Ready detection of small amounts of lactulose in dairy products by thin-layer chromatography

Summary Ready detection of lactulose in milk and in mixtures with other sugars is achieved by diluting the sample ten times with acetone and successive thin-layer chromatographic separation on silica gel-boric acid, developed with acetonitrile: water 5020. The method allows detection of up to 0.02% lactulose on total carbohydrates and permits a semi-quantitative estimation of lactulose in milk.     

Use of gas chromatography-mass spectrometry for identification of a new disaccharide in honey

Gas chromatography-mass spectrometry has been used to separate and identify disaccharides of edible honey. According to the characteristic fragmentation behaviour of disaccharide TMS-oximes, fructofuranosyl-(2-1)-fructose (inulobiose) has been structurally characterized. Identification was carried out on the basis of retention time on two columns of different polarity and mass spectrometric analysis. Inulobiose was found in honeys of different origins for the first time, varying within 0.93 and 6.14 mg/g of honey. Its occurrence in honeys is discussed.     

Functional polyisobutylenes via a click chemistry approach

1‐(ω‐Azidoalkyl)pyrrolyl‐terminated polyisobutylene (PIB) was successfully synthesized both by substitution of the terminal halide of 1‐(ω‐haloalkyl)pyrrolyl‐terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1‐(ω‐azidoalkyl)pyrrole. Azide substitution of the terminal halide was carried out in 50/50 heptane/DMF at 90 °C for 24 h using excess azide. The 1‐(ω‐haloalkyl)pyrrolyl‐PIB precursors included 1‐(2‐chloroethyl)pyrrolyl‐PIB, 1‐(2‐bromoethyl)pyrrolyl‐PIB, and 1‐(3‐bromopropyl)pyrrolyl‐PIB. In situ quenching involved direct addition of 1‐(2‐azidoethyl)pyrrole to quasiliving PIB initiated from 5‐tert‐butyl‐1,3‐di(1‐chloro‐1‐methylethyl)benzene (bDCC)/TiCl₄ at ?70 °C in hexane/CH₃Cl (60/40, v/v). ¹H NMR analysis of the quenched product revealed mixed isomeric end groups in which PIB was attached at either C₂ or C₃ of the pyrrole ring (C₂/C₃ = 0.40/0.60). SEC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono‐substitution on each pyrrole ring. 1‐(3‐Azidopropyl)pyrrolyl‐PIB was reacted in modular fashion with various functional alkynes, propargyl alcohol, propargyl acrylate, glycidyl propargyl ether, and 3‐dimethylamino‐1‐propyne, via a Huisgen 1,3‐dipolar cycloaddition (Click) reaction, using Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine or bromtris(triphenylphosphine)Cu(I) as catalyst. The reactions were quantitative and produced PIBs bearing terminal hydroxyl, acrylate, glycidyl, or dimethylaminomethyl groups attached via exclusively four‐substituted triazole linkages. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2533–2545, 2010     

Chromatographic determination of lactulose

Summary Lactulose is a disaccharide with important implications in medicine, nutrition and dairy technology. It has to be determined usually as a minor component in complex matrices containing many other sugars. This paper describes the different chromatographic techniques (planar, liquid and gas chromatography) which have been proposed for the separation and quantification of lactulose in mixtures with other carbohydrates; the advantages of each technique are compared and some features where more research is necessary are outlined.     

Polyisobutylene-block-poly(methacrylic acid) diblock copolymers: self-assembly in aqueous media

Ionic amphiphilic diblock copolymer polyisobutylene-block-poly(methacrylic acid) (PIBx-b-PMAAy), with various lengths of nonpolar (x=25-75) and polyelectrolyte (y=170-2600) blocks, spontaneously dissolve in aqueous media at pH>4, generating macromolecular assemblies, the aggregation number of which depends on external stimuli (pH and ionic strength). Spherical micellar morphology with a compact core formed by the PIB blocks and a swollen corona built up from the PMAA blocks was deduced by cryogenic transmission electron microscopy. The micelles were further characterized by means of dynamic and static light scattering as well as small-angle neutron scattering. The critical micellization concentration, estimated by means of fluorescence spectroscopy with the use of pyrene as a polarity probe, is decisively determined by the length of the PIB block and is insensitive to changes in the length of the PMAA block.     

Photolysis of N-nitrosamines in neutral media

The photolysis of N-nitrosamines in solutions of acetonitrile follows a first-order reaction with respect to the concentration of nitrosamine. Quantum yields are very low (≈ 0.1) and depend on the concentration of nitrosamine, with the observation of a linear correlation between the reciprocal of quantum yield and the reciprocal of nitrosamine concentration. For all the nitrosamines studied, the final product of the photolysis appears to be unique, alkylidenimine, which in the case of nitroso methyl benzyl amine undergoes a relatively rapid hydrolysis, giving rise to benzaldehyde, following second order kinetics. A provisional model consistent with the experimental results obtained in this work is proposed. © 1993 John Wiley & Sons, Inc.