2D autocovariance function for comprehensive analysis of two-way GC-MS data matrix: application to environmental samples

This paper describes a signal processing method for comprehensive analysis of the large data set generated by hyphenated GC-MS technique. It is based on the study of the 2D autocovariance function (2D-EACVF) computed on the raw GC-MS data matrix, extending the procedure previously developed for 1D to 2D signals. It appears specifically promising for GC-MS investigation, in particular to single out ordered patterns in complex data: such patterns can be simply identified by visual inspection from deterministic peaks in the 2D-EACVF plot.A case of order along the retention time axis (x = t_R) is represented by a horizontal sequence of peaks, located at the same interdistance Δt_R = b_x, e.g., b_x is the CH₂ retention time increment between subsequent terms of an homologous series. The order along the fragment mass axis (y = m/z) contains information on analyte fragmentation patterns. Deterministic peaks appear in the 2D-EACVF plot at Δm/z values corresponding to the most abundant ion fragments - dominating fragments in MS spectrum - or to ions generated by repetitive loss of the same ion fragment, i.e., Δm/z = 14 amu produced by the [CH₂] group loss in n-alkanes.Method applicability was tested by processing GC-MS data of organic extracts of atmospheric aerosol samples: attention is focused on identifying and characterizing homologous series of organics, i.e., n-alkanes and n-alkanoic acids, since they are considered molecular tracers able to track the origin and fate of different organics in the environment.     

Simultaneous detection of total and halogenated hydrocarbons in complex environmental samples

A state-of-the-art gas chromatographic system for automatic simultaneous detection of halogenated and normal hydrocarbons has been developed, which consists of a standard Hewlett-Packard 5880 with a fused silica capillary column, whose effluent is split between the standard flame ionization detector and a Tracor Hall electroconductivity detector. The system provedes excellent capillary chromatography results and high sensitivity for halogenated compounds (a detection limit of 1 ppm Archlor 1254 in fuel oil). Reliability has been provides in the daily analysis of complex environmental samples. Emergency response cleanup and the containment of hazardous chemical spills and chemical dump sites forces one to deal with samples that are very complex. The contain large numbers of naturally occurring organic compounds and varying types of organic pollutants. Capillary chromatographic techniques of gas chromatographic and gas chromatographic/mass spectrometric analyses are necessary to achieve the resolution required for the analysis of these samples.     

Determination of technetium-99 in environmental samples: A review

Due to the lack of a stable technetium isotope, and the high mobility and long half-life, ⁹⁹Tc is considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. ⁹⁹Tc is also an important tracer for oceanographic research due to the high technetium solubility in seawater as TcO₄⁻. A number of analytical methods, using chemical separation combined with radiometric and mass spectrometric measurement techniques, have been developed over the past decades for determination of ⁹⁹Tc in different environmental samples. This article summarizes and compares recently reported chemical separation procedures and measurement methods for determination of ⁹⁹Tc. Due to the extremely low concentration of ⁹⁹Tc in environmental samples, the sample preparation, pre-concentration, chemical separation and purification for removal of the interferences for detection of ⁹⁹Tc are the most important issues governing the accurate determination of ⁹⁹Tc. These aspects are discussed in detail in this article. Meanwhile, the different measurement techniques for ⁹⁹Tc are also compared with respect to advantages and drawbacks. Novel automated analytical methods for rapid determination of ⁹⁹Tc using solid extraction or ion exchange chromatography for separation of ⁹⁹Tc, employing flow injection or sequential injection approaches are also discussed.     

Synthesis and characterization of a novel linear trinuclear ruthenium(II) complex: variation of photosensitization ability with chain length in a homologous series

A new, one-step preparation of 1,4-di(2,2':6',2' '-terpyridin-4'-yl)benzene was employed in the synthesis of a linear trinuclear Ru(II) complex, which was compared to mononuclear and dinuclear analogues using UV-vis spectrometry, cyclic voltammetry, and ability to sensitize the photogeneration of methyl viologen radical cation. The chain length-dependent increase in sensitization ability was consistent with an increasing molar absorbance and with an end-on approach of the photoreactants mitigating the increasing charge.     

Characterization of carbon nanotubes and analytical methods for their determination in environmental and biological samples: A review

In the present paper, a critical overview of the most commonly used techniques for the characterization and the determination of carbon nanotubes (CNTs) is given on the basis of 170 references (2000–2014). The analytical techniques used for CNT characterization (including microscopic and diffraction, spectroscopic, thermal and separation techniques) are classified, described, and illustrated with applied examples. Furthermore, the performance of sampling procedures as well as the available methods for the determination of CNTs in real biological and environmental samples are reviewed and discussed according to their analytical characteristics. In addition, future trends and perspectives in this field of work are critically presented.     

