Liquid-Liquid Extraction-Spectrophotometric Investigations of Three Ternary Complexes of Vanadium(V)

Complex formation and liquid-liquid extraction (LLE) were studied in systems containing vanadi-um(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 (Tetrazolium violet, TV), and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT). Concentration of the reagents (TAO and TZS), pH of the aqueous medium, and shaking time were subjects of optimization experi-ments. Formation of ternary complexes with a composition of 2:2:2 was demonstrated by a set of dif-ferent methods. Some key characteristics concerning the analytical application of the studied LLE-chromogenic systems were established as well

Extraction of Gallium(III) with a New Azo Dye in The Presence or Absence of Xylometazoline Hydrochloride

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 HTAR is in its deprotonated form L2–. Some key extraction-spectrophotometric characteristics were determined: absorption maximum (521 nm), apparent molar absorptivity (5.8 × 104 dm3 mol–1 cm–1), limit of detection (18 ng cm–3), limit of quantitation (60 ng cm–3), extraction constant (LogK = 4.44), distribution ratio (LogD = 2.2) and fraction extracted (99.3 %). In the absence of XMH, the extracted chelate contains one deprotonated and one monoprotonated HTAR: [GaIII(HL–)(L2–)]. It has an absorption maximum at 523 nm and a shoulder at 580–590 nm. The pKa of HTAR (H2L ⇄ H+ + HL– equilibrium) was calculated (5.4) and the effect of foreign ions was studied. This work is licensed under a Creative Commons Attribution 4.0 International License

Does Sendivogius’ alchemy cancel the celebration of the 250th anniversary of the discovery of oxygen?

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 NaNO3, as well as by dissolving pyrolusite in sulfuric acid (1772). The name “oxygen” was given a few years later (1779) by Antoine Lavoisier. This great scientist, often accused of taking advantage of the discoveries of others, conducted experiments related to the decomposition of water vapour over heated iron, as well as the synthesis of water from hydrogen and oxygen. His work was of great importance because it revealed the elemental nature of oxygen and its role in the processes of combustion and respiration. The present article draws attention to the prehistory of the “oxygen theory”. It emphasises the natural philosophy of a forgotten alchemist, healer, and diplomat - Michael Sendivogius (1566-1636) - who popularised his belief that the substance (“Water of life that does not wet the hands”) obtained by heating the “Central Salt” (nitre, KNO3) is part of the air. It is the “secret food of life” used invisibly by every living thing

Ion-Association Complexes of Gallium(III) - 4-(2-Pyridylazo)-resorcinol Anionic Chelates and Dicationic Tetrazolium Reagents

Abstract 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 (DT 2

An extraction-chromogenic system for vanadium(IV,V) based on 2,3-dihydroxynaphtahlene

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 triphenyltetrazolium cations (TT+) and chelate anions {[VIVO(DN)(DNH)]− (I) and/or [VIV(OH)(DN)2]− (II)}. When the initial oxidation state of vanadium is V and the DN concentration is high, vanadium(V) is reduced by DN to a lower oxidation state, V(IV). However, at low DN concentration, vanadium(V) can enter the organic phase as a part of an ion-pair consisting of TT+ and [VVO2(DN)]− (III). The ground-state equilibrium geometries of the anions I, II, and III were optimized by quantum chemical calculations using BLYP/6-31++G⋆. The following characteristics were determined under the optimum conditions for VIV extraction: absorption maximum λmax = 333 nm, molar absorptivity ε333= 2.1x104 dm3 mol−1 cm−1, Sandell’s sensitivity SS = 2.4 ng cm−2, and fraction extracted E = 98%. The conditional extraction constant was calculated by two independent methods. The calibration graph was linear in the range 0.1-3.1 μg cm−3 (R2=0.9994) and the limit of detection was 0.03 μg cm−3

Extractive Spectrophotometric Determination and Theoretical Investigations of Two New Vanadium(V) Complexes

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]phenyl]-3,5-diphenyltetrazol-2-ium;dichloride, NTC). The cations (abbreviated as TT+ and NTC+) impart high hydrophobicity to the ternary complexes, allowing vanadium to be easily extracted and preconcentrated in one step. The complexes have different stoichiometry. The V(V)–HTAR–TTC complex dimerizes in the organic phase (chloroform) and can be represented by the formula [(TT+)[VO2(HTAR)]]2. The other complex is monomeric (NTC+)[VO2(HTAR)]. The cation has a +1 charge because one of the two chloride ions remains undissociated: NTC+ = (NT2+Cl−)+. The ground-state equilibrium geometries of the constituent cations and final complexes were optimized at the B3LYP and HF levels of theory. The dimer [(TT+)[VO2(HTAR)]]2 is more suitable for practical applications due to its better extraction characteristics and wider pH interval of formation and extraction. It was used for cheap and reliable extraction–spectrophotometric determination of V(V) traces in real samples. The absorption maximum, molar absorptivity coefficient, limit of detection, and linear working range were 549 nm, 5.2 × 104 L mol−1 cm−1, 4.6 ng mL−1, and 0.015–2.0 μg mL−1, respectively

Spectrophotometric Determination of Molybdenum(VI) as a Ternary Complex with 4-Nitrocatechol and Benzalkonium Chloride

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) were found: concentrations of 4NC and BZC (7.5 × 10−4 mol dm−3 and 1.9 × 10−4 mol dm−3, respectively), acidity (3.75 × 10−2 mol dm−3 H2SO4), extraction time (3 min), and wavelength (439 nm). The molar absorptivity, limit of detection, and linear working range were 5.5 × 104 dm3 mol−1 cm−1, 5.6 ng cm−3, and 18.6–3100 μg cm−3, respectively. The effect of foreign ions was examined, and the developed procedure was applied to the analysis of synthetic mixtures and real samples (potable waters and steels). The composition of the extracted complex was 1:1:2 (Mo:4NC:BZ). Three possible structures of its anionic part [MoVI(4NC)O2(OH)2]2− were discussed based on optimizations at the B3LYP/3-21G level of theory, and simulated UV/Vis absorption spectra were obtained with the TD Hamiltonian