Background theory and applications of microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) is an electrodriven separation technique. Separations are achieved using microemulsions which are nanometre-sized oil droplets suspended in aqueous buffer. The surface tension between the oil and water components is reduced by covered the oil droplet with an anionic surfactant such as sodium dodecyl sulphate and a co-surfactant such as a short-chain alcohol. This review summarises the various microemulsion types and compositions that have been used in MEEKC. The effects of key operating variables such as pH and temperature are also described. The application areas of MEEKC are also described in some detail. MEEKC has been applied to a wide range of water-soluble and insoluble both charged and neutral compounds. Examples are described which include analysis of derivatised sugars, proteins, pesticides and a wide range of pharmaceuticals. At present there are only a limited number of publications describing the use of MEEKC but it is anticipated that this number will increase rapidly in the near future as more awareness of the separation possibilities that MEEKC presents increases.     

Photoproteins as luminescent labels in binding assays

Certain marine organisms produce calcium-activated photoproteins that allow them to emit light for a variety of purposes, such as defense, feeding, breeding, etc. Even though there are many bioluminescent organisms in nature, only a few photoproteins have been isolated and characterized. The mechanism of emission of light in the blue region is the result of an internal chemical reaction. Because there is no need for excitation through external irradiation for the emission of bioluminescence, the signal produced has virtually no background. This allows for the detection of the proteins at extremely low levels, making these photoproteins attractive labels for analytical applications. In that regard, the use of certain photoproteins, namely, aequorin, obelin, and the green fluorescent protein as labels in the design and development of binding assays for biomolecules has been reviewed. In addition, a related fluorescent photoprotein, the green fluorescent protein (GFP), has been recently employed in bioanalysis. The use of GFP in binding assays is also discussed in this review.     

Simultaneous ab initio calculations of isoelectronic diatomic molecules

Large gaussian basis sets are employed in simultaneous configuration interaction calculations for the ground states of isoelectronic diatomic molecules. The resulting potential energy curves for three members respectively of four different isoelectronic molecule sequences show the applicability of the method. Comparisons with available results of standard configuration interaction calculations for selected molecules are given. Using our method we often get lower upper bounds for the electronic energy, save computer time and treat physically totally different molecules simultaneously.     

Conversion of 2-amino-5-R-phenyl-1,3,4-oxadiazoles into 3-R-phenyl-5-alkoxy-1,2,4-triazoles

2-Amino-5-R-phenyl-1,3,4-oxadiazoles have been shown to isomerize in alcoholic potassium hydroxide solution to 3-R-phenyl-5-alkoxy-1,2,4-triazoles. The dissociative ionization of 3-R-phenyl-5-alkoxy-1,2,4-triazoles and 3-R-phenyl-1,2,4-triazolin-5-ones has been examined. The mass spectra of the oxadiazoles have been compared with those of the triazoles.Translated from Khimiya Geterotslklicheskikh Soedinenii, No. 11, pp. 1553–1556, November, 1986.     

Fluoridolyse von Cyclophosphazenen und linearen Polyphosphazenen

Fluoridolysis of Cyclophosphazenes and Lineary Polyphosphazenes The fluorination of nongeminal trans P₃N₃Cl₄(NEt₂)₂ and nongeminal trans P₃N₃Cl₃(NEt₂)₃ with the fluorination agent Et₃N · 0,6 HF ( B ) occurs under retention of configuration yielding P₃N₃Cl₂F₂(NEt₂)₂ and P₃N₃F₄(NEt₂)₂ or P₃N₃F₃(NEt₂)₃, respectively. P₃N₃Cl₆ is nearly quantitatively converted into P₃N₃F₆. Poly(dichlorophosphazene) reacts to a poly(difluorophosphazene), (PNF₂)_n, distinguished by a moderate solubility in THF.     

Polymethine dyes — Indolo[3,2-d]thiazole derivatives

New polymethine dyes with an indolo[3,2-d]thiazole residue are described, and their spectral properties are discussed. Replacement of the vinylene group in the naphtho[1,2-d]thiazole residue by an NH group leads to a considerably greater bathochromic shift of the absorption maximum of carbo- and merocyanines as compared with replacement by a sulfur atom. The basicity of the indolo[3,2-d]thiazole residue is higher than the basicity of the naphtho[1,2-d]-thiazole and thionaphtheno[3,2-d]thiazole residues.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1606–1610, December, 1972.     

Selective complexometric determination of palladium, with thiourea as masking agent

A method is proposed for selective complexometric determination of palladium, thiourea being used as masking agent. An excess of EDTA is added and the surplus EDTA is back-titrated at pH 5-5.5 with lead nitrate, with Xylenol Orange as indicator. Thiourea is then added to decompose the palladium-EDTA complex and the liberated EDTA is again back-titrated with lead nitrate. The interference of various cations has been studied.     

Use of long-chain alkylamines for preconcentration and determination of traces of molybdenum, tungsten and rhenium by atomic-absorption spectroscopy-II: molybdenum in soils, sediments and natural waters

Molybdenum is extracted as the thiocyanate complex with the quaternary long-chain aliphatic amine Aliquat 336 in chloroform, followed by evaporation of the solvent, dissolution in MIBK, and atomic-absorption spectroscopy. The method is simple, rapid and sensitive, with few interference problems for the determination of the Mo content of soils and sediments in the range 0.1-1.0 ppm with a relative standard deviation better than 5% when 1-g samples are used. Quantitative extraction from large volumes of aqueous solution has also been confirmed, allowing the determination of Mo in natural waters in the ppM range.     

N-quaternary compounds—XLIV: Synthesis and circular dichroism of α-N,N-dimethylamino and α-N,N,N-trimethylammonio ketones

CD spectra of acyclic α-N,N-dimethylamino ketones exhibit two absorption bands of opposite sign at ca. 240 and 305–315 nm. Both bands are ascribed to the same conformers. On protonation only one CD band is seen. The single CD band of α-N,N,N-trimethylammonio ketones has the same sign and almost the same wavelength maximum as the protonated amino ketones.