Direct coupling of supported liquid membranes to capillary electrophoresis for analysis of complex samples: A tutorial

This tutorial provides an overview of direct coupling of extraction techniques based on supported liquid membranes (SLMs) to capillary electrophoresis (CE) for treatment and subsequent analysis of complex samples. Pros and cons of using each of the described instrumental arrangement are addressed and where relevant, comments with personal experience of the authors are presented. Solid porous membrane based extraction techniques coupled directly to CE are also presented in this tutorial and a comprehensive discussion is included on their instrumental set-ups and their possible adaptation for use with SLMs.     

Data processing pipelines for comprehensive profiling of proteomics samples by label-free LC-MS for biomarker discovery

Label-free quantitative LC-MS profiling of complex body fluids has become an important analytical tool for biomarker and biological knowledge discovery in the past decade. Accurate processing, statistical analysis and validation of acquired data diversified by the different types of mass spectrometers, mass spectrometer parameter settings and applied sample preparation steps are essential to answer complex life science research questions and understand the molecular mechanism of disease onset and developments. This review provides insight into the main modules of label-free data processing pipelines with statistical analysis and validation and discusses recent developments. Special emphasis is devoted to quality control methods, performance assessment of complete workflows and algorithms of individual modules. Finally, the review discusses the current state and trends in high throughput data processing and analysis solutions for users with little bioinformatics knowledge.     

Identification and characterization of the chemical constituents of Simiao Wan by ultra high performance liquid chromatography with mass spectrometry coupled to an automated multiple data processing method

The chemical constituents of Simiao Wan (SW), a traditional Chinese medicine preparation, are difficult to determine and remain unclear. To more efficiently detect ions, a multiple data processing approach has been used in the characterization of the compounds. In this study, a rapid and sensitive method based on ultra high performance liquid chromatography with mass spectrometry and the multiple data processing approach was established to characterize the chemical constituents of SW. Ultra high performance liquid chromatography with mass spectrometry coupled with the multiple data processing approach could efficiently remove nonrelated ion signals from accurate mass data. We report the application of the multiple data processing approach for comprehensive detection and rapid identification of chemical constituents of SW. Of note, the total analysis time for separation was less than 20 min without losing any resolution. In the variable, importance in projection plot of orthogonal projection to latent structure‐discriminant analysis, a total of 72 ions of interest (37 ions in positive mode, 38 ions in negative mode and three ions in both mode) were extracted or tentatively characterized based on their retention times, exact mass measurement for each molecular ion and subsequent fragment ions. In summary, the methodology proposed in this study could be valuable for the structural characterization and identification of the multiple constituents in the traditional Chinese medicine formula SW.     

An effective method for determining the ingredients of Shuanghuanglian formula in blood samples using high‐resolution LC–MS coupled with background subtraction and a multiple data processing approach

Shuanghuanglian formula (SF) is a combination of Flos lonicerae japonicae, Radix scutellariae, and Fructus forsythiae, commonly used to treat viral or bacterial infections. However, the constituents absorbed into the blood after oral administration of SF are difficult to determine and thus remain unclear. Here, we report the application of an accurate background subtraction and multiple data processing approach (Bs‐Mpa) for the comprehensive detection of compounds of SF in vivo. A sensitive and reliable ultra‐performance LC coupled with ESI quadrupole TOF MS (UPLC–ESI‐Q‐TOF‐MS) approach coupled with Bs‐Mpa, which is implemented in the Strip tool from UPLC to remove nonrelated ion signals from accurate mass LC–MS data, was established to characterize the chemical constituents and rat metabolites of SF. In the loading plot of the principal component analysis, 68 ions of interest were extracted from blood samples, among them, 39 absorbed prototype components of SF and 29 metabolites were identified in vivo. It is concluded that the integrative Bs‐Mpa method can be successfully applied for the rapid discovery of multiple components from a traditional Chinese medicine. The above challenge was addressed by using the proposed Bs‐Mpa method and it was particularly suitable for applying to the global characterization of the constituents or metabolites in rat blood after oral administration of other well‐known formulae.     

