Hyphenation and hypernation the practice and prospects of multiple hyphenation

Characterization of Fe-Containing and Pb-Containing Nanoparticles Resulting from Corrosion of Plumbing Materials in Tap Water Using a Hyphenated ATM-DMA-spICP-MS System

Single-particle inductively coupled plasma mass spectrometry (spICP-MS) has been used to characterize metallic nanoparticles (NPs) assuming that all NPs are spherical and composed of pure element. However, environmental NPs generally do not meet these criteria, suggesting that spICP-MS may underestimate their true sizes. This study employed a system hyphenating the atomizer (ATM), differential mobility analyzer (DMA), and spICP-MS to characterize metallic NPs in tap water. Its performance was validated by using reference Au nanoparticles (AuNPs) and Ag-shelled AuNPs. The hyphenated system can determine the actual size and metal composition of both NPs with additional heating after ATM, while stand-alone spICP-MS misidentified the Ag-shelled AuNPs as smaller individual AgNPs and AuNPs. Dissolved metal ions could introduce artifact NPs after heating but could be eliminated by centrifugation. The hyphenated system was applied to characterize Fe-containing and Pb-containing NPs resulting from the corrosion of plumbing materials in tap water. The mode sizes of Fe-containing and Pb-containing NPs were determined to be 110 and 100 nm and the particle number concentrations were determined to be 4.99 × 107 and 1.40 × 106 #/mL, respectively. Cautions should be paid to potential changes in particle size induced by heating for metallic NPs with a low melting point or a high organic content.

Structure Elucidation Using Gas Chromatography-Infrared Spectroscopy/Mass Spectrometry Supported by Quantum Chemical IR Spectrum Simulations

An improved strategy for compound identification incorporating gas chromatography hyphenated with Fourier transform infrared spectroscopy and mass spectroscopy (GC-FTIR/MS) is reported. (Over)reliance on MS may lead either to ambiguous identity or to incorrect identification of a compound. However, the MS result is useful to provide a cohort of possible compounds. The IR result for each tentative compound match was then simulated using molecular modeling, to provide functional group and isomer differentiation information, and then compared with the experimental FTIR result, offering identification based on both MS and IR. Several basis sets were evaluated for IR simulations; Def2-TZVPP was a suitable basis set and correlated well with experimental data. The approach was applied to industrial applications, confirming the isomers of 2,3-bis(thiosulfanyl)-but-2-enedinitrile, bromination products of 1-bromo-2,3-dimethylbenzene, and autoxidative degradation of phenyl-di-tert-butylphosphine.

Comprehensive and Rapid Quality Evaluation Method for the Ayurvedic Medicine Divya-Swasari-Vati Using Two Analytical Techniques: UPLC/QToF MS and HPLC-DAD

Divya-Swasari-Vati (DSV) is a calcium-containing herbal medicine formulated for the symptomatic control of respiratory illnesses observed in the current COVID-19 pandemic. DSV is an Ayurvedic medicine used for the treatment of chronic cough and inflammation. The formulation has shown its pharmacological effects against SARS-CoV-2 induced inflammation in the humanized zebrafish model. The present inventive research aimed to establish comprehensive quality parameters of the DSV formulation using validated chromatographic analytical tools. Exhaustive identification of signature marker compounds present in the plant ingredients was carried out using ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC/QToF MS). This was followed by simultaneous estimation of selected marker components using rapid and reliable high-performance liquid chromatography (HPLC) analysis. Eleven marker components, namely gallic acid, protocatechuic acid, methyl gallate, ellagic acid, coumarin, cinnamic acid, glycyrrhizin, eugenol, 6-gingerol, piperine and glabridin, were selected out of seventy-four identified makers for the quantitative analysis in DSV formulation. Validation of the HPLC method was evaluated by its linearity, precision, and accuracy tests as per the International Council of Harmonization (ICH) guidelines. Calibration curves for the eleven marker compounds showed good linear regression (r2 > 0.999). The relative standard deviation (RSD) value of intraday and interday precision tests were within the prescribed limits. The accuracy test results ranged from 92.75% to 100.13%. Thus, the present inclusive approach is first of its kind employing multi-chromatographic platforms for identification and quantification of the marker components in DSV, which could be applied for routine standardization of DSV and other related formulations.

