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Topic Review

Nitroaldol Reaction

The Henry Reaction (also referred to as the nitro-aldol reaction) is a classic carbon–carbon bond formation reaction in organic chemistry. Discovered in 1895 by the Belgian chemist Louis Henry (1834-1913), it is the combination of a nitroalkane and an aldehyde or ketone in the presence of a base to form β-Nitro alcohols. This type of reaction is commonly referred to as a "nitro-aldol" reaction (nitroalkane, aldehyde, and alcohol) It is nearly analogous to the aldol reaction that had been discovered 23 years prior that couples two carbonyl compounds to form β-hydroxy carbonyl compounds known as "aldols" (aldehyde and alcohol). The Henry reaction is a useful technique in the area of organic chemistry due to the synthetic utility of its corresponding products, as they can be easily converted to other useful synthetic intermediates. These conversions include subsequent dehydration to yield nitroalkenes, oxidation of the secondary alcohol to yield α-nitro ketones, or reduction of the nitro group to yield β-amino alcohols. Many of these uses have been exemplified in the syntheses of various pharmaceuticals including the β-blocker (S)-propranolol, the HIV protease inhibitor Amprenavir (Vertex 478), and construction of the carbohydrate subunit of the anthracycline class of antibiotics, L-Acosamine. The synthetic scheme of the L-Acosamine synthesis can be found in the Examples section of this article.

2.8K
14 Oct 2022

Topic Review

Living Anionic Polymerization

Living anionic polymerization is a living polymerization technique involving an anionic propagating species. Living anionic polymerization was demonstrated by Szwarc and co workers in 1956. Their initial work was based on the polymerization of styrene and dienes. One of the remarkable features of living anionic polymerization is that the mechanism involves no formal termination step. In the absence of impurities, the carbanion would still be active and capable of adding another monomer. The chains will remain active indefinitely unless there is inadvertent or deliberate termination or chain transfer. This gave rise to two important consequences: The following experimental criteria have been proposed as a tool for identifying a system as living polymerization system. However, in practice, even in the absence of terminating agents, the concentration of the living anions will reduce with time due to a decay mechanism termed as spontaneous termination.

2.8K
31 Oct 2022

Topic Review

Graphene oxide (GO) is a chemical compound with a form similar to graphene that consists of one-atom-thick two-dimensional layers of sp2-bonded carbon. Graphene oxide exhibits high hydrophilicity and dispersibility. Thus, it is difficult to be separated from aqueous solutions. Therefore, functionalization with magnetic nanoparticles is performed in order to prepare a magnetic GO nanocomposite that combines the sufficient adsorption capacity of graphene oxide and the convenience of magnetic separation. Moreover, the magnetic material can be further functionalized with different groups to prevent aggregation and extends its potential application. Until today, a plethora of magnetic GO hybrid materials have been synthesized and successfully employed for the magnetic solid-phase extraction of organic compounds from environmental, agricultural, biological, and food samples. The developed GO nanocomposites exhibit satisfactory stability in aqueous solutions, as well as sufficient surface area. Thus, they are considered as an alternative to conventional sorbents by enriching the analytical toolbox for the analysis of trace organic compounds.

2.8K
15 Jan 2021

Topic Review

Sample Preparation Techniques Used in Food Analysis

Food samples are complex heterogenous matrices, where all analytes are distributed in a random manner. Food analysis involves sampling, homogenization, and sample preparation that increase the analytical accuracy and precision. Focusing on sample preparation it usually involves storage, particle size reduction, homogenization, weighting, dilution, filtration, extraction, clean-up, and derivatization. Proper sample preparation protocols result in matrix interference elimination and analyte preconcentration, thus affecting the selectivity, sensitivity, detection capability, and the overall performance of an analytical technique. The most time-consuming step in analytical method development is the optimization of the sample preparation protocol that includes analyte extraction and clean-up. Some of the most common sample preparation techniques used in food analysis are liquid-liquid extraction (LLE), solid-liquid extraction (SLE), solid-phase extraction (SPE), solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), ultrasonic, and Soxhlet extraction.

2.8K
17 Jul 2023

Topic Review

Reaction of CO2 with Epoxides

Coupling of CO2 with epoxides is a green emerging alternative for the synthesis of cyclic organic carbonates (COC) and aliphatic polycarbonates (APC). The scope of this work is to provide a comprehensive overview of metal complexes having sulfur-containing ligands as homogeneous catalytic systems able to efficiently promote this transformation with a concise discussion of the most significant results. The crucial role of sulfur as the hemilabile ligand and its influence on the catalytic activity are highlighted as well.