Detection,characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

The increasing demand of analytical information related to inorganic engineered nanomaterials requires the adaptation of existing techniques and methods, or the development of new ones. The challenge for the analytical sciences has been to consider the nanoparticles as a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g. size, shape, aggregation). Moreover, information about the species derived from the nanoparticles themselves and their transformations must also be supplied. Whereas techniques commonly used for nanoparticle characterization, such as light scattering techniques, show serious limitations when applied to complex samples, other well-established techniques, like electron microscopy and atomic spectrometry, can provide useful information in most cases. Furthermore, separation techniques, including flow field flow fractionation, capillary electrophoresis and hydrodynamic chromatography, are moving to the nano domain, mostly hyphenated to inductively coupled plasma mass spectrometry as element specific detector. Emerging techniques based on the detection of single nanoparticles by using ICP-MS, but also coulometry, are in their way to gain a position. Chemical sensors selective to nanoparticles are in their early stages, but they are very promising considering their portability and simplicity. Although the field is in continuous evolution, at this moment it is moving from proofs-of-concept in simple matrices to methods dealing with matrices of higher complexity and relevant analyte concentrations. To achieve this goal, sample preparation methods are essential to manage such complex situations. Apart from size fractionation methods, matrix digestion, extraction and concentration methods capable of preserving the nature of the nanoparticles are being developed. This review presents and discusses the state-of-the-art analytical techniques and sample preparation methods suitable for dealing with complex samples. Single- and multi-method approaches applied to solve the nanometrological challenges posed by a variety of stakeholders are also presented.     

Synthesis, spectroscopic characterization, DFT studies and biological assays of a novel gold(I) complex with 2-mercaptothiazoline

A new gold(I) complex with 2-mercaptothiazoline (MTZ) with the coordination formula [AuCN(C₃H₅NS₂)] was synthesized and characterized by chemical and spectroscopic measurements, DFT studies and biological assays. Infrared (IR) and ¹H, ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopic measurements indicate coordination of the ligand to gold(I) through the nitrogen atom. Studies based on DFT confirmed nitrogen coordination to gold(I) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Thermal decomposition starts at temperatures near 160 °C, leading to the formation of Au⁰ as the final residue at 1000 °C. The gold(I) complex with 2-mercaptothiazoline (Au-MTZ) is soluble in dimethyl sulfoxide (DMSO), and is insoluble in water, methanol, ethanol, acetonitrile and hexane. The antibacterial activities of the Au-MTZ complex were evaluated by an antibiogram assay using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of the cytotoxic effect of the Au-MTZ complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a potent cytotoxic activity, inducing 85% of cell death at a concentration of 2.0 μmol L⁻¹.     

Reprint of: Application of micro-thin-layer chromatography as a simple fractionation tool for fast screening of raw extracts derived from complex biological,pharmaceutical and environmental samples

The main goal of present paper is to demonstrate the separation and detection capability of micro-TLC technique involving simple one step liquid extraction protocols of complex materials without multi-steps sample pre-purification. In the present studies target components (cyanobacteria pigments, lipids and fullerenes) were isolated from heavy loading complex matrices including spirulina dried cells, birds’ feathers and fatty oils as well as soot samples derived from biomass fuel and fossils-fired home heating systems. In each case isocratic separation protocol involving less that 1 mL of one component or binary mixture mobile phases can be completed within time of 5–8 min. Sensitive detection of components of interest was performed via fluorescence or staining techniques using iodine or phosphomolybdic acid. Described methodology can be applied for fast fractionation or screening of whole range of target substances as well as chemo-taxonomic studies and fingerprinting of complex mixtures, which are present in raw biological or environmental samples.     

Comprehensive data analysis of femtosecond transient absorption spectra: A review

Nowadays, time-resolved spectroscopy data can be routinely and accurately collected in UV-vis femtosecond transient absorption spectroscopy. However, the data analysis strategy and the postulation of a physically valid model for this kind of measurements may be tackled with many different approaches ranging from pure soft-modeling (model-free) to hard-modeling, where the elaboration of a parametric spectro-temporal model may be required. This paper reviews methods that are used in practice for the analysis of femtosecond transient absorption spectroscopy data. Model-based methods, common in photochemistry, are revisited, and soft-modeling methods, which originate from the chemometrics field and that recently disseminated in the photo(bio)chemistry literature, are presented. These soft-modeling methods are designed to suit the intrinsic nature of the multivariate (or multi-way) measurement. Soft-modeling tools do not require a priori physical or mechanistic models to provide a decomposition of the data on the time and wavelength dimensions, the only requirement being that these two (or more) dimensions are separable. Additionally, Bayesian data analysis, which provides a probabilistic framework for data analysis, is considered in detail, since it allows uncertainty quantification and validation of the model selection step.     