Recent Advances in Standardization of Herbal Drugs

Background:

Herbal drugs play a significant role to maintain the human healthiness and to treat the ailments since the dawn of civilization. Moreover, these plants have provided many lead compounds that culminated in modern medicine. A single herb is regarded as mini-combinatorial library of phytoconstituents hence the quality control of herbal drugs in an herbal formulation is not an easy task because a number of factors impact their pharmacological efficiency and consistent therapeutic effects. Hence, to provide consistent beneficial therapeutic effects, standardized herbal products of consistent quality and purity are required.

Methods:

This review is based on publications obtained by a selective search in PubMed using the keywords “Standardized herbal products”, “fingerprinting”, “authentication”, “chemometric, hyphenated techniques”, “quality control of herbal drugs”, “identification”.

Results:

In the era of modernization, chromatographic techniques coupled with sophisticated spectroscopic analytical methods are used in estimating the authenticity, identity and characteristic of herbal products. Further, with the advancement of computer technology, chemometrics methods have become a leading tool with an unsupervised pattern recognition technique for handling multivariate data without prior knowledge about the studied samples and mines more beneficial and valuable information about the chemical entities from the raw data.

Conclusion:

Standardization of HDs chromatographic fingerprint is not always a perfect way to present all compounds. To assess the quality of medicinal plants, new ways are regularly being explored such as combination chemical fingerprint with biological methods, biofingerprint and metabolic fingerprint quality metrology, pharmacodynamics and export system of medicinal plants have been researched in some groups but still a significant amount of work is required to achieve a perfect system for quality evaluation of herbal drugs. Further, novel chemometric techniques have been unfolded that mines more beneficial and valuable information about the chemical entities from the raw data. So this review emphasis mainly on hyphenated techniques associated with chemometric method used in herbal drugs for identifying more valuable information and various methods for providing data, among which most commonly used techniques are chemometric resolution method and Principal Component Analysis (PCA) method.

Relationships in Gas Chromatography—Fourier Transform Infrared Spectroscopy—Comprehensive and Multilinear Analysis

Molecular spectroscopic detection techniques, such as Fourier transform infrared spectroscopy (FTIR), provides additional specificity for isomers where often mass spectrometry (MS) fails, due to similar fragmentation patterns. A hyphenated system of gas chromatography (GC) with FTIR via a light-pipe interface is reported in this study to explore a number of GC–FTIR analytical capabilities. Various compound classes were analyzed—aromatics, essential oils and oximes. Variation in chromatographic peak parameters due to the light-pipe was observed via sequentially-located flame ionization detection data. Unique FTIR spectra were observed for separated mixtures of essential oil isomers having similar mass spectra. Presentation of GC×FTIR allows a ‘comprehensive’-style experiment to be developed. This was used to obtain spectroscopic/separation profiles for interconverting oxime species with their individual spectra in the overlap region being displayed on a color contour plot. Partial least square regression provides multivariate quantitative analysis of co-eluting cresol isomers derived from GC–FTIR data. The model resulted in an R2 of 0.99. Prediction was obtained with R2 prediction value of 0.88 and RMSEP of 0.57, confirming the method’s suitability. This study explores the potential of GC–FTIR hyphenation and re-iterates its value to derive unambiguous and detailed molecular information which is complementary to MS.

