Photochemistry of some quinoxaline 1,4-dioxides

The photochemical reactions of some 2,3-diarylquinoxaline 1, 4-dioxides are described. A mechanistic interpretation of the experimental results is also offered.     

Bilirubin Removal from Human Plasma with Albumin Immobilised Magnetic Poly(2‐hydroxyethyl methacrylate) Beads

Bioaffinity separation has a unique and powerful role as a support tool in the removal of toxic substances from human plasma. Magnetic beads have advantages as supports in comparison to conventional nonmagnetic beads because of low pressure drop, high mass transfer rates, and good fluid‐solid contact. In addition, they eliminate internal diffusion limitations. Human serum albumin (HSA) immobilised onto magnetic poly(2‐hydroxyethyl methacrylate) (mPHEMA) beads were investigated as an adsorbent for the selective bilirubin removal from human plasma. The mPHEMA beads were prepared by a modified suspension polymerisation. HSA was covalently coupled to the mPHEMA beads. Bilirubin adsorption was investigated from hyperbilirubinemic human plasma on the mPHEMA beads containing different amounts of immobilised HSA, (between 11–100 mg/g). The nonspecific bilirubin adsorption on the unmodified mPHEMA beads was 0.47 mg/g. Higher bilirubin adsorption capacities, up to 64.7 mg/g, were obtained with the HSA‐immobilised magnetic beads. Bilirubin adsorption increased with increasing temperature.

Effect of HSA loading on bilirubin adsorption.     

Microdetermination of ascorbic acid and tryptophan by colorimetry

Summary Ascorbic acid reacts with 2,3,5-triphenyltetrazolium chloride in alkaline medium giving pink color having 5g/ml as visual limit of identification. This color reaction has been utilized for the colorinietric determination of ascorbic acid from pharmaceutical preparations in minute quantities. The maximum tolerable amount of other vitamins, sugars and organic compounds during determination of ascorbic acid is reported.Tryptophan reacts with hexamine to give yellow color having 5g/ml as limit of identification. The color reaction provides the basis of a new method for colorimetric determination of tryptophan. The maximum tolerable amount of various amino acids and vitamins is reported. The mechanism of the color reaction is not clear.

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Zusammenfassung Ascorbinsäure reagiert mit 2,3,5-Triphenyrtetrazoliumchlorid in alkalischem Milieu unter Rosafärbung. Erfassungsgrenze: 5g/ml. Diese Farbreaktion wurde zur kolorimetrischen Bestimmung kleiner Mengen Ascorbinsäure in pharmazeutischen Präparaten verwendet. Die tolerierbare Höchstmenge an anderen Vitaminen, Zuckern und organischen Verbindungen wurde angegeben. Tryptophan reagiert mit Hexamin unter Gelbfärbung. Erfassungsgrenze: 5g/ml. Die Farbreaktion dient als neue Methode zur kolorimetrischen Tryptophanbestimmung. Die nicht störenden Höchstmengen an anderen Aminosäuren und Vitaminen sind angegeben. Der Reaktionsmechanismus ist nicht geklärt.

     

Electrochemical oxidation of 2-thiouracil at pyrolytic graphite electrode

2-Thiouracil has been studied in phosphate buffers of pH 1.95-11.08 using linear and cyclic sweep voltammetry, coulometry, controlled potential electrolysis and spectral studies. One well-defined oxidation peak I(a) in the pH range 1.95-11.08 was noticed. The number of electrons involved in peak I(a) was found to be four in a thin layer cell whereas under exhaustive electrolysis condition oxidation was found to involve six electrons. A reduction peak II(c) (2e, 2H(+)) is noticed in the reverse sweep. Spectral studies during oxidation were carried out at different pH. Kinetic studies indicated that the decay of the UV-absorbing intermediate is a first order reaction. The products of the electrooxidation have been characterized and a tentative EC mechanism has been suggested for the oxidation of 2-thiouracil.     

Separation of noble metals by circular thin-layer chromatography

Summary A method has been described for the separation and identification of noble metals by circular thin-layer chromatography. The method is simple and convenient and separation is complete within 2 min. Best results have been obtained on alumina layers with acetone/aoetylacetone/2 M hydrochloric acid (100103) as solvent mixture. Reagents used for detection were rubeanic acid, thiourea, and stannous chloride. The following elements could be detected with sensitivities ranging from 0.1 g to 3.0 g: Rh, Ru, Pt, Au, Os, Pd, Ir, and Cu. Interferences are caused by Ni, Go, Mn, and Fe, yet it is possible to distinguish these from the noble metals on separate chromatograms.

