New method for detection and spectrophotometric determination of quinones

The reaction between 3-phenylthiazolidine-2,4-dione (I) and p-benzoquinone (II), tetrachloro-p-benzoquinone (III), and 1,4-naphthoquinone (IV) in ammoniacal medium is applied for detection and spectrophotometric determination of quinones. The absorbance-concentration relationship is linear up to 18 μg/ml of quinone concentration. The lower limits of identification in the detection reaction are 2.5, 3.0, and 1 μg for (II), (III), and (IV), respectively, which reflect high sensitivity. The reaction between (I) and quinones is proved to be a condensation reaction and highly selective.     

Spectrofluorimetric determination of guanethidine sulphate, guanoxan sulphate and amiloride hydrochloride in tablets and in biological fluids using 9,10-phenanthraquinone

A highly sensitive spectrofluorimetric method for the determination of some drugs of the monosubstituted guanidine derivatives in laboratory made tablets, in spiked human serum and in urine samples is presented. The method is based on the reaction of guanethidine sulphate (I), guanoxan sulphate (II) and amiloride hydrochloride (III) with 9,10-phenanthraquinone (IV) to give highly fluorescent derivatives. The linearity ranges were found to be 0.06-0.96 mug/ml for (I) and (II) and 0.04-0.28 mug/ml for (III), with relative standard deviation less than 2%. Mean percentage recoveries for tablets were found to be 99.9 +/- 1.3, 100.5 +/- 1.1 and 100.0 +/- 1.6 for I, II and III, respectively. For I and III the results are highly correlated with the B.P. methods. Using the synchronous fluorimetry, differentiation between I and II was possible. Chloroform, dichloromethane and ethyl acetate have been used to extract I, II and III, respectively from serum and urine at basic pH, followed by applying the proposed fluorimetric method. Percentage recoveries were found to be 95.7-102.2%. The limit of detection is 0.04 mug/ml for I and II and 0.02 mug/ml for III.     

Some spectrofluorimetric applications of the cerium(IV)-cerium(III) system

Cerium(III) ions in dilute sulphuric acid medium exhibit a characteristic fluorescence which has its excitation maximum at 260 nm and its fluorescence emission maximum at 350 nm. By utilising the osmium-catalysed redox reaction between cerium(IV) and arsenic(III), microgram amounts of arsenic (7.5–37.5 μg) may be determined by spectrofluorimetric measurement of the ceriurm(III) produced. The principle may be applied to the determination of several other ions which cannot yet be determined by direct spectrofluorimetry, e.g.. Fe(II) (5.6–28 μg), oxalate (8.8–44μg). Osmium(VIII) (0.05–0.2 μg) and iodide (0.6–2.5 μg) may be determined by their catalytic action.     

The determination of p-cresol in chloroform with an enzyme electrode used in the organic phase

An enzyme electrode that operates in chloroform is described. Polyphenol oxidase (tyrosinase; EC.1.14.18.1) is used to detect p-cresol via electrochemical reduction of the product, 4-methyl- 1,2-benzoquinone, at a graphite foil electode. The response is linear for p-cresol concentrations of 0–0.10 mM, with a limit of detection of 1 μM. After an initial rise from 1.9 μA to 4.0 μA in the first three assays, the response of the electrode to 0.10 mM p-cresol remained stable for twelve consecutive assays ($\text{x}$=4.6, SD=0.49). After intermittent usage for 204 days with appropriate storage, the enzyme electrode remained active. The electrode is sensitive to a broad range of phenols. The feasibility of detecting p-cresol contamination of water is demonstrated.     

Rapid electrochemical assay for theophylline in whole blood based on the inhibition of bovine liver alkaline phosphatase

A disposable electrochemical test strip for determining clinically relevant concentrations of theophylline (0–300 μM) in whole blood is described, based on the generation of p-aminophenol from p-aminophenyl phosphate by the action of bovine liver alkaline phosphatase. Theophylline is an uncompetitive inhibitor of alkaline phosphatase and thus inhibits this process. The test strip consists of a screen-printed, carbon-based electrode system containing the enzyme and substrate in separate layers. Application of a 20-μl blood sample to the strip initiates the enzymic reaction, which will proceed to an extent that is inversely dependent on the amount of theophylline in the sample. After a 2-min incubation, the p-aminophenol generated is quantified by its electrochemical oxidation at + 150 mV (vs. Ag/AgCl) on the underlying carbon electrode. Caffeine and theobromine (0–1 mM), phenylalanine (< mM) and endogenous alkaline phosphatase (<2 U ml ^?1) do not interfere.     