Detection and characterization of ticlopidine conjugates in rat bile using high‐resolution mass spectrometry: applications of various data acquisition and processing tools

Ticlopidine, an antiplatelet drug, undergoes extensive oxidative metabolism to form S‐oxide, N‐oxide, hydroxylated and dealkylated metabolites. However, metabolism of ticlopidine via conjugation has not been thoroughly investigated. In this study, multiple data acquisition and processing tools were applied to the detection and characterization of ticlopidine conjugates in rat bile. Accurate full‐scan mass spectrometry (MS) and collision‐induced dissociation (CID) MS/MS data sets were recorded using isotope pattern‐dependent acquisition on an LTQ/Orbitrap system. In addition, mass spectral data from online H/D exchanging and high collision energy dissociation (HCD) were recorded. Data processes were carried out using extracted ion chromatography (EIC), mass defect filter (MDF) and isotope pattern filter (IPF). The total ion chromatogram displayed a few major conjugated metabolites and many endogenous components. Profiles from EIC and IPF processes exhibited multiple conjugates with no or minimal false positives. However, ticlopidine conjugates that were not predictable or lost a chorine atom were not found by EIC or IPF, respectively. MDF was able to detect almost all of ticlopidine conjugates although it led to a few more false positives. In addition to CID spectra, data from HCD, H/D exchanging experiments and isotope pattern simulation facilitated structural characterization of unknown conjugates. Consequently, 20 significant ticlopidine conjugates, including glucuronide, glutathione, cysteinylglycine, cysteine and N‐acetylcysteine conjugates, were identified in rat bile, a majority of which are associated with bioactivation and not previously reported. This study demonstrates the utility and limitation of various high‐resolution MS‐based data acquisition and processing techniques in detection and characterization of conjugated metabolites. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl-l-cysteine

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC₅H₈NO₃S·H₂O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state ¹³C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag-NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol, acetone and hexane. Antibacterial activity of the silver complex with N-acetyl-l-cysteine (Ag-NAC) was evaluated by antibiogram assays using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of a potential cytotoxic effect of Ag-NAC was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a significant cytotoxic activity, inducing 80% of cell death at a concentration of 200 μmol L⁻¹.     

The spectrophotometric study of a fluorescence‐enhanced inclusion complex threaded with β‐cyclodextrin: Synthesis and characterization

A novel achiral monomer end‐capped with a phenyl‐[1,3,4]oxadiazolyl group and threaded through β‐cyclodextrin was synthesized to investigate the host‐guest interactions in the inclusion complex. ¹H NMR studies revealed that one or two cyclodextrin molecules were threaded onto the synthesized achiral monomer, leading to the formation of a fibrous construction of self‐assembled inclusion complexes. The formation of a self‐assembled inclusion complex was identified using SEM and TEM. The highly ordered alignment of self‐assembled supramolecules was confirmed using polarized optical microscopy. We demonstrate an easy process for the fabrication of nano‐structured self‐assembled inclusion complexes in pyridine/ethanol (1 mL/10 mL) as well as the enhancement of photo‐induced fluorescence via monomers end‐capped with a phenyl‐[1,3,4]oxadiazolyl moiety threaded with β‐cyclodextrins. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3368–3374, 2010     

Comprehensive characterization and quantification of multiple components in Dan‐Huang‐Qu‐Yu capsule using a multivariate data processing approach based on microwave‐assisted extraction with UHPLC and Q Exactive quadrupole‐orbitrap high‐resolution mass spectrometry

Dan‐Huang‐Qu‐Yu capsule, a Chinese herbal medicine compound preparation, is widely used for chronic pelvic inflammatory disease. In this study, a rapid, selective, and sensitive microwave‐assisted extraction ultra‐high‐performance liquid chromatography‐Q Exactive quadrupole‐orbitrap high‐resolution mass spectrometry method was developed for analyzing its chemical compositions. A total of 85 compounds, including 22 flavonoids, 8 terpenoids, 5 quinones, 5 phthaleolactone, 23 organic acids, and 22 other compounds were identified from Dan‐Huang‐Qu‐Yu capsule. Among them, 35 major compounds were unambiguously detected by comparing them with reference standards and selected as quality control markers, which were simultaneously determined in Dan‐Huang‐Qu‐Yu capsule. The established method was successfully validated and applied for simultaneous determination of 35 bioactive compounds in Dan‐Huang‐Qu‐Yu capsule from ten sample batches. The quantitative data of the analytes were analyzed by principal component analysis for quality assessment of Dan‐Huang‐Qu‐Yu capsule. Six compounds (e.g., astragaloside IV, salvianolic acid B, ellagic acid, chlorogenic acid, N‐butylidenephthalide, and luteolin) were screened out and regarded as chemical markers for quality control of Dan‐Huang‐Qu‐Yu capsule. The established method has been proved to be a novel and useful tool for rapid research of Dan‐Huang‐Qu‐Yu capsule. This research will provide reference for the scientific research of traditional Chinese medicines.