2.7K
22 Jan 2021

Topic Review

Mixture Designs of Experiments

The experimental designs for mixtures are a subclass of experimental designs useful for studying the effects of ingredients/components in formulations.

2.7K
04 Jun 2021

Topic Review

Metal Nanoclusters

Metal nanoclusters (NCs), comprising only a few to roughly hundreds of metal atoms, have a metal core-protective agent shell structure. Owing to the size of metal NCs approaching the Fermi wavelength of electrons, the spatial confinement of free electrons in metal NCs generates discrete electronic transitions, thereby exhibiting intriguing molecular-like properties. Therefore, metal NCs are deemed to bridge the gap between molecules and nanoparticles.

2.7K
01 Dec 2020

Topic Review

Natural Deep Eutectic Solvents for Sustainable Extraction Techniques

The analysis of foods is a comprehensive process of extraction, identification, and quantification of several classes of compounds from natural matrices. The detection and quantification of primary metabolites (sugars, amino acids, vitamins, and lipids), contaminants (toxins, heavy metals, and allergens), and secondary metabolites (polyphenolics, flavonoids, terpenes, and alkaloids) is a crucial practice for ensuring the safety and quality of foods and related functional products. Due to the variable structure of food analytes, a gap in a universal method suitable for the extraction and analysis of all compounds is lacking. Moreover, conventional extractants are usually made of organic solvents and common extraction techniques usually require a long extraction time to exhaust the matrix. The actual discussions about climatic changes provide a growing awareness of the scientific and industrial community to reduce the environmental impact by using sustainable processes. In general, the main principles of “green chemistry” are based on the design of processes aimed to reduce energy consumption and the use of eco-friendly solvents with less toxicity to the environment and human health.

2.6K
09 Jan 2023

Topic Review

Seaweed Phenolics

Seaweed, also referred to as macroalgae, have been studied as potential aquafeed ingredients since the late 1970s but have been implemented as a poultry feed supplement since the 1950s. Seaweed phenolics provide alternative ingredients that are complementary to synthetic additives used in aquaculture, possessing a broad spectrum of bioactive properties such as antimicrobial, antiviral, antifungal, anti-stress, antioxidant, anti-inflammatory, immunostimulant, and appetite stimulation. Also, their antioxidant properties retard lipid oxidation and preserve feed quality improving shelf life.

2.6K
19 Jul 2022

Topic Review

Applications of High Performance Liquid Chromatography with Fluorescence

Steroids are compounds widely available in nature and synthesized for therapeutic and medical purposes. Steroids can be found in various environmental samples, including water, plant, and animal samples as well as in a variety of pharmaceutical forms. Due its sensitivity and selectivity, high performance liquid chromatography with fluorescence detection (HPLC-FLD) is widely used for detection of steroids in pharmaceutical and environmental samples.

2.5K
11 Apr 2022

Topic Review

Swabs are used to collect body fluid samples for testing in the forensic and clinical settings. However, swabs made of different materials and are differently shaped may impact the DNA that can be recovered from the body fluids absorbed by the swabs. Recovering a higher quantity of DNA can be important for DNA typing and obtaining a full profile, especially in low template samples. In this study, swabs made of cotton, paper and foam materials from various commercial suppliers were evaluated to determine which swab released the highest quantity of DNA from a fifty-microliter sample of blood applied to the swab. DNA extraction was performed using the phenol chloroform-isoamyl alcohol method and human DNA was quantified using a quantitative real-time PCR assay using the Plexor HY human quantification kit. Overall, Puritan cotton-tipped swabs performed best in this study.

2.5K
08 Sep 2021

Topic Review

Fluorescence Polarization-Based Bioassays

Fluorescence polarization holds considerable promise for bioanalytical systems because it allows the detection of selective interactions in real time and a choice of fluorophores, the detection of which the biosample matrix does not influence; thus, their choice simplifies and accelerates the preparation of samples. For decades, these possibilities were successfully applied in fluorescence polarization immunoassays based on differences in the polarization of fluorophore emissions excited by plane-polarized light, whether in a free state or as part of an immune complex. However, the results of recent studies demonstrate the efficacy of fluorescence polarization as a detected signal in many bioanalytical methods.

2.5K
17 Dec 2020

Topic Review

Identification of New Psychoactive Substances

New (or novel) psychoactive substances (NPS) or “designer drugs”, substances that are not controlled by the 1961 Single Convention on Narcotic Drugs or the 1971 Convention on Psychotropic Substances, pose public health threats. NPS are widely available on the web, through local head shops, on streets and in schools. Many chemical and nucleic acid based methods can be used to detect and identify these substances.

