Dilute-and-shoot approach for determination of several biomarkers and pharmaceuticals in wastewater using nanoflow liquid chromatography – Orbitrap mass spectrometry

A new method for quantitative analysis of several biomarkers and pharmaceutical compounds in wastewater has been developed employing nanoflow liquid chromatography with Orbitrap mass spectrometry. An easy dilute-and-shoot approach has been used for sample preparation with a dilution factor of 5. Improved retention of ionic and highly polar compounds has been achieved by the addition of tetrabutylammonium bromide as an ion pair reagent into the final diluted sample. The new nanoflow liquid chromatography method has demonstrated low matrix effects (70%–111%), high sensitivity in terms of limits of quantification (0.005 to 0.3 μg/L), low injection volume (70 nl) and solvent consumption, and the ability to analyze diverse polar and ionic analytes within one run using a single reversed-phase nanoflow liquid chromatography column. Wastewater samples (n = 116) from the wastewater treatment plants of different cities in Latvia were analyzed using the developed method. The observed concentrations of biomarkers were in line with the literature data.     

Confined plasmons in nanofabricated single silver particle pairs: experimental observations of strong interparticle interactions

We report on the optical properties of single isolated silver nanodisks and pairs of disks fabricated by electron beam lithography. By systematically varying the disk size and surface separation and recording elastic scattering spectra in different polarization configurations, we found evidence for extremely strong interparticle interactions. The dipolar surface plasmon resonance for polarization parallel to the dimer axis exhibited a red shift as the interdimer separation was decreased; as expected from previous work, an extremely strong shift was observed. The scattering spectra of single particles and pairs separated by more than one particle radius can be well described by the coupled dipole approximation (CDA), where the particles are approximated as point dipoles using a modified dipole polarizability for oblate spheroids. For smaller particle separations (d < 20 nm), the simple dipole model severely underestimates the particle interaction, indicating the importance of multipolar fields and finite-size effects. The discrete dipole approximation (DDA), which is a finite-element method, describes the experimental results well even at d < 20 nm, including particles that have metallic bridges.     

Classical dynamics of the supersymmetric Liouville theory

We solve the supersymmetric Liouville theory in the strip $\text{[0, π] ×}\text{R}$ with boundary conditions appropriate to the supersymmetric string dynamics recently discussed by Polyakov.     

FLASH PHOTOLYSIS OF 3-IODOTYROSINE IN AQUEOUS SOLUTION AT pH 5

Abstract— The 3-tyrosinyl free radicals (3-Tyr) and iodine atom are formed by flash photolysis of 3-iodotyrosine (3-Tyr-I) in aqueous solutions at pH 5. The presence of iodine atoms in the medium is characterized by the absorption spectrum and the decay kinetics of I formed when KI is added to the system. In the absence of radical scavengers, the 3-Tyr adds to or reacts with the parent molecule to produce a transient species, probably a radical dimer, which has an absorption maximum at 405 nm. The decay of this transient follows second order kinetics whose rate constant increases with decreasing 3-iodotyrosine concentration. Measurements of the dependence of the transient yield on the concentration of added ethanol indicate that the 3-Tyr radical reacts with ethanol by hydrogen abstraction. The rate constants of reaction of the 3-Tyr radical with 3-iodotyrosine and ethanol are deduced from results.     

A GENERAL METHOD FOR THE IDENTIFICATION OF PRIMARY REACTIONS IN SENSITIZED PHOTOOXIDATIONS*

Abstract— A kinetic method for the identification of primary reactions in sensitized photooxidations is described. It is based on the calculation of Fractions of primary reactions of triplet sensitizer (³S) and singlet oxygen (¹O₂) as a function of substrate concentration (A) and on the comparison of experimental and theoretical curves. The theoretical curve that coincides with the experimental one indicates the mechanism of the chemical change observed. Only the quenching rate constants of ³S and ¹O₂ are needed for this calculation. The method enables one to distinguish the free radical and ¹O₂ mechanism. Applications of the method with 3-indole acetic acid, 1-histidine and N^-₃ using phenosafranine as the sensitizing dye (aqueous solutions, pH 7.C7.2) are described. The chemical change followed in these experiments is the bleaching of p-nitrosodimethylaniline (RNO) which gives precise and reproducible results. The bleaching of RNO is induced by the presence of some substrates which produce reactive intermediates with an oxidizing character. The kinetic method can be applied to any chemical change observed in different systems of sensitized photooxidations. The quantum yield of ³S and ¹O₂ formation need not be known.