Hyphenation of Supercritical Fluid Chromatography and NMR with In-Line Sample Concentration

By coupling supercritical fluid chromatography (SFC) and nuclear magnetic resonance (NMR) in-line, a powerful analytical method arises that enables chemically specific analysis of a broad range of complex mixtures. However, during chromatography, the compounds are diluted in the mobile phase, in this case supercritical CO₂ (scCO₂), often resulting in concentrations that are too low to be detected by NMR spectroscopy or at least requiring excessive signal averaging. We present a hyphenated SFC-NMR setup with an integrated approach for concentrating samples in-line, which are diluted in scCO₂ during chromatography. This in-line concentration is achieved by controlled in-line expansion of the scCO₂. As a proof of concept four isomers of vitamin E (tocopherol) were isolated by SFC, concentrated in-line by expanding CO₂ from 120 to 50 bar, and finally shuttled to the NMR spectrometer fitted with a dedicated probehead for spectroscopic characterization of microfluidic samples. The abundant isomers were readily detected, supporting the viability of SFC-NMR as a powerful analytical tool.

Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS

Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSⁿ spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.

Occurrence and reproductive roles of hormones in seminal plasma

Only 2-5% of seminal fluid is composed of spermatozoa, while the rest is seminal plasma. The seminal plasma is a rich cocktail of organic and inorganic compounds including hormones, serving as a source of nutrients for sperm development and maturation, protecting them from infection and enabling them to overcome the immunological and chemical environment of the female reproductive tract. In this review, a survey of the hormones found in human seminal plasma, with particular emphasis on reproductive hormones is provided. Their participation in fertilization is discussed including their indispensable role in ovum fertilization. The origin of individual hormones found in seminal plasma is discussed, along with differences in the concentrations in seminal plasma and blood plasma. A part of review is devoted to methods of measurement, emphasising particular instances in which they differ from measurement in blood plasma. These methods include separation techniques, overcoming the matrix effect and current ways for end-point measurement, focusing on so called hyphenated techniques as a combination of chromatographic separation and mass spectrometry. Finally, the informative value of their determination as markers of male fertility disorders (impaired spermatogenesis, abnormal sperm parameters, varicocele) is discussed, along with instances where measuring their levels in seminal plasma is preferable to measurement of levels in blood plasma.

LC coupled to ESI, MALDI and ICP MS - A multiple hyphenation for metalloproteomic studies

A new multiple detection arrangement for liquid chromatography (LC) that supplements conventional electrospray ionization (ESI) mass spectrometry (MS) detection with two complementary detection techniques, matrix-assisted laser desorption/ionization (MALDI) MS and substrate-assisted laser desorption inductively coupled plasma (SALD ICP) MS has been developed. The combination of the molecular and elemental detectors in a single separation run is accomplished by utilizing a commercial MALDI target made of conductive plastic. The proposed platform provides a number of benefits in today's metalloproteomic applications, which are demonstrated by analysis of a metallothionein mixture. To maintain metallothionein complexes, separation is carried out at a neutral pH. The effluent is split; a major portion is directed to ESI MS while the remaining 1.8% fraction is deposited onto a plastic MALDI target. Dried droplets are overlaid with MALDI matrix and analysed consecutively by MALDI MS and SALD ICP MS. In the ESI MS spectra, the MT isoform complexes with metals and their stoichiometry are determined; the apoforms are revealed in the MALDI MS spectra. Quantitative determination of metallothionein isoforms is performed via determination of metals in the complexes of the individual protein isoforms using SALD ICP MS.

Mass spectrometry-based plant metabolomics: Metabolite responses to abiotic stress

Metabolomics is one omics approach that can be used to acquire comprehensive information on the composition of a metabolite pool to provide a functional screen of the cellular state. Studies of the plant metabolome include analysis of a wide range of chemical species with diverse physical properties, from ionic inorganic compounds to biochemically derived hydrophilic carbohydrates, organic and amino acids, and a range of hydrophobic lipid-related compounds. This complexitiy brings huge challenges to the analytical technologies employed in current plant metabolomics programs, and powerful analytical tools are required for the separation and characterization of this extremely high compound diversity present in biological sample matrices. The use of mass spectrometry (MS)-based analytical platforms to profile stress-responsive metabolites that allow some plants to adapt to adverse environmental conditions is fundamental in current plant biotechnology research programs for the understanding and development of stress-tolerant plants. In this review, we describe recent applications of metabolomics and emphasize its increasing application to study plant responses to environmental (stress-) factors, including drought, salt, low oxygen caused by waterlogging or flooding of the soil, temperature, light and oxidative stress (or a combination of them). Advances in understanding the global changes occurring in plant metabolism under specific abiotic stress conditions are fundamental to enhance plant fitness and increase stress tolerance. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:620-649, 2016.

