Analytical Spectroscopy Research Articles

Recent applications of quantitative analytical FTIR spectroscopy in pharmaceutical, biomedical, and clinical fields: A brief review

Abstract Qualitative Fourier transform infrared (FTIR) spectroscopy has long been established and implemented in a wide variety of fields including pharmaceutical, biomedical, and clinical fields. While the quantitative applications are yet to reach their full potential, this technique is flourishing. It is tempting to shed light on modern engaging and the applicability of analytical quantitative FTIR spectroscopy in the aforementioned fields. More importantly, the credibility, validity, and generality of the application will be thoroughly demonstrated by reviewing the latest published work in the scientific literature. Utilizing FTIR spectroscopy in a quantitative approach in pharmaceutical, biomedical, and interdisciplinary fields has many undeniable advantages over traditional procedures. An insightful account will be undertaken in this regard. The technique will be introduced as an appealing alternative to common methods such as high performance liquid chromatography. It is anticipated that the review will offer researchers an update of the current status and prospect on the subject among the pharmacy and biomedical sciences both in academic and industrial fields.

Revealing the structural and chemical properties of copper-based nanoparticles released from copper treated wood.

Copper-based preservatives consisting of micronized and nanoscale copper particles have been widely used in applications for wood protection. The widespread use of these preservatives along with the potential release of copper-containing nanoparticles (Cu NPs) during the life cycle of treated wood, has raised concerns over the impacts on the environment and occupational exposure. Along with assessing the potential hazards of these materials, a critical step is determining the chemical and morphological characteristics of the copper species released from copper-treated wood. Therefore, a combination of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) was utilized to characterize and differentiate the released copper-containing particles based on their structures, sizing, and chemical properties. Airborne wood dust samples were collected during the abrasion and sawing of micronized copper (MC) treated wood in a laboratory testing system. Based on the signature Cu L2,3 edge of EEL spectra, three different copper species (i.e., basic copper carbonate, copper, and copper–wood complex) were identified as major components of the embedded particles in wood dust. In addition, two types of individual Cu NPs consisting of basic copper carbonate and copper were identified. The variation of morphologies and chemical properties of copper-containing particles indicates the importance of copper–wood interactions to determine the formation and distribution of copper species in wood components. Our findings will advance the fundamental understanding of their released forms, potential transformation, and environmental fate during the life cycle.

Design and applications of water irradiation devoid RF pulses for ultra-high field biomolecular NMR spectroscopy.

Water suppression is of paramount importance for many biological and analytical NMR spectroscopy applications. Here, we report the design of a new set of binomial-like radio frequency (RF) pulses that elude water irradiation while exciting or refocusing the remainder of the 1H spectrum. These pulses were generated using a combination of an evolutionary algorithm and artificial intelligence. They display higher sensitivity relative to classical water suppression schemes and tunable water selectivity to avoid suppressing 1H resonances near the water signal. The broad bandwidth excitation obtained with these RF pulses makes them suitable for several NMR applications at high and ultra-high-field magnetic fields.

Green Synthesis of Silver Nanoparticles Incorporated Aromatherapies Utilized for Their Antioxidant and Antimicrobial Activities against Some Clinical Bacterial Isolates

