Valence parity renders z(*)-type ions chemically distinct

Here we report that the odd electron z (*) -type ions formed by the electron-based peptide dissociation methods (electron capture or transfer, ECD or ETD) have distinctive chemical compositions from other common product ion types. Specifically, b-, c-, and y-type ions have an odd number of atoms with an odd valence (e.g., N and H), while z (*)-type ions contain an even number of atoms with an odd valence. This tenet, referred to as the valence parity rule, mandates that no c-type ion shall have the same chemical composition, and by extension mass, as a z (*) -type ion. By experiment we demonstrate that nearly half of all observed c- and z (*) -type product ions resulting from 226 ETD product ion spectra can be assigned to a single, correct, chemical composition and ion type by simple inspection of the m/ z peaks. The assignments provide (1) a platform to directly determine amino acid composition, (2) an input for database search algorithms, or (3) a basis for de novo sequence analysis.     

Detection of Cd, Pb, and Cu in non-pretreated natural waters and urine with thiol functionalized mesoporous silica and Nafion composite electrodes

Electrochemical sensors have great potential for environmental monitoring of toxic metal ions in waters due to their portability, field-deployability and excellent detection limits. However, electrochemical sensors employing mercury-free approaches typically suffer from binding competition for metal ions and fouling by organic substances and surfactants in natural waters, making sample pretreatments such as wet ashing necessary. In this work, we have developed mercury-free sensors by coating a composite of thiol self-assembled monolayers on mesoporous supports (SH-SAMMS™) and Nafion on glassy-carbon electrodes. With the combined benefit of SH-SAMMS™ as an outstanding metal preconcentrator and Nafion as an antifouling binder, the sensors could detect 0.5 ppb of Pb and 2.5 ppb of Cd in river water, Hanford groundwater, and seawater with a minimal amount of preconcentration time (few minutes) and without any sample pretreatment. The sensor could also detect 2.5 ppb of Cd, Pb, and Cu simultaneously. The electrodes have long service times and excellent single and inter-electrode reproducibility (5% R.S.D. after 8 consecutive measurements). Unlike SAMMS™-carbon paste electrodes, the SAMMS™-Nafion electrodes were not fouled in samples containing albumin and successfully detected Cd in human urine. Other potentially confounding factors affecting metal detection at SAMMS™-Nafion electrodes were studied, including pH effect, transport resistance of metal ions, and detection interference. With the ability to reliably detect low metal concentration ranges without sample pretreatment and fouling, SAMMS™-Nafion composite sensors have the potential to become the next-generation metal analyzers for environmental and bio-monitoring of toxic metals.     

First identification and thermodynamic characterization of the ternary U(VI) species, UO2(O2)(CO3)2(4-), in UO2-H2O2-K2CO3 solutions

In alkaline carbonate solutions, hydrogen peroxide can selectively replace one of the carbonate ligands in UO2(CO3)3(4-) to form the ternary mixed U(VI) peroxo-carbonato species UO2(O2)(CO3)2(4-). Orange rectangular plates of K4[UO2(CO3)2(O2)].H2O were isolated and characterized by single crystal X-ray diffraction studies. Crystallographic data: monoclinic, space group P2(1)/ n, a = 6.9670(14) A, b = 9.2158(10) A, c = 18.052(4) A, Z = 4. Spectrophotometric titrations with H 2O 2 were performed in 0.5 M K 2CO 3, with UO2(O2)(CO3)2(4-) concentrations ranging from 0.1 to 0.55 mM. The molar absorptivities (M(-1) cm(-1)) for UO2(CO3)3(4-) and UO2(O2)(CO3)2(4-) were determined to be 23.3 +/- 0.3 at 448.5 nm and 1022.7 +/- 19.0 at 347.5 nm, respectively. Stoichiometric analyses coupled with spectroscopic comparisons between solution and solid state indicate that the stable solution species is UO2(O2)(CO3)2(4-), which has an apparent formation constant of log K' = 4.70 +/- 0.02 relative to the tris-carbonato complex.     

Wisdom: Understanding and the Good Life

I argue that a necessary condition for being wise is: understanding how to live well. The condition, by requiring understanding rather than a wide variety of justified beliefs or knowledge, as Ryan and Whitcomb respectively require, yields the desirable result that being wise is compatible with having some false beliefs but not just any false beliefs about how to live well—regardless of whether those beliefs are justified or not. In arguing for understanding how to live well as a necessary condition for wisdom, I reject the view, proposed by both Ryan and Whitcomb, that subjects such as chemistry lies within the domain of wisdom. I show that the argued for condition yields the desirable result that being wise is not a common achievement, but that it is not something that can only plausibly be achieved in the modern era.     

