The potential of mid infrared spectroscopy (MIRS) for real time bioprocess monitoring

The need for effective bioprocess (fermentation) monitoring is growing in importance due to the rapid pace of change in the fermentation industry, and attendant financial pressures. Vibrational spectroscopy has shown great promise in bioprocess monitoring. In particular, recently attention has been focused on the capability of mid infrared spectroscopy (MIRS) to monitor multiple analytes in highly complex fermentation fluids. The potential of this powerful analytical technique is critically evaluated by discussion of relevant studies. The advantages and limitations of MIR are discussed in the context of “rival” technologies, such as near infrared, focusing especially on employing such techniques in bioprocesses for real time (either in situ or ex situ) measurements. The potential barriers to the development of MIRS for real time monitoring are identified and further research directions highlighted.     

Application of multivariate data-analysis techniques to biomedical diagnostics based on mid-infrared spectroscopy

The objective of this contribution is to review the application of advanced multivariate data-analysis techniques in the field of mid-infrared (MIR) spectroscopic biomedical diagnosis. MIR spectroscopy is a powerful chemical analysis tool for detecting biomedically relevant constituents such as DNA/RNA, proteins, carbohydrates, lipids, etc., and even diseases or disease progression that may induce changes in the chemical composition or structure of biological systems including cells, tissues, and bio-fluids. However, MIR spectra of multiple constituents are usually characterized by strongly overlapping spectral features reflecting the complexity of biological samples. Consequently, MIR spectra of biological samples are frequently difficult to interpret by simple data-analysis techniques. Hence, with increasing complexity of the sample matrix more sophisticated mathematical and statistical data analysis routines are required for deconvoluting spectroscopic data and for providing useful results from information-rich spectroscopic signals. A large body of work relates to the combination of multivariate data-analysis techniques with MIR spectroscopy, and has been applied by a variety of research groups to biomedically relevant areas such as cancer detection and analysis, artery diseases, biomarkers, and other pathologies. The reported results indeed reveal a promising perspective for more widespread application of multivariate data analysis in assisting MIR spectroscopy as a screening or diagnostic tool in biomedical research and clinical studies. While the authors do not mean to ignore any relevant contributions to biomedical analysis across the entire electromagnetic spectrum, they confine the discussion in this contribution to the mid-infrared spectral range as a potentially very useful, yet underutilized frequency region. Selected representative examples without claiming completeness will demonstrate a range of biomedical diagnostic applications with particular emphasis on the advantageous interaction between multivariate data analysis and MIR spectroscopy.     

Radicals Containing Hydrogen,Carbon and Oxygen Atoms

There is much new information available on radicals containing C, H and O atoms. Indeed, most of the data discussed in this review did not exist twenty years ago. New, more powerful laser and microwave experimental techniques have greatly expanded our knowledge of the energetics, spectra, reactions and decomposition processes of these radicals. This review attempts to give a unified discussion of the radicals.     

Methods for extracting biochemical information from bacterial Raman spectra: focus on a group of structurally similar biomolecules--fatty acids

In this paper we explore the possibilities of Raman spectroscopy in order to deduce information on the fatty acid composition of bacterial cells. Therefore, representative strains of two bacterial taxa were each cultured in different conditions and in parallel analyzed by Raman spectroscopy and gaschromatographic FAME analysis. Raman spectra of pure fatty acids were recorded and used as reference spectra. The culturing conditions for each strain could be easily distinguished by the fatty acid information retrieved from bacterial Raman spectra. Chemometric techniques such as EMSC and PCA allowed to extract information about groups of fatty acids, that was consistent with the results from FAME analysis. Although the information retrieved from Raman spectroscopy is not as refined as that from FAME analysis, the presented methods could be useful to obtain basic information on the fatty acid present in bacteria when performing Raman spectroscopic analysis for fast whole cell profiling, which provides information for different types of cell components (fatty acids, amino acids, primary metabolites, etc.).     

The degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the Cocoon lamps. Part 2

After the systematic study of poly(vinyl acetate) degradation presented in part 1, this work reports results from the analysis of polymeric materials from five Italian design lamps from the 1960s made of the material known as cocoon. Micro- and non-destructive molecular spectroscopic techniques have been applied directly on the object surfaces using an optical fibre probe and through examination of micro-samples: the combined use of Fourier-transform infrared spectroscopy (FTIR), pyrolysis gas-chromatography/mass-spectrometry (py-GC/MS) and Fluorescence spectroscopy allowed the assessment of the material composition and the chemical modifications of the polymers related to on-going deterioration processes. Fluorescence spectroscopy proved particularly sensitive for the detection of variations in composition among lamps and between areas on the same object, and was used to classify objects in different groups using principal component analysis of excitation emission spectra. Specific degradation products have been mapped using FTIR on micro-samples. Moreover, the interpretation of the emission spectra of the studied polymeric lamps suggests that fluorescence spectroscopy can be used for non-destructive monitoring of the degradation of historical polymeric objects.     

Spectroscopic evidences of EDTA interaction with inorganic supports during the preparation of supported metal catalysts

Chelating compounds (etylenediaminetetraacetic acid (EDTA)-type reagents) are broadly applied in many chemical processes. One of the possible applications is their use in the preparation of the catalysts. A short summary based on my own experience in the spectroscopic studies on chelating molecules interaction with the surface of inorganic oxides is presented. The application of spectroscopic techniques allow to describe the nature and type of interactions. Particularly, the experiments conducted by an infrared spectroscopy method deliver valuable information which is of great importance for the adsorption and catalytic investigations.     

Chemometrics in pharmaceutical analysis: an introduction, review, and future perspectives

Chemometrics is the application of statistical and mathematical methods to analytical data to permit maximum collection and extraction of useful information. The utility of chemometric techniques as tools enabling multidimensional calibration of selected spectroscopic, electrochemical, and chromatographic methods is demonstrated. Application of this approach mainly for interpretation of UV-Vis and near-IR (NIR) spectra, as well as for data obtained by other instrumental methods, makes identification and quantitative analysis of active substances in complex mixtures possible, especially in the analysis of pharmaceutical preparations present in the market. Such analytical work is carried out by the use of advanced chemical instruments and data processing, which has led to a need for advanced methods to design experiments, calibrate instruments, and analyze the resulting data. The purpose of this review is to describe various chemometric methods in combination with UV-Vis spectrophotometry, NIR spectroscopy, fluorescence spectroscopy, electroanalysis, chromatographic separation, and flow-injection analysis for the analysis of drugs in pharmaceutical preparations. Theoretical and practical aspects are described with pharmaceutical examples of chemometric applications. This review will concentrate on gaining an understanding of how chemometrics can be useful in the modern analytical laboratory. A selection of the most challenging problems faced in pharmaceutical analysis is presented, the potential for chemometrics is considered, and some consequent implications for utilization are discussed. The reader can refer to the citations wherever appropriate.     

A Review of Wine Authentication Using Spectroscopic Approaches in Combination with Chemometrics

In a global context where trading of wines involves considerable economic value, the requirement to guarantee wine authenticity can never be underestimated. With the ever-increasing advancements in analytical platforms, research into spectroscopic methods is thriving as they offer a powerful tool for rapid wine authentication. In particular, spectroscopic techniques have been identified as a user-friendly and economical alternative to traditional analyses involving more complex instrumentation that may not readily be deployable in an industry setting. Chemometrics plays an indispensable role in the interpretation and modelling of spectral data and is frequently used in conjunction with spectroscopy for sample classification. Considering the variety of available techniques under the banner of spectroscopy, this review aims to provide an update on the most popular spectroscopic approaches and chemometric data analysis procedures that are applicable to wine authentication.     

Quantitative monitoring of an activated sludge reactor using on-line UV-visible and near-infrared spectroscopy

The performance of an activated sludge reactor can be significantly enhanced through use of continuous and real-time process-state monitoring, which avoids the need to sample for off-line analysis and to use chemicals. Despite the complexity associated with wastewater treatment systems, spectroscopic methods coupled with chemometric tools have been shown to be powerful tools for bioprocess monitoring and control. Once implemented and optimized, these methods are fast, nondestructive, user friendly, and most importantly, they can be implemented in situ, permitting rapid inference of the process state at any moment. In this work, UV-visible and NIR spectroscopy were used to monitor an activated sludge reactor using in situ immersion probes connected to the respective analyzers by optical fibers. During the monitoring period, disturbances to the biological system were induced to test the ability of each spectroscopic method to detect the changes in the system. Calibration models based on partial least squares (PLS) regression were developed for three key process parameters, namely chemical oxygen demand (COD), nitrate concentration (N-NO₃⁻), and total suspended solids (TSS). For NIR, the best results were achieved for TSS, with a relative error of 14.1% and a correlation coefficient of 0.91. The UV-visible technique gave similar results for the three parameters: an error of ~25% and correlation coefficients of ~0.82 for COD and TSS and 0.87 for N-NO₃⁻. The results obtained demonstrate that both techniques are suitable for consideration as alternative methods for monitoring and controlling wastewater treatment processes, presenting clear advantages when compared with the reference methods for wastewater treatment process qualification.     

