Food metabolomics: Latest hardware—developments for nontargeted food authenticity and food safety testing

The analytical requirements for food testing have increased significantly in recent years. On the one hand, because food fraud is becoming an ever-greater challenge worldwide, and on the other hand because food safety is often difficult to monitor due to the far-reaching trade chains. In addition, the expectations of consumers on the quality of food have increased, and they are demanding extensive information. Cutting-edge analytical methods are required to meet these demands. In this context, non-targeted metabolomics strategies using mass and nuclear magnetic resonance spectrometers (mass spectrometry [MS]) have proven to be very suitable. MS-based approaches are of particular importance as they provide a comparatively high analytical coverage of the metabolome. Accordingly, the efficiency to address even challenging issues is high. A variety of hardware developments, which are explained in this review, have contributed to these advances. In addition, the potential of future developments is highlighted, some of which are currently not yet commercially available or only used to a comparatively small extent but are expected to gain in importance in the coming years.     

Recent Analytical Approaches for the Study of Bioavailability and Metabolism of Bioactive Phenolic Compounds

The study of the bioavailability of bioactive compounds is a fundamental step for the development of applications based on them, such as nutraceuticals, functional foods or cosmeceuticals. It is well-known that these compounds can undergo metabolic reactions before reaching therapeutic targets, which may also affect their bioactivity and possible applications. All recent studies that have focused on bioavailability and metabolism of phenolic and terpenoid compounds have been developed because of the advances in analytical chemistry and metabolomics approaches. The purpose of this review is to show the role of analytical chemistry and metabolomics in this field of knowledge. In this context, the different steps of the analytical chemistry workflow (design study, sample treatment, analytical techniques and data processing) applied in bioavailability and metabolism in vivo studies are detailed, as well as the most relevant results obtained from them.     

Inductively coupled plasma-mass spectrometry for the determination of elements and elemental species in food: a review

Inductively coupled plasma-mass spectrometry (ICP-MS) has definitely emerged as a powerful technique for total element determination and as a sensitive and selective detector in hyphenated methods for speciation analyses of elements in foods. In this review, the analytical challenges of elemental analysis of food and agricultural matrixes are discussed and several applications are examined. Selected examples illustrate the analytical approaches being used so far to address specific issues in various areas of food and nutrition research. The applications discussed include studies on dietary intake, element metabolism in man, transfer of elements through the food chain, effects of food processing and domestic preparation, and authenticity and origin assessment. The use of ICP-MS in the field of analytical quality assurance, food control, evaluation of food contact materials, and radionuclide contamination is also examined. Finally, the hyphenated techniques with ICP-MS detection used for elemental speciation in food are reviewed, and an overview of the main applications currently in the literature is presented. Throughout, recent trends and analytical developments likely to have a major impact on food-related areas are highlighted.     

Recent advances in the preparation and application of monolithic capillary columns in separation science

Novel column technologies involving various materials and efficient reactions have been investigated for the fabrication of monolithic capillary columns in the field of analytical chemistry. In addition to the development of these miniaturized systems, a variety of microscale separation applications have achieved noteworthy results, providing a stepping stone for new types of chromatographic columns with improved efficiency and selectivity. Three novel strategies for the preparation of capillary monoliths, including ionic liquid-based approaches, nanoparticle-based approaches and “click chemistry”, are highlighted in this review. Furthermore, we present the employment of state-of-the-art capillary monolithic stationary phases for enantioseparation, solid-phase microextraction, mixed-mode separation and immobilized enzyme reactors. The review concludes with recommendations for future studies and improvements in this field of research.     

Review of validation and reporting of non-targeted fingerprinting approaches for food authentication

Food fingerprinting approaches are expected to become a very potent tool in authentication processes aiming at a comprehensive characterization of complex food matrices. By non-targeted spectrometric or spectroscopic chemical analysis with a subsequent (multivariate) statistical evaluation of acquired data, food matrices can be investigated in terms of their geographical origin, species variety or possible adulterations. Although many successful research projects have already demonstrated the feasibility of non-targeted fingerprinting approaches, their uptake and implementation into routine analysis and food surveillance is still limited. In many proof-of-principle studies, the prediction ability of only one data set was explored, measured within a limited period of time using one instrument within one laboratory. Thorough validation strategies that guarantee reliability of the respective data basis and that allow conclusion on the applicability of the respective approaches for its fit-for-purpose have not yet been proposed. Within this review, critical steps of the fingerprinting workflow were explored to develop a generic scheme for multivariate model validation. As a result, a proposed scheme for “good practice” shall guide users through validation and reporting of non-targeted fingerprinting results. Furthermore, food fingerprinting studies were selected by a systematic search approach and reviewed with regard to (a) transparency of data processing and (b) validity of study results. Subsequently, the studies were inspected for measures of statistical model validation, analytical method validation and quality assurance measures. In this context, issues and recommendations were found that might be considered as an actual starting point for developing validation standards of non-targeted metabolomics approaches for food authentication in the future. Hence, this review intends to contribute to the harmonization and standardization of food fingerprinting, both required as a prior condition for the authentication of food in routine analysis and official control.     

Computation of the physio-chemical properties and data mining of large molecular collections

Very large data sets of molecules screened against a broad range of targets have become available due to the advent of combinatorial chemistry. This information has led to the realization that ADME (absorption, distribution, metabolism, and excretion) and toxicity issues are important to consider prior to library synthesis. Furthermore, these large data sets provide a unique and important source of information regarding what types of molecular shapes may interact with specific receptor or target classes. Thus, the requirement for rapid and accurate data mining tools became paramount. To address these issues Pharmacopeia, Inc. formed a computational research group, The Center for Informatics and Drug Discovery (CIDD).* In this review we cover the work done by this group to address both in silico ADME modeling and data mining issues faced by Pharmacopeia because of the availability of a large and diverse collection (over 6 million discrete compounds) of drug-like molecules. In particular, in the data mining arena we discuss rapid docking tools and how we employ them, and we describe a novel data mining tool based on a ID representation of a molecule followed by a molecular sequence alignment step. For the ADME area we discuss the development and application of absorption, blood-brain barrier (BBB) and solubility models. Finally, we summarize the impact the tools and approaches might have on the drug discovery process.     

Analytical approaches on some selected toxic heavy metals in the environment and their socio-environmental impacts: A meticulous review

Heavy metals are a group of metals and metalloids that have relatively high density and are toxic even at ppb levels. The excess intake of heavy metals in human bodies though the environment may cause various humans health problems. Analytical approaches of some selected toxic heavy metals in the environment and their socio-environmental impacts are discussed in this review. In this present investigation, we have also discussed the design and development of nanomaterials for the detection of metal ions along with kinetic approaches. The isolation or pre-concentration and determination of heavy metals from complex matrices become challenging for analytical chemists and researchers. The fundamentals on sample preparation and analysis of some selected heavy metals employing different analytical tools for qualitative and quantitative determination of these pollutants in real samples are also discussed. In addition, this compiled work enhanced our knowledge in learning about pathway mechanisms and the degree of their risk assessment.     

Avoiding pitfalls with chemometrics and PAT in the pharmaceutical and biotech industries

This article is to help pharmaceutical scientists, especially those who do not specialize in chemometrics, to avoid obvious errors and pitfalls. It is also intended to inform the wider analytical community about the possibilities and the limitations of different chemometric approaches. While several of these issues can apply to the general use of chemometric tools, others are more specific to the recent increase in their use in development and manufacture of pharmaceuticals. This review covers the basics of chemometrics and critically discusses common errors and dangers encountered when uninitiated scientists apply the techniques.     

Recent and potential developments in the analysis of urine: a review

Analysis of urine is a widely used diagnostic tool that traditionally measured one or, at most, a few metabolites. However, the recognition of the need for a holistic approach to metabolism led to the application of metabolomics to urine for disease diagnostics. This review looks at various aspects of urinalysis including sampling and traditional approaches before reviewing recent developments using metabolomics. Spectrometric approaches are covered briefly since there are already a number of very good reviews on NMR spectroscopy and mass spectrometry and other spectrometries are not as highly developed in their applications to metabolomics. On the other hand, there has been a recent surge in chromatographic applications dedicated to characterising the human urinary metabolome. While developments in the analysis of urine encompassing both classical approaches of urinalysis and metabolomics are covered, it must be emphasized that these approaches are not orthogonal - they both have their uses and are complementary. Regardless, the need to normalise analytical data remains an important impediment.     

Detection and analysis of airborne particles of biological origin: present and future

Detection and identification of bioaerosols in the environment presents a unique analytical challenge. The complexity and variation of the analyte, coupled with the disparity of the end users required information has led to the establishment of a huge number of approaches for detection. In general these approaches may be divided into two elements; sampling, describing the physical process used to capture the bioaerosols and analysis, the method by which the bioaerosols are counted and identified. There are a large number of methodologies for both these elements, mainly due to the diversity of applications, and a very unhealthy absence of consensus on standardisation for these approaches. This is an analytical application where 'one size does not fit all'; nevertheless standardisation is still essential. The focus of this review will clarify the challenge, by discussing the many different bioaerosols to be measured and the required user output, also to give a critique of the various analytical approaches that exist to date, including other promising methodologies that could be applied.     

Recent developments in rapid multiplexed bioanalytical methods for foodborne pathogenic bacteria detection

Foodborne illnesses caused by pathogenic bacteria represent a widespread and growing problem to public health, and there is an obvious need for rapid detection of food pathogens. Traditional culture-based techniques require tedious sample workup and are time-consuming. It is expected that new and more rapid methods can replace current techniques. To enable large scale screening procedures, new multiplex analytical formats are being developed, and these allow the detection and/or identification of more than one pathogen in a single analytical run, thus cutting assay times and costs. We review here recent advancements in the field of rapid multiplex analytical methods for foodborne pathogenic bacteria. A variety of strategies, such as multiplex polymerase chain reaction assays, microarray- or multichannel-based immunoassays, biosensors, and fingerprint-based approaches (such as mass spectrometry, electronic nose, or vibrational spectroscopic analysis of whole bacterial cells), have been explored. In addition, various technological solutions have been adopted to improve detectability and to eliminate interferences, although in most cases a brief pre-enrichment step is still required. This review also covers the progress, limitations and future challenges of these approaches and emphasizes the advantages of new separative techniques to selectively fractionate bacteria, thus increasing multiplexing capabilities and simplifying sample preparation procedures.

Monitoring and characterization of polyaromatic compounds in the environment

This paper provides an overview of analytical techniques and instruments used to monitor and characterize polycyclic aromatic compounds (PACs) in the environment. The basic operating principles of various analytical approaches and systems are presented. The review deals specifically with spectroscopic methods, chromatographic and hyphenated techniques, and field monitoring devices. Emphasis is given to portable devices that can be used under field conditions. Specific examples of analytical techniques and instruments developed in the authors's laboratories will be discussed to illustrate the usefulness and potential of these approaches for environmental monitoring and characterization of PACs.     

DNA microarrays: is there a role for analytical chemistry?

DNA microarrays, or "DNA chips", represent a relatively new technology that is having a profound impact on biology and medicine, yet analytical research into this area is somewhat sparse. This article presents an overview of DNA microarrays and their application to gene expression analysis from the perspective of analytical chemistry, treating aspects of array platforms, measurement, image analysis, experimental design, normalization, and data analysis. Typical approaches are described and unresolved issues are discussed, with a view to identifying some of the contributions that might be made by analytical chemists.     

State of the art of environmentally friendly sample preparation approaches for determination of PBDEs and metabolites in environmental and biological samples: A critical review

Green chemistry principles for developing methodologies have gained attention in analytical chemistry in recent decades. A growing number of analytical techniques have been proposed for determination of organic persistent pollutants in environmental and biological samples. In this light, the current review aims to present state-of-the-art sample preparation approaches based on green analytical principles proposed for the determination of polybrominated diphenyl ethers (PBDEs) and metabolites (OH-PBDEs and MeO-PBDEs) in environmental and biological samples. Approaches to lower the solvent consumption and accelerate the extraction, such as pressurized liquid extraction, microwave-assisted extraction, and ultrasound-assisted extraction, are discussed in this review. Special attention is paid to miniaturized sample preparation methodologies and strategies proposed to reduce organic solvent consumption. Additionally, extraction techniques based on alternative solvents (surfactants, supercritical fluids, or ionic liquids) are also commented in this work, even though these are scarcely used for determination of PBDEs. In addition to liquid-based extraction techniques, solid-based analytical techniques are also addressed. The development of greener, faster and simpler sample preparation approaches has increased in recent years (2003–2013). Among green extraction techniques, those based on the liquid phase predominate over those based on the solid phase (71% vs. 29%, respectively). For solid samples, solvent assisted extraction techniques are preferred for leaching of PBDEs, and liquid phase microextraction techniques are mostly used for liquid samples. Likewise, green characteristics of the instrumental analysis used after the extraction and clean-up steps are briefly discussed.     

Enantioselective LC analysis and determination of selective serotonin reuptake inhibitors

LC separation of biologically and pharmaceutically important enantiomers (from racemic or non-racemic mixtures) remains a subject of importance. The present review article deals with the liquid chromatographic enantioseparation of chiral selective serotonin reuptake inhibitors (SSRIs), namely citalopram, paroxetine, sertraline and fluoxetine. It is now known that the enantiomers of numerous psychotropic drugs exhibit distinct pharmacodynamics, pharmacokinetic patterns and receptor binding properties, and psychiatric patients are frequently taking more than one medication. Therefore, monitoring of the levels of these analytes in biological fluids is important to determine the levels of enantiomer concentrations; the present paper may be helpful in understanding the present state of available methods (along with a critical discussion of applicability of the methods) and in developing the new ones for this purpose. Different approaches using LC discussed herein may be applied for determining the enantiomeric composition (and enantiomeric purity) of SSRIs and numerous other racemic drugs, of current/future pharmaceutical importance and utility, using simple separation methods, instrumentation, inexpensive reagents and potentially significant analytical approaches. The contents cover the essential data to understand the various separation techniques and associated issues, if any, with documented examples.     

Experimental choices for the determination of carbonyl compounds in air

The analysis of carbonyls in ambient air has received a great deal of scientific attention with the advancement of analytical techniques and increased demand for the build-up of its data base. In this review article, we have attempted to provide some insight into the relative performance of different instrumental approaches available for the analysis of ambient carbonyls with a major emphasis on high performance liquid chromatographic and gas chromatographic methods. Reported in several international standard procedures, derivatization of carbonyls with 2,4-dinitrophenylhydrazine (2,4-DNPH) with either an impinger or cartridges is the most commonly used method of HPLC detection. In this respect, a number of alternative hydrazine reagents have also been discussed for use with HPLC. In contrast, GC methods based on the combined application of adsorptive enrichment on solid sorbents and thermal desorption are examined with regard to their suitability for carbonyl analysis in air. Particular emphasis has been directed towards the advantages and drawbacks of these different instrumental techniques for ambient carbonyls. Based on this comparative approach, we discuss the suitability for each method for carbonyl analysis.     

Applications of NMR metabolomics to the study of foodstuffs: Truffle, kiwifruit, lettuce, and sea bass

In this review, four examples of the NMR metabolomic approach to foodstuff investigation are reported. Different types of foodstuff of different origin (namely truffle, kiwifruit, lettuce, and sea bass), with different metabolite composition, processing, and storage procedures have been chosen to demonstrate the versatility and potentiality of NMR in the foodstuff analysis. Fundamental aspects of NMR methodology such as sample preparation, metabolites extraction, quantitative elaboration of spectral data, and statistical analysis have been described. Metabolic profilings of aqueous and/or organic extracts as obtained by one- and two-dimensional NMR experiments have been reported together with the results obtained from their statistical elaboration. Discrimination between wild and farmed sea bass and between genetically modified and wild lettuces as well as changes in the kiwifruit metabolic profiles monitored over the season have been investigated. For each foodstuff, some complementary findings provided by other analytical methods are also described to underline the importance of different analytical approaches to explore specific aspects related to foodstuff.     

Novel analytical procedures for screening of drug residues in water, waste water, sediment and sludge

Traces of pharmaceuticals are continuously introduced into the aquatic environment mainly by sewage treatment plant effluents. Final data about their impact on the ecosystem are still partly missing. Progress in instrumental analytical chemistry has resulted in the availability of methods that allow a monitoring of these pollutants at ng L⁻¹ levels. In this review the state-of-the-art of residue analysis of pharmaceuticals by chromatographic and electrophoretic techniques is summarized. Improvements in detection limits over the past years have mainly been due to sophisticated mass spectrometric detection techniques. Furthermore, robust sample preparation and preconcentration protocols based on solid-phase extraction and related procedures have contributed significantly to the achievements observed so far. This review also covers several immunochemical approaches which may serve as an inexpensive alternative for quick screening of samples.     

Supramolecular optical sensor arrays for on-site analytical devices

Supramolecular optical chemosensors are useful tools in analytical chemistry for the visualization of molecular recognition information. One advantage is that they can be utilized for array systems to detect multiple analytes. However, chemosensor arrays have been evaluated mainly in the solution phase, which limits a wide range of practical applications. Thus, appropriate solid support materials such as polymer gels and papers are required to broaden the scope of the application of chemosensors as on-site analytical tools. In this review, we summarize the actual approaches for the fabrication of solid-state chemosensor arrays combined with powerful data processing techniques and portable digital recorders for real-world applications.     

Antibiotics in food: Legislation and validation of analytical methodologies

In this paper, European food safety legislation is presented, and special attention is devoted to monitoring residues of veterinary drugs in foodstuffs of animal origin. After a short review of the state of the art of analytical methodology for antibiotic residue analysis, the paper focuses on validation of analytical methods, with Decision 657/2002/EC as reference document. Finally, the main issues of the quality control of the analytical data, i.e. analysis of reference materials and participation in proficiency tests, are briefly addressed.