Electrochemical derivatization‐capillary electrophoresis‐contactless conductivity detection: A versatile strategy for simultaneous determination of cationic,anionic, and neutral analytes

The simultaneous determination of cationic, anionic, and neutral analytes in a real sample was demonstrated by coupling electrochemical (EC) derivatization with counter‐EOF CE‐C⁴D. An EC flow cell was used to oxidize alcohols from an antiseptic mouthwash sample into carboxylic acids at a platinum electrode in acid medium. The carboxylates formed in the derivatization process and other sample ingredients, such as benzoate, saccharinate, and sodium ions, were separated in counter‐flow mode and detected in one run in Tris‐HCl buffer, pH 8.6. Fewer than 5 min were needed to complete each analysis with the automated flow system comprising solenoid pumps for the management of solutions. Insights into the electrochemistry of benzoic acid, present in the sample matrix, were also gained by EC‐CE‐C⁴D; more specifically, by applying potentials higher than 1.47 V to the platinum electrode, some formiate and minute amounts of salicylate were detected.     

Synthesis of functionalized N-triazolyl maleimides

An easy and mild two-step one-pot reaction allowed the synthesis of functionalized N-triazolyl maleimide. Next, the addition of propargyl alcohol and propargyl amine to the N-acyliminium ion mediated by Lewis acid, In(OTf)₃, allowed the introduction of a second 1,2,3-triazol ring at position 5 of the amide. The products in both reactions were achieved in moderate to good yields.     

Radioanalytical assessment of environmental contamination around non-remediated uranium mining legacy site and radium mobility

During the past century extensive uranium mining took place in Portugal for radium and uranium production. One such uranium mine was the Boco Mine, in operation during the 1960s and 70s. Mining waste and open pits were left uncovered since mine closure. During the nineties a quarry for sand extraction was operated in the same site and water from a local stream was extensively used in sand sieving. Downstream the mine area, agriculture soil is used for cattle grazing. Water from the stream, water wells, soil, pasture and sheep meat were now analyzed for radionuclides of uranium natural series. The U-series radionuclide ²²⁶Ra was generally the highest in concentrations especially in soil, pasture, and in internal organs of sheep. ²²⁶Ra concentrations were 1,093 ± 96 Bq/kg (dry weight, dw) in soil, 43 ± 3 Bq/kg (dw) in pasture, and 193 ± 84 mBq/kg (wet weight, ww) in muscle tissue of sheep. Other sheep internal organs displayed much higher ²²⁶Ra concentrations, such as the brain and kidneys with 1,850 ± 613 mBq/kg (ww) and 6,043 ± 6,023 mBq/kg (ww), respectively. Results of analyses of tissue samples from sheep grown in a comparison area were 2 to 16 times lower, depending on the organ. Absorbed radiation doses for internal organs were computed and may exceed 5.2 mGy/y in the case of kidneys, near three times higher than in animals from the reference area, but below the threshold for biological effects. Radionuclide transfer in the terrestrial food chain and radiation exposure of the human population is discussed.     

Determination of parabens in wastewater samples via robot-assisted dynamic single-drop microextraction and liquid chromatography–tandem mass spectrometry

Dynamic single-drop microextraction (SDME) was automatized employing an Arduino-based lab-made Cartesian robot and implemented to determine parabens in wastewater samples in combination with liquid chromatography–tandem mass spectrometry. A dedicated Arduino sketch controls the auto-performance of all the stages of the SDME process, including syringe filling, drop exposition, solvent recycling, and extract collection. Univariate and multivariate experiments investigated the main variables affecting the SDME performance, including robot-dependent and additional operational parameters. Under selected conditions, limit of detections were established at 0.3 µg/L for all the analytes, and the method provided linear responses in the range between 0.6 and 10 µg/L, with adequate reproducibility, measured as intraday relative standard deviations (RSDs) between 5.54% and 17.94%, (n = 6), and inter-days RSDs between 8.97% and 16.49% (n = 9). The robot-assisted technique eased the control of dynamic SDME, making the process more feasible, robust, and reliable so that the developed setup demonstrated to be a competitive strategy for the automated extraction of organic pollutants from water samples.     

Thermal and viscosity characterization of two asphalt emulsions

Journal of Thermal Analysis and Calorimetry - Asphalt emulsion is a versatile product that can be used for different waterproofing applications in civil construction and highway constructions....     

Pressure-induced two-color photoluminescence in MnF(2) at room temperature

A novel two-color photoluminescence (PL) is found in MnF(2) at room temperature under high pressure. Contrary to low-temperature PL, PL at room temperature is unusual in transition-metal concentrated materials like MnF(2), since the deexcitation process at room temperature is fully governed by energy transfer to nonradiative centers. We show that room-temperature PL in MnF(2) originates from two distinct Mn(2+) emissions in the high-pressure cotunnite phase. The electronic structure and the excited-state dynamics are investigated by time-resolved emission and excitation spectroscopy at high pressure.     

The harmonic inversion of the field-swept fixed-frequency resonance spectrum

When the spin Hamiltonian is a linear function of the magnetic field intensity the resonance fields can be determined, in principle, by an eigenfield equation. In this report, we show a new technical approach to the resonance field problem where the eigenfield equation leads to a dynamic equation or, more specifically, to a first order differential equation of a variable L(x), where x is associated with the magnetic field h. Such differential equation has the property that: its stationary solution is the eigenfield equation and the spectral information contained in L(x) is directly related to the resonance spectrum. Such procedure, known as the "harmonic inversion problem" (HIP), can be solved by the "filter diagonalization method" (FDM) providing sufficient precision and resolution for the spectral analysis of the dynamic signals. Some examples are shown where the resonance fields are precisely determined in a single procedure, without the need to solve eigenvalue equations.     

Karyotype characterization of Eurysternus caribaeus: the smallest diploid number among Scarabaeidae (Coleoptera: Scarabaeoidea)

Eurysternus caribaeus was analyzed cytologically by conventional chromosomal staining. The species presents a diploid number of 2n=8, chromosomes with two arms and an XY sex determining mechanism. This is the first karyotype described for the genus Eurysternus and the tribe Eurysternini, and is also the smallest diploid number observed in the family Scarabaeidae and superfamily Scarabaeoidea.     

Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster

Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum.