Instrumental Analysis Techniques Research Articles

Is the Solution Dilution? Hidden Uncertainty in Gas Chromatography (GC) Methods

Used by chemists and nonchemists alike, gas chromatography (GC) is considered mature and among the most widely used instrumental techniques for chemical analysis. Because instruments have become both more sensitive and easier to use, columns have achieved higher resolution and stationary phases have greater selectivity. As a result, gas chromatographs have taken on a “black box” view. With greater sensitivity, resolution, and advanced data handling capabilities, a new set of experimental uncertainties emerge that may not be apparent to most users, especially those who were not formally trained as analytical chemists. In this installment of ”GC Connections,” we examine these uncertainties in typical GC methods, especially as they relate to quantitative analysis. We look at hidden experimental uncertainty, especially in the glassware used for sample preparation. We also comment on injection and detection with an eye toward understanding the sources of the errors. It is important to understand the experimental error and uncertainty are inherent in all analytical techniques; they can be reduced but cannot be eliminated.

Mass Spectrometry for Comprehensive Analysis of Metabolites

Mass spectrometry is a highly sensitive high output instrumental analytical technique. It is used to determine the molecular mass but also gives the information on molecular structure and is used for quantification as well. It involves the measurement of mass to charge ratios of ions. It has become an essential tool in biological research and can be used to characterize a wide variety of biomolecules such as sugars, proteins, and oligonucleotides. Although it was developed 100 years ago, it continues to evolve both with respect to merit and applications in various fields of science and technology. Mass spectrometry is a field of studying macromolecules like proteins and complexes and has very high sensitivity also now compounds at the atom level can also be studied. In this present review, a brief history of mass spectrometry is discussed, and the basic principles of the technology are introduced. A summary of some current applications of mass spectrometry, current methods used to identify, quantify, and characterize proteins and peptides are then reviewed. The range of applications of mass spectrometry is considerable and only promises to grow as the technology continues to improve. Keywords: Mass spectrometry, Biomolecules, Structure Elucidation, Molecular mass, Natural, Medicines drugs

Student perceptions of online biology learning during the COVID-19 pandemic

This study aims to determine students' perceptions of the online biology learning process in class X IPA 1 SMA Negeri 1 Manokwari. This type of research uses a survey method. This study's data collection techniques used a questionnaire instrument and data analysis techniques using percentages. The population in this study amounted to 35 students of class X IPA 1 SMA Negeri 1 Manokwari by using the saturated sampling technique so that the determination of the number of samples is that all members of the population are sampled. Based on overall learning outcomes with an average indicator value of 64.43%, it was concluded that students' perceptions of the online biology learning process in class X IPA 1 SMA Negeri 1 Manokwari were in the passable category.

Production and distribution of Late Antique utilitarian wares in the micro-region of Vallès (Catalonia, Spain): A perspective from the rural hinterland of Barcino

Cooking and common wares presumably produced regionally are frequent in archaeological context of Late Antique rural sites in northeastern Spain. 142 of these wares from four settlements in the region of Vallès, in the surroundings of the ancient city of Barcino/Barcelona, were characterized through a combination of instrumental analytical techniques (OM, WD-XRF, and XRD), with the aim of investigating their provenance and production technology. The results confirm their regional provenance and suggest a local production of a part of the pottery assemblages, while also provide evidence of at least a secondary micro-regional trade during this period.