There is a need to synthesize eco-friendly nanoparticles with more effective and potent antibacterial activities. A green and cost-effective method for the synthesis of silver nanoparticles (AgNPs) using Thymus vulgaris, Mentha piperita, and Zingiber officinale extracts was developed. The analytical instrumentation, namely, UV/Vis, absorption spectroscopy, FTIR, and scanning electron microscopy (SEM), was used to determine the developed AgNPs, confirming the functional groups involved in their reduction. Acidic molybdate, DPPH, and FRAP regents were reacted with AgNPs extract to evaluate their antioxidant, scavenging, and oxidative activities. The agar well diffusion method was used to determine the antibacterial potential of AgNPs extracts using clinical isolates. The developed AgNPs showed peaks at 25 cum\\Diff, 50 cum\\Diff, and 75 cum\\Diff, respectively, of 16.59 ± 0.78, 45.94 ± 1.07, and 81.04 ± 0.98 nm, for Thymus vulgaris, Mentha piperita, and Zingiber officinale. SEM revealed uniform prepared and encapsulated AgNPs by plant extracts matrix. The FTIR shows the involvement of amide (-CO-NH2), carbonyl (-CO), and hydroxyl (-OH), which resulted in the reduction of AgNPs. The AgNPs extract showed significantly higher TAA, DPPH, and FRAP values than free AgNPs and plant extract (p < 0.05). Antibacterial of AgNPs extracts revealed various degrees of inhibition zones against Escherichia coli, Acinetobacter baumannii, and Staphylococcus aureus. The developed AgNPs extract showed acceptable antioxidant activities and noticeable antibacterial potential. The prepared green synthesized AgNPs showed a promising antibacterial activity against four multidrug-resistant clinical isolates, Escherichia coli, Acinetobacter baumannii, and Staphylococcus aureus. Further, fractionated extracts other than crude extracts will be utilized in the preparation of AgNPs to get more efficient antibacterial activities for future work.

Rapid analytical CEST spectroscopy of competitive host–guest interactions using spatial parallelization with a combined approach of variable flip angle, keyhole and averaging (CAVKA)

A serious limitation of high resolution 129Xe chemical exchange saturation transfer (CEST) NMR spectroscopy for comparing competitive host-guest interactions from different samples is the long acquisition time due to step-wise encoding of the chemical shift dimension. A method of optimized use of 129Xe spin magnetization to enable the accelerated and simultaneous acquisition of CEST spectra from multiple samples or regions in a setup is described. The method is applied to investigate the host-guest system of commercially available cucurbit[7]uril (CB7) and xenon with competing guests: cis-1,4-bis(aminomethyl)cyclohexane, cadaverine, and putrescine. Interactions with the different guests prove that the observed CEST signal is from a CB6 impurity and that CB7 itself does not produce a CEST signal. Instead, rapid interactions between xenon and CB7 manifest in the spectrum as a broad saturation response that could be suppressed by cis-1,4-bis(aminomethyl)cyclohexane. This guest prevents interactions at the CB7 portals. The suggested method represents a type of spectroscopic imaging that is capable of capturing the exchange kinetics information of systems that otherwise suffer from shortened T2 times and yields multiple spectra for comparing exchange conditions with a reduction of >95% in acquisition time. The spectral quality is sufficient to perform quantitative analysis and quantifications relative to a CB6 standard as well as relative to a known blocker concentration (putrescine) that both reveal an unexpectedly high CB6 impurity of ca. 8%.

Isolation and characterization of anti-proliferative and anti-oxidative mannan from Saccharomyces cerevisiae

Mannan oligosaccharide is one of the major components of the yeast cell wall. In the present study, the production, characterization, and bioactivity of yeast mannan were investigated. Four indigenous yeast isolates were obtained from various kinds of juice collected from local markets in Al-Ahsa, KSA, and analyzed using morphological and biochemical methods. Isolate RY1 showed the highest production of mannan. RY1 was identified as Saccharomyces cerevisiae based on morphological characteristics and sequencing of the 18S rRNA gene (GenBank accession number LC479088.1). Mannan-RY1 was characterized by polymer analytical methods, 13C and 1H nuclear magnetic resonance spectroscopy (NMR), and infrared spectroscopy (IR). Interestingly, the mannan extracted from RY1 showed a significant ability to scavenge hydroxyl radicals and superoxide anions. In addition, mannan was found to have pronounced anti-tumor activity against liver (HepG2) and breast cancer (MCF7) cell lines. The results presented in this study confirm the bio-therapeutic activity of S. cerevisiae mannan, which could be used as a potential drug for cancer treatment.

ACD/Structure Elucidator: 20 Years in the History of Development.

The first methods associated with the Computer-Assisted Structure Elucidation (CASE) of small molecules were published over fifty years ago when spectroscopy and computer science were both in their infancy. The incredible leaps in both areas of technology could not have been envisaged at that time, but both have enabled CASE expert systems to achieve performance levels that in their present state can outperform many scientists in terms of speed to solution. The computer-assisted analysis of enormous matrices of data exemplified 1D and 2D high-resolution NMR spectroscopy datasets can easily solve what just a few years ago would have been deemed to be complex structures. While not a panacea, the application of such tools can provide support to even the most skilled spectroscopist. By this point the structures of a great number of molecular skeletons, including hundreds of complex natural products, have been elucidated using such programs. At this juncture, the expert system ACD/Structure Elucidator is likely the most advanced CASE system available and, being a commercial software product, is installed and used in many organizations. This article will provide an overview of the research and development required to pursue the lofty goals set almost two decades ago to facilitate highly automated approaches to solving complex structures from analytical spectroscopy data, using NMR as the primary data-type.

Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)

Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)

1,5,6,7-Tetrahydro-4H-indazol-4-ones as human neutrophil elastase (HNE) inhibitors

Human neutrophil elastase (HNE) is a serine protease that is expressed in polymorphonuclear neutrophils. It has been recognized as an important therapeutic target for treating inflammatory diseases, especially related to the respiratory system, but also for various types of cancer. Thus, compounds able to inhibit HNE are of great interest in medicinal chemistry. In the present paper, we report the synthesis and biological evaluation of a new series of HNE inhibitors with an innovative 1,5,6,7-tetrahydro-4H-indazol-4-one core that was developed as a molecular modification of our previously reported indazole-based HNE inhibitors. Since the 1,5,6,7-tetrahydro-4H-indazol-4-one scaffold can occur in two possible tautomeric forms, the acylation/alkylation reactions resulted in a mixture of the two isomers, often widely unbalanced in favor of one form. Using analytical techniques and NMR spectroscopy, we characterized and separated the isomer pairs and confirmed the compounds used in biological testing. Analysis of the compounds for HNE inhibitory activity showed that they were potent inhibitors, with Ki values in the low nanomolar range (6–35 nM). They also had reasonable stability in aqueous buffer, with half-lives over 1 h. Overall, our results indicate that the 1,5,6,7-tetrahydro-4H-indazol-4-one core is suitable for the synthesis of potent HNE inhibitors that could be useful in the development of new therapeutics for treating diseases involving excessive HNE activity.

Orthogonality constrained inverse regression to improve model selectivity and analyte predictions from vibrational spectroscopic measurements

In analytical chemistry spectroscopy is attractive for high-throughput quantification, which often relies on inverse regression, like partial least squares regression. Due to a multivariate nature of spectroscopic measurements an analyte can be quantified in presence of interferences. However, if the model is not fully selective against interferences, analyte predictions may be biased. The degree of model selectivity against an interferent is defined by the inner relation between the regression vector and the pure interfering signal. If the regression vector is orthogonal to the signal, this inner relation equals zero and the model is fully selective. The degree of model selectivity largely depends on calibration data quality. Strong correlations may deteriorate calibration data resulting in poorly selective models. We show this using a fructose-maltose model system. Furthermore, we modify the NIPALS algorithm to improve model selectivity when calibration data are deteriorated. This modification is done by incorporating a projection matrix into the algorithm, which constrains regression vector estimation to the null-space of known interfering signals. This way known interfering signals are handled, while unknown signals are accounted for by latent variables. We test the modified algorithm and compare it to the conventional NIPALS algorithm using both simulated and industrial process data. The industrial process data consist of mid-infrared measurements obtained on mixtures of beta-lactoglobulin (analyte of interest), and alpha-lactalbumin and caseinoglycomacropeptide (interfering species). The root mean squared error of beta-lactoglobulin (% w/w) predictions of a test set was 0.92 and 0.33 when applying the conventional and the modified NIPALS algorithm, respectively. Our modification of the algorithm returns simpler models with improved selectivity and analyte predictions. This paper shows how known interfering signals may be utilized in a direct fashion, while benefitting from a latent variable approach. The modified algorithm can be viewed as a fusion between ordinary least squares regression and partial least squares regression and may be very useful when knowledge of some (but not all) interfering species is available.

