Topographical properties of polymer films deposited in capillaries for electrophoretic separations of large organic molecules

Topography and thickness of hydrophilic polymer coatings of fused-silica capillaries for capillary electrophoresis (CE) were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and profilometry. Three hydrogels, poly(2-hydroxyethyl methacrylate) [poly(HEMA)], poly(diethylene glycol monomethacrylate) [poly(DEGMA)], and poly(triethylene glycol monomethacrylate) [poly(TEGMA)], were deposited using two procedures, either by simple physical sorption of the polymers, or by derivatization of the capillary wall surface with glycidyl methacrylate (EPMA) followed by polymerization of the appropriate monomers. The performance of the modified capillaries was tested under CE conditions (decrease in the electroosmotic flow, EOF dependence on pH, separation of milk and standard proteins). It has been found that the most important property of the polymer coating is its thickness, whereas its topography and the degree of its hydrophobicity are less significant. Film deposition by physical adsorption is preferable to polymerization on the derivatized surface.     

Study of perrhenate reduction by capillary electrophoresis

The influence of perrhenate concentration, the concentration of the reducing agent and pH of the reaction mixture on the yield of perrhenate reduction were studied to find a possibility to decrease the stannous chloride concentration in the reaction mixture without negative changes on the yield of perrhenate reduction. Britton-Robinson buffer solutions were selected as the background electrolytes because of their buffering capacity in a wide pH interval. The highest degree of perrhenate reduction was obtained at pH 2 at perrhenate concentrations ranging from 10(-4) to 10(-3) mol/L. The stability of reduced rhenium against pH change from 2 to 5.5 and against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy were studied as well. The results obtained by capillary electrophoresis and by thin-layer chromatography with radiometric detection were compared.     

Sulfur Compounds. 183. A Derivative of Perthiocarbonic Acid H2CS4: X-ray structural analysis of bis(triphenylmethyl) perthiocarbonate (Ph3C)2CS4

The molecular structure of Ph₃CSSC(S)SCPh₃ · CS₂ has been determined by X-ray structural analysis. The substance crystallizes in the triclinic crystal system [a = 884.9(2) pm, b = 1 039.5(2) pm, c = 2 064.6(3) pm, α = 75.86(1)°, β = 79.83(2)°, γ = 77.31(5)°, Z = 2, space group P1 ]. The CS₃ group is planar; the S? S-bond (201.4 pm) forms an angle of 5.7° with the CS₃ plane. The torsional angle CSSC equals 96.3°. (Ph₃C)₂CS₄ was obtained by reaction of TosNSCl₂ (Tos = p-MeC₆H₄SO₂) with Ph₃CSH in CS₂ in the presence of triethylamine. The reaction mechanism is discussed.     

Stille-type cross-coupling-An efficient way to various symmetrically and unsymmetrically substituted methyl-bipyridines: toward new ATRP catalysts

Various mono- and disubstituted 2,2'-bipyridines were synthesized in high yields and multigram scales utilizing Stille-type coupling procedures. The corresponding bromo-picoline and tributyltin-picoline building blocks were prepared from commercially available amino-picoline compounds. As first examples of metal complexes, 4,5'-dimethyl-2,2'-bipyridine was reacted with copper(II) and iron(II) ions and investigated as catalyst in ATRP.     

Strukturanalyse organischer Sulfide mit Hilfe der Gras-Chromatographie

Zusammenfassung Eine Methode der Identifizierung von Alkyl- und Arylgruppen organischer Sulfide wurde ausgearbeitet, die die Spaltung dieser Stoffe mit Raney-Nickel zur gaschromatographischen Bestimmung der dabei entstandenen Kohlenwasserstoffe ausnützt.

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Summary A method was developed for identifying alkyl- and aryl groups of organic sulfides. The method employs the cleavage of these materials with Raney nickel for the gas chromatographic determination of the resulting hydrocarbons.

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Résumé On a mis au point une méthode d'identification des groupes alkylés et arylés des sulfures organiques exploitant la dissociation de ceux-ci par le nickel Raney pour le dosage par chromatographic en phase gazeuse des carbures d'hydrogène qui se forment.

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Die Autoren danken den Kollegen Dr.M. Veea, Ing.J. Petránek und Ing.J. Gaspari für die Überlassung von Proben organischer Sulfide.     

Synthese und Charakterisierung funktionalisierter β‐Hydroxydithiozimtsäuren und deren Ester. Komplexchemisches Verhalten gegenüber Nickel(II), Palladium(II) und Platin(II)

Synthesis and Analytical Characterization of Functionalized β‐Hydroxydithiocinnamic Acids and their Esters. Complex Chemistry towards Nickel(II), Palladium(II), and Platin(II) Starting from silyl‐protected 4‐hydroxy acetophenone ( 1 ) the 1,1‐ethenedihiolato complexes 3 – 5 were synthesised using carbon disulfide and potassium‐tert‐butylate as a base. After being deprotected, the resulting 4‐hydroxy‐substituted complexes 6 – 8 were esterified with DL‐α‐lipoic acid to obtain the compounds 9 – 11 . The resulting complexes were characterized using NMR spectroscopy, mass spectrometry and IR spectroscopy. 3‐substituted β‐hydroxydithiocinnamic acid methyl ester ( 12 ) was obtained via an analogous path of reaction using silyl‐protected 3‐hydroxy acetophenone ( 2 ), carbon disulfide and methyl iodide. After removing of the silyl group the resulting hydroxy group was esterified with DL‐α‐lipoic acid. Using the dithioacid ester 14 as a ligand the Ni^II ( 15 ), Pd^II ( 16 ) and Pt^II ( 17 ) [O,S] complexes were obtained.     

Characterization of three agave species by gas chromatography and solid-phase microextraction-gas chromatography-mass spectrometry

Steam distillation (SD) extraction-solid-phase microextraction coupled to GC-MS was developed for the determination of terpenes and Bligh-Dyer extraction-derivatization coupled with GC for the determination of fatty acids such as ethyl esters were used. It was found that the three different Agave species have the same profile of fatty acids; the quantity of these compounds is different in each Agave variety. On the other hand, different terpenes were identified in the three Agave plants studied: nine in A. salmiana, eight in A. angustifolia and 32 in A. tequilana Weber var. azul.     

A fast $$(2 + \frac{2}{7})$$ ( 2 + 2 7 ) -approximation algorithm for capacitated cycle covering

Mathematical Programming - We consider the capacitated cycle covering problem: given an undirected, complete graph G with metric edge lengths and demands on the vertices, we want to cover the...