs: 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) or 2-hydroxy-5-iodothiophenol (HITP)} and aromatic amine (AA) were studied. Aniline (An), N-methylaniline (mAn), N,N-dimethylaniline (dAn), o-toluidine (o-Tol), m-toluidine...

Nickel(II) forms well chloroform-extractable ternary complex with 2-hydroxyl-5-iodothiophenol (HITP) and diphenylguanidine (DPG). The complex, which has a composition of 1:2:2 (Ni:HITP:DPG) and a two-phase stability constant of Log b = 6.62, could be used for selective, sensitive, and reliable extractive spectrophotometric determination of nickel....

Four liquid-liquid extraction-chromogenic systems containing Fe(III), 4-(2-thiazolylazo)resorcinol (TAR), tetrazolium salt (TZS), water and chloroform were studied. 2,3,5-Triphenyl-2H-tetrazolium chloride (TTC), 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (TV), and 2-(4-io...

The ion-pairing between some 2,3,5-substituted monotetrazolium cations (T+) and anions deriving from 4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR) was studied by water-chloroform extraction and spectrophotometry. The following tetrazolium salts (TS) were used as a source of T+: i) 2,3,5-triphenyl-2H-tetrazolium chloride (TT...

Nitroderivatives of catechol (NDCs) are reviewed with special emphasis on their complexes and applications. Binary, ternary and quaternary NDC complexes with more than 40 elements (aluminum, arsenic, boron, beryllium, calcium, cobalt, copper, iron, gallium, germanium, magnesium, manganese, molybdenum, niobium, rare earth elements, silicon, tin, str...

Complex formation and liquid-liquid extraction in a system containing iron(III), 4-nitrocatechol (4NC), 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), water, and chloroform were studied. The effect of some experimental parameters (pH, shaking time, concentration of reagents) was investigated, and the optimum conditions for Fe(III) extraction as an...

A system containing zirconium (IV), 4-(2-pyridylazo) resorcinol (PAR), 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), acetate buffer, water and organic solvents was studied. The optimum conditions for zirconium (IV) flotation and spectrophotometric determination as an ion-association complex were found: flotation solvent (chloroform), shaking time...

The formation and liquid-liquid extraction of ion-association complexes between gallium(III)-4-(2-pyridylazo)resorcinol (PAR) anionic chelates and cations of four ditetrazolium chlorides (DT2+) were studied: Neotetrazolium chloride (NTC), Blue Tetrazolium chloride (BTC), Nitro Blue Tetrazolium chloride (NBT) and Tetranitro Blue Tetrazolium chloride...

Complex formation and liquid-liquid extraction were studied in a system containing iron(III), 4-(2-pyridylazo)resorcinol (PAR), 2,3,5-triphenyl-2H-tetrazolium chloride (TTC), water, and chloroform. The optimum conditions for iron(III) extraction from water to chloroform as an ion-association complex, (TT+)[Fe3+(PAR)2]−, were found: pH, concentratio...

Complex formation and liquid-liquid extraction were studied in a system containing indium(III), 4-(2-pyridylazo) resorcinol (PAR), 3,3'-(4,4'-biphenylene) bis(2,5-diphenyl-2H-tetrazolium chloride) (Neotetrazolium chloride, NTC), water and chloroform. The optimum conditions for indium(III) extraction as an 1:2 ion-associate of the In(III)-PAR anioni...

Ion-association complexes (IAC) are the basis of various analytical techniques, among which extraction-spectrophotometric are notable by virtue of their simplicity, low-cost instrumentation, high sensitivity and applicability for speciation analysis. In order to take maximum advantage of the great analytical potential of these compounds, the experi...

Complex formation and liquid-liquid extraction were studied in a system containing cobalt(II), 4-(2-pyridylazo)resorcinol (PAR), 1,4-diphenyl-3-(phenylamino)-1H-1,2,4-triazole (Nitron, Nt), water, and chloroform. The effect of some experimental parameters (pH, shaking time, concentration of PAR, and concentration of Nt) was systematically investiga...