Chemometrics-assisted excitation-emission fluorescence analytical data for rapid and selective determination of optical brighteners in the presence of uncalibrated interferences

This study describes a novel approach for the simultaneous determination of CBS-X and CXT as widely used optical brighteners in household detergent, by combining the advantage of the high sensitivity of molecular fluorescence, and the selectivity of second-order chemometric methods. The proposed method is assisted by second-order chemometric analyses employing the PARAFAC, SWATLD and APTLD that help us to determine CBS-X and CXT in laundry powders and environmental samples, through the unique decomposition of the three-way data array. Proposed method can provide the extraction of relative concentrations of the analytes, as well as the spectral profiles. This approach achieves the second-order advantage and in principle could be able to overcome the spectral uncalibrated interference problems in the determination of CBS-X and CXT at the ng g(-1) level. By spiking the known concentrations of these compounds to the real samples, the accuracy of the proposed methods was validated and recoveries of the spiked values were calculated. High recoveries (90.00%-113.33%) for the spiked laundry powders and real environmental samples indicate the present method successfully faces this complex challenge without the necessity of applying separation and preconcentration steps in environmental contaminations.

Polymethoxyflavones Isolated from the Peel of Miaray Mandarin (Citrus miaray) Have Biofilm Inhibitory Activity in Vibrio harveyi

Citrus fruits are a good source of bioactive compounds with numerous beneficial biological activities. In the present study, fruits of the unexplored Miaray mandarin were used for the isolation of 10 bioactive compounds. Dried peels were sequentially extracted with hexane and chloroform in a Soxhlet-type apparatus for 8 h. The extracts were concentrated under vacuum and separated by flash chromatography to obtain nine polymethoxyflavones and a limonoid. The purity of each compound was analyzed by high-performance liquid chromatography (HPLC), and the compounds were identified by spectral analysis using MALDI-TOF-MS and NMR. The isolated compounds were identified as 5-hydroxy-3,7,3',4'-tetramethoxyflavone, 5,6,7,8,4'-pentamethoxyflavone (tangeretin), 3,5,6,7,8,3',4'-heptamethoxyflavone, 5,6,7,8,3',4'-hexamethoxyflavone (nobiletin), 3,5,7,8,3',4'-hexamethoxyflavone, 3,5,7,3',4'-pentamethoxyflavone (pentamethylquercetin), 5,7,4'-trimethoxyflavone, 5,7,8,4'-tetramethoxyflavone, 5,7,8,3',4'-pentamethoxyflavone, and limonin. These compounds were further tested for their ability to inhibit cell-cell signaling and biofilm formation in Vibrio harveyi. Among the evaluated polymethoxyflavones, 3,5,6,7,8,3',4'-heptamethoxyflavone and 3,5,7,8,3',4'-hexamethoxyflavone inhibited autoinducer-mediated cell-cell signaling and biofilm formation. These results suggest that Miaray mandarin fruits are a good source of polymethoxyflavones. This is the first report on the isolation of bioactive compounds from Miaray mandarin and evaluation of their biofilm inhibitory activity as well as isolation of pentamethylquercetin from the Citrus genus.

Combined SAXS/UV-vis/Raman as a diagnostic and structure resolving tool in materials and life sciences applications

In order to diagnose and fully correlate structural, chemical, and functional features of macromolecules and particles in solution, we propose the integration of spectroscopy and scattering on the same measuring volume and at the same time in a dedicated sample environment with multiple probes. Combined SAXS/UV-vis and SAXS/Raman information are employed to study the radiation damage effect in proteins in solution and the scattering from single wall carbon nanotubes (SWNTs) in SDS dispersion, respectively. In the first case, a clear correlation is observed between the time dependence of the radius of gyration (Rg) of the protein determined by SAXS and the turbidity of the protein solution extracted from simultaneous UV-vis measurements. In the second case, the ratio of bundled/isolated carbon nanotubes is obtained unambiguously through proper modeling of the scattering data and cross-validated with the Raman information. The uses of convex constraint analysis (CCA) and two-dimensional correlation analyses (2DCOS and 2DHCOS) are introduced to fully explore the combination of data sets from different techniques and to extract unique insights from the sample.

Introduction to hyphenated techniques and their applications in pharmacy

The hyphenated technique is developed from the coupling of a separation technique and an on-line spectroscopic detection technology. The remarkable improvements in hyphenated analytical methods over the last two decades have significantly broadened their applications in the analysis of biomaterials, especially natural products. In this article, recent advances in the applications of various hyphenated techniques, e.g., GC-MS, LC-MS, LC-FTIR, LC-NMR, CE-MS, etc. in the context of pre-isolation analyses of crude extracts or fraction from various natural sources, isolation and on-line detection of natural products, chemotaxonomic studies, chemical fingerprinting, quality control of herbal products, dereplication of natural products, and metabolomic studies are discussed with appropriate examples.

The importance of hyphenated techniques in the discovery of new lead compounds from nature

Nature represents an extraordinary reservoir of novel molecules and there is currently a resurgence of interest in natural products as a possible source of new lead compounds for introduction into therapeutical screening programmes. To discover new bioactive natural products, the dereplication of crude extracts performed prior to isolation work is of crucial importance for avoiding the tedious isolation of known constituents. In this respect, chemical screening strategies based on hyphenated techniques such as liquid chromatography-ultraviolet photodiode array detection, liquid chromatography-mass spectrometry, liquid chromatography tandom mass spectrometry and liquid chromatography-nuclear magnetic resonance (LC-NMR) are more and more extensively used. In the laboratory of Hostettmann's group, these analytical methods have been fully integrated into the isolation process and are used for the chemical screening of crude plant extracts, in complement with online or at-line bioassays, for rapid localisation and identification of new bioactive compounds. In this paper, possibilities and limitations of hyphenated techniques for de novo online natural product identification are discussed. As LC-NMR is playing a key role in this respect, the main part of the paper is dedicated to this technique. In particular, various ways of integrating NMR in the dereplication process are illustrated and strategies involving either direct or indirect hyphenation are presented.

Hyphenated techniques and their applications in natural products analysis

A technique where a separation technique is coupled with an online spectroscopic detection technology is known as hyphenated technique, e.g., GC-MS, LC-PDA, LC-MS, LC-FTIR, LC-NMR, LC-NMR-MS, and CE-MS. Recent advances in hyphenated analytical techniques have remarkably widened their applications to the analysis of complex biomaterials, especially natural products. This chapter focuses on the applications of hyphenated techniques to pre-isolation and isolation of natural products, dereplication, online partial identification of compounds, chemotaxonomic studies, chemical finger-printing, quality control of herbal products, and metabolomic studies, and presents specific examples. However, a particular emphasis has been given on the hyphenated techniques that involve an LC as the separation tool.

Application of different modes of thin-layer chromatography and mass spectrometry for the separation and detection of large and small biomolecules

Biomolecules are widespread throughout the world. A biomolecule is any organic molecule produced by a living organism, including large polymeric molecules such as proteins, polysaccharides and nucleic acids. Many sample preparation techniques are used in biomolecule analysis; the method selected depends on the complexity of the sample, the nature of the matrix and the analytes, and the analytical technique available. This review covers the current state of knowledge on thin-layer chromatography and mass spectrometry for qualitative analysis of biomolecules. In the first part of the paper the reader will gain useful information to avoid some problems about performing various modes of thin-layer chromatography combined with mass spectrometry experiments and in the second part he will find useful information for application of these techniques for separation, detection, and qualitative investigation of structures and quantitative determination of biomolecules such as proteins, peptides, oligonucleotides, amino acids, DNA, RNA, and lipids.