Reactivity of monoenic and conjugated diene systems present in unsaturated olefin terpolymers—I. Reactions with t-butoxy radicals (CH3)3 CO•

The relative rate constants for the hydrogen abstraction and the double bond addition reactions of t-butoxy radicals (CH₃)₃ CO^? with the model compounds 5-ethylidennorbornane (I), dihydrodicyclopentene (II), isopropylidendicyclopentene (III) and methylcyclopentadienylnorbornylmethane (IV) have been determined by using as a reference reaction the hydrogen abstraction for iso-octane. With (I), (III) and (IV) the predominant process is the hydrogen abstraction, whilst for (II) both mechanisms are important. The results have been applied for the elucidation of some aspects of the initiating mechanism of peroxide-induced cross-linking of EPDM and EPTM terpolymers containing (I)-(IV) pendants.     

Thermal decomposition of some metal chelates of substituted hydrazopyrazolones

The thermal dissociation of 1-phenyl-3-methyl-4-(X-phenylhydrazo)-5-pyrazolone metal chelates [M(XPhHyPy)](X=m-OH (I),m-OCH₃(II),m-COOH (III),p-CH₃ (IV),p-OCH₃ (V) orp-COCH₃ (VI) was studied by TG, DTG and differential thermal analysis (DTA). A rough sequence of thermal stability, obtained from the peak maximum temperatures, for the various metal chelates was Hg(II)2(II). The bonding of the ligands to metal ions was investigated by elemental analysis and infrared spectroscopy. The number and relative energies of nitrate combiantion frequencies are discussed in terms of the complexation of para-substituted hydrazopyrazolone with Th(IV) and UO₂(II) metal ions.     

Synthesis and properties of titanomagnetite (Fe3−xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system

Titanomagnetite (Fe_3−xTi_xO₄) nanoparticles were synthesized by room temperature aqueous precipitation, in which Ti(IV) replaces Fe(III) and is charge compensated by conversion of Fe(III) to Fe(II) in the unit cell. A comprehensive suite of tools was used to probe composition, structure, and magnetic properties down to site-occupancy level, emphasizing distribution and accessibility of Fe(II) as a function of x. Synthesis of nanoparticles in the range 0 ? x ? 0.6 was attempted; Ti, total Fe and Fe(II) content were verified by chemical analysis. TEM indicated homogeneous spherical 9-12 nm particles. μ-XRD and Mössbauer spectroscopy on anoxic aqueous suspensions verified the inverse spinel structure and Ti(IV) incorporation in the unit cell up to x ? 0.38, based on Fe(II)/Fe(III) ratio deduced from the unit cell edge and Mössbauer spectra. Nanoparticles with a higher value of x possessed a minor amorphous secondary Fe(II)/Ti(IV) phase. XANES/EXAFS indicated Ti(IV) incorporation in the octahedral sublattice (B-site) and proportional increases in Fe(II)/Fe(III) ratio. XA/XMCD indicated that increases arise from increasing B-site Fe(II), and that these charge-balancing equivalents segregate to those B-sites near particle surfaces. Dissolution studies showed that this segregation persists after release of Fe(II) into solution, in amounts systematically proportional to x and thus the Fe(II)/Fe(III) ratio. A mechanistic reaction model was developed entailing mobile B-site Fe(II) supplying a highly interactive surface phase that undergoes interfacial electron transfer with oxidants in solution, sustained by outward Fe(II) migration from particle interiors and concurrent inward migration of charge-balancing cationic vacancies in a ratio of 3:1.     