Resolving Component Overlap in Multiwavelength Kinetic Spectroscopy: Application to Raman Scattering from Intermediates in Triplet-State Photoreactions

Abstract— Understanding of reaction mechanisms in photochemistry is advanced both by kinetic measurements to determine rates of reaction and by spectroscopic studies of the structures of precursors and photoproducts. When kinetics and spectroscopy are combined in a time-resolved, multiwavelength spectroscopic measurement on a reacting system, spectra and structures of intermediates can also be determined. In this paper, the application of multidimensional least-squares and factor analysis techniques for resolving overlapped spectra from intermediates in photochemical kinetics are discussed. The methods are employed specifically to resolve Raman spectra of intermediates in triplet-state photoreactions. By varying excitation intensity, spectra of excited-triplet states are resolved from ground states and solvent. By varying the concentration of a triplet quencher in the sample, the Raman spectrum of a sensitizer excited state (benzophe-none) can be resolved from those of acceptor-triplet states or radical photoproducts. Applications of these concepts in other areas of photochemical kinetics are addressed.     

From single to multiple microcoil flow probe NMR and related capillary techniques: a review

Nuclear magnetic resonance (NMR) spectroscopy is one of the most important and powerful instrumental analytical techniques for structural elucidation of unknown small and large (complex) isolated and synthesized compounds in organic and inorganic chemistry. X-ray crystallography, neutron scattering (neutron diffraction), and NMR spectroscopy are the only suitable methods for three-dimensional structure determination at atomic resolution. Moreover, these methods are complementary. However, by means of NMR spectroscopy, reaction dynamics and interaction processes can also be investigated. Unfortunately, this technique is very insensitive in comparison with other spectrometric (e.g., mass spectrometry) and spectroscopic (e.g., infrared spectroscopy) methods. Mainly through the development of stronger magnets and more sensitive solenoidal microcoil flow probes, this drawback has been successfully counteracted. Capillary NMR spectroscopy increases the mass-based sensitivity of the NMR spectroscopic analysis up to 100-fold compared with conventional 5-mm NMR probes, and thus can be coupled online and off-line with other microseparation and detection techniques. It offers not only higher sensitivity, but in many cases provides better quality spectra than traditional methods. Owing to the immense number of compounds (e.g., of natural product extracts and compound libraries) to be examined, single microcoil flow probe NMR spectroscopy will soon be far from being sufficiently effective as a screening method. For this reason, an inevitable trend towards coupled microseparation–multiple microcoil flow probe NMR techniques, which allow simultaneous online and off-line detection of several compounds, will occur. In this review we describe the current status and possible future developments of single and multiple microcoil capillary flow probe NMR spectroscopy and its application as a high-throughput tool for the analysis of a large number of mass-limited samples. The advantages and drawbacks of different coupled microseparation–capillary NMR spectroscopy techniques, such as capillary high-performance liquid chromatography–NMR spectroscopy, capillary electrophoresis–NMR spectroscopy, and capillary gas chromatography–NMR spectroscopy, are discussed and demonstrated by specific applications. Another subject of discussion is the progress in parallel NMR detection techniques. Furthermore, the applicability and mixing capability of tiny reactor systems, termed “microreactors” or “micromixers,” implemented in NMR probes is demonstrated by carbamate- and imine-forming reactions.     

Probing the Interactions of Porphyrins with Macromolecules Using NMR Spectroscopy Techniques

Porphyrinic compounds are widespread in nature and play key roles in biological processes such as oxygen transport in blood, enzymatic redox reactions or photosynthesis. In addition, both naturally derived as well as synthetic porphyrinic compounds are extensively explored for biomedical and technical applications such as photodynamic therapy (PDT) or photovoltaic systems, respectively. Their unique electronic structures and photophysical properties make this class of compounds so interesting for the multiple functions encountered. It is therefore not surprising that optical methods are typically the prevalent analytical tool applied in characterization and processes involving porphyrinic compounds. However, a wealth of complementary information can be obtained from NMR spectroscopic techniques. Based on the advantage of providing structural and dynamic information with atomic resolution simultaneously, NMR spectroscopy is a powerful method for studying molecular interactions between porphyrinic compounds and macromolecules. Such interactions are of special interest in medical applications of porphyrinic photosensitizers that are mostly combined with macromolecular carrier systems. The macromolecular surrounding typically stabilizes the encapsulated drug and may also modify its physical properties. Moreover, the interaction with macromolecular physiological components needs to be explored to understand and control mechanisms of action and therapeutic efficacy. This review focuses on such non-covalent interactions of porphyrinic drugs with synthetic polymers as well as with biomolecules such as phospholipids or proteins. A brief introduction into various NMR spectroscopic techniques is given including chemical shift perturbation methods, NOE enhancement spectroscopy, relaxation time measurements and diffusion-ordered spectroscopy. How these NMR tools are used to address porphyrin–macromolecule interactions with respect to their function in biomedical applications is the central point of the current review.     