2.5K
29 Oct 2020

Topic Review

CRISPR/Cas-Based Detection

Rapid, accurate, and portable on-site detection is critical in the face of public health emergencies. Infectious disease control and public health emergency policymaking can both be aided by effective and trustworthy point of care tests (POCT). A very promising POCT method appears to be the clustered regularly interspaced short palindromic repeats and associated protein (CRISPR/Cas)-based molecular diagnosis. For on-site detection, CRISPR/Cas-based detection can be combined with multiple signal sensing methods and integrated into smart devices.

2.5K
15 Feb 2023

Topic Review

Pesticide residues detection by Characteristics

The excessive use or abuse of pesticides leads to residues in food, which can threaten human health. Therefore, there is an extremely urgent need for multi-analyte analysis techniques for the detection of pesticide residues, which can be applied as screening techniques for food safety monitoring and detection. Recent developments related to rapid multi-residue detection methods for pesticide residues are reviewed herein. Methods based on the inherent characteristics of pesticides are described in detail. Enzymatic inhibition-based sensors, near-infrared spectroscopy, and SERS spectroscopy based on the inherent characteristics are discussed.

2.4K
26 Aug 2020

Topic Review

Mass Spectrometry in Determination of Pesticide Residues

The extensive use of pesticides represents a risk to human health. Consequently, legal frameworks have been established to ensure food safety, including control programs for pesticide residues. In this context, the performance of analytical methods acquires special relevance. Such methods are expected to be able to determine the largest number of compounds at trace concentration levels in complex food matrices, which represents a great analytical challenge. Technical advances in mass spectrometry (MS) have led to the development of more efficient analytical methods for the determination of pesticides.

2.4K
15 Jun 2022

Topic Review

Discriminating between Parallel, Anti-Parallel and Hybrid G-Quadruplexes

G-quadruplexes (G4) are now extensively recognised as a peculiar non-canonical DNA geometry that plays a prime importance role in processes of biological relevance whose number is increasing continuously. The same is true for the less-studied RNA G4 counterpart. G4s are stable structures; their geometrical parameters may be finely tuned not only by the presence of particular sequences of nucleotides but also by the salt content of the medium or by a small molecule that may act as a peculiar topology inducer.

2.4K
14 Jul 2022

Topic Review Peer Reviewed

Enantiomers and Their Resolution

Enantiomers share the same chemical formula but have different chemical structures, i.e., type of isomers. Enantiomers are present in several drugs, perfumes, food, and are a fundamental part of biomolecules. This subject is highly important for pharmaceutical companies. Enantiomeric drugs present different actuation in the human body; depending on the compound, one might combat the symptom, whereas its pair might cause damage. The separation of pairs of enantiomers requires a chiral environment that provokes a structural imbalance that conventional methods cannot provide. Enantioresolution is one of the most promissory studies that benefit several areas, such as pharmaceutical, biotechnology, food industry, and fine chemistry. Its resolution is of great importance, therefore, its main mechanisms of resolution will be explained herein.

2.4K
14 Apr 2022

Topic Review

Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.).

2.3K
02 Aug 2022

Topic Review

Plasmonic biosensing schemes for virus

The uncertain proportions of pandemic outbreaks have triggered the need of reliable and cost-effective protocols easily adaptable to the changing virulence of virus strains. In recent years, plasmonic biosensors are being increasingly applied for clinical diagnosis of viral and other infectious diseases. Typical plasmonic biosensing strategies rely on the versatility of SPR and LSPR as label-free detection systems capable of monitoring binding interactions in a short period of time. Nevertheless, the incorporation of technological advancements has precipitated the development of nanomaterial-based applications for improving the sensitivity and specificity of classical configurations. The unique optical properties of plasmonic nanostructures has been exploited in combination with SERS colorimetric, fluorescence or luminescence enhancement for viral diagnosis. Likewise, the development of plasmonic virus sensing approaches has also benefitted from the variety of virus biomarkers. Thus, a high number of virus plasmonic biosensors have prompted the advance of novel functionalization strategies to achieve the effective coverage of the biological receptor while ensuring the affinity and specificity towards the target viral nucleic acids, proteins or whole virus. The huge potential for single virus detection along with the effectiveness and simplicity of current plasmonic configurations will impact on the routine surveillance of virus in clinical settings during this decade.

2.3K
27 Oct 2020

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