Investigation of volatile metabolites during growth of Escherichia coli and Pseudomonas aeruginosa by needle trap-GC-MS

A new method for the growth-dependent headspace analysis of bacterial cultures by needle trap (NT)-gas chromatography-mass spectrometry (GC-MS) was established. NTs were used for the first time as enrichment technique for volatile organic compounds (VOCs) in the headspace of laboratory cultures. Reference strains of Escherichia coli and Pseudomonas aeruginosa were grown in different liquid culture media for 48 h at 36 °C. In the course of growth, bacterial culture headspace was analysed by NT-GC-MS. In parallel, the abiotic release of volatile organic compounds (VOC) from nutrient media was investigated by the same method. By examination of microbial headspace samples in comparison with those of uninoculated media, it could be clearly differentiated between products and compounds which serve as substrates. Specific microbial metabolites were detected and quantified during the stationary growth phase. P. aeruginosa produced dimethyl sulfide (max. 125 μg L^?1??1) and 2-nonanone (max. 200 μg L^?1), whereas E. coli produced carbon disulfide, butanal and indole (max. 149 mg L^?1). Both organisms produced isoprene. Graphical Abstract

MVOCs produced by P. aeruginosa and E. coli at T = 36 °C in autoclaved LB + TRP medium      

Analysis of thermo-oxidation products of polypropylene and polyethylene by Gas chromatography/mass spectrometry

Thermal and thermo-oxidative degradation of polyethylene and polypropylene is discussed. The products of thermal and thermo-oxidative degradation are analysed using a GC-MS after previous adsorption in a column containing a sorbent of styrene divinyl benzene copolymer type. Aldehydes are the products mostly resulting from the thermo-oxidation of polyethylene and methyl ketones are those resulting from the thermo-oxidation of polypropylene.     

Ultrasound-promoted Friedel-Crafts acylation of arenes and cyclic anhydrides catalyzed by ionic liquid of [bmim]Br/AlCl3

A simple and efficient method of Friedel-Crafts acylation of arenes with succinic anhydride, phthalic anhydride and glutaric anhydride under the action of 1-butyl-3-ethylimidazolium ([bmim]Br/AlCl₃ ([bmim]⁺) cation (ionic liquid) and ultrasound irradiation is presented. Thy purity of products was tested by GC-MS and their structures evaluated by IR and ¹H NMR spectroscopy.     

Chitosan-poly(m-phenylenediamine)@Fe3O4 nanocomposite for magnetic solid-phase extraction of polychlorinated biphenyls from water samples

A extraction medium based on chitosan-poly(m-phenylenediamine) (CS-PPD) @Fe₃O₄ nanocomposite was synthesized by chemical polymerization of m-phenylenediamine in the presence of chitosan coated magnetic nanocomposite, and for the first time, used as the sorbent for the magnetic solid-phase extraction (MSPE) of seven polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) at trace levels in water samples. Gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was used for PCBs quantification and detection. Several factors related to MSPE efficiencies, such as type and amount of sorbent, extraction time, sample pH, and desorption conditions were investigated. Under the optimized conditions, an excellent linearity was observed in the range of 1.0–200 ng L^–1 for PCB180, 0.5–200 ng L^–1 for the other six PCBs with the correlation coefficients ranging from 0.9954 to 0.9993. The good recoveries at spiked levels of 10.0, 20.0, and 50.0 ng L^–1 were obtained in the range of 94 %–108 %, and the coefficients of variations were less than 6 %. The proposed method was feasible, rapid, and easy to operate for the trace analysis of the PCBs in local aquaculture water, livestock breeding water, and sewage water samples. Graphical Abstract

Fig. 1 Schematic diagram for the preparation of chitosan–poly(m-phenylenediamine) @Fe₃O₄ nanocomposite.     

Application of mixed solvents for elution of organophosphate pesticides extracted from raw propolis by matrix solid-phase dispersion and analysis by GC-MS

The excessive application of organophosphate pesticides (OPPs) in crop fields close to hives and its application in beekeeping practices are potential sources of contamination of propolis. Pesticides were extracted from raw propolis by matrix solid-phase dispersion. Because of the complex chemical composition of propolis, binary solvent mixtures based on acetonitrile and a relatively non-polar solvent in different proportions were tested for the selective elution of OPPs. The effect of mixed solvents on clean-up was evaluated by GC-MS and the main interfering compounds co-eluted with pesticides were identified. In addition, three volumes of the solvent mixture and the volume of the sample were evaluated in an experimental factorial design. The final experimental conditions were 1 mL of dissolved propolis and 8 mL of acetonitrile/dichloromethane (g4 _r = 25: 75). Mean recoveries ranged from 55 % to 96 % (relative standard deviation < 8 %) with an inter-day precision lower than 24 %. The proposed method was applied to the analysis of real samples obtained from local beekeepers.     

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL^?1 and a dynamic range as wide as from 0.001 to 100 ng mL^?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.

The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.     

Density functional calculation of conformations and potentials of internal rotation in polychlorinated biphenyls

Full geometry optimization for all 209 isomers of polychlorinated biphenyls (PCBs) and calculations of internal rotation potentials for 154 isomers have been performed by density functional method B3LYP/6-31G(d, p). Conformations and internal rotation barriers in PCBs were proved to depend on a number of chlorine atoms in ortho-positions and, less, the presence of chlorine atoms in adjacent meta-positions. Subject to the number of chlorine atoms in ortho-and adjacent meta-positions, 209 PCB isomers were classified into 18 groups, within each of them molecules having very close conformations and potentials of internal rotation. It makes possible to evaluate with high accuracy the potential functions of the last 55 PCB molecules for which potential curve calculations have not been made.     

Solid-phase microextraction/gas chromatography–mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles

A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO₂ NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66?±?0.23 and 4.44?±?0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health. Graphical Abstract

The basic principle of SPME/GC-MS method for characterization of nanoparticles surface adsorption forces     

Features of Sulfonation of Polychlorinated Biphenyl Congeners

Sulfonation of polychlorinated biphenyls (PCBs) and their commercial mixture (Trichlorobiphenyl) with oleum has been studied. General sulfonation patterns have been revealed for PCB congeners having no substituents in the ortho positions. The sulfonation of PCBs with chlorine atoms in only one aromatic ring gives exclusively the corresponding polychlorobiphenylmonosulfonic acids. The sulfonation of PCBs with chlorine atoms in both aromatic rings is accompanied by side formation of polychlorodibenzothiophene S,S-dioxides.     

GC-MS analysis of hydroxy and epoxy acids from seed oil of Hippophaë rhamnoides

By the GC-MS method using a packed column, in the mixture of TMS derivatives of hydroxy acid methyl esters obtained from the seed oil of the sea buckthorn, in ten chromatographic peaks (CPs) 13 monohydroxy compounds have been characterized by their mass spectra, the main ones being derivatives of dimorphecolic and coriolic acids. Structures are proposed for four dihydroxy acids of the C₁₇–C₂₀ series. The mixture of methyl esters of di- and tetra-TMS derivatives obtained from the mixture of epoxy acids from the same source has been analyzed by a similar method. In seven CPs, 11 compounds, reflecting the presence of nine epoxy acids in the initial mixture, have been characterized by their mass spectra. The main component of the mixture was 15,16-epoxyoctadeca-9,12-dienoic acid.     

Identification of biomarkers in the hair of dogs: new diagnostic possibilities in the study and control of visceral leishmaniasis

Visceral leishmaniasis (VL) is a zoonosis whose etiologic agent in the Americas is Leishmania infantum, and dogs are the main host. Research and innovation in diagnostic techniques are essential to improve the surveillance and control of VL in endemic areas. The present study investigates the profile of the volatile organic compounds (VOCs) emitted by healthy dogs and by dogs infected by L. infantum to detect variations in the VOCs that may be used as biomarkers in the diagnosis of VL. In total, 36 dogs were selected from an endemic area and divided into three groups: G1, not infected with L. infantum; G2, infected without clinical signs of VL; and G3, infected with clinical signs of VL. To analyze the profiles of the VOCs emitted by dogs from the three groups, solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used. Variations were observed between the profiles of the VOCs emitted in the three groups studied, and they also differentiated infected animals with or without clinical signs. Six VOCs were identified as potential biomarkers of infection, with significant variations between healthy dogs (G1) and infected dogs (G2?+?G3). The detection of variations between groups G2 and G3 suggested that the profiles of some VOCs may be related to the type of immune response and the parasite load of the infected dogs. This study demonstrated the possibility of analysis of VOCs as biomarkers of VL in diagnostic, clinical, and epidemiological work.     

