Composition and analysis of liquid smoke flavouring primary products

Smoke flavourings are produced on a large scale and have been applied to a variety of food products for more than 30 years. The use of them has many advantages compared to traditional smoking techniques. Among others, the amount of (known) toxic compounds deriving from combustion processes can be more easily controlled in smoke flavourings. In order to ensure safe products, a new European Regulation requests data on the composition and lays down, in particular, the maximum permitted concentrations for selected polycyclic aromatic hydrocarbons (PAHs). This review compiles results published on the chemical composition of liquid smoke flavouring primary products, partly in relation to production process parameters, and the analytical methods involved. The methods cover chromatographic techniques for analysis of specific compounds including extraction methods and clean-up procedures. Analysis of sensorial and bulk parameters such as acidity and total phenolic compounds are described as well as they are used as standard methods for analysis of liquid smoke flavourings. A special section is devoted to discussing the analysis of PAHs.     

Are Clusters Important in Understanding the Mechanisms in Atmospheric Pressure Ionization? Part 1: Reagent Ion Generation and Chemical Control of Ion Populations

It is well documented since the early days of the development of atmospheric pressure ionization methods, which operate in the gas phase, that cluster ions are ubiquitous. This holds true for atmospheric pressure chemical ionization, as well as for more recent techniques, such as atmospheric pressure photoionization, direct analysis in real time, and many more. In fact, it is well established that cluster ions are the primary carriers of the net charge generated. Nevertheless, cluster ion chemistry has only been sporadically included in the numerous proposed ionization mechanisms leading to charged target analytes, which are often protonated molecules. This paper series, consisting of two parts, attempts to highlight the role of cluster ion chemistry with regard to the generation of analyte ions. In addition, the impact of the changing reaction matrix and the non-thermal collisions of ions en route from the atmospheric pressure ion source to the high vacuum analyzer region are discussed. This work addresses such issues as extent of protonation versus deuteration, the extent of analyte fragmentation, as well as highly variable ionization efficiencies, among others. In Part 1, the nature of the reagent ion generation is examined, as well as the extent of thermodynamic versus kinetic control of the resulting ion population entering the analyzer region.

Catching an Entatic State—A Pair of Copper Complexes

The structures of two types of guanidine–quinoline copper complexes have been investigated by single‐crystal X‐ray crystallography, K‐edge X‐ray absorption spectroscopy (XAS), resonance Raman and UV/Vis spectroscopy, cyclic voltammetry, and density functional theory (DFT). Independent of the oxidation state, the two structures, which are virtually identical for solids and complexes in solution, resemble each other strongly and are connected by a reversible electron transfer at 0.33 V. By resonant excitation of the two entatic copper complexes, the transition state of the electron transfer is accessible through vibrational modes, which are coupled to metal–ligand charge transfer (MLCT) and ligand–metal charge transfer (LMCT) states.     

Atomic imaging of nucleation of trimethylaluminum on clean and H2O functionalized Ge(100) surfaces

The direct reaction of trimethylaluminum (TMA) on a Ge(100) surface and the effects of monolayer H(2)O pre-dosing were investigated using ultrahigh vacuum techniques, such as scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). At room temperature (RT), a saturation TMA dose produced 0.8 monolayers (ML) of semi-ordered species on a Ge(100) surface due to the dissociative chemisorption of TMA. STS confirmed the chemisorption of TMA passivated the bandgap states due to dangling bonds. By annealing the TMA-dosed Ge surface, the STM observed coverage of TMA sites decreased to 0.4 ML at 250?°C, and to 0.15 ML at 450?°C. XPS analysis showed that only carbon content was reduced during annealing, while the Al coverage was maintained at 0.15 ML, consistent with the desorption of methyl (-CH(3)) groups from the TMA adsorbates. Conversely, saturation TMA dosing at RT on the monolayer H(2)O pre-dosed Ge(100) surface followed by annealing at 200?°C formed a layer of Ge-O-Al bonds with an Al coverage a factor of two greater than the TMA only dosed Ge(100), consistent with Ge-OH activation of TMA chemisorption and Ge-H blocking of CH(3) chemisorption. The DFT shows that the reaction of TMA has lower activation energy and is more exothermic on Ge-OH than Ge-H sites. It is proposed that the H(2)O pre-dosing enhances the concentration of adsorbed Al and forms thermally stable Ge-O-Al bonds along the Ge dimer row which could serve as a nearly ideal atomic layer deposition nucleation layer on Ge(100) surface.     