Pressurized liquid extraction as a green approach in food and herbal plants extraction: A review

Pressurized liquid extraction is a "green" technology for the extraction of nutraceuticals from foods and herbal plants. This review discusses the extraction principles and the optimization of the extraction parameters that improves the extraction efficiency. The use of different solvent mixtures and other extraction additives to enhance the efficiency of the extraction are discussed. Dynamic mode of extraction in Pressurized liquid extraction, and the use of combined and hyphenated sample preparation and analytical techniques are presented. This work discusses how different studies used Pressurized liquid extraction to enrich phenolic compounds, lignans, carotenoids, oils and lipids, essential oils and other nutraceuticals from foods and herbal plants.

Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s12566-010-0015-9) contains supplementary material, which is available to authorized users.

Metabolomic applications of HILIC-LC-MS

Hydrophilic interaction liquid chromatography (HILIC), although not a new technique, has enjoyed a recent renaissance with the introduction of robust and reproducible stationary phases. It is consequently finding application in metabolomics studies, which have traditionally relied on the stability of reversed phases (RPs), since the biofluids analyzed are predominantly aqueous and thus contain many polar analytes. HILIC's retention of those polar compounds and use of solvents readily compatible with mass spectrometry have seen its increasing adoption in studies of complex aqueous metabolomes. This review describes the stationary phases and their features, surveys HILIC-LC-MS's role in metabolomics experiments, discusses approaches to data extraction and analysis including multivariate analysis, and reviews the literature on HILIC-MS applications in metabolomics.

Automated molecular formula determination by tandem mass spectrometry (MS/MS)

Automated software was developed to analyze the molecular formula of organic molecules and peptides based on high-resolution MS/MS spectroscopic data. The software was validated with 96 compounds including a few small peptides in the mass range of 138-1569 Da containing the elements carbon, hydrogen, nitrogen and oxygen. A Micromass Waters Q-TOF Ultima Global mass spectrometer was used to measure the molecular masses of precursor and fragment ions. Our software assigned correct molecular formulas for 91 compounds, incorrect molecular formulas for 3 compounds, and no molecular formula for 2 compounds. The obtained 95% success rate indicates high reliability of the software. The mass accuracy of the precursor ion and the fragment ions, which is critical for the success of the analysis, was high, i.e. the accuracy and the precision of 850 data were 0.0012 Da and 0.0016 Da, respectively. For the precursor and fragment ions below 500 Da, 60% and 90% of the data showed accuracy within < or = 0.001 Da and < or = 0.002 Da, respectively. The precursor and fragment ions above 500 Da showed slightly lower accuracy, i.e. 40% and 70% of them showed accuracy within < or = 0.001 Da and < or = 0.002 Da, respectively. The molecular formulas of the precursor and the fragments were further used to analyze possible mass spectrometric fragmentation pathways, which would be a powerful tool in structural analysis and identification of small molecules. The method is valuable in the rapid screening and identification of small molecules such as the dereplication of natural products, characterization of drug metabolites, and identification of small peptide fragments in proteomics. The analysis was also extended to compounds that contain a chlorine or bromine atom.

High Resolution Separations and Improved Ion Production and Transmission in Metabolomics

The goal of metabolomics analyses is the detection and quantitation of as many sample components as reasonably possible in order to identify compounds or "features" that can be used to characterize the samples under study. When utilizing electrospray ionization to produce ions for analysis by mass spectrometry (MS), it is important that metabolome sample constituents be efficiently separated prior to ion production, in order to minimize ionization suppression and thereby extend the dynamic range of the measurement, as well as the coverage of the metabolome. Similarly, optimization of the MS inlet and interface can lead to increased measurement sensitivity. This perspective review will focus on the role of high resolution liquid chromatography (LC) separations in conjunction with improved ion production and transmission for LC-MS-based metabolomics. Additional emphasis will be placed on the compromise between metabolome coverage and sample analysis throughput.

