Ultra-performance liquid chromatography for the determination of pesticide residues in foods by tandem quadrupole mass spectrometry with polarity switching

An ultra-performance liquid chromatographic (UPLC) electrospray ionisation tandem quadrupole mass spectrometric method has been developed for the determination of 52 pesticides in cereal-based baby foods, oranges and potatoes. The fast polarity switching capability of the mass spectrometer used enabled the determination of 44 of the compounds in the positive ionisation mode and 8 of the compounds in the negative ionisation mode in a single run. Prior to analysis, co-extractives were removed from acetonitrile extracts using dispersive solid-phase extraction with primary secondary amine (50 mg). The UPLC method separates all of the pesticides, resolves structural isomers (e.g. butocarboxim sulfoxide and aldicarb sulfoxide) and has a short (7 min) cycle time. Extracts spiked with pesticides at 0.10 and 0.01 mg kg(-1) yielded average recoveries in the range of 66-124% with relative standard deviations less than 19% for the majority of the analytes.     

Laparoscopic photodynamic diagnosis of ovarian cancer peritoneal micro metastasis: an experimental study

The goal of this study was to assess the interest of photodynamic diagnosis (PDD) for laparoscopic detection of peritoneal micro metastasis in ovarian carcinoma. Using an experimental animal model, intraperitoneal injection of aminolevulinic acid (ALA) and hexylester of aminolevulinic acid (He-ALA) were compared in order to improve laparoscopic detection of ovarian peritoneal carcinomatosis. Twenty-one 344 Fischer female rats received an intra peritoneal injection of 106 NuTu-19 cells. At day 22, carcinomatosis with micro peritoneal metastasis was obtained. Rats were randomized in three groups concerning intra peritoneal injection before laparoscopic staging: 5-ALA hydrochloride, HE-ALA and sterile water. Using D Light system, laparoscopic peritoneal exploration was performed with white light (WL) first and then with blue light (BL). The main objective was to assess feasibility and sensibility of laparoscopic PDD for nonvisible peritoneal micro metastasis of ovarian cancer. The main parameter was the confirmation of neoplasic status of fluorescent foci by histology. Concerning PDD after intraperitoneal injection of 5-ALA, mean values of lesions seen is higher than without fluorescence (32 vs 20.7; P = 0.01). Using He-ALA, mean values of detected lesions is higher than without fluorescence (42.9 vs 33.6; P < 0.001). Neoplasic status of fluorescent foci was confirmed in 92.8% of cases (39/42). Using 5-ALA, fluorescence of cancerous tissue is significantly higher than that of normal tissue in all the rats (ratio 1.17) (P = 0.01). With He-ALA, intensity of fluorescence is significantly higher in cancerous tissue compared to normal tissue, irrespective of the rat studied (ratio 1.22; P < 0.001).     

Single eye analysis and contralateral eye comparison of tear proteins in normal and dry eye model rabbits by MALDI-ToF mass spectrometry using wax-coated target plates

A study of rabbit tear protein expression in a dry eye rabbit model was performed to determine if a pattern in expressed proteins could be identified. The uniqueness of the model allows the comparison of normal (control) eye tear protein expression with surgically induced dry eye tear protein expression in individual animals. The sensitivity of the method allows for single eye analysis. One-dimensional mini-gel electrophoresis of the tear proteins did not show substantial differences between band patterns of the normal versus the dry eye, but was used to assess the molecular weight ranges of the major proteins. Specific assignments of some of the predominant proteins were obtained by tandem mass spectrometry (MS) which showed that the lower molecular weight lipid-binding proteins (approximately 10 kDa to 36 kDa) constitute a considerable amount of the observed protein, followed in lesser quantities by the transferrins which have higher molecular weights ranging from 70 kDa to 85 kDa. Enhancement of matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) MS linear mode analysis of intact proteins in tear fluid was demonstrated through the use of wax-coated MALDI plates and spot washing. MALDI-ToF MS analysis of the expressed tear proteins illustrates that differences between normal eye tear and dry eye tear protein content are manifested in changes in the lower molecular weight lipid-binding proteins such as lipophilin which exhibits an increase in concentration in the dry eye, and β-2 microglobulin which undergoes a decrease.     

