A novel derivative for the assessment of urinary and salivary nitrate using gas chromatography/mass spectrometry

Previous gas chromatography/mass spectrometry (GC/MS) methods for determining nitrate in biological samples involve either hazardous chemicals or produce multiple isomers that can be difficult to quantitate. Modification of these methods, by the nitration of mesitylene instead of benzene and in the presence of trifluoroacetic anhydride rather than sulphuric acid, should enable simple isotopic quantitation for use in tracer studies, for example, in the measurement of nitric oxide production. Desiccated urine and saliva samples, in addition to aqueous labelled and unlabelled nitrate standards, were treated with trifluoroacetic anhydride and mesitylene at 70°C for 1 h, cooled, then sequentially washed with deionised water and aqueous sodium bicarbonate. The solution of nitromesitylene in mesitylene was separated, dried and analysed by GC/MS. The full mass spectra exhibited abundant ions at m/z 165 and 166 corresponding to the unlabelled and labelled molecular species of nitromesitylene, respectively. Selected ion monitoring of these masses for a series of gravimetrically prepared standards indicated good agreement with isotopic enrichments in the range 0.0625–5 mole % excess, and at nitrate concentrations within the physiological range of 0.078–2 mmol/L. Derivatised samples were stable with respect to isotopic enrichments and nitrate concentrations at −20°C for up to 21 days and exhibited excellent repeatability. Nitration of mesitylene proved to be a simple and rapid method for the measurement of isotope ratios in aqueous nitrates by GC/MS, which has applications in tracer studies and in concentration determinations by isotope dilution techniques for nitric oxide production. Copyright © 2008 John Wiley & Sons, Ltd.     

Alternating ethylene–alkyl acrylate copolymers. II. Polymer properties

Properties such as viscosity correlations and spectral data of alternating ethylene–ethyl acrylate copolymers are described. The proton and ¹³C-NMR spectra show that there is a considerable amount of tacticity in these polymers. Although the alternating configuration predominates, there is also some random structure present. Terpolymers were prepared with cure-site monomers, such as 2-chloroethyl acrylate. The terpolymers were compounded with carbon black and cured to give vulcanizates with excellent properties. The cured products are resistant to oil, water, heat, and oxidation. They also have good low temperature properties (stiffening temperature ?31°C, brittleness temperature ?50°C), tensile properties (tensile strength 17.2 MPa, elongation at break 250%) and compression sets (25% at 150°C for 70 hr).     

Measuring moisture in cheese by near infrared absorption spectroscopy

Data in the literature indicate that the measurement of moisture in cheese by near infrared transmittance (NIT) is more accurate than by reflectance (NIR). The accuracy of the NIT measurement (SEP) was calculated for Edam, Gouda, Brie, Colby, and Cheddar. A range of SEP values (0.12-0.35) was obtained using different methods of calibration for different types of samples. There was close agreement between these results, as they related to the precision of the reference method. The calibration validation technique described as Standard Error of Cross Validation (SECV) generated results that compared very closely to the equivalent SEP values for independent sample sets.     

Bio‐based copolymers obtained through miniemulsion copolymerization of methyl esters of acrylated fatty acids and styrene

Polymers based on renewable sources are promising materials, and can find many uses in coatings and adhesive applications. The goal of this work was to synthesize and characterize bio‐based styrene/acrylated fatty acid methyl ester (AFAME) copolymer—poly(styrene‐co‐AFAME) prepared by miniemulsion polymerization. The main strategy adopted was to functionalize the bio‐monomer with acrylic acid that was confirmed by ¹H NMR and FTIR measurements, to allow its free‐radical homo‐ or copolymerization with styrene. Poly(styrene‐co‐AFAME) with different AFAME content were obtained and their composition were evaluated by ¹H NMR. Dynamic light scattering measurements throughout the reactions have indicated a very stable colloidal systems and average particles size ranges 100–150 nm. The structural and physical properties of poly(styrene‐co‐AFAME) were investigated by DTG‐DTA, DSC which displayed a decreasing of glass transition temperature with increase of AFAME content. The results showed in this study have indicated that the poly(styrene‐co‐AFAME) can be used in several fields because their characteristics are totally distinct. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1422–1432     

Extremely fragile glass‐formers? Calorimetric and rheological determinations

We use calorimetry and rheology to investigate reports of extremely fragile polymers and the speculation that d,l ‐lactic acid should be extremely fragile. The dynamic fragilities of lactic acid, polysulfone, bisphenol‐A polycarbonate, and poly(vinyl chloride) were studied. The polymers were used as received and after a wash‐precipitation treatment. The current dynamic fragility findings are not in agreement with those reported by C. Evans, H. Deng, W. Jager, J. Torkelson, Macromolecules 2013 , 46 (15), 6091–6103 of extremely high fragilities for the mentioned polymers. We also found no sample preparation history effect on the dynamic fragility values. The calorimetric and rheological results for the d,l ‐lactic acid show dynamic fragility values that are consistent with each other and are not extremely fragile. Calorimetric measurements that use a broad range of cooling rates gave smaller dynamic fragility values than those obtained from a limited range at higher cooling rates. The importance of the results is discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1261–1272