Adlayers based on molecular platforms of trioxatriangulenium

The platform approach for preparation of molecular adlayers with freestanding functional groups was extended to systems on the basis of the trioxatriangulenium ion. Self-assembled monolayers of these compounds were prepared on Au(111) surfaces and characterized by scanning tunneling microscopy, revealing highly-ordered structures.     

Comparison of four mobility particle sizers with different time resolution for stationary exposure measurements

Exposure to airborne ultrafine and nanoparticles has raised increased interest over the recent years as they may cause adverse health effects. A common way to quantify exposure to airborne particles is to measure particle number size distributions through electrical mobility analysis. Four mobility particle sizers have been subject to a detailed intercomparison study, a TSI Fast Mobility Particle Sizer (FMPS), a Grimm Sequential Mobility Particle Sizer (SMPS+C), and two TSI Scanning Mobility Particle Sizers (SMPSs), equipped with two different condensation particle counters (CPC). The instruments were challenged with either NaCl or diesel soot particles. The results indicate that the sizing of all tested instrument was similar with only the FMPS size distributions consistently shifted toward smaller particle sizes. The Grimm SMPS generally measured higher concentrations and broader distributions than the TSI instruments. The two Grimm DMAs agreed well with each other; however, the TSI SMPS results showed a reproducible dependence on the flow rates. While TSI and Grimm SMPS delivered consistent results for sodium chloride (NaCl) and diesel soot, the FMPS seemed to react differently to the changing particle source than the SMPSs, which may be caused by either the different morphology or particle size dependent effects. For NaCl particles, the FMPS delivered the narrowest distributions and concentrations comparable with TSI SMPSs, whereas for diesel soot, it delivered the broadest distributions and higher concentrations than TSI SMPSs.     

Catalysts as Key Enablers for the Synthesis of Bioplastics with Sophisticated Architectures

Bioplastics are one of the answers to environmental pollution and linear material flows. The most promising bioplastic polylactide (PLA) is already replacing conventional plastics in a number of applications. The properties of PLA, however, do not fit for all potential application areas, but they can be altered by the introduction of comonomers. The copolymerization of lactide (LA) with other lactones like ϵ-caprolactone (CL) has been established for several years. Nevertheless, controlling copolymerizations remains a challenge due to the high complexity of the system. Copolymerization of LA with other monomer classes is much less investigated, but has the chance to overcome the limitations in material properties that occur when only lactones are used. The crucial factor for all copolymerizations is the catalyst. It dominates the reaction kinetics and determines the resulting microstructure. In this review, copolymerization catalysts for LA are presented divided into catalysts for the synthesis of lactone block copolymers, lactone random copolymers, and multimechanistically synthesized copolymers. The selected catalysts are highlighted either owing to their industrially applicable polymerization conditions or their non-standard mechanism.     

Capillary electrophoresis applied for the determination of acidity constants and limiting electrophoretic mobilities of ionizable herbicides including glyphosate and its metabolites and for their simultaneous separation

Thermodynamic acidity constants and limiting ionic mobilities were determined for polyprotic non-chromophore analytes using capillary electrophoresis with capacitively coupled contactless conductivity detection. It was not necessary to work with buffers of identical ionic strength as ionic strength effects on effective electrophoretic mobilities were corrected by modeling during data evaluation (software AnglerFish). The mobility data from capillary electrophoresis coupled to conductivity detection were determined in the pH range from 1.25 to 12.02 with a high resolution (36 pH steps). With this strategy, thermodynamic acidity constants and limiting ionic mobilities for various acidic herbicides were determined, sometimes for the first time. The model analytes included glyphosate, its metabolites, and its acetylated derivates (aminomethyl phosphonic acid, glyoxylic acid, sarcosine, glycine, N-acetyl glyphosate, N-acetyl aminomethyl phosphonic acid, hydroxymethyl phosphonic acid). The obtained data were used in simulations to optimize separations by capillary electrophoresis. Simulations correlated very well to experimental results. With the new method, the separation of glyphosate from interfering components like phosphate in beer samples was possible.