Ruthenium Carbonyl Cluster Complexes with Phenylgermyl Ligands from the Reactions of Ph<Subscript>3</Subscript>GeH with Ru(CO)<Subscript>5</Subscript> and Ru<Subscript>3</Subscript>(CO)<Subscript>12</Subscript>

Four new triphenylgermylruthenium carbonyl compounds HRu(CO)₄GePh₃, 14; Ru(CO)₄(GePh₃)₂, 15; Ru₂(CO)₈(GePh₃)₂, 16; and Ru₃(CO)₉(GePh₃)₃(μ-H)₃, 17 were obtained from the reaction of Ru(CO)₅ with Ph₃GeH in hexane solvent at reflux, 68 °C. The major product 14 was formed by loss of CO from the Ru(CO)₅ and an oxidative addition of the GeH bond of the Ph₃GeH to the metal atom. This six coordinate complex contains one terminal hydrido ligand. Compound 15 is formed from 14 and contains two trans-positioned GePh₃ ligands in the six coordinate complex. Compound 16 contains two Ru(CO)₄(GePh₃) fragments joined by an Ru–Ru single bond. Compound 17 contains a triangular cluster of three ruthenium atoms with three bridging hydrido ligands and one terminal GePh₃ ligand on each metal atom. When heated to 125 °C, 14 was converted to the new triruthenium compound Ru₃(CO)₁₀(μ-GePh₂)₂, 18. Compound 18 consists of a triangular tri-ruthenium cluster with two GePh₂ ligands bridging two different edges of the cluster and one bridging CO ligand. Ru₃(CO)₁₂ was found to react with Ph₃GeH at 97 °C to yield three products: 15, and two new compounds Ru₃(CO)₉(μ-GePh₂)₃, 19 and Ru₂(CO)₆(μ-GePh₂)₂(GePh₃)₂, 20 were obtained. Compound 19 is similar to 18 having a triangular tri-ruthenium cluster but has three bridging GePh₂ ligands, one on each Ru–Ru bond. Compound 20 contains only two ruthenium atoms joined by a single Ru–Ru bond that has two bridging GePh₂ ligands and a terminal GePh₃ ligand on each metal atom. All compounds were characterized by a combination of IR, ¹H NMR, single-crystal X-ray diffraction analyses. This report is dedicated to Professor Dieter Fenske on the occasion of his 65th birthday for his many pioneering contributions to the chemistry of metal chalcogenide cluster complexes.     

New In-situ Sampling and Analysis of the Production of CeO<Subscript>2</Subscript> Powders from Liquid Precursors using a Novel Wet Collection System in a rf Inductively Coupled Thermal Plasma Reactor. Part 1: Reactor System and Sampling Probe

A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of CeO₂ powders produced from dissolved cerium nitrate salts. The conical reactor minimized particle recirculation and provided a highly symmetrical and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of CeO₂ powders. Both a calorimetric study of the reactor and a thermodynamic analysis of CeO₂ formation were conducted. The sampling probe is described and near-isokinetic sampling was achieved. The sampled particles were collected using a miniature wet collection system, i.e. a mist atomizer and a custom-made spray chamber. A numerical simulation of the velocity and temperature fields of the plasma gas in the reactor was done using Fluent. A comprehensive droplet-to-particle formation mechanism presented elsewhere is revisited and expanded based on calorimetry, thermodynamics of CeO₂ formation, numerical simulations and collected particles. No traces of other oxidation states other than CeO₂ were found.     

Novel calix[4]arene-thiacrown ether for selective and efficient extraction of Ba(II), Pb(II), and Hg(II)

A di-ionizable p-tert-butylcalix[4]arene-1,3-thiacrown-5 ether extractant was synthesized. Its cone conformation and polyether ring attachment regioselectivity were verified by NMR spectroscopy. The metal ion-complexing properties of this ligand were evaluated by solvent extractions of metal cations from aqueous solutions into chloroform. The ligand was found to be an efficient extractant with Ba²⁺ selectivity in competitive solvent extraction of alkaline earth metal cations. It also exhibits high extraction ability for Pb²⁺ and for Hg²⁺ in single species solvent extractions.     