FEATURES OF QUANTITATIVE ESTIMATION OF FLAVONOID CONTENT IN JUGLANS NIGRA L. BARKS PREPARATIONS

The aim of the research is the development of quantification procedures of flavonoids in Juglans nigra L. barks preparations using modern instrumental analytical techniques (spectrophotometry, high performance liquid chromatography).Materials and methods. The subjects of research were tincture and dry extract of Juglans nigra L. bark, the samples of which were prepared in March and April 2020 in the Botanical Garden of Samara State Medical University (Samara); the standard samples (SS) of myricitrin, myricetin. The registration of the electronic spectra was carried out with a spectrophotometer «Specord 40» (Analytik Jena, Germany). The chromatographic analysis was carried out by the method of reversed-phase HPLC on a microcolumn liquid chromatograph “Milichrom-6” (NPAO “Nauchpribor”, Russia).Results. Using differential spectrophotometry, methods for the quantitative determination of the total amount of flavonoids in terms of myricitrin in the tincture and dry extract of Juglans nigra L. bark, has been developed. It has been determined that the content of the total amount of flavonoids in terms of myricitrin in the tincture and dry extract of Juglans nigra L., is 0.84±0.07% and 12.38±0.24%, respectively. The error of a single determination of the total amount of flavonoids in terms of myricitrin in the tincture and dry extract of Juglans nigra L. bark with a confidence probability of 95%, is ± 8.91% and ± 2.10%, respectively. Methods for the quantitative determination of myricitrin in the tincture and dry extract of Juglans nigra L. bark by HPLC has been developed. The content of the dominant flavonoid – myricitrin (myricetin-3-O-α-L-rhamnopyranoside) – in the tincture and dry extract of Juglans nigra L., was 0.42±0.06% and 8.45±0.24%, respectively. The error of the single determination of myricitrin in the tincture and dry extract of Juglans nigra L. with a confidence probability of 95% is ± 15.04% and ±2.96%, respectively.Conclusion. The developed methods for the quantitative determination of flavonoids in the preparations of Juglans nigra L. barks L. can be used in solving the problems of standardization of Juglans nigra L. preparations.

Twenty years in the 21st century: identification technologies for and multimodal research on chemical changes in exploration of processing mechanism of Chinese medicine

Chinese medicine undergoes complex chemical changes during processing and identifying these changes is the key to the processing mechanism. In the past 20 years of the 21 st century, research on the chemical changes in Chinese medicine after processing has focused the changes in the biopharmaceutical process in addition to the variation during processing. With the surging of information technologies, various identification technologies(instrumental analysis techniques, molecular biological techniques, data mining techniques, and biotransformation techniques) have developed rapidly and been widely applied to the research on processing mechanism. Thus, based on the chemical changes in the processing and biopharmaceutical process, the author suggested a research tactic of multimodal identification as the core by reorganizing key technologies for chemical identification from studies of the processing mechanism of Chinese me-dicine, aiming at establishing an interdisciplinary multi-dimensional research model for the processing mechanism of Chinese medicine.

Sustainable development and firm performance: Evidence from Thailand's sufficiency economy philosophy

AbstractThis study aims to examine the relationship between sufficiency economy philosophy (SEP) performance and the firm performance of Thai listed companies from 2013 to 2018 by using a novel measurement of SEP performance based on global reporting initiative guidelines. The higher SEP scores imply the firm is engaging more in SEP activities. Our empirical evidence shows support of our hypothesis, suggesting that SEP practice enhances firm accounting performance. Furthermore, several robustness checks confirm the results, including an instrumental variable analysis and propensity score matching technique.

Aliphatic Polyurethane Films Based on Hexamethylene Diisocyanate and Saccharides for Biocompatible Transparent Coating on Optic Medical Devices

AbstractPolyurethanes are widely used in daily life, from the textile industry to medical applications. In this study, a biocompatible and transparent coating from polyethylene glycol‐based polyurethanes including different type of saccharide (xylose as monosaccharide, sucrose as disaccharide, or starch as polysaccharide) is prepared. Prepared optically transparent polyurethanes are characterized with different instrumental analysis techniques and contact‐angle measurements. Thermogravimetric analysis data allow understanding that the synthesized saccharide based polyurethanes are resistant to high temperatures, which means that medical devices can be easily coated with one of the saccharide‐based polymers during the manufacturing process. The study results also show that synthesized polyurethane samples having a different kind of saccharides present high biocompatibility and transparency properties via In vitro cytotoxicity analysis and optic transparency tests. For xylose, sucrose, or starch containing polyurethanes, the tranmittance values are 97.72%, 85.20%, and 89.23%, respectively. In addition, scanning electron microscope images show that the samples also have smooth surfaces which can be used for proper coating of medical devices. Consequently, this manuscript addresses synthesis and characterization of the optically transparent polyurethanes based on specific saccharides for biocompatible and transparent surfaces especially in optic medical devices such as colonoscopy applications and laparoscopic detection probes.