Gamma-ray irradiation and characterization of synthesized bidentate and tetradentate Schiff base ligands and their complexes with some transition metal ions

Salen ligands are essential for coordinating a diverse group of metals in their respective oxidation states. This creates significant complexes of salen metals that are used in different fields. Condensation of ehylenediamine (en) with p-methoxybenzaldehyde (L¹) or o-hydroxyacetophenone (L²) with a ratio 1: 2 (en: p-methoxybenzaldehyde or o-hydroxyacetophenone) or by the interaction of o-phenylenediamine (phen) with o-hydroxybenzaldehyde (L³) or p-hydroxybenzaldehyde (L⁴) with a ratio 1: 2 (phen: o-hydroxybenzaldehyde or p-hydroxybenzaldehyde) has been used to prepare four symmetrical Schiff bases (L¹-L⁴). The UV–vis spectroscopy has been used to investigate the diverse electronic transitions associated with the Schiff bases molecules as well as how these transitions are impacted by diverse polarities of solvents. Elemental analysis, FT-IR, UV–vis spectra, molar conductivity, and ¹H NMR have been used to characterise all the compounds obtained in this process. The continuous variation applied alongside molar ratio spectral methods showed the formation of different complexes arising from the reaction of the ligand (L^1-L⁴) with the metal ions Mn(II), Fe(III) and Cu(II) is 1: 1 and/ or 1: 2 (M: L). A series of universal buffer solutions (20 % ethanol v/v) with varying pH values were used in spectrophotometry to determine the acid dissociation constants of the L² and L⁴ ligands. Gamma radiation was applied to examine the compounds’ irradiation stability. Additionally, the absorptions of the main functional groups were screened using FT-IR spectra before and after Gamma irradiation. The results show that all the compounds are stable after irradiation process; therefore, it could be used as enhancing agents in cancer therapy.     

Locating redox couples in the layered sulfides with application to Cu[Cr2]S4

Use of LiPF₆ in EC:DEC as electrolyte has allowed electrochemical extraction of Li from LiV_1−yM_yS₂ and LiTi_1−yM_yS₂ (M=Cr or Fe). The data show access not only to the Ti(IV)/Ti(III) and V(IV)/V(III) redox couples, but also to the V(V)/V(IV) and Fe(III)/Fe(II) couples in these layered sulfides. However, the Cr(IV)/Cr(III) couple could not be accessed. The concept of redox-couple pinning is outlined and applied to the V(V)/V(IV) and Fe(III)/Fe(II) couples, which are pinned at the top of the S-3p bands. Holes associated with the “pinned” couples occupy orbitals of dominant S-3p character, but they have sufficient cation-3d character to prevent condensation of the holes into p-p antibonding states of disulfide bonds. Strong covalent bonding in the pinned couples creates itinerant-electron states in the partially occupied couples. Application to the metallic, ferromagnetic thiospinel Cu[Cr₂]S₄ favors location of the itinerant holes in states of a pinned Cu(II)/Cu(I) couple having primarily S-3p character.     

Mandelazo I As A Reagent For Zr(IV) Determination

Abstract

A spectromeric study of the reaction of the Zr(IV) ions with Mandelazo I was carried out. Absorption spectra revealed that the maximum absorption of the zirconium compound appears at a wavelength (316 nm) different from the maxima of the reagent (253 and 390 nm). Beer-Lambert law is followed for zirconium concentrations of the order of 8.8x 10^?5 M (i.e. 8 μg Zr (IV)/mL). Possible interferences of ions such as Be(II), Cu(II), Zn(II), Al(III), Th(IV), U(VI), Mn(II), Fe(III), Co(II) and Ni(II) were investigated in connection with some masking agents such as SO₄ ^2- and C₂O₄ ^2-. Also, the solid state Zr(IV)-Mandelazo I compound was prepared and characterized by nitrogen and thermogravimetric analyses.     

Conformational studies on somep-dimethylaminostyryl dyes

PCILO computations have been carried out on the conformations of five p-dimethylaminostyryl dyes derived from quinoline-4 (I), quinoline-2 (II), pyridine-4 (III), pyridine-2 (IV) and benzothiazole (V). The stable conformations of I–IV are found to be nonplanar, while V is almost planar. The results have been explained in terms of various possible steric interactions.     