On-probe pyrolysis desorption electrospray ionization (DESI) mass spectrometry for the analysis of non-volatile pyrolysis products

An on-probe pyrolyzer has been constructed and interfaced with desorption electrospray ionization (DESI) mass spectrometry (MS) for the rapid analysis of non-volatile pyrolysis products. The detection and analysis of non-volatile pyrolysis products of peptides, proteins and the synthetic polymer poly(ethylene glycol) were demonstrated with this instrument. The on-probe pyrolyzer can be operated off-line or on-line with the DESI source and was interfaced with a tandem MS (MS/MS) instrument, which allowed for structure characterization of the non-volatile pyrolytic products. Advantages of this system are its simplicity and speed of analysis since the pyrolysis is performed in situ on the DESI source probe and hence, it avoids extraction steps and/or the use of matrices (e.g., as in MALDI–MS analyses).     

Time-resolved ultraviolet laser-induced breakdown spectroscopy for organic material analysis

Ultraviolet pulses (266 nm) delivered by a quadrupled Nd:YAG laser were used to analyze organic samples with laser-induced breakdown spectroscopy (LIBS). We present characteristics of the spectra obtained from organic samples with special attentions on the emissions of organic elements, O and N, and molecular bonds CN. The choice of these atomic or molecular species is justified on one hand, by the importance of these species to specify organic or biological materials; and on the other hand by the possible interferences with ambient air when laser ablation takes place in the atmosphere. Time-resolved LIBS was used to determine the time-evolution of line intensity emitted from these species. We demonstrate different kinetic behaviors corresponding to different origins of emitters: native atomic or molecular species directly vaporized from the sample or those generated through dissociation or recombination due to interaction between laser-induced plasma and air molecules. Our results show the ability of time-resolved UV-LIBS for detection and identification of native atomic or molecular species from an organic sample.     

Determination,by inductively coupled plasma mass spectrometry,of changes in cellular metal content resulting from herpes simplex virus-1 (HSV-1) infection

Metals and metal-containing compounds are known to play important roles in many biological processes, including metabolic and detoxification pathways and the formation and function of proteins. Like all organisms, viruses are expected to contain different metals. These metals, either by themselves or in the form of metalloproteins, may be involved in the virus’s ability to infect healthy cells and replicate within them. Identification and speciation of metals in control cells and in cells affected by a virus could be helpful in elucidating infection and replication mechanisms; these might, in turn, be vital to the development of more effective treatments. There has, however, been no extensive investigation of the metals specific viruses contain or affect. The objective of this study was to investigate changes in cellular metal content resulting from herpes simplex virus 1 (HSV-1) infection. Inductively coupled plasma mass spectrometry was used to identify differences between metal concentrations in uninfected and HSV-1-infected mammalian cells. Although it can be assumed that decreases in metal content are a result of cellular response to the virus, increases can be attributed either to cellular response or to the HSV-1 virus itself. Microwave digestion and flow injection methods suitable for small sample volumes were used, and the effects of different virus inactivation procedures were explored. This work is the first step in the identification of metals pertinent to HSV-1 infection and lays the foundation for future studies concentrating on characterization of these metal-associated or containing molecules.     

<Emphasis Type="Italic">Brønsted</Emphasis> Acids in Ionic Liquids: Fundamentals,Organic Reactions,and Comparisons

Summary. A background for studying acids in various solvents is developed, emphasizing the importance of knowing to what extent a solvent conducts electricity and is therefore ionized, the dissociation equilibria of common molecular solvents and the acidic and basic species generated by solvent leveling. Acidity measurements in the atypical solvent water are discussed and the common method of expressing acidity in other systems – by Hammett values – is introduced. Representative examples of reactions involving Br?nsted acids in ionic liquids are presented and attention paid to the questions of speciation and acidity values. It is found that the gas phase proton affinity of a base is often a better guide to the acidity of its conjugate acid in an ionic liquid than is the dissociation constant of the said acid in water.