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Zusammenfassung Zur Trennung und Identifizierung von Edelmetallen wird das Verfahren der Zirktdar-Dünnschichtchromatographie empfohlen. Die Methode ist einfach durchzuführen und erfordert nur 2 min für eine vollständige Trennung. Am besten hat sich ein Lösungsmittel aus Aceton, Acetylaceton und 2 m Salzsäure (100103) und Aluminiumoxid als Dünnschichtmaterial bewährt. Als Nachweisreagentien werden Rubeanwasserstoff, Thioharnstoff und Zinn(II)-chlorid verwendet. Folgende Elemente wurden mit Empfindlichkeiten zwischen 0,1 und 3,0 g erfaßt: Rh, Ru, Pt, Au, Os, Pd, Ir und Cu. Störungen wurden durch Ni, Co, Mn und Fe verursacht, jedoch können diese von den Edelmetallen auf getrennten Chromatogrammen unterschieden werden.

     

Two-dimensional composition diagram of the Al(OH)3-dien-HFaq.-ethanol system: Evidence of a new tetrahedral (Al4F18) polyanion

Six domains appear in the 2D composition diagram of the Al(OH)₃-dien-HF_aq.-ethanol system at 190 °C and [Al³⁺] = 1 mol L⁻¹ under microwave heating. Four organic-inorganic fluorides crystallise: [H₃dien]·(AlF₆) (P2₁/c, Z = 4), [H₃dien]₂·(AlF₅(H₂O))₃·2H₂O (P2₁/n, Z = 4), [H₃dien]·(AlF₆)·2H₂O, which was previously known, and [H₃dien]₂·(Al₄F₁₈) (C2/c, Z = 4). A new (Al₄F₁₈)⁶⁻ polyanion, which results from the tetrahedral association of four AlF₆ octahedra linked by corners, is evidenced in [H₃dien]₂·(Al₄F₁₈).     

Colorimetric determination of isonicotinic acid hydrazide

Summary Isonicotinic acid hydrazide reacts with catechol in alkaline medium to give a pinkish-orange color which obeys Beer's law. This color reaction is specific for isonicotinic acid hydrazide and is used for its determination in blood or urine. The visual limit of identification is 1 g/ml.

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Zusammenfassung Isonikotinsäurehydrazid reagiert in alkalischem Milieu mit Brenzcatechin. Dabei bildet sich eine Rosa-orange-Färbung, die dem Beerschen Gesetz entspricht. Diese Farbreaktion ist für Isonikotinsäurehydrazid spezifisch und für dessen Bestimmung in Blut und Harn geeignet. Die Nachweisgrenze liegt bei 1 g/ml.

     

Molecular structure, vibrational and chemical shift assignments of 8-hydroxy-1-methylquinolinium iodide hydrate by density functional theory (DFT) and ab initio Hartree-Fock (HF) calculations

The molecular geometry, the normal mode frequencies and corresponding vibrational assignments, (1)H and (13)C NMR chemical shift values of 8-hydroxy-1-methylquinolinium iodide monohydrate [(C(10)H(10)NO)(+)I(-)H(2)O] in the ground state were performed by HF and B3LYP levels of theory using the LanL2DZ basis set. The optimized bond lengths and bond angles are in good agreement with the X-ray data. The vibrational spectra of the title compound which is calculated by HF and DFT methods, reproduces vibrational wave numbers and intensities with an accuracy which allows reliable vibrational assignments. The title compound [(C(10)H(10)NO)(+)I(-)H(2)O] have been studied theoretically in the 4, 000-200 cm(-1) region and the assignment of all the observed bands were made. The analysis of the infrared spectra indicates that there are some structure-spectra correlations. These methods are proposed as a tool to be applied in the structural characterization of 8-hydroxy-1-methylquinolinium iodide monohydrate [(C(10)H(10)NO)(+)I(-)H(2)O], and thus providing useful support in the interpretation of experimental NMR data.     

Quantum dot nanocrystals having guanosine imprinted nanoshell for DNA recognition

Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoparticles have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to CdS quantum dots (QDs), reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for DNA recognition. In this method, methacryloylamidohistidine-platinium (MAH-Pt(II)) is used as a new metal-chelating monomer via metal coordination-chelation interactions and guanosine templates of DNA. Nanoshell sensors with guanosine templates give a cavity that is selective for guanosine and its analogues. The guanosine can simultaneously chelate to Pt(II) metal ion and fit into the shape-selective cavity. Thus, the interaction between Pt(II) ion and free coordination spheres has an effect on the binding ability of the CdS QD nanosensor. The binding affinity of the guanosine imprinted nanocrystals has investigated by using the Langmuir and Scatchard methods, and experiments have shown the shape-selective cavity formation with O6 and N7 of a guanosine nucleotide (K(a) = 4.841x10(6) mol L(-1)) and a free guanine base (K(a) = 0.894x10(6) mol L(-1)). Additionally, the guanosine template of the nanocrystals is more favored for single stranded DNA compared to double stranded DNA.