Toward Compositional Contrast by Cryo-STEM.

Electron microscopy (EM) is the most versatile tool for the study of matter at scales ranging from subatomic to visible. The high vacuum environment and the charged irradiation require careful stabilization of many specimens of interest. Biological samples are particularly sensitive due to their composition of light elements suspended in an aqueous medium. Early investigators developed techniques of embedding and staining with heavy metal salts for contrast enhancement. Indeed, the Nobel Prize in 1974 recognized Claude, de Duve, and Palade for establishment of the field of cell biology, largely due to their developments in separation and preservation of cellular components for electron microscopy. A decade later, cryogenic fixation was introduced. Vitrification of the water avoids the need for dehydration and provides an ideal matrix in which the organic macromolecules are suspended; the specimen represents a native state, suddenly frozen in time at temperatures below -150 °C. The low temperature maintains a low vapor pressure for the electron microscope, and the amorphous nature of the medium avoids diffraction contrast from crystalline ice. Such samples are extremely delicate, however, and cryo-EM imaging is a race for information in the face of ongoing damage by electron irradiation. Through this journey, cryo-EM enhanced the resolution scale from membranes to molecules and most recently to atoms. Cryo-EM pioneers, Dubochet, Frank, and Henderson, were awarded the Nobel Prize in 2017 for high resolution structure determination of biological macromolecules.A relatively untapped feature of cryo-EM is its preservation of composition. Nothing is added and nothing removed. Analytical spectroscopies based on electron energy loss or X-ray emission can be applied, but the very small interaction cross sections conflict with the weak exposures required to preserve sample integrity. To what extent can we interpret quantitatively the pixel intensities in images themselves? Conventional cryo-transmission electron microscopy (TEM) is limited in this respect, due to the strong dependence of the contrast transfer on defocus and the absence of contrast at low spatial frequencies.Inspiration comes largely from a different modality for cryo-tomography, using soft X-rays. Contrast depends on the difference in atomic absorption between carbon and oxygen in a region of the spectrum between their core level ionization energies, the so-called water window. Three dimensional (3D) reconstruction provides a map of the local X-ray absorption coefficient. The quantitative contrast enables the visualization of organic materials without stain and measurement of their concentration quantitatively. We asked, what aspects of the quantitative contrast might be transferred to cryo-electron microscopy?Compositional contrast is accessible in scanning transmission EM (STEM) via incoherent elastic scattering, which is sensitive to the atomic number Z. STEM can be regarded as a high energy, low angle diffraction measurement performed pixel by pixel with a weakly convergent beam. When coherent diffraction effects are absent, that is, in amorphous materials, a dark field signal measures quantitatively the flux scattered from the specimen integrated over the detector area. Learning to interpret these signals will open a new dimension in cryo-EM. This Account describes our efforts so far to introduce STEM for cryo-EM and tomography of biological specimens. We conclude with some thoughts on further developments.

Millisecond-long suppression of spectroscopic optical signals using laser filamentation.

Ultrashort laser pulse filamentation in air can extend the delivery of focused laser energy to distances greatly exceeding the Rayleigh length. In this way, remote measurements can be conducted using many standard methods of analytical spectroscopy. The performance of spectroscopic techniques can be enhanced by temporal gating, which rejects the unwanted noise and background. In the present work, we investigate the thermal relaxation of air in the wake of single-filament plasmas using shadowgraphy. We demonstrate that the transient change in refractive index associated with relaxation of the gas can be used to reject both continuous and time-varying spectroscopic signals, including emission from laser-produced plasmas. This method can augment temporal gating of simple optical detectors.