Synthese,spektroskopische Charakterisierung und bakterizide Wirksamkeit neuer Organylbis(thiophenolato)bismut(III)-Komplexe

New Organobis(thiophenolate)bismuth(III) derivatives C₆H₅Bi(SC₆H₄Cl-p)₂ (I), Ch₃Bi(SC₆H₄NH₂-p)₂ (II) and CH₃AS(SC₆H₄NH₂-p)₂ (III) can be prepared by the reaction of phenyldibromobismuth(III), methyldibromobismuth(III) and -arsenic(III), respectively, with stoichiometric amounts of lithium-p-chlorothiophenolate (for I), and lithium-p-aminothiophenolate. II reacts with an excess of iodomethane to form the bis(mercaptoanilinium) complex [CH₃Bi(SC₆H₄NH₂CH₃-p₂]²⁺ (I⁻)₂ (IV). Treating IV with adequate amounts of AgNO₃ or TINO₃ yields the analogous nitrate derivative [CH₃Bi(SC₆H₄NH₂CH₃-p)₂]²⁺ (NO₃⁻)₂ (V). The new compounds were characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy and some of the compounds were also characterized by vapour pressure molecular weight osmometry too.The microbiological effect of the organometallic arsenic(III)- and bismuth(III)-bis(thiolates) I-IV was studied, the bismuth compounds generally inhibited bacterial growth more than the arsenic derivative. The aminothiophenolate complexes II and IV in particular were not inferior to the well-known organothiolatomercury(II) complexes with regard to their inhibition of bacterial growth. The hydrophilic mercaptoanilinium derivative IV has potential as a novel bactericide.     

Electrophoretic determination of thioamides, pyridine and pyrimidine derivatives

We have optimized the conditions for the separation and quantification of a mixture of heteroaromatic thioamides, potential thyreostatics: pyridine-2-thione (I), 5-trifluoromethylpyridine-2-thione (II), pyrimidine-2-thiol (III), 4-trifluoromethylpyrimidine-2-thiol (IV) by capillary zone electrophoresis using a 60 cm × 75 μm capillary (effective length of 50 cm), 15-kV voltage, and borate buffer solution (pH 9.18) as the running electrolyte. The procedure provides the estimation of analyte concentrations in the range from 6.7 × 10^?6 to 1.0 × 10^?4 M with the detection limits (by electrophoretic peak areas) 0.72 (I), 0.47 (II), 0.43 (III), and 0.76 (IV) μg/mL.     

Ethyl Xanthate and Propyl Xanthate as Activators and Inhibitors of Mushroom Tyrosinase in Different Concentrations

The effect of ethyl xanthate(I) and propyl xanthate(II) on the kinetics of hydroxylation by mushroom tyrosinase (MT) has been investigated at 20°C in 10 mM phosphate buffer solution, pH 6.8. 4‐[(4‐Methyl‐phenyl)azo]‐phenol (MePAPh) was used as a synthetic substrate for the enzyme for cresolase reaction. The results show that ethyl xanthate and propyl xanthate can activate or inhibit the cresolase activity of mushroom tyrosinase depending on the concentration of these effectors. Both I and II act uncompetitive at relatively high concentrations (20‐50 μM). The inhibition constant (K_i) values for I and II are 13.8 and 11 μM, respectively. However, both I and II act as activators at relatively low concentrations (0‐11.5 μM). Activation of the enzyme in low concentrations of xanthates arises from increasing the affinity of binding for the substrate as well as increasing the enzyme catalytic constant. The activation constant (K_a) values for I and II are 1.88 and 2.68 μM, respectively. The enzyme has two distinct sites for both effectors. The first one is a high‐affinity activation site and the other is a low‐affinity inhibition site.     