Monitoring of pigmented and wooden surfaces in accelerated ageing processes by FT-Raman spectroscopy and multivariate control charts

Two of the most suitable analytical techniques used in the field of cultural heritage are NIR (near-infrared) and Raman spectroscopy. FT-Raman spectroscopy coupled to multivariate control charts is applied here for the development of a new method for monitoring the conservation state of pigmented and wooden surfaces. These materials were exposed to different accelerated ageing processes in order to evaluate the effect of the applied treatments on the goods surfaces. In this work, a new approach based on the principles of statistical process control (SPC) to the monitoring of cultural heritage, has been developed: the conservation state of samples simulating works-of-art has been treated like an industrial process, monitored with multivariate control charts, owing to the complexity of the spectroscopic data collected.The Raman spectra were analysed by principal component analysis (PCA) and the relevant principal components (PCs) were used for constructing multivariate Shewhart and cumulative sum (CUSUM) control charts. These tools were successfully applied for the identification of the presence of relevant modifications occurring on the surfaces. CUSUM charts however proved to be more effective in the identification of the exact beginning of the applied treatment. In the case of wooden boards, where a sufficient number of PCs were available, simultaneous scores monitoring and residuals tracking (SMART) charts were also investigated. The exposure to a basic attack and to high temperatures produced deep changes on the wooden samples, clearly identified by the multivariate Shewhart, CUSUM and SMART charts. A change on the pigment surface was detected after exposure to an acidic solution and to the UV light, while no effect was identified on the painted surface after the exposure to natural atmospheric events.     

Determining electronic spectra at interfaces by electronic sum frequency generation: one- and two-photon double resonant oxazine 750 at the air/water interface

The second-order nonlinear electronic spectra were measured for a dye oxazine 750 (OX750) adsorbed at the air/water interface using the multiplex electronic sum frequency generation (ESFG) spectroscopy recently developed by our group. The excitation-wavelength dependence of the ESFG spectrum was investigated, and a global fitting analysis was performed to separate contributions of one- and two-photon resonances. The analysis yielded linear interface electronic spectra in the one- and two-photon resonance regions, which can be directly compared to bulk absorption spectra. A two-dimensional plot of the linear interface electronic spectra is newly proposed to graphically represent all the essential information on the electronic structure of interfacial molecules. On this new analytical basis of the ESFG spectroscopy, the spectroscopic properties of OX750 at the interface are discussed.     

Dynamics of small,floppy molecules studied by high-resolution spectroscopic techniques

In molecular spectroscopy one of the common interests is how to transform the information obtained by high-resolution spectroscopic techniques into some reliable approximation of the potential energy surface of a particular molecule. Traditionally vibrational spectroscopy has been used. Rotational spectroscopy can only probe, at least at room temperature, molecular transitions arising from excited vibrational states up to approximately 1000 cm^?1. This corresponds roughly to 10% of a typical bond dissociation energy. However, floppy molecules which exhibit a large-amplitude, low-lying vibrational mode can be studied to a large extent by rotational spectroscopy in the microwave, millimeter and submillimeter wave range. Quasilinearity is a special form of large-amplitude motion, which complicates the observed molecular spectra substantially and which presents a real challenge to theoretical spectroscopists. In this lecture the highlights of quasilinear behavior of the molecules HCNO, OCCCO, HNCS and HNCO will be discussed. Another form of large amplitude motion is the inversion exhibited primarily by molecules derived from NH₃. Isocyanamide will be discussed and its special spectroscopic features will be shown. Cyanamide and isocyanamide are potential prebiotic molecules: cyanamide has been detected as a constituent in the interstellar medium. The analysis of the molecular dynamics of these molecules is shown to be necessary for understanding the frequencies and intensities of the observed spectra in the laboratory and in interstellar space.     