Curbing the Opioid Epidemic at Its Root: The Effect of Provider Discordance After Opioid Initiation

Although medical research has addressed the clinical management of chronic opioid users, little is known about how operational interventions shortly after opioid initiation can impact a patient’s likelihood of long-term opioid use. Using a nationwide U.S. database of medical and pharmaceutical claims, we investigate the care delivery process at the most common entry point to opioid use: the primary care setting. For patients who return to primary care for a follow-up appointment within 30 days of opioid initiation, we ask who should revisit and potentially revise the opioid-based treatment plan: the initial prescriber (provider concordance) or an alternate clinician (provider discordance)? First, using a fully controlled logistic model, we find that provider discordance reduces the likelihood of long-term opioid use 12 months after opioid initiation by 31% (95% Confidence Interval: [18%, 43%]). Both the instrumental variable analysis technique and propensity-score matching (utilizing the minimum-bias estimator approach) account for omitted variable bias and indicate that this is a conservative estimate of the true causal effect. Second, looking at patient activities immediately after the follow-up appointment, we find that this long-term reduction is at least partially explained by an immediate reduction in opioids prescribed after the follow-up appointment. Third, the data suggest that the benefit associated with provider discordance remains significant regardless of whether the patient’s initial prescriber was their regular primary care provider or another clinician. Overall, our analysis indicates that systematic, operational changes in the early stages of managing new opioid patients may offer a promising, and hitherto overlooked, opportunity to curb the opioid epidemic.This paper was accepted by David Simchi-Levi, healthcare management.

The application of thymol-loaded chitosan nanoparticles to control the biodeterioration of cultural heritage sites

Biocides are widely used to impede the growth of harmful microorganisms, whose colonization will cause biodeterioration of cultural heritage sites. However, frequent application of biocides is costly and hazardous to both humans and the environment. In this study, a series of thymol-loaded chitosan nanoparticles were prepared by the emulsification-ionic gelation method and verified by instrumental analytical techniques (UV–Vis spectrophotometry, SEM/TEM, FTIR, and TGA/DTG). The results show that thymol is encapsulated within chitosan nanoparticles, thus the release of the natural biocides can be controlled. Compared with free thymol, thymol-loaded chitosan nanoparticles demonstrate a better performance against Aspergillus niger, a class of fungus isolated from the Feilaifeng limestone. This novel strategy could be applied to the preservation and protection of outdoor stone-built cultural heritage sites to reduce the amount and frequency of biocides application.

Advances and trends in analytical techniques in natural product research: Challenges and future perspective

Advances in analytical methods and bioassay development have helped to push forward the research in natural products. Their high chemical diversity and the effects of evolutionary pressure to create biologically active molecules could be attributed to success in drug discovery. Despite the availability of modern analytical instrumentation techniques, metabolic profiling covers the identification of a selected group of metabolites. The phytochemical analysis is commonly performed using standard techniques such as thin-layer chromatography, high-performance thin-layer chromatography, high-performance liquid chromatography, gas chromatography and more recently mass spectrometry and nuclear magnetic resonance spectrometry. Two-dimensional J-resolved Nuclear Magnetic Resonance (NMR) spectra and multivariate data analysis techniques were applied to avoid low resolution and overlapping signals hampering the identification of the individual components of botanicals. On-targeted metabolomic analysis via the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) was utilised to localise compounds belonging to various chemical classes (i.e. oxygenated fatty acids, flavonols, phenolic acids, and sinapoyl choline derivatives). Rotation planar chromatography over-pressured layer chromatography and electro planar chromatography are the other innovations. Parallel and serially coupled layers open up new avenues for the analysis of a large number of samples for high-throughput screening and very complex matrices in a natural product. Analytical strategies with applications to natural extracts and novel methods that have strong potential, regardless of how often they are used are discussed with respect to their potential applications challenges and future trends.

