Targeted analysis with benchtop quadrupole–orbitrap hybrid mass spectrometer: Application to determination of synthetic hormones in animal urine

Sensitive and unequivocal determination of analytes/contaminants in complex matrices is a challenge in the field of food safety control. In this study, various acquisition modes (Full MS/AIF, Full MS + tMS/MS, Full MS/dd MS/MS and tSIM/ddMS/MS) and parameters of a quadrupole–orbitrap hybrid mass spectrometer (Q Exactive) were studied in detail. One of the main conclusions has been that, reducing the scan range for Full MS (using the quadrupole) and targeted modes give higher signal-to-noise (S/N) ratios and thereby better detection limits for analytes in matrix. The use of Q Exactive in a complex case, for the confirmatory analysis of hormones in animal urine is presented. A targeted SIM data dependent MS/MS (tSIM/ddMS/MS) acquisition method for determination of eight synthetic hormones (trenbolone, 17α ethinylestradiol, zeranol, stanozolol, dienestrol, diethylstilbestrol, hexestrol, taleranol) and a naturally occurring hormone (zearalenone) in animal urine were optimized to have sensitive precursors from targeted SIM mode and trigger MS/MS scans over the entire chromatograph peak. The method was validated according to EC/657/2002. CCα (decision limit) for the analytes ranged between 0.11 μg L⁻¹ and 0.69 μg L⁻¹ and CCβ (detection capability) ranged between 0.29 μg L⁻¹ and 0.90 μg L⁻¹.     

Anion Recognition and Induced Self‐Assembly of an α,γ‐Cyclic Peptide To Form Spherical Clusters

A cyclic octapeptide composed of hydroxy‐functionalized γ‐amino acids folds in a “V‐shaped” conformation that allows the selective recognition of anions such as chloride, nitrate, and carbonate. The process involves the simultaneous self‐assembly of six peptide subunits and the recognition of four anions to form a tetrahedral structure, in which the anions are located at the corners of the resulting structure. Each anion is coordinated to three different peptides. The structure was fully characterized by several techniques, including NMR spectroscopy and X‐ray diffraction, and the material was able to facilitate the transmembrane transport of chloride ions.     

Evidence of water reorientation on model electrocatalytic surfaces from nanosecond-laser-pulsed experiments

The behavior of water at the interface formed between a quasi-perfect Pt(111) single-crystal electrode and an aqueous electrolyte solution is studied by means of the laser-induced temperature jump method. This method is based on the use of nanosecond laser pulses to suddenly increase the temperature at the interface. The measurement of the response of the interface toward the laser heating under coulostatic conditions provides evidence on the net orientation of water at the interface. Especially interesting is the study of the effect on the interfacial water caused by the selective deposition of foreign metal adatoms, because these bimetallic systems usually exhibit appealing electrocatalytic properties. The T-jump methodology shows that the surface composition strongly affects the interaction of water with the surface. The most representative parameter to characterize this interaction is the potential where water reorientation occurs; this potential shifts in different directions, depending on the relative values of the electronegativity of the adatom and the substrate. These results are discussed in the light of available information about the effect of adatom deposition on the work function and the surface potential of the modified surface. Finally, some implications on the enhancement of the electrocatalytic activity are briefly discussed.     

A mesoporous 3D hybrid material with dual functionality for Hg2+ detection and adsorption

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.     

Study of tungstate–protein interaction in human serum by LC–ICP-MS and MALDI-TOF

Oral administration of sodium tungstate is an effective treatment for type 1 and 2 diabetes in animal models; it does not incur significant side effects, and it may constitute an alternative to insulin. However, the mechanism by which tungstate exerts its observed metabolic effects in vivo is still not completely understood. In this work, serum-containing proteins which bind tungstate have been characterized. Size exclusion chromatography (SEC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) with a Phenomenex Bio-Sep-S 2000 column and 20 mM HEPES and 150 mM NaCl at pH 7.4 as the mobile phase was chosen as the most appropriate methodology to screen for tungsten–protein complexes. When human serum was incubated with tungstate, three analytical peaks were observed, one related to tungstate–albumin binding, one to free tungstate, and one to an unknown protein binding (MW higher than 300 kDa). Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometric analysis of the tungsten-containing fractions collected from SEC–ICP-MS chromatograms, after desalting and preconcentration processes, confirmed the association of tungstate with albumin and the other unknown protein. Figure SEC-ICP-MS // MALDI-TOF     