Untargeted large-scale plant metabolomics using liquid chromatography coupled to mass spectrometry

Untargeted metabolomics aims to gather information on as many metabolites as possible in biological systems by taking into account all information present in the data sets. Here we describe a detailed protocol for large-scale untargeted metabolomics of plant tissues, based on reversed phase liquid chromatography coupled to high-resolution mass spectrometry (LC-QTOF MS) of aqueous methanol extracts. Dedicated software, MetAlign, is used for automated baseline correction and alignment of all extracted mass peaks across all samples, producing detailed information on the relative abundance of thousands of mass signals representing hundreds of metabolites. Subsequent statistics and bioinformatics tools can be used to provide a detailed view on the differences and similarities between (groups of) samples or to link metabolomics data to other systems biology information, genetic markers and/or specific quality parameters. The complete procedure from metabolite extraction to assembly of a data matrix with aligned mass signal intensities takes about 6 days for 50 samples.

Supramolecular systems-based extraction-separation techniques coupled to mass spectrometry

The combination of supramolecular chemistry and MS has not only been fruitful in the field of gas-phase fundamental studies of host-guest complexes and supramolecular assemblies. Mass spectrometric analysis has also benefited from the ability of supramolecular systems to behave as pseudophases in which solutes partition from the bulk solvent phase. Supramolecular systems-based extraction and concentration schemes and separation techniques have been widely used in different fields of analytical chemistry and are ideally suited for coupling with MS. This review describes the present status of the application of supramolecular chemistry in mass spectrometric analysis and includes topics such as the use of coacervative liquid-liquid extraction and hemimicelle/admicelle-based SPE of organic compounds prior to chromatography and electrophoresis. It also discusses the recent advances in enantioselective analysis using CD in electrophoresis- and chromatography-MS. The potential and analytical challenges of these approaches in environmental and bioanalytical chemistry, where one can expect significant developments in the future, are outlined.

Theodor Bücher Lecture. Metabolomics, modelling and machine learning in systems biology - towards an understanding of the languages of cells. Delivered on 3 July 2005 at the 30th FEBS Congress and the 9th IUBMB conference in Budapest

The newly emerging field of systems biology involves a judicious interplay between high-throughput 'wet' experimentation, computational modelling and technology development, coupled to the world of ideas and theory. This interplay involves iterative cycles, such that systems biology is not at all confined to hypothesis-dependent studies, with intelligent, principled, hypothesis-generating studies being of high importance and consequently very far from aimless fishing expeditions. I seek to illustrate each of these facets. Novel technology development in metabolomics can increase substantially the dynamic range and number of metabolites that one can detect, and these can be exploited as disease markers and in the consequent and principled generation of hypotheses that are consistent with the data and achieve this in a value-free manner. Much of classical biochemistry and signalling pathway analysis has concentrated on the analyses of changes in the concentrations of intermediates, with 'local' equations - such as that of Michaelis and Menten v=(Vmax x S)/(S+K m) - that describe individual steps being based solely on the instantaneous values of these concentrations. Recent work using single cells (that are not subject to the intellectually unsupportable averaging of the variable displayed by heterogeneous cells possessing nonlinear kinetics) has led to the recognition that some protein signalling pathways may encode their signals not (just) as concentrations (AM or amplitude-modulated in a radio analogy) but via changes in the dynamics of those concentrations (the signals are FM or frequency-modulated). This contributes in principle to a straightforward solution of the crosstalk problem, leads to a profound reassessment of how to understand the downstream effects of dynamic changes in the concentrations of elements in these pathways, and stresses the role of signal processing (and not merely the intermediates) in biological signalling. It is this signal processing that lies at the heart of understanding the languages of cells. The resolution of many of the modern and postgenomic problems of biochemistry requires the development of a myriad of new technologies (and maybe a new culture), and thus regular input from the physical sciences, engineering, mathematics and computer science. One solution, that we are adopting in the Manchester Interdisciplinary Biocentre (http://www.mib.ac.uk/) and the Manchester Centre for Integrative Systems Biology (http://www.mcisb.org/), is thus to colocate individuals with the necessary combinations of skills. Novel disciplines that require such an integrative approach continue to emerge. These include fields such as chemical genomics, synthetic biology, distributed computational environments for biological data and modelling, single cell diagnostics/bionanotechnology, and computational linguistics/text mining.