Characterization of binders and pigments using an integrated analytical approach: Application to wooden reliefs created by Vasko Lipovac in the 1970s

This contribution describes the study conducted on two painted wooden reliefs created in the early 1970s by Vasko Lipovac, a prominent Croatian contemporary artist. Due to the poor condition in which the artworks were found, it was important to establish a strategy for conservation and long-term preservation. Accordingly, preliminary knowledge about chemical composition of the paint pigments and binders was pointed out as significant information addressed in this study. Since the chemical composition of the paint determines the conservation methodology and materials, the proper treatment ensures stability of the original materials, and accordingly, long term preservation of an artwork. An integrated analytical approach involving different instrumental analytical techniques was applied to each of the microsamples collected in the paintings. For the elemental characterization of the pigments, total reflection X-ray fluorescence spectroscopy (TXRF) was used, and the obtained results were complemented with the information about mineral phases present in the pigments by X-ray diffraction (XRD) analysis. The TXRF results demonstrated that most of the pigments related with the named “skin tone” contain appreciable amounts of Cd (1.8–9%) with constant presence but variable amounts of Se (0.24–1.1%), reinforcing the interpretation that the pigment originally used is cadmium sulfoselenide (the so-called “cadmium red”), although by XRD we only observed the presence of its alteration to cadmium sulfate. The XRD results revealed a complex mixture of different inorganic compounds present in the painted wooden reliefs (i.e., barite, rutile, quartz, calcite, chlorite, etc). The presence of zinc white with wurtzite structure in almost all the samples can be considered as the main constituent of the coloring painting layer. Raman spectroscopy contributed to a more accurate characterization of the analysed paint samples, since the vibrational spectra as a result of Raman scattering proved very useful to obtain information on the presence and type of the synthetic pigments.Fourier transform infrared spectroscopy (FTIR) and pyrolytic gas chromatography coupled with mass spectrometry (Py-GC/MS) were used to determine the chemical composition of the paint samples binders. Py-GC/MS clarified the doubts about acrylic and alkyd components in paints where polyvinyl acetate (PVAc) is predominant by detecting acrylate monomers and phthalic anhydrides and provided information about their relative presence in the samples. On the other hand, FTIR spectroscopy was a necessary tool for unambiguous identification of nitrocellulose in the white and black samples from one of the paintings, as well as for the firm assumption of its presence in most of the other samples since Py-GC/MS is not suitable for its detection.

Direct Electrochemical Extraction of Sm from SmCl3 in a Molecular Liquid Solvent Supported By LiNO3

Low-temperature electrochemical extraction of rare earth metals from their corresponding chlorides in ionic liquids has long been a scientific challenge. In this study, a new class of task-specific ionic liquids (ILs) containing Li elements, i.e. Li-containing solvate ionic liquids ([Li(DMI)n]3+NO3 —, 0.15 M LiNO3 dissolved in DMI (1,3-Dimethy-l-2-imidazolidinone)), is developed and used for metallic Sm electrodeposition from SmCl3. To elucidate the electrochemical deposition mechanism, the ionic component of the DMI/LiNO3 system was characterized by a range of instrumental analysis techniques (including 7Li NMR, UV-vis) and theoretical calculations. Cyclic voltammetry was used to explore the electrochemical behavior of Sm-containing species in the ionic liquid. Finally, metallic Sm was successfully obtained using constant potential deposition on high purity Al substrates which was confirmed by XPS and SEM. Li-containing solvate ILs have immense potential in green electrometallurgy because of their higher tunability and similar properties to ILs.