Carboxylic acids as substrates in homogeneous catalysis

In organic molecules carboxylic acid groups are among the most common functionalities. Activated derivatives of carboxylic acids have long served as versatile connection points in derivatizations and in the construction of carbon frameworks. In more recent years numerous catalytic transformations have been discovered which have made it possible for carboxylic acids to be used as building blocks without the need for additional activation steps. A large number of different product classes have become accessible from this single functionality along multifaceted reaction pathways. The frontispiece illustrates an important reason for this: In the catalytic cycles carbon monoxide gas can be released from acyl metal complexes, and gaseous carbon dioxide from carboxylate complexes, with different organometallic species being formed in each case. Thus, carboxylic acids can be used as synthetic equivalents of acyl, aryl, or alkyl halides, as well as organometallic reagents. This review provides an overview of interesting catalytic transformations of carboxylic acids and a number of derivatives accessible from them in situ. It serves to provide an invitation to complement, refine, and use these new methods in organic synthesis.     

Atomistic Simulations of CO Vibrations in Ices Relevant to Astrochemistry

The experimental absorption band of carbon monoxide (CO) in mixed ices has been extensively studied in the past. The astrophysical interest in this band is related to its characteristic shape, which appears to depend on the surrounding ice structure. Herein, molecular dynamics simulations are carried out to analyze the relationship between the structure of the ice and the infrared (IR) spectrum of embedded CO molecules at different concentrations. Instead of conventional force fields, anharmonic potentials are used for the bonded interactions. The electrostatic interactions are more accurately described by means of fluctuating atomic multipole moments (up to quadrupole). The experimentally observed splitting of the CO absorption band (gas phase: 2143 cm^?1) into a blue‐ (2152 cm^?1) and a red‐shifted (2138 cm^?1) signal is also found in the simulations. Complementary atomistic simulations allow us to relate the spectra with the structural features. The distinction between interstitial and substitutional CO molecules as the origin of this splitting is found to be qualitatively correct. However, at increasing CO concentrations, additional effects—such as mutual interactions between CO molecules—become important, and the simplistic picture needs to be revised.     

Per-6-O-(tert-butyldimethylsilyl)cyclodextrins (TBDMS-CDs) in Langmuir monolayers: the importance of a spreading solvent in the preparation of LB layers suitable for sensor application

Commercially available amphiphilic cyclodextrins, namely per-6-O-(tert-butyldimethylsilyl) alpha, beta and gamma cyclodextrins (TBDMS-alpha-, -beta-, and -gamma-CDs) were subjected to a thorough Langmuir monolayer characterization, using both traditional methods of surface manometry (pi/A isotherms, stability experiments) and modern micrometer/nanometer resolution (BAM, AFM) surface techniques. It has been found that inconsistent behavior regarding the isotherms reproducibility obtained upon compression of TBDMS-beta-CDs is due to the aggregation of the investigated molecules in chloroform and hexane, while good reproducibility ensured a mixed spreading solvent system of hexane/isopropanol 7:3 (v/v). Although the stability of films dropped from chloroform and hexane/isopropanol solvents below the equilibrium surface pressure (ESP) was comparable, pronounced differences were observed at pressures above ESP. The investigated TBDMS-CDs were successfully transferred onto cadmium stearate covered mica substrates. AFM images confirmed the presence of discontinuous multilayered films (10 nm heights) spread from chloroform versus monomolecular dispersion achieved in hexane/isopropanol.     

Palladium-catalyzed Suzuki-Miyaura reaction involving a secondary sp3 carbon: studies of stereochemistry and scope of the reaction

Palladium-catalyzed C--C bond formation involving secondary sp3-hybridized carbon is described. These reactions occur with secondary 1-bromoethyl arylsulfoxides and different arylboronic acids, to produce the corresponding arylated sulfoxides in moderate to high yields and with complete stereospecificity. Despite the presence of beta hydrogens in the substrate, the competitive beta-hydride elimination is not a significant side reaction when coordinating solvents are used. The reported cross-coupling involves secondary C(sp3)--C(sp2) bond formation: this is the first time that a mechanistic study has been carried out with such substrates. The reaction proceeds with inversion of configuration at the stereogenic C(sp3) carbon. The high stereospecificity of the coupling and the mildness of the reaction conditions allow for the preservation of the optical purities of reagents and products and the preparation of useful chiral targets.