Antioxidants and stabilisers—Part XCII: Activity of 2,2′-thiobis(4,6-di-tert-butylphenol) as a hydroperoxide decomposer. A model study

The effect of an antioxidant, 2,2′-thiobis(4,6-di-tert-butylphenol) (I) and of the derived sulphoxide (II) and sulphone (III), on the decomposition of tert-butyl hydroperoxide (IV) at 65, 75, 85 and 100°C was investigated. The results indicate a change in the rate of decomposition of IV with sulphide, I, after consumption of about 2 moles of IV per mole of I and the active rôle played by II and III in the process. The formation of new compounds in the reaction mixture, which may be connected with an acceleration of the decomposition of IV, was identified by means of TLC. 7     

Solvent extraction of trivalent indium from succinate solution by 2-octylaminopyridine in chloroform

Extraction processes of indium(III) with 2-octylaminopyridine (2-OAP) from media of various complexing ability, succinate and salicylate, in chloroform have been elucidated. The ion-pair complex has also quantitative extraction in xylene and 1,2-dichloroethane. Indium(III) from organic phase was stripped with 1.0 M hydrochloric acid and determined complexometrically with EDTA. The stoichiometry of the extracted species was found out on the basis of slope analysis. The extraction of indium(III) proceeds by an anion exchange mechanism and the extracted species is [RR′NH₂ ⁺In(succinate)₂ ^-]_(org). Temperature dependence of the extraction equilibrium constant was also examined to estimate the apparent thermodynamic functions (ΔH, ΔG and ΔS) for extraction reaction. It is possible to separate indium(III) from Zn(II), Cd(II), Pb(II), Hg(II), Bi(III), Tl(I), Tl(III), Ga(III), Al(III), Te(IV), Se(IV), Sb(III), Fe(III) and Sn(IV). The method is simple, rapid and reproducible and can be used to determine the indium from samples like alloys.     

Reaction of 6-phenyl-2-(p-toluenesulfonyl)-3(2H)pyridazinone with grignard reagents

6-Phenyl-2-(p-toluenesulfonyl)-3(2H)pyridazinone (I) reacted with Grignard reagents to give 5-substituted 4,5-dihydro-3(2H)pyridazinones II and two types of dihydropyridazines, III and IV. The ratio of II, III, and IV was sensitively dependent on the reaction conditions. Further, by quenching the reaction mixture with alcohol, the ring-opened product VII was mainly isolated.     

Stark broadening and regularities of ionized neon and argon spectral lines

Stark widths of five Ne III, five Ne IV, one Ar III and nine ArIV spectral lines have been measured in a linear-pinch discharge plasma. The results were compared with existing experimental and theoretical results, and used to establish several types of regularities. Electron densities determined with single-wavelength laser interferometry were 2.18·10²³ m^?3 and 2.80·10²³ m^?3 in neon and argon plasma, respectively. The electron temperatures determined from the Boltzmann slope of several Ne III spectral lines, and ratios of Ne III to Ne IV or Ar III to Ar IV spectral lines were 59 000 K and 42 000 K in neon and argon plasma, respectively. The investigated spectral lines originate predominantly, from 3s–3p and 3s′–3p′ Ne III and Ne IV, and from 4s–4p and 4s′–4p′ Ar III and Ar IV transition arrays. The emphasis is on the Stark width (θ) dependence on the upper level ionization potential (I), the emitter core net charge (z) and electron temperature (T) for a given electron density. This dependence was found to be of the form: θ=az ² T ^?1/2 I ^?b , wherea andb are constants within(i) several stages of ionization of neon or argon and(ii) within nitrogen like (NI, O II, F III and Ne IV) 3s–3p or phosphorus like (P I, S II, Cl III and Ar IV) 4s–4p transition arrays. The established overall trends were used to predict the Stark widths of univestigated spectral lines originating from the given transition arrays.     

Determination of myo-inositol in a flow-injection system with co-immobilized enzyme reactors and amperometric detection

A selective and sensitive flow-injection system for the determination of myo-inositol (hexahydroxycyclohexane) is described. Inositol dehydrogenase, IDH, lactate dehydrogenase, LDH, and lactate oxidase, LOD, are co-immobilized on porous glass and used in a packed-bed enzyme reactor. myo-Inositol reacts to produce an equivalent amount of hydrogen peroxide, which oxidizes hexacyanoferrate(II) to hexacyanoferrate(III) in a second reactor containing immobilized peroxidase. The hexacyanoferrate(III) is then detected amperometrically at 0 mV vs. SCE in a flow-through detector. The system responds linearly to injected samples of myo-inositol (25 μl) in the concentration range 1–300 μM. The maximum throughput was 90 samples per hour. The IDH/LDH/LOD reactor was stable for at least 5 weeks.