Equilibrium adsorption and kinetic study of CO2 and N2 on synthesized carbon Black–Zeolite composite

In this study, the preparation of a composite of zeolite-carbon black (CB) for enhancing the CO2 adsorption capacity of zeolites has been investigated. The composites were prepared by adding 5 wt% CB to zeolite 13X crystals via a hydrothermal synthesis method. The standard instrumental analysis techniques, including X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and obtaining N2 adsorption/desorption isotherms at 77 K, were used to characterize the as-prepared composite. The adsorption isotherms of CO2 and N2 on the composite were measured by a volumetric method at 283, 303, and 323 K and up to 2.2 bar. Employing the Sips and Toth isotherm models, it was found that the Toth model has the best adaptability to the experimental isotherms data. The isosteric heats of adsorption were evaluated with the Clausius-Clapeyron equation. The binary adsorption isotherm and selectivity of CO2 over N2 were predicted using the ideal adsorbed solution theory. The adsorption kinetics of CO2 and N2 on the composite were determined by the non-isothermal kinetic model. The microporous diffusional time constants obtained from correlating the kinetic model with the experimental uptake curves were also compared with those of zeolite 13X. The results show the significant improvements in the adsorption capacity and rate by adding around 5 wt% CB to zeolite 13X.

Highly Selective and Sensitive Aggregation-Induced Emission of Fluorescein-Coated Metal Oxide Nanoparticles.

We report the synthesis, characterization, and photophysical properties of novel metal oxide nanoparticles (NPs) coated with specially designed fluorescein substituents which are capped with electron‐withdrawing groups. The fluorescein‐coated nanoparticles were synthesized in excellent yields, and their structures were confirmed using various advanced spectroscopic, instrumental, and surface analysis techniques, revealing the formation of the target functionalized nanoparticles (FNPs) which show superior chemical and thermal stabilities. In addition, the photophysical properties of the FNPs were examined using UV‐visible absorption and fluorescence spectroscopy. These latter techniques disclosed aggregation‐induced emission (AIE) properties for most of the target FNPs, namely those which are soluble in common organic solvents at selective concentration ranges of water fractions in the solvent mixture.

Manodisciplines Applied to Understand the Complexity of Mudstones and its Links with the Instability of Slopes: Interrelationships between Endogenous and Exogenous Contributing Factors, Weathering Agents & Dynamics, Next to other Environmental Considerations

The Mudstones – in spanish ‘lodolitas or fangolitas’, so called in Ibero and Suramérica – are natural materials conformed up of the subclasses silt and clay, or their combinations, which usually also include the sand grain size, fine to very fine; are overconsolidated rocks, from an geotechnical point of view. These sediments can be evaluated both by classical methods and instrumental analysis techniques, revealing unknown and important variables in the genesis of wide and acute processes that compromise the Crust, object of study of modern geodynamics exogenous. While it is true that the problems in clay shales (mudstones) date back many years, it was only from the early 1960’s that they were extensively studied [1].

A review of environmental occurrence, analysis, bioaccumulation, and toxicity of organophosphate esters.

The ban and restriction of polychlorinated biphenyls (PCBs) and major brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) and polybrominated diphenyl ethers (PBDEs), due to their confirmed detrimental effects on wildlife and humans have paved the way for the wide application of organophosphate esters (OPEs). OPEs have been extensively used as alternative flame retardants, plasticizer, and antifoaming agents in various industrial and consumer products, which leads to an increase in production, usage, and discharge in the environment. We compile recent information on the production/usage and physicochemical properties of OPEs and discussed and compared the available sample treatment and analysis techniques of OPEs, including extraction, clean-up, and instrumental analysis. The occurrence of OPEs in sediment, aquatic biota, surface, and drinking water is documented. Toxicity, human exposure, and ecological risks of OPEs were summarized; toxicological data of several OPEs shows different adverse health effects on aquatic organisms and humans. Much attention was given to document evidence regarding the bioaccumulation and biomagnification potential of OPEs in aquatic organisms. Finally, identified research gaps and avenues for future studies are forwarded.