High-Pressure Mechanistic Insight into Bioinorganic NO Chemistry

Pressure is one of the most important parameters controlling the kinetics of chemical reactions. The ability to combine high-pressure techniques with time-resolved spectroscopy has provided a powerful tool in the study of reaction mechanisms. This review is focused on the supporting role of high-pressure kinetic and spectroscopic methods in the exploration of nitric oxide bioinorganic chemistry. Nitric oxide and other reactive nitrogen species (RNS) are important biological mediators involved in both physiological and pathological processes. Understanding molecular mechanisms of their interactions with redox-active metal/non-metal centers in biological targets, such as cofactors, prosthetic groups, and proteins, is crucial for the improved therapy of various diseases. The present review is an attempt to demonstrate how the application of high-pressure kinetic and spectroscopic methods can add additional information, thus enabling the mechanistic interpretation of various NO bioinorganic reactions.     

FT-Raman,FT-infrared and NIR spectroscopic characterization of oxygen-delignified kraft pulp treated with hydrogen peroxide under acidic and alkaline conditions

The effects of bleaching treatment of oxygen-delignified softwood kraft pulp with hydrogen peroxide under acidic and alkaline conditions were studied using standard technological techniques and spectroscopic analytical methods: near-infrared (NIR), Fourier-transform infrared (FTIR) and Fourier-transform (FT) Raman spectroscopies. Among the three tested spectroscopic techniques, NIR analysis appeared to be the most appropriate in terms of possible technological applications. The use of NIR spectroscopy combined with multivariate data analysis allowed to create models for pulp bleaching monitoring based on CIE L*a*b* measurements. Near-infrared and FTIR spectroscopic studies allowed differentiating between the effects of the acidic and alkaline peroxide bleaching stages, but failed in relation to the delignification process. The most representative bands in the FTIR and FT-Raman spectra in terms of delignification and chromophore removal exhibited no correlation with standard technological measurement results.     

Protein Structure Determination with Three- and Four-Dimensional NMR Spectroscopy

Structural biology has made important contributions to the understanding of biological processes. In recent years an increasing amount of structural information has also been derived from NMR spectroscopic studies, often with special emphasis on dynamic aspects. The introduction of three- and four-dimensional techniques has greatly simplified protein structure determination by NMR Spectroscopy, which has in fact become routine. In the past it was more of an art to interpret the complicated NOESY spectra of proteins, but the application of three-dimensional techniques now makes the interpretation of protein spectra straightforward. In this review we discuss the most important multidimensional NMR techniques along with suitable applications. The emphasis is put less on the discussion of individual pulse sequences than on their application to the structure determination of proteins.     

Micro-Raman and Tip-Enhanced Raman Spectroscopy of Carbon Allotropes

Summary: Raman spectroscopic data are obtained on various carbon allotropes like diamond, amorphous carbon, graphite, graphene and single wall carbon nanotubes by micro-Raman spectroscopy, tip-enhanced Raman spectroscopy and tip-enhanced Raman spectroscopy imaging, and the potentials of these techniques for advanced analysis of carbon structures are discussed. Depending on the local organisation of carbon the characteristic Raman bands can be found at different wavenumber positions, and e.g. quality or dimensions of structures of the samples quantitatively can be calculated. In particular tip-enhanced Raman spectroscopy allows the investigation of individual single wall carbon nanotubes and graphene sheets and imaging of e.g. local defects with nanometer lateral resolution. Raman spectra of all carbon allotropes are presented and discussed.     

Infrared and Raman imaging of heterogeneous catalysts

The miniaturization of in situ spectroscopic tools has been recognized as a forefront instrumental development for the characterization of heterogeneous catalysts. With the multitude of micro-spectroscopic methods available fundamental insight into the structure-function relationships of catalytic processes can be obtained. Among these techniques vibrational spectroscopy is one of the most versatile methods and capable to shed insight into the molecular structure of reaction intermediates and products, the chemical state of catalyst materials during reaction as well as the nature of interactions between reactants/intermediates/products and the catalyst surface. In this tutorial review we discuss the recent developments in the field of infrared (IR) and Raman micro-spectroscopy and illustrate their potential. Showcase examples include (1) chemical imaging of spatial heterogeneities during catalyst preparation, (2) high-throughput catalyst screening, (3) transport and adsorption phenomena within catalytic solids and (4) reactivity studies of porous oxides, such as zeolites. Finally, new in situ spectroscopy tools based on vibrational spectroscopy and their potential in the catalysis domain are discussed.