Summary

Sample preparation is the most crucial step in the analytical procedure designed for implementation in any analytical application (food analysis, bionalysis, forensics, toxicology, environmental monitoring etc). It is the limiting factor in chemical analysis since it is time consuming and it can potentially introduce errors. No one can doubt that the best approach would be the direct introduction of the sample to the instrument; however, this is rarely feasible. Efficient sample pretreatment is inevitably required as the instrument technology has produced highly sophisticated and sensitive analytical equipment. Hence, the analytical scientists have to develop and apply a suitable sample preparation protocol that ensures that the composition of the sample remains unchanged, no impurities are introduced during handling, all interferences have been left back, and the analytes’ concentration is not only at detectable levels, but it can also be quantified precisely and accurately and that the matrix of the sample is compatible with the analytical technique. Extraction techniques are the most powerful tool available to analytical chemists and lab practitioners. Whether sorbent-based or solvent-based, extraction techniques provide the necessary tools to handle the sample in a way that can reveal all the important information. All advantages in instrumentation have been exploited to the fullest and the lifetime of the instrument is prolonged in a seamless operation mode. This entry collection aims to highlight some applications of extraction techniques in sample preparation.

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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.
  • 893
  • 09 Jan 2023
Topic Review
Supercritical Antisolvent Technique for the Preparation of Nanocatalysts
In an era where sustainability is becoming the main driving force for research and development, supercritical fluids-based techniques are presented as a very efficient alternative technology to conventional extraction, purification, and recrystallization processes. Supercritical antisolvent (SAS) precipitation is a novel technique that can replace liquid antisolvent precipitation techniques. Additionally, through the optimization of precipitation operating conditions, morphology, particle size, and particle size distribution of nanoparticles can be controlled. As an antisolvent, supercritical carbon dioxide (scCO2) is far more sustainable than its conventional liquid counterparts; not only does it have a critical point (304 K and 73.8 bar) on its phase diagram that allows for the precipitation processes to be developed so close to room temperature, but also its recovery and, consequently, the precipitated solute purification stage is considerably simpler. This technique can be used efficiently for preparing nanocatalysts to be used in biodiesel production processes.
  • 891
  • 21 Dec 2022
Topic Review
Froth Washing in Flotation
Froth flotation is a mineral processing technique that is popular when processing low-grade ores. It involves introducing chemically treated, finely ground ore in the form of a slurry into a flotation cell where the air is also added in the form of bubbles. The cell is agitated resulting in the air bubbles rising to the top and creating a froth, as bubbles rise, hydrophilic particles attach to the rising bubbles creating a froth which is collected in the weir or using launders for further treatment. The froth is washed using various froth-washing techniques to reduce entrainment and improve the grade of the froth. Froth washing can be achieved using froth washing jets or froth washing trays, this can be achieved internally/externally with regards to the position in the froth layer.
  • 1.1K
  • 30 Nov 2022
Topic Review
Procedures for Extraction of Anthocyanins from Different Food
Anthocyanins are water-soluble pigments characterized by various intense colors found in fruits and vegetables. The extraction and separation of anthocyanins from plants is important, especially due to the instability of plant anthocyanins, selecting and optimizing. Anthocyanins are prone to degradation by several factors, including pH, temperature, oxygen, water activity, co-pigments and enzymes. Unwanted compounds, such as sugars, proteins, lipids, acids and other flavonoids, can also be removed from plant material by appropriate extraction methods. The most used method for anthocyanin extraction is the conventional one, solid–liquid extraction, also known as solvent extraction, during which anthocyanins can be dissolved in polar solvents (methanol/glycolic acid and acetone), followed by their quantification, achieved by using spectrophotometry, the differential pH method, which is a rapid and convenient quantitative assay. Starting from this point, it has developed and there are many anthocyanin-extraction methods, such as conventional solvent extraction (CSE), enzyme-assisted extraction (EAE), fermentation extraction (FE), supercritical fluid extraction (SFE) (CO2) extraction, microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), high-hydrostatic-pressure extraction (HHPE) and pressurized-liquid extraction (PLE). One of the most frequent techniques for obtaining anthocyanins from plants is conventional solvent extraction. In order to meet the demands of safety and environmental sustainability, new extraction technologies with shorter extraction periods and higher yields have been developed (e.g., PLE, EFS, UAE, MAE, EAE, etc.).
  • 1.9K
  • 29 Nov 2022
Topic Review
Extraction of Metals from Copper Tailings through Leaching
A copper tailing is a residue, product of the flotation of sulfide minerals, which contain a variety of elements that can be valorized. The extraction of metals from copper tailings consist of applying metallurgical techniques, such as acid leaching or magnetic concentration, to obtain a valuable product. Currently, this is an important objective, given that mining operations have increased the generation of tailings. Acid leaching is a process that consists of dissolving a solid material, such as a tailing, by applying an acid solution. This process forms two final products: an insoluble solid, rich in aluminosilicates, and an acid liquid solution with different metal ions. Both products may have different characteristics and can be used for subsequent applications.
  • 1.4K
  • 05 Dec 2022
Topic Review
Chemical Analysis of Synthetic Antioxidants in Foodstuffs
The information obtained by the systematic search in ScienceDirect® databases, indicated the predominance of the use of separation chromatography, followed by detection techniques in the development of analytical methods for the detection of phenolic antioxidants in foodstuffs. This is because these techniques allow the simultaneous determination of different types of antioxidants, through the separation of these compounds at different stages of a column, thus obtaining different retention times, which are related to the physicochemical characteristics of the antioxidants and their interaction between the stationary and mobile phase. After the separation, the antioxidants are identified and quantified using specific chromatographic detectors, such as ultraviolet–visible, diode array, thermal conductivity, and mass spectroscopy, resulting in a suitable sensitivity and selectivity. However, separation and detection chromatographic, despite being very accurate in the detection of antioxidants, have as their main disadvantage the use of large amounts of organic solvents or inert gases, with elevated purity and, consequently, high cost. Additionally, the use of these techniques requires rigorous steps of extraction and cleanup to prepare the foodstuff samples for analysis, remove interference compounds, and/or preconcentrate the antioxidants to obtain reliable information. Extraction steps can increase the time and costs in the analysis, promote a reduction in the analytical frequency, and generate a great quantity of residues, which goes against a very important principle, taken very seriously today, green chemistry, which orients the reduction or elimination of toxic residues in chemical products and processes, including all cycles of a chemical, in its design, manufacture, use, and final disposal.
  • 514
  • 04 Nov 2022
Topic Review
High-Energy Methods for Pretreatment of Mineral Complexes
Pulsed power technologies have been proposed based on the conversion of energy into a short-pulsed form and exposing geomaterials (minerals, rocks, and ores) to strictly dosed high-power pulsed electric and magnetic fields, beams of charged particles, microwave radiation, neutrons and X-ray quanta, and low-temperature plasma flows. Such pulsed energy impacts are promising methods for the pretreatment of refractory mineral feeds (refractory ores and concentration products) to increase the disintegration, softening, and liberation performance of finely disseminated mineral complexes, as well as the contrast between the physicochemical and process properties of mineral components. The most important research and practical developments in the application of high-energy effects in the beneficiation and deep processing of complex ores