The Effect of Elicitors and Canopy Management in the Chemical Composition of Vitis vinifera Red Varieties in Warm and Hot Areas in Spain

Canopy management practices in vineyards, such as sprawling systems and shoot trimming, can change the accumulation of metabolites in grapes. The use of elicitors of biological origin on grapevines of Vitis vinifera red grape varieties may also modulate the chemical composition of the berries. These modifications are often observed in the accumulation of phenolic compounds, including pigments. Both technical approaches are alternatives involved in minimizing the effects of global climate change in warm areas. The increase of temperature related to climate change accelerates the accumulation of sugars, but produces unbalanced grapes. This work establishes the use of button sensors to monitor the climate changes occurring at grape cluster level. Together with climate monitoring, conventional instrumental analytical techniques are used to follow up the chemical composition and the phenolic fraction of grapes in four different production areas in Spain. The effect of either treatment seems variable and to be affected by external factors besides the treatment itself and the climate conditions. While there is a fine effect that correlates with the use of elicitors in varieties like Merlot and Tempranillo, there is minimal improvement observed in Tintilla de Rota. The total phenolic index increases were between 2.3% and 11.8% in the first two parcels. The same happened with the vineyard’s canopy management systems, with increased pigment accumulation and the total phenolic index rising (37.7% to 68.7%) after applying intense shoot trimming, or a variation in sugar concentrations when using sprawl conduction. This study aims to provide viticulturists and oenologists in particular, and farmers in general, with data on the field regarding the use of alternative sustainable practices in the cultivation of grapes. The techniques used involved 100% natural products without adjuvants. The benefits obtained from applying some of these practices would be to produce technically mature grapes despite climate changes, and the elaboration of more balanced wines.

Selected Instrumental Techniques Applied in Food and Feed: Quality, Safety and Adulteration Analysis.

This review presents an overall glance at selected instrumental analytical techniques and methods used in food analysis, focusing on their primary food science research applications. The methods described represent approaches that have already been developed or are currently being implemented in our laboratories. Some techniques are widespread and well known and hence we will focus only in very specific examples, whilst the relatively less common techniques applied in food science are covered in a wider fashion. We made a particular emphasis on the works published on this topic in the last five years. When appropriate, we referred the reader to specialized reports highlighting each technique’s principle and focused on said technologies’ applications in the food analysis field. Each example forwarded will consider the advantages and limitations of the application. Certain study cases will typify that several of the techniques mentioned are used simultaneously to resolve an issue, support novel data, or gather further information from the food sample.

Carbon dioxide storage in Dead Sea water

In this paper, the Dead Sea (DS) environment as a carbon dioxide (CO2) potential storage site was investigated. Firstly, the storage capacity of CO2 in ultra-pure and Dead Sea water (DSW) was studied at ambient temperature and pressure. The effect of CO2 pressure on the storage capacity of CO2 in DSW was also studied at different contact times at the ambient temperature. Finally, for comparison purposes, CO2 gas was injected into a solution containing only dissolved calcium ions. Different analytical and instrumental analysis techniques were used to characterize both liquid and solid samples including acid base titration, Atomic Absorption Spectrometry (AAS), X-ray Diffraction analysis (XRD), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Based on the titration method, the storage capacity of CO2 in both pure water and DSW was found to be 1.7 and 1.53mmol/l, respectively, at ambient temperature (15°C) and ambient pressure. DSW water was found to contain 1.6Ca wt% and 4.3wt% Mg based on AAS analysis. The storage capacity of CO2 in DSW increased with the increase of pressure and despite the high content of Ca and Mg in DSW, no precipitation was observed even at a CO2 pressure of 25bar and 76h of contact time. When DSW, saturated with CO2, was titrated (using NaOH), precipitates were obtained containing aragonite, brucite and magnesite as identified by XRD, TGA and SEM analysis techniques. The major finding of this work is that DS water is suitable environment to be used to sequester CO2.