A Review of Grain Boundary and Heterointerface Characterization in Polycrystalline Oxides by (Scanning) Transmission Electron Microscopy

Interfaces such as grain boundaries (GBs) and heterointerfaces (HIs) are known to play a crucial role in structure-property relationships of polycrystalline materials. While several methods have been used to characterize such interfaces, advanced transmission electron microscopy (TEM) and scanning TEM (STEM) techniques have proven to be uniquely powerful tools, enabling quantification of atomic structure, electronic structure, chemistry, order/disorder, and point defect distributions below the atomic scale. This review focuses on recent progress in characterization of polycrystalline oxide interfaces using S/TEM techniques including imaging, analytical spectroscopies such as energy dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) and scanning diffraction methods such as precession electron nano diffraction (PEND) and 4D-STEM. First, a brief introduction to interfaces, GBs, HIs, and relevant techniques is given. Then, experimental studies which directly correlate GB/HI S/TEM characterization with measured properties of polycrystalline oxides are presented to both strengthen our understanding of these interfaces, and to demonstrate the instrumental capabilities available in the S/TEM. Finally, existing challenges and future development opportunities are discussed. In summary, this article is prepared as a guide for scientists and engineers interested in learning about, and/or using advanced S/TEM techniques to characterize interfaces in polycrystalline materials, particularly ceramic oxides.

Coherent plasmonic absorption in the femtosecond regime

Dissipation of electromagnetic energy through absorption is a fundamental process that underpins phenomena ranging from photovoltaics to photography, analytical spectroscopy, photosynthesis, and human vision. Absorption is also a dynamic process that depends on the duration of the optical illumination. Here we report on the resonant plasmonic absorption of a nanostructured metamaterial and the non-resonant absorption of an unstructured gold film at different optical pulse durations. By examining the absorption in travelling and standing waves, we observe a plasmonic relaxation time of 11 fs as the characteristic transition time. The metamaterial acts as a beam-splitter with low absorption for shorter pulses, while as a good absorber for longer pulses. The transient nature of the absorption puts a frequency limit of ~90 THz on the bandwidth of coherently-controlled, all-optical switching devices, which is still a thousand times faster than other leading switching technologies.

Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)

Abstract Recommendations are given concerning the terminology of concepts and methods used in spectroscopy in analytical chemistry, covering nuclear magnetic resonance spectroscopy, atomic spectroscopy, and vibrational spectroscopy.

A New Nanocomposite Packaging Based on LASiS-Generated AgNPs for the Preservation of Apple Juice.

Designing bioactive materials, with controlled metal ion release, exerting a significant biological action and associated to low toxicity for humans, is nowadays one of the most important challenges for our community. The most looked-for nanoantimicrobials are capable of releasing metal species with defined kinetic profiles, either by slowing down or inhibiting bacterial growth and pathogenic microorganism diffusion. In this study, laser ablation synthesis in solution (LASiS) has been used to produce bioactive Ag-based nanocolloids, in isopropyl alcohol, which can be used as water-insoluble nano-reservoirs in composite materials like poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Infrared spectroscopy was used to evaluate the chemical state of pristine polymer and final composite material, thus providing useful information about synthesis processes, as well as storage and processing conditions. Transmission electron microscopy was exploited to study the morphology of nano-colloids, along with UV-Vis for bulk chemical characterization, highlighting the presence of spheroidal particles with average diameter around 12 nm. Electro-thermal atomic absorption spectroscopy was used to investigate metal ion release from Ag-modified products, showing a maximum release around 60 ppb, which ensures an efficient antimicrobial activity, being much lower than what recommended by health institutions. Analytical spectroscopy results were matched with bioactivity tests carried out on target microorganisms of food spoilage.

Classical Food Quality Attributes and the Metabolic Profile of Cambuci, a Native Brazilian Atlantic Rainforest Fruit.

The cambuci is a native Brazilian fruit from the Atlantic Forest biome. A soft and astringent pulp, a green color, and a sweet aroma are its main characteristics. Classical food quality attributes (fresh fruit mass, fruit height, diameters, total soluble solid, titratable acidity, and ratio) and the metabolic profile from ten accessions from three different locations were analyzed herein by analytical methods (refractometry and neutralization titration) and nuclear magnetic resonance spectroscopy. Concerning sugar content, sucrose was the predominant compound, with glucose and fructose alternating in second, depending on the accession. Citric acid was the most relevant acid, followed by shikimic and quinic acids in quite variable amounts. These three main acids vary in amounts for each accession. Ascorbic acid content emerges as an important quality attribute and makes this fruit nutritionally attractive, due to values comparable to those contained in citric fruits. The main amino acids identified in cambuci were glutamic acid individually or in comprising the tripeptide glutathione (glutamic acid, cysteine, glycine). The quality diversity of the evaluated accessions suggests the potentiality of cambuci use in future breeding programs.

