The microanalysis of fluorine-containing organic compounds

Summary Kirsten's method for the determination of nitrogen has been applied to the analysis of fluorine-containing organic compounds. Some slight modifications to the original method have been introduced.

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Zusammenfassung Die vonKirsten angegebene Methode zur Bestimmung von Stickstoff wurde für die Analyse fluorhältiger organischer Verbindungen angewendet. Einige geringfügige Modifikationen des ursprünglichen Verfahrens werden angegeben.

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Résumé On a employé la méthode deKirsten pour la détermination de l'azote de composés organiques contenant du fluor. On a introduit quelques légères modifications à la méthode originale.

     

A comparative study of some lanthanon chelates of alizarin complexan as reagents for fluoride

A study has been made of the comparative suitability of the cerium^III, lanthanum and praseodymium chelates of alizarin complexan as reagents for the spectrophotometric determination of microgram amounts of fluoride. The cerium^III reagent is most sensitive at pH < 4.5 and the lanthanum reagent at pH 5.0. An enhancement of sensitivity may be obtained for both reagents at pH 4.3 by addition of acetone to 25 % v/v, but the most sensitive means of determination is to use the lanthanum reagent in aqueous solution at pH 5.2 with measurement at 281 mμ. This procedure is 200% more sensitive than the standard method at 620 mμ.     

Titrimetric determination of microgram amounts of bismuth after precipitation as Bi[Cr(SCN)(6)] followed by thiocyanate amplification

Bismuth (10-100 mug) is precipitated as Bi[Cr(SCN)(6)]. After filtration, the precipitate is treated with bicarbonate solution, and the thiocyanate dissolved is oxidized by iodine in alkaline medium to sulphate. After acidification, the excess of iodine is extracted into chloroform, and the iodide in the aqueous solution is amplified by bromine oxidation and subsequent treatment with more iodide. The titrimetric procedure provides 228 iodine atoms for each original bismuth ion. Only Hg(2+)(2), Hg(2+) and AsO(3-)(4) interfere seriously.     

Measuring the metabolome: current analytical technologies

The post-genomics era has brought with it ever increasing demands to observe and characterise variation within biological systems. This variation has been studied at the genomic (gene function), proteomic (protein regulation) and the metabolomic (small molecular weight metabolite) levels. Whilst genomics and proteomics are generally studied using microarrays (genomics) and 2D-gels or mass spectrometry (proteomics), the technique of choice is less obvious in the area of metabolomics. Much work has been published employing mass spectrometry, NMR spectroscopy and vibrational spectroscopic techniques, amongst others, for the study of variations within the metabolome in many animal, plant and microbial systems. This review discusses the advantages and disadvantages of each technique, putting the current status of the field of metabolomics in context, and providing examples of applications for each technique employed.     

The microanalysis of fluorine-containing organic compounds

Summary Methods are described for the micro determination of chlorine, bromine, and iodine in organic compounds containing fluorine. The sample is heated with sodium in a nickel bomb, and the chloride ion produced is determined titrimetrically by a modified procedure involving the use of mercuric oxycyanide. Bromide is determined titrimetrically after oxidation to bromate with sodium hypochlorite; iodide is also determined by an amplified procedure after oxidation to iodate with bromine.The method has been extended to the simultaneous determination of chlorine, bromine, and iodine when present in organic compounds containing fluorine. All four halogens, and all possible combinations of halogens, can be determined in one compound after a single fusion.

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Zusammenfassung Es werden Methoden zur Mikrobestimmung von Chlor, Brom und Jod in fluorhaltigen organischen Substanzen beschrieben. Die Probe wird in einer Nickelbombe mit Natrium erhitzt. Das hierbei entstehende Chlorid wird mit Quecksilberoxycyanid nach einem modifizierten Verfahren titriert. Das Bromid wird nach Oxydation zu Bromat mit Natriumhypochlorit titriert. Das Jodid wird mit Brom zu Jodat oxydiert. Nach Zugabe von Jodid wird die sechsfache Jodmenge mit Thiosulfat bestimmt.Das Verfahren wurde für die gleichzeitige Bestimmung von Chlor, Brom und Jod in fluorhaltigen organischen Substanzen erweitert. Alle vier Halogene können somit unabhängig von ihrem gegenseitigen Verhältnis in einer Verbindung nebeneinander ineiner Einwaage bestimmt werden.