Enzyme-Mediated Bacterial Biodegradation of an Azo Dye (C.I. Acid Blue 113): Reuse of Treated Dye Wastewater in Post-Tanning Operations

“Dyeing” is a common practice used to color the hides during the post-tanning operations in leather processing generating plenty of wastewater. The waste stream containing dye as pollutant is severely harmful to living beings. An azo dye (C.I. Acid Blue 113) has been biodegraded effectively by bacterial culture mediated with azoreductase enzyme to reduce the pollution load in the present investigation. The maximum rate of dye degradation was found to be 96?±?4 and 92?±?4 % for the initial concentrations of 100 and 200 mg/l, respectively. The enzyme activity was measured using NADH as a substrate. Fourier transform infrared spectroscopy (FT-IR) analysis was confirmed that the transformation of azo linkage could be transformed into N₂ or NH₃ or incorporated into complete biomass. Breaking down of dye molecules to various metabolites (such as aniline, naphthalene-1,4-diamine, 3-aminobenzenesulfonic acid, naphthalene-1-sulfonic acid, 8-aminonaphthalene-1-sulfonic acid, 5,8-diaminonaphthalene-1-sulfonic acid) was confirmed by gas chromatography and mass spectra (GC-MS) and mass (electrospray ionization (ESI)) spectra analysis. The treated wastewater could be reused for dyeing operation in the leather processing, and the properties of produced leather were evaluated by conventional methods that revealed to have improved dye penetration into the grain layer of experimental leather sample and resulted in high levelness of dyeing, which helps to obtain the desired smoothness and soft leather properties.     

Chlorination of geminal bis(alkoxy-NNO-azoxy) compounds with sodium hypochlorite

Chlorination of geminal bis(alkoxy-NNO-azoxy) compounds with sodium hypochlorite involves the central carbon atom and gives 1,1-bis(alkoxy-NNO-azoxy)-1-chloroalkanes with high yield. Dichlorobis-(methoxy-NNO-azoxy)methane oxidizes sodium iodide to elemental iodine. The signal from the central carbon atom in the ¹³C NMR spectra of bis(alkoxy-NNO-azoxy)dichloromethanes is broadened and displaced downfield relative to those of the initial compounds.     

Gas chromatography/tandem mass spectrometry method for the simultaneous analysis of 19 brominated compounds in environmental and biological samples

A methodology for the simultaneous analysis of eight polybrominated diphenyl ethers (PBDEs); eight methoxylated PBDEs (MeO-PBDEs); and three emerging flame retardants, hexabromobenzene (HBB), pentabromoethyl benzene (PBEB), and decabromodiphenyl ethane (DBDPE) by gas chromatography coupled to tandem mass spectrometry (GC-MS-MS) was developed for two environmental matrices (sediment and sludge) and three biological matrices (fish, dolphin blubber, and bird eggs). The use of selective reaction monitoring (SRM) allows a high selectivity, which is critical in the analysis of complex samples like blubber. Analytical parameters such as linearity, reproducibility, or accuracy were evaluated. Method limits of detection and quantification were evaluated and compared with GC-EI-MS and GC-NCI-MS. Method detection limits were valid for the environmental analysis in all cases, with values between 0.01 and 1.65 ng/g dw for sediment, 0.05 and 2.78 ng/g dw for sludge, 0.04 and 10.6 ng/g lw for fish, 0.01 and 1.11 ng/g lw for dolphin blubber, and 0.03 and 3.20 ng/g lw for bird eggs. The developed method was applied to five samples of each matrix. PBDEs were detected in all samples, while MeO-PBDEs were only detected in dolphin blubber. DBDPE was detected in sediment and sludge.     

Liquid—Vapor Phase Equilibria and the Thermodynamic Properties of Binary Solutions of n-Alkylbenzenes

Liquid—vapor phase equilibria were studied for binary systems formed by n-alkylbenzenes. The contributions of intermolecular interactions to the thermodynamic functions of n-alkylbenzenes and their binary solutions were calculated. The contributions of intermolecular interactions to the Helmholtz energy of binary solutions of constant molar concentrations formed by n-butylbenzene and n-alkylbenzenes were found to depend linearly on the molecular weight of n-alkylbenzene in the homologous series. The corresponding equations were suggested.     