Validity and reliability of Raman spectroscopy for carotenoid assessment in cattle skin

Carotenoids are powerful antioxidants capable of helping to protect the skin from the damaging effects of exposure to sun by reducing the free radicals in skin produced by exposure to ultraviolet radiation, and they may also have a physical protective effect in human skin. Since carotenoids are lipophilic molecules which can be ingested with the diet, they can accumulate in significant quantities in the skin. Several studies on humans have been conducted to evaluate the protective function of carotenoids against various diseases, but there is very limited published information available to understand the mechanism of carotenoid bioavailability in animals. The current study was conducted to investigate the skin carotenoid level (SCL) in two cattle skin sets – weaners with an unknown feeding regime and New Generation Beef (NGB) cattle with monitored feed at three different ages. Rapid analytical and sensitive Raman spectroscopy has been shown to be of interest as a powerful technique for the detection of carotenoids in cattle skin due to the strong resonance enhancement with 532 nm laser excitation. The spectral difference of both types of skin were measured and quantified using univariate and linear discriminant analysis. SCL was higher in NGB cattle than weaners and there is a perfect classification accuracy between weaners and NGB cattle skin using carotenoid markers as a basis. Further work carried out on carotenoid rich NGB cattle skin of 8, 12 and 24 months of age identified an increasing trend in SCL with age. The present work validated the ability of Raman spectroscopy to determine the skin carotenoid level in cattle by comparing it with established HPLC methods. There is an excellent correlation of R2 = 0.96 between the two methods that could serve as a model for future application for larger population studies.

Magnetic Chemistry and Its Possible Applications in Analytical Spectroscopy and Related Fields

Developments in chemistry have stemmed from applying principles from other fields that develops into a field itself. Magnetism applied to chemistry - Magnetic chemistry is one of them. Taking electrochemistry that uses an electric field/current inducing a reaction that doesn’t occur in natural conditions; magnetic chemistry uses a magnetic field inducing conditions and possibly reactions. Three areas are discussed; principles involved, results from using a magnetic field on hydrocarbon fuels, and possible implements in analytical spectroscopy. Starting on how Faraday’s Induction Law is used in altering compound properties. Then, discussing paramagnetism/diamagnetism of atoms/compounds emphasizing diamagnetic compounds, then on intermolecular forces emphasizing on cohesive forces and pseudo structures formed (“clustering”) then discussing quantum principles - emphasizing electron coupling interactions focusing on angular momenta, spin-orbit interaction, and Zeeman Effect. Then, showing results of how applying a magnetic field alters hydrocarbon fuels properties. Explaining how it reduces the “clustering” of molecules, surface tension, viscosity, pollution and increasing volatility and efficiency. Then explaining how an applied field affects the molecules emphasizing on how increasing field strength increases affects and mentioning on how it actually enhances infrared and UV-Vis spectra. Then discussing how the results can be applied to analytical spectroscopy. The increased volatility can improve atomization/nebulization for ICP and GC, thus more target compounds analyzed with less waste reducing need for derivatizing agents. Spectra enhancement for spectra signals that are very weak in infrared and UV-Vis spectroscopy. Reducing mobile phase surface tension/viscosity thus conditions (flow rate, etc.) better adjusted for HPLC. Then showing how a NMR field can be used to do this. Concluding, magnetic chemistry can be utilized to change properties/conditions of compounds and possibly induce reactions. By discussing underlying principles involved; Induction Law, paramagnetism, diamagnetism, intermolecular forces, and quantum principles, explaining how it occurs and results on applying a magnetic field to hydrocarbon fuels which has possible uses in analytical spectroscopy.

Focus on analytical equipment, spectroscopy, and spectrometry

Focus on analytical equipment, spectroscopy, and spectrometry