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Résumé Des méthodes sont décrites pour le microdosage du chlore, du brome, de l'iode dans les composés organiques contenant du fluor. L'échantillon est chauffé avec du sodium dans une bombe de nickel et l'ion chlorhydrique produit est déterminé titrimétriquement par une méthode modifiée mettant en jeu l'emploi d'oxycyanure mercurique. Le brome est dosé volumétriquement après oxydation en bromate a ec l'hypochlorite de sodium. L'iode est déterminé également par une methode amplifiée après oxydation en iodate par le brome.La méthode a été étendue au dosage simultané du chlore, du brome, de l'iode quand ils sont présents dans des composés organiques contenant du fluor. Les 4 halogènes et toutes les combinaisons possibles d'halogènes peuvent être déterminées sur un seul composé après une simple fusion.

     

The simultaneous determination of copper and nickel by solvent extraction and gas-liquid chromatography with bis (acetylpivalylmethane) ethylenediimine as reagent

The copper(II), nickel(II) and palladium(II) chelates of the bridged β-ketoamine, bis(acetylpivalylmethane) ethylenediimine, are described. The copper and nickel complexes are readily extracted by cyclohexane at pH 8.0 from aqueous solution. The gas chromatographic separation of the copper and palladium, the nickel and palladium, and the copper and nickel chelates is reported on a silicone gum rubber phase (E-350) supported on Universal B at 285°C. Optimal conditions for the complete separation of copper and nickel are reported; the solvent extraction—gas chromatographic procedures are applied to the determination of the individual metal ions (limit of detection, 1 ng) and to the simultaneous determination of copper and nickel in solution and in alloy samples. A rapid method for the determination of copper in domestic water samples is also described.     

MALDI-MS of drugs: Profiling,imaging, and steps towards quantitative analysis

Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization technique which can be used in mass spectrometry to produce ions from biomolecules without inducing the fragmentation associated with traditional methods of ionization. When used with small molecules, the lack of fragmentation allows identification of specific molecules against a background of alternative signals; thus, for example, the presence of drug molecules and metabolites can be distinguished from a range of alternative biomolecules present within a tissue sample. Using highly collimated lasers in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows imaging of a tissue sample whereby the laser is rastered across the sample and individual mass spectra are collected in a serial manner. Thus, the distribution of the molecules within the tissue sample can be presented in the form of a 2D image. While the detection of specific drug molecules and metabolites within biological samples has its uses, quantification of those same molecules would be of greater benefit in a clinical setting. However, accurate quantification presents additional challenges. We present an overview of the MALDI-MS technique followed by recent progress in profiling drugs and their metabolites through imaging drug distributions within tissues and finish with recent developments in the quantification of drugs in tissues by MALDI-MSI.     

Investigation of the doping efficiency of poly(styrene sulfonic acid) in poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) dispersions by capillary electrophoresis

CE can efficiently separate poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) complexes and free PSS in dispersions and can be used to estimate the degree of PSS doping. We investigated the doping efficiency of PSS on PEDOT in dispersions using CE and its effect on the conductivity of the resulting PEDOT/PSS films. Results of this study indicate that dispersions containing 1:2.5–3 EDOT:PSS feed ratio (by weight) exhibiting 72–73% PSS doping generate highly processable and highly conductive films. Conductivity can be optimized by limiting the time of reaction to 12 h. At this point of the reaction, the PEDOT/PSS segments, appearing as broad band in the electropherogram, could still exist in an extended coil conformation favoring charge transport resulting in high conductivity. Above a threshold PEDOT length formed at reaction times longer than 12 h, the PEDOT/PSS complex, appearing as spikes in the electropherogram, most likely have undergone a conformational change to coiled core‐shell structure restricting charge transport resulting in low conductivity. The optimal conductivity (5.2 S/cm) of films from dispersions synthesized for 12 h is significantly higher than those from its commercial equivalent Clevios P and other reported values obtained under similar conditions without the addition of codopants.     

Modification of the surface properties of polyimide films using polyhedral oligomeric silsesquioxane deposition and oxygen plasma exposure

Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), on Kapton^® HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104° for unexposed POSS-coated surfaces to ∼5° for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory. Changes in surface energy are related to potential adhesive interactions with lunar dust simulant particles.     

Anion sensing 'venus flytrap' hosts: a modular approach

A series of podands based on three hydrogen bonding 'arms' have been prepared and their affinities for simple inorganic anions measured.