Determination of molar absorptivity coefficients for major type-B trichothecenes and certification of calibrators for deoxynivalenol and nivalenol

This paper presents results from the European Commission-funded project Doncalibrant, the objective of which was to produce calibrators with certified mass fractions of the Fusarium toxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-Ac-DON), 15-acetyldeoxynivalenol (15-Ac-DON), and nivalenol (NIV), in acetonitrile. The calibrators, available in ampoules, were sufficiently homogeneous, with between-bottle variations (s _bb) of less than 2%. Long-term stability studies performed at four different temperatures between −18 and 40 °C revealed no significant negative trends (at a confidence level of 95%). Molar absorptivity coefficients (in L mol⁻¹ cm⁻¹) were determined for all four toxins (DON: 6805 ± 126, NIV: 6955 ± 205, 3-Ac-DON: 6983 ± 141, 15-Ac-DON: 6935 ± 142) on the basis of a mini-interlaboratory exercise. The overall uncertainty of the calibrators’ target values for DON and NIV were evaluated on the basis of gravimetric preparation data and include uncertainty contributions from possible heterogeneity, storage, and transport. The Doncalibrant project resulted in the production of calibrators for DON (IRMM-315) and NIV (IRMM-316) in acetonitrile with certified mass fractions of 25.1 ± 1.2 μg g⁻¹ and 24.0 ± 1.1 μg g⁻¹, respectively. Both CRMs became commercially available from the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) at the beginning of 2007.     

A rapid method for the determination of the Fusarium mycotoxinbeauvericin in maize

The development of a rapid method for the determination of the Fusarium mycotoxin beauvericin (BEA) in corn and cereals is described. This method allows to prepare at least 5 times more samples simultaneously with similar analytical performance characteristics as previously published analytical methods.     

Interlaboratory comparison study for the determination of halogenated hydrocarbons in water

Sixty laboratories of five different countries participated in a large-scale interlaboratory comparison test for the determination of halogenated hydrocarbons in water. Participants used their in-house method with 44 laboratories applying head space GC ECD analysis and 5 using liquid/liquid extraction. A set of two artificially produced samples was prepared; the halogenated hydrocarbons investigated were trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, trichloromethane, tetrachloromethane, 1,1-dichloroethylene, dichloromethane, dibromochloromethane, bromodichloromethane, 1,2-dichloroethane and tribromomethane. The procedure of sample preparation, storage and distribution was monitored by an extensive quality assurance system including homogeneity tests, stability tests, and trend analysis of the submitted data. The analytical results submitted by the participants exhibited RSD values of up to 35% and outlier rates of up to 19%. The percentage of false positive and false negative results was at the highest 12% for selected substances. Recovery rates varying from 86% to 106% proved the correctness of the analytical results submitted by the participants and showed that the procedure developed in this study for sample preparation and distribution is well suited for the performance of large-scale interlaboratory comparison tests of halogenated hydrocarbons in water.     

Effect of sub-Tg relaxations on chromophore reorientation in corona-poled polymers

Activation volumes for chromophore reorientation were measured for a series of guest–host polymeric materials, indicating a significant coupling between chromophore motion and the glassy α and β relaxation dynamics of the polymer host. The specific systems studied were formed by individually dissolving N,N-dimethyl-p-nitroaniline (DpNA), 4-(dimethylamino)-4′-nitrotolane (DMANT), 4-(diethylamino)-4′-nitrotolane (DEANT), and 1-((4-(dimethylamino)phenyl)ethynyl)-4-((4-nitrophenyl)ethynyl)benzene (DMAPEANT) in poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(isobutyl methacrylate) (PiBMA). In each of these systems, the isothermal, sub-T_g decay of the second-order optical susceptibility χ⁽²⁾ was monitored as a function of pressure using second harmonic generation. In each system, the observed decay of χ⁽²⁾ was represented by a stretched exponential equation from which the decay time τ₀ and decay distribution width β_KWW were determined. For each dopant molecule, the decrease in activation volume with the increasing size of the polymer host's alkyl side group and the pressure dependence of β_KWW were indicative of partial coupling between chromophore rotation and the glassy β relaxation dynamics of the polymer host. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1013–1024, 1998     

Dissolution of uranium oxides under alkaline oxidizing conditions

Bench scale experiments were conducted to determine the dissolution characteristics of UO₂, U₃O₈, and UO₃ in aqueous peroxide-containing carbonate solutions. The experimental parameters investigated included carbonate countercation (NH₄ ⁺, Na⁺, K⁺, and Rb⁺) and H₂O₂ concentration. The carbonate countercation had a dramatic influence on the dissolution behavior of UO₂ in 1 M carbonate solutions containing 0.1 M H₂O₂, with the most rapid dissolution occurring in (NH₄)₂CO₃ solution. The initial dissolution rate (y) of UO₂ in 1 M (NH₄)₂CO₃ increased linearly with peroxide concentration (x) ranging from 0.05 to 2 M according to: y = 2.41x + 1.14. The trend in initial dissolution rates for the three U oxides under study was UO₃ ≫ U₃O₈ > UO₂.     

Rapid test strips for analysis of mycotoxins in food and feed

An overview is given on recent trends and applications of rapid immunodiagnostic tests for screening of food and feed for mycotoxins. Different test formats are discussed, and challenges in the development of lateral-flow devices for on-site determination of mycotoxins, with requirements such as being robust, fast, and cost-effective, are briefly elucidated.