Gas chromatographic/mass spectrometric determination of 3-methoxy-1,2-propanediol and cyclic diglycerols, by-products of technical glycerol, in wine: interlaboratory study

The aim of the present study was to provide the official wine control authorities with an internationally validated method for the determination of 3-methoxy-1,2-propanediol (3-MPD) and cyclic diglycerols (CycDs)-both of which are recognized as impurities of technical glycerol-in different types of wine. Because glycerol gives a sweet flavor to wine and contributes to its full-body taste, an economic incentive is to add glycerol to a wine to mask its poor quality. Furthermore, it is known that glycerol, depending on whether it is produced from triglycerides or petrochemicals, may contain considerable amounts of 3-MPD in the first case or CycDs in the second. However, because these compounds are not natural wine components, it is possible to detect glycerol added to wine illegally by determining the above-mentioned by-products. To this end, one of the published methods was adopted, modified, and tested in a collaborative study. The method is based on gas chromatographic/mass spectrometric analysis of diethyl ether extracts after salting out with potassium carbonate. The interlaboratory study for the determination of 3-MPD and CycDs in wine was performed in 11 laboratories in 4 countries. Wine samples were prepared and sent to participants as 5 blind duplicate test materials and 1 single test material. The concentrations covered ranges of 0.1-0.8 mg/L for 3-MPD and 0.5-1.5 mg/L for CycDs. The precision of the method was within the range predicted by the Horwitz equation. HORRAT values obtained for 3-MPD ranged from 0.8 to 1.7, and those obtained for CycDs ranged from 0.9 to 1.3. Average recoveries were 104 and 109%, respectively.     

Variable cant angle winglets for improvement of aircraft flight performance

Meccanica - Traditional winglets are designed as fixed devices attached at the tips of the wings. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving...     

Chiral and meso‐bis([2.2]­para­cyclo­phan‐4‐yl)­methane and meso‐bis­([2.2]­para­cyclo­phan‐4‐yl) sulfide

The [2.2]­para­cyclo­phane groups of the title compounds, chiral and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl)­methane (the former as a racemate), C₃₃H₃₂, and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl) sulfide, C₃₂H₃₀S, show the characteristic structural features of the parent compound [2.2]­para­cyclo­phane and the related compound di­methylbis([2.2]­para­cyclo­phan‐4‐yl)­silane, C₃₄­H₃₆­Si: the aromatic rings are puckered, resulting in a boat conformation. The planes of the four coplanar C atoms are slightly twisted with respect to each other. The Csp³—Csp³ bond lengths of the ethyl­ene bridges are elongated by the electronic and steric effects of the skeleton.     

Zur Analytik mikrobiocider Isothiazolone

Zusammenfassung Methylisothiazolon-PrÄparate wurden nach Extraktion und dünnschicht-chromatographischer Fraktionierung mittels Capillar-Gas-Chromatographie/ Massenspektrometrie untersucht. 2-Methyl-isothiazol-3-on and 5-Chlor-2-methyl-isothiazol-3-on wurden als Hauptbestandteile sowie 4,5-Dichlor-2-methyl-isothiazol-3-on, 3-Chlor-N-methyl-propionamid und Dichlor-N-methyl-acetamid als Nebenbestandteile identifiziert. In dem untersuchten Octylisothiazolon-PrÄparat wurde als Wirkstoff 2-n-Octyl-isothiazol-3-on identifiziert; chlorierte Verbindungen konnten nicht nachgewiesen werden.

---

Analysis of microbiocidal isothiazolonesI. Identification by gas chromatography/mass spectrometry

Summary Methyl-isothiazolone products were investigated with capillary gas chromatography/mass Spectrometry after extraction and thin-layer chromatographic separation. 2-methyl-isothiazol-3-one and 5-chloro-2-methyl-isothiazol-3-one were identified as major components and 4,5-dichloro-2-methyl-isothiazol-3-one, 3-chloro-N-methylpropionamide and dichloro-N-methyl-acetamide as minor components. 2-n-octyl-isothiazol-3-one was identified as the active agent in an octyl isothiazolone product whereas chlorinated compounds could not be found.

     

Towards a Comprehensive Hydride Donor Ability Scale

Rates of hydride transfer from several hydride donors to benzhydrylium ions have been measured at 20 °C and used for the determination of empirical nucleophilicity parameters N and s_N according to the linear free energy relationship log k_{20 °C}=s_N(N+E). Comparison of the rate constants of hydride abstraction by tritylium ions with those calculated from the reactivity parameters s_N, N, and E showed fair agreement. Therefore, it was possible to convert the large number of literature data on hydride abstraction by tritylium ions into N and s_N parameters for the corresponding hydride donors, and construct a reactivity scale for hydride donors covering more than 20 orders of magnitude.