Determination of "net carbohydrates" using high-performance anion exchange chromatography

For labeling purposes, the carbohydrate content of foods has traditionally been determined by difference. This value includes sugars, starches, fiber, dextrins, sugar alcohols, polydextrose, and various other organic compounds. In some cases, the current method may lack sufficient specificity, precision, and accuracy. These are subsequently quantitated by high performance anion exchange chromatography with pulsed amperometric detection and expressed as total nonfiber saccharides or percent "net carbohydrates." In this research, a new method was developed to address this need. The method consists of enzyme digestions to convert starches, dextrins, sugars, and polysaccharides to their respective monosaccharide components. These are subsequently quantified by high-performance anion exchange chromatography with pulsed amperometric detector and expressed as total nonfiber saccharides or percent "net carbohydrates." Hydrolyzed end products of various novel fibers and similar carbohydrates have been evaluated to ensure that they do not register as false positives in the new test method. The data generated using the "net carbohydrate" method were, in many cases, significantly different than the values produced using the traditional methodology. The recoveries obtained in a fortified drink matrix ranged from 94.9 to 105%. The coefficient of variation was 3.3%.     

The addition of fluorine to perhalogenated compounds containing carbon-nitrogen double bonds

The reaction of elementary fluorine with ten perhalogenated compounds containing carbon-nitrogen double bonds is reported. The reactions were carried out without added catalysts in a static system. With CF₃N=CF₂, (CF₃)₂NCF=NCF₃, SF₅N=CF₂, CF₂=NCl, CF₃CF=NCl and CF₂=NF a simple addition of fluorine to the carbon-nitrogen double bond was observed forming the respective N-fluoroamines in high yield. Two imines, CF₃CF=NF and (CF=NF)₂, were unreactive under the same conditions and reactions of CF₃CF₂CF=NF and (CF₃)₂C=NF were explosive.     

Effect of trans‐ and cis‐isomeric defects on the localization of the charged excitations in π‐conjugated organic polymers

We use the long‐range‐corrected hybrid density functional theory models to study the effect of various conformational distortions of weak‐trans and strong‐cis nature on the spatial localization of charged states in poly(p‐phenylene vinylene) (PPV) and its derivative poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene] (MEH‐PPV). The extent of self‐trapping of positive (P⁺) and negative (P^?) polarons is observed to be highly sensitive to molecular conformation that, in turn, controls the distribution of atomic charges within the polymers. It is shown that, to reach good agreement with recent experimental data on lattice distortion for P⁺ and P^? excitations, the polarization of the medium plays a critical role. The introduction of weak‐trans defects along the MEH‐PPV chain breaks the observed symmetry for P⁺ and P^? excitations. The P^? states exhibit more spatial localization owing to lattice relaxation than their vacuum counterparts in contrast to P⁺. These observations suggest higher mobilities of holes than that of electrons in MEH‐PPV, in agreement with the experimental observations. The predicted binding, reorganization, and solvation energies for PPV and MEH‐PPV are analyzed for this difference in the response behavior of holes and electrons for trans and cis distortions. This study allows for a better understanding of charge‐transport and photophysical properties in π‐conjugated organic materials by analyzing their underlying structure–property correlations. © 2013 Wiley Periodicals, Inc. 1 1 This article is a U.S. Government work, and as such, is in the public domain in the United States of America.
J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 935–942     

Solution Properties of a 3D Stochastic Euler Fluid Equation

We prove local well-posedness in regular spaces and a Beale–Kato–Majda blow-up criterion for a recently derived stochastic model of the 3D Euler fluid equation for incompressible flow. This model describes incompressible fluid motions whose Lagrangian particle paths follow a stochastic process with cylindrical noise and also satisfy Newton’s second law in every Lagrangian domain.

     

Excited state (formal) intramolecular proton transfer (ESIPT) in p-hydroxyphenyl ketones mediated by water

Evidence is presented that show p-hydroxyphenyl ketones 6–8 undergo excited state intramolecular proton transfer (ESIPT, via the singlet excited state), mediated by water, which formally transfers the phenol proton to the carbonyl oxygen of the ketone. ESIPT was not observed in neat CH₃CN. The ESIPT process in aqueous media generates the corresponding p-quinone methides 9–11 (and the corresponding conjugate bases (phenolate ions) 12–14), as detected by laser flash photolysis (LFP). It competes effectively with intersystem crossing to the excited triplet state. The respective p-methoxyphenyl ketones 15 and 16 failed to undergo the reaction consistent with the expected lack of proton transfer in these systems. Results for the biphenyl ketone 8 indicate that formal ESIPT can also take place over an extended range, suggesting that the process is likely general for all p-hydroxyaromatic ketones which opens up the possibility for designing photoswitchable processes based on this general phenomenon.     

Application of ultra-high-performance liquid chromatography/tandem mass spectrometry for the measurement of vitamin D in infant formula and adult/pediatric nutritional formula: First Action 2011.11

In an effort to measure vitamin D, ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) was applied to samples. The use of UHPLC-MS/MS decreased the run time by 50%. The UHPLC-MS/MS achieved equal or better separation efficiency with complex food matrixes compared to HPLC-MS/MS. It was also observed that under the optimized conditions of UHPLC, all previtamins of vitamin D3, D2, and isotope-labeled vitamin D3 were baseline-separated from their corresponding vitamins. The sterol isomers found in complex food matrixes that interfere in the analysis were well separated from the analytes. The accuracy of the method was evaluated by analyzing National Institute of Standards and Technology Standard Reference Material 1849 infant reference material. The average vitamin D3 concentration was 0.251 +/- 0.012 microg/g. This showed excellent agreement with the certified value of 0.251 +/- 0.027 microg/g. The spike recovery study of a commercial infant formula matrix showed a range of recovery from 100 to 108%. The LOQ values determined were 0.0022 and 0.0028 microg/g for vitamins D3 and D2, respectively; LOD values were 0.00065 and 0.00083 microg/g for vitamins D3 and D2, respectively.