Tandem (quadrupole-time-of-flight) electrospray mass spectrometry of oligo(vinyl acetates) with isopropylol or (1-hydroxyethyl)-2-oxyisopropanyl end groups

Poly(vinyl acetates) with either isopropylol or (1-hydroxyethyl)-2-oxyisopropanyl end groups were analysed by tandem mass spectrometry using a quadrupole-time-of-flight (Q-TOF) instrument. Random scission along the polymer backbone was not observed. Instead the initial scissions were derived from the cleavage of end-group species. The resultant macrocations were subject to further elimination reactions that eventually produced polyene macrocations. A smaller fraction of the initial macrocations also reacted by loss of ketene and this reaction produced macrocations containing vinyl alcohol units.     

Efficacy testing of disinfectants

The U.S. Environmental Protection Agency's (EPA) Office of Pesticide Programs (OPP) has the responsibility for regulating antimicrobial products, including sporicides, used to treat and decontaminate inanimate surfaces. In response to the anthrax (Bacillus anthracis) attacks of 2001 and the associated need for verifying the performance of chemicals for building decontamination, the EPA initiated research in late 2003 to evaluate and improve efficacy test methods for sporicides. The OPP Microbiology Laboratory located at the Environmental Science Center, Ft. Meade, MD is the lead laboratory. Through funding provided by EPA's Office of Research and Development (Safe Buildings Program), a collaborative research plan has been established to address several key issues. Research is currently being conducted on 2 fronts: (1) the evaluation of quantitative methodology for assessing the efficacy of sporicides, and (2) the development and comparative testing of selected modifications to improve the AOAC Sporicidal Activity Test (AOAC Method 966.04). Future studies will include the evaluation of candidate surrogates of B. anthracis using a quantitative method, and a multilaboratory validation study of a quantitative method-surrogate combination. The General Referee is serving as the Principal Investigator for all research described in this report, and has the overall responsibility for the technical conduct of the projects. In cases where the General Referee has oversight of projects that involve official collaborative studies and validation support from AOAC INTERNATIONAL, AOAC officials and the Committee Chair will determine the appropriate mechanism for formal study review. The 2003 General Referee report provides the background on the development and direction of the research projects. The preliminary data, general conclusions, next steps, and recommendations are provided in this report.     

Field and flow programming in frit-inlet asymmetrical flow field-flow fractionation

The separation of wide molecular mass (Mr) ranges of macromolecules using frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) has been improved by implementing a combination of field and flow programming. In this first implementation, field strength (governed by the cross flow-rate through the membrane-covered accumulation wall) is decreased with time to obtain faster elution and improved detection of the more strongly retained (high Mr) materials. The channel outlet flow-rate is optionally held constant, increased, or decreased with time. With circulation of the flow exiting the accumulation wall to the inlet frit, the dual programming of cross flow and channel outlet flow could be implemented using just two pumps. With this flow configuration, the channel outlet flow-rate is always equal to the channel inlet flow-rate, and these may be programmed independently of the cross flow-rate through the membrane. FI-AFlFFF retains its operational advantage over conventional asymmetrical flow FFF (AFlFFF). Unlike conventional AFlFFF, FI-AFlFFF does not require time consuming, and experimentally inconvenient, sample focusing and relaxation steps involving valve switching and interruption of sample migration. The advantages of employing dual programming with FI-AFlFFF are demonstrated for sets of polystyrene sulfonate standards in the molecular mass range of 4 to 1000 kDa. It is shown that programmed FI-AFlFFF successfully expands the dynamic separation range of molecular mass.     

Mild cleavage of methoxymethyl (MOM) ethers with trimethylsilyl bromide

Trimethylsilyl bromide is an effective reagent for the deprotection of methoxymethyl ethers under mild conditions.     

Cumulative subject index volumes 41–45

Orbital correlation diagrams for the black phosphorus to A7 (arsenic) phase transformation for various points in the Brillouin zone are presented and analyzed in symmetry terms. The level doublings observed at the black phosphorus geometry for several points are directly attributable to the nonsymmorphic nature of the space group (Herring's theorem). Doublings observed at the A7 structure derive from the choice of a four-atom, rather than two-atom, unit cell to view the geometrical transformation. The space group requirements at the beginning and end points of the transformation process simply control the form of orbital correlation diagrams. In general, $\text{HOMO}\text{LUMO}$ crossings are found at $\text{k = (}\text{1}\text{2}\text{,α,β)}$ where bonds are made and broken along the x direction, a result with simple analogies to more easily visualized one-dimensional problems.     

The temperature dependence of the d-electron dipole strengths of cobalt(II) tetrahalides

The dipole strengths of the ⁴A₂ → ⁴T₁(F), ⁴T₁(P), d-electron transitions of the cobalt(II) tetrahalides are found to decrease with an increase in temperature, in agreement with a dynamic ligand-polarisation model for the absorption mechanism. The reduction in dipole strength is accounted for by a decrease in the coulombic coupling between the quadrupole moment of the d-electron transition of the metal ion and the transient electric dipole moment induced in the ligands, due to the anharmonic increase in the mean bond length and the progressively larger mean-square amplitudes of the bending modes of the complex ion in its ground electronic state as the temperature is raised.     

Bioluminescent detection of insect pheromones using an enzyme-based flow injection analysis system

The combination of flow injection analysis with chemiluminescent detection is shown to provide extremely selective and sensitive detection of insect pheromones which possess an aldehyde moiety. The flow injection analysis system provides reproducible control of both the reaction chemistry and the sample introduction process. Microliter volume samples can be precisely handled and analyzed with this experimental configuration. The detection system is based on the luciferase-catalyzed oxidation of reduced flavin mononucleotide which occurs in the presence of aldehydes with carbon backbones of between 14 and 16 carbons. A limit of detection of 3 fmol of tetradecyl aldehyde is demonstrated and the system is shown to be insensitive to the presence of various organic solvents up to concentrations of approximately 10%. The key experimental variables which control sensitive detection of pheromone at the femtomole level with be investigated and discussed.     

Pentalene complexes of group 7 metal carbonyls: an organometallic mixed-valence system with very large metal-metal electronic coupling

The bimetallic complexes [M(CO)(3)](2)(mu:eta(5):eta(5)-Pn) (Pn = pentalene, C(8)H(6); M = Mn, Re) have been synthesized and characterized crystallographically; the Mn compound was isolated as solely the anti-isomer, while the Re analogue was formed as a mixture of anti- and syn-isomers. [Mn(CO)(3)](2)(mu:eta(5):eta(5)-Pn) may be reduced chemically to its mono- and dianions; the mixed-valence Mn(I)/Mn(0) monoanion is shown by ESR, vibrational, and electronic spectroscopies to be a Robin-Day class III system with an exceptionally large electronic coupling between the metal centers.