Electron spin resonance studies of group IV organometallic radical anions : I. Organometal-substituted benzenes

Electron spin resonance spectra have been measured under uniform conditions for a series of trimethylsilyl-substituted benzene anion radicals. These ESR results have been used to derive a general set of Hückel molecular orbital parameters by treating the organosilyl substituent as a pseudo-heteroatom. ESR data for radical anions of organosilyl-substituted benzenes, biphenyls and naphthalenes are reproduced accurately by MO calculations employing h_Si = –2.0 and k_CSi = 0.7. For these series of compounds, the silicon-methyl proton ESR splittings, while not related to the π electron density on silicon alone or to the density on the aromatic carbon to which silicon is bonded, may be related to a combination of the π spin densities by a semiempirical relation:

     

Effective synthesis and X-ray investigation of (±)-2<Emphasis Type="Italic">S</Emphasis>-2-(2-chlorophenyl)-3-acetyl-1,3-oxazolidine

The crystal and molecular structure of (±)-2S-2-(2-chlorophenyl)-3-acetyl-1,3-oxazolidine was determined by X-ray diffraction analysis. Orthorhombic crystal with unit cell parameters a = 6.7419(8) Å, b = 10.3797(12) Å, c = 14.9233(18) Å; space group P2₁2₁2₁, Z = 4, ρ _calc = 1.436 g/cm³, composition C₁₁H₁₂ClNO₂. The deviation of the chlorine atom from the mean square plane of the phenyl cycle is ?0.010(5) Å. The five-membered oxazolidine cycle has an envelope conformation, which is typical for this class of compounds; the cycle is rotated at the C-C bond with respect to the phenyl fragment (the dihedral angle is 79.7(1)°). The spatial structure of the C2 chiral center lying in the plane of the 2-chlorophenyl fragment may be described as a distorted tetrahedron with an S configuration of the sp ³ hybridized carbon atom. Analysis of torsion angles and deviation of the nitrogen atom from the surrounding three-angle plane by ?0.017(3) Å allows one to speak about a tendency toward a pyramidal structure for the trisubstituted nitrogen atom. The 3D crystal structure is formed by intermolecular hydrogen bonds of C-H...O type and a strong intermolecular contact of 3.164(3) Å between the chlorine atom and the carbonyl oxygen of the acyl group.     

Cycloaddition and chlorotropic transformations in reactions of dichloromethylenetrifluoroacetamide with phosphites

Reactions of dichlormethylenetrifluoroacetamide with triphenyl phosphite, diethylchlorophosphite (o-phenylene)diethylamidophosphite, (o-phenylene)chlorphosphite, and 2-fluoro-3-isopropyl-5-tert-butyl-1,3,2-oxazaphospholine proceeded as cheletropic [4+1]-cycloaddition. The formed λ⁵-1,4,2-oxazaphospholines underwent 1,3-migration of the chlorine atom in C=N–C cyclic triad.     

Synthesis,characterization, and antibacterial activity of two zinc(II) complexes with Schiff bases derived from rimantadine

The reactions of zinc(II) chloride and two Schiff base ligands derived from rimantadine and 5-chlorosalicylaldehyde/4-methoxysalicylaldehydes, generated two novel complexes [Zn(L¹)₂Cl₂] (I) and [Zn(L²)₂Cl₂] (II), where L¹ = 2-((1-(1-adamantan-1-yl)ethyl)-iminomethyl)-4-chlorophenol, L² = 2-((1-(1-adamantan-1-yl)ethyl)iminomethyl)-5-methoxyphenol. The complexes were characterized by the means of IR, ¹H NMR, elemental analysis, molar conductance and thermal analysis. A single-crystal X-ray diffraction analysis reveals that both complexes crystallize in orthorhombic system, space group Fdd2 for I and Pbcn for II. In two complexes crystals, each asymmetric unit consists of one zinc(II) ion, two corresponding Schiff base ligands and two chlorine atoms; the central zinc atom lies on a twofold rotation axis and is four-coordinate via two chlorine atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.