Complex formation and liquid-liquid extraction were studied in systems containing Co(II), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS) {2,3,5-triphenyl-2H-tetrazolium chloride (TTC) or 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT)}, water and chloroform. The optimum conditions for the extraction of Co were fo...

The complex formation and a liquid-liquid extraction in the cobalt(II) - 4-(2- thiazolylazo)resorcinol (TAR) - 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) - water - chloroform system was studied. The optimum extractionspectrophotometric conditions were found. The molar ratio of the reacting species was determined to be 1:2:1 (Co:TAR:TTC). The fol...

Complex formation and liquid-liquid extraction were studied in systems containing M(III) (M = gallium or indium), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) and 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chlorid...

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), phenylmethoxybis(tetrazolium) salt (MBT), water and chloroform. The following MBTs, which differ only by the number of -NO2 groups in their cationic parts, were used: 3,3′-(3,3′-dimetoxy-4,4′-biphenylene)bis(2,5-diphenyl-...

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions for the extraction of Ga(III) as an ion-associate complex were found:...

Complex formation and liquid-liquid extraction were studied in a system containing gallium(III), 4-(2-pyridylazo)resorcinol (PAR), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (Thiazolyl Blue Tetrazolium, MTT), water and chloroform. The optimum conditions for gallium(III) extraction as an ion-association complex, (MTT+)[Ga(PAR)2...

Several liquid-liquid extraction systems containing vanadium {vanadium(IV) or vanadium(V)}, azoderivative of resorcinol {ADR: 4-(2-pyridylazo)-resorcinol (PAR) or 4-(2-thiazolylazo)-resorcinol (TAR)} and (phenylmethoxibis)tetrazolium salts {MBT: 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)-bis(2,5-diphenyl-2H-tetrazolium) chloride (Blue Tetrazolium, BT) o...

Nitroderivatives of catechol (NDCs) are reviewed with special emphasis on their complexes and applications. Binary, ternary and quaternary NDC complexes with more than 40 elements (aluminum, arsenic, boron, beryllium, calcium, cobalt, copper, iron, gallium, germanium, magnesium, manganese, molybdenum, niobium, rare earth elements, silicon, tin, str...

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The optimum conditions f...

Complex formation and liquid-liquid extraction (LLE) have been studied for ternary complexes of vanadium(IV) with 4-(2-thiazolylazo)resorcinol (TAR) and tetrazolium salts (TS). The following parameters have been optimized: TS, organic solvent, pH, extraction time, amount of TAR, amount of TS. The specific TSs used in the present study were: i) 2,3,...

Complex formation and liquid-liquid extraction have been studied for ternary complexes of vanadium(IV) with 4-(2-pyridylazo)-resorcinol (PAR) and ditetrazolium chlorides (DTC) in a water-chloroform medium. The specific ditetrazolium compounds investigated were i) 3,3′-(4,4′-biphenylene)-bis(2,5-diphenyl-2H-tetrazolium) chloride (Neotetrazolium chlo...

The formation and liquid-liquid extraction of a yellow ternary complex of vanadium(V) with 4-nitrocatechol (NC) and the ion-pair reagent Thiazolyl Blue Tetrazolium ⨑ub;3-(4,5-dimethyl-2-thiazol)-2,5diphenyltetrazolium bromide, MTT⫂ub; with 1: 2: 3 stoichiometry (V: NC: MTT) was studied. The optimum extraction conditions (pH, concentration of the re...

The complex formation and liquid-liquid extraction in the niobium(V) – 4-nitrocatechol (4-NC) – Thiazolyl Blue Tetrazolium (MTT) – water – organic solvent system was studied. Two ion-associated complexes with suggested formulae (MTT)2[NbO(OH)(4-NC)2] (I) and (MTT)3[NbO(4-NC)3] (II) were detected in the organic phase after shaking at certain conditi...