Analytical separation and detection methods for flavonoids

Flavonoids receive considerable attention in the literature, specifically because of their biological and physiological importance. This review focuses on separation and detection methods for flavonoids and their application to plants, food, drinks and biological fluids. The topics that will be discussed are sample treatment, column liquid chromatography (LC), but also methods such as gas chromatography (GC), capillary electrophoresis (CE) and thin-layer chromatography (TLC), various detection methods and structural characterization. Because of the increasing interest in structure elucidation of flavonoids, special attention will be devoted to the use of tandem-mass spectrometric (MS/MS) techniques for the characterization of several important sub-classes, and to the potential of combined diode-array UV (DAD UV), tandem-MS and nuclear magnetic resonance (NMR) detection for unambiguous identification. Emphasis will be on recent developments and trends.

Identification and Quantification of Homologous Series of Compound in Complex Mixtures: Autocovariance Study of GC/MS Chromatograms

The paper describes a method for determining homologous classes of compounds in a multicomponent complex chromatogram obtained under programming elution conditions. The method is based on the computation of the autocovariance function of the experimental chromatogram (EACVF). The EACVF plot, if properly interpreted, can be regarded as a "class chromatogram" i.e., a virtual chromatogram formed by peaks whose positions and heights allow identification and quantification of the different homologous series, even if they are embedded in a random complex chromatogram. Theoretical models were developed to describe complex chromatograms displaying random retention pattern, ordered sequences or a combination of them. On the basis of theoretical autocovariance function, the properties of the chromatogram can be experimentally evaluated, under well-defined conditions: in particular, the two components of the chromatogram, ordered and random, can be identified. Moreover, the total number of single components (SCs) and the separated number of the SCs belonging to the random and ordered components can be determined, when the two components display the same concentration. If the mixture contains several homologous series with common frequency and different phase values, the number and identity of the different homologous series as well as the number of SCs belonging to each of them can be evaluated. Moreover, the power of the EACVF method can be magnified by applying it to the single ion monitoring (SIM) signals to selectively detect specific compound classes in order to identify the different homologous series. By this way, a full "decoding" of the complex multicomponent chromatogram is achieved. The method was validated on synthetic mixtures containing known amount of SCs belonging to homologous series of hydrocarbon, alcohols, ketones, and aromatic compounds in addition to other not structurally related SCs. The method was applied to both the total ion monitoring (TIC) and the SIM signals, to describe step by step the essence of the procedure. Moreover, the systematic use of both SIM and TIC can simplify the decoding procedure of complex chromatograms by singling out only specific compound classes or by confirming the identification of the different homologous series. The method was further applied to a sample containing unknown number of compounds and homologous series (a petroleum benzin, bp 140-160 degrees C): the results obtained were meaningful in terms of both the identified number of components and identified homologous series.

Development and validation of a sensitive GC–MS method for the determination of trace levels of an alkylating reagent in a β-lactam active pharmaceutical ingredient

A direct injection gas chromatographic method utilizing selected-ion monitoring (SIM) mode mass selective detection was developed and validated for the trace analysis of an impurity, carbonic acid chloromethyl tetrahydro-pyran-4-yl ester (CCMTHP), present in a beta-lactam active pharmaceutical ingredient (API). A variety of analytical techniques including LC-MS, GC-FID, GC-ECD and GC-MS were evaluated during the method development. GC-MS with SIM at m/z=49 demonstrated the best detection sensitivity. A 10 ppm (5 pg on column) limit of quantitation (LOQ) was attained and the linearity of the method was demonstrated in the range of 10-1000 ppm. Accurate and precise quantitation of the impurity in drug substance was achieved with external standardization. A 10:1 split injection was applied to limit the amount of non-volatile API loading onto the column. The effects of injection and detection parameters such as split ratio, liner type, injection temperature and number of mass ions monitored were studied. Full validation proved the accuracy, precision and specificity of the method, which was successfully employed to analyze many pilot lots of the API.