The formation and solvent extraction of new ion-association complexes between anionic chelates of niobium(V) with nitroderivatives of catechol {NDC: 3,5-dinitrocatechol (3,5-DNC) and 4-nitrocatechol (4-NC)} and tetrazolium cations {2,3,5-triphenyl-2H-tetrazolium (TT+) and 3,3’-[3,3’-dimetoxy(1,1’-biphenyl)–4,4’-diyl]-bis[2,5-diphenyl–2Htetrazolium]...

The complex formation and liquid-liquid extraction in the vanadium(IV) - 4-(2-pyridylazo)-resorcinol (PAR) -ditetrazolium chloride i) 3,3'-(4,4'-biphenylene)-bis(2,5-diphenyl-2H-tetrazolium) chloride (Neotetrazolium chloride, NTC); ii) 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)-bis(2,5-diphenyl-2H tetrazolium) chloride (Blue Tetrazolium chloride, BTC);...

The complex formation and liquid-liquid extraction in the vanadium(IV) – 4-(2-pyridylazo)-resorcinol (PAR) – tetrazolium salt {TS: 2,3,5-triphenyl-2H-tetrazolium chloride, 3-(1-naphtyl)-2,5-diphenyl-2H- tetrazolium chloride and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride} – water – chloroform system have been studied. The op...

Several commercially available 2H-tetrazolium salts (TS) {2,3,5-triphenyl-2H-tetrazolium chloride (TTC), 3-(1-naphthyl)-2,5-diphenyl- 2H-tetrazolium chloride (Tetrazolium Violet, TV), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT) and 3,3′-(3,3′-dimet...

The possibility of application of 4-nitrocatechol (4-NC) - tetrazolium salt - organic solvent systems for liquid-liquid extraction-spectrophotometric vanadium (IV and V) speciation was studied. Six commercially available tetrazolium salts (2,3,5-triphenyltetrazolium chloride (TTC), 3-(2-naphtyl)-2,5-diphenyltetrazolium chloride (Tetrazolium Violet,...

The formation and liquid-liquid extraction of ion-associated complexes between the vanadium(V) – 4-(2- pyridylazo)-resorcinol (PAR) anionic chelate and the cations of some metoxybis(tetrazolium) salts (MT2+), which contain different number of nitro groups {3,3’-(3,3’-dimetoxy-4,4’-biphenylene)bis[2,5-di(4-nitrophenyl)-2Htetrazolium]chloride (Tetran...

In slightly acidic medium V(IV) forms with 4-nitrocatechol (NC) and 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyltetrazolium bromide (Thiazolyl Blue Tetrazolium, MTT) a well extractable into chloroform, intensively colored (ε405=3.5×104 l mol-1 cm-1) 1:2:2 complex. The optimal conditions for extractive-spectrophotometric determination of V(IV) were found...

The use of tetrazolium salts for extraction, spectrophotometric and potentiometric determination of various elements and ions is described. The optimum conditions for extraction of tetrazolium ion-associated complexes are analysed. Chromogenic and other systems derived from tetrazolium salts and their applications in the analysis of industrial and...

The system vanadium(V) - 2,3-dihydmxynaphtalene (DHN) - tetrazolium violet (TV) - water - chloroform was studied. The composition of the ternary ion-associate complex was established and the optimum conditions for extractive-spectrophotometric determination of vanadium were found.Beer's law was obeyed up to 1.7 mug cm-3 vanadium(V) with a molar abs...

The formation and extraction of ion-associate complexes between the vanadium(V)-4-(2-thiazolylazo)resorcinol (TAR) anionic chelate and the cations of some mono-and ditetrazolium salts {3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (Thiazolyl blue, MTT), 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (Tetrazolium violet), 2-(4-i...

The formation of a new tenary complex of molybdenum(VI) with 4-nitrocatechol (NC) and tetrazolium blue chloride (BTC), which is easily extractable from water into dichloroethane, is reported. The optimum extraction conditions (pH, concentration of the reagents, extraction time) and composition of the complex (Mo: NC: BTC = 1: 2: 1) were found. The...

Polyphenols (PPh) are of grate importance in inorganic analysis. Alone, or in combination with organic bases they are widely used for solvent extraction and spectrophotometric determination of many metal ions. In presence of tetrazolium salts (TS) PPh form ternary ion-association complexes with molybdenum(VI), tungsten(VI) and vanadium(IV,V) having...

The vanadium (IV) – 4-nitrocatechol (NC) – neotetrazolium chloride (NTC) – water – organic solvent system was studied by using an extractionspectrophotometric method. The optimum extraction conditions (pH, concentration of the reagents, organic solvent, extraction time), the composition of the extracted species and their spectrophotometric characte...

The formation of a new ternary ion-associate complex of vanadium(V) with 2,3-dihydroxynaphthalene and iodonitrotetrazolium chloride with a composition ratio of 1:2:1 is reported. The complex is quantitatively extracted from water into chloroform. The molar absorptivity (ɛ) of the extract at λ max=340 nm is 2.5 × 104 dm3/mol cm, and Beer’s law is ob...

A new ternary ion-association complex of tungsten(VI), 4-nitrocatechol (NC), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (Thiazolyl Blue, MTT) was obtained and studied using an extraction-spectrophotometric method. The optimum pH, reagent concentrations, and extraction time were determined. The composition of the complex was fo...

A new ternary complex of vanadium(V) with 4-(2-pyridilazo)-resorcinol (PAR) and thiazolyl blue (MTT) has been obtained and studied by using an extraction-spectrophotometric method. The complex absorbs light at 560 nm with a molar absorptivity coefficient of 3.84x104 L mol-1 cm-1 at the optimum extraction conditions: pH=5.8±0.7, CPAR=1.2x10-4 mol L-...

A thesis is supported in the literature for existence of a linear relationship between the association constants of the tetrazolium ion-associated complexes β(TIAC) and their molecular weights. The present investigations show that β(TIAC) of the complexes containing nitro-phenyl substituents in the tetrazolium cation are significantly lower than th...

An extractive-spectrophotometric method for determination of V(V) and.V(lV) has been developed. V(V) was converted to ternary ion-associate complex with 4-(2-pyridyIazo)-resorcinol and tetrazolium violet. In the presence of diaminocyclohexanetetraacetic acid and NH4F as the masking agents determination of V(V) was highly selective, and V(I V) was a...

The extraction process of ternary ion-association complexes of molybdenum (VI) with some polyphenols (4-nitrocatechol, 2,3-dihydroxy naphthalene) and thiazolyl blue has been investigated by using an extraction-spectrophotometric method. The optimum conditions for their quantitative preparation in aqueous medium and subsequent extraction into an org...

Two sensitive extraction-spectmphotometric methods for determination of vanadium in catalysts of conversion of sulfur dioxide to sulfur trioxide have been developed. They are based on the ternary ion-association complexes of vanadium(V) with azoderivatives of resorcinol(4-(2-pyridy1azo)-resorcinol (PAR), 4-(2-thiazoly1azo)-resorcinol (TAR)} on the...

The system vanadium(IV) – 4-nitrocatechol (NC) – iodonitrotetrazolium chloride (INT) - water – chloroform is studied. The optimum conditions for complex formation and extraction into chloroform are found: pH=3.9-4.5 and reagent concentrations at least 2x10-4 mol l-1 NC and 1.2x10-4 mol l-1 INT. The composition of the ternary complex is found to be...

The system vanadium(V) - 4-(2-thiazoly1azo)-resorcinol (TAR) - triphenyltetrazolium chloride (TTC) - water - chloroform is studied using an extractionspectrophotometric method. The optimum conditions for extraction of vanadium are found: pH=4.75, reagent concentration in aqueous phase - C(TAR)=2x10-4 mol/l, C(TTC)=3.0x10-4 mol/l, extraction time -...

The system vanadiumm - 4-(2-pyridy1azo)-resorcinol (PAR) - tetrazol violet (TV) - water - 1,2-dichloroetane is studied using an extraction-spectrophotometric method. The optimum conditions for extraction of vanadium are found: reagent concentration in aqueous phase - C(PAR)=C(TV)=2x10-4 mol/l, pH=5.8, extraction time - 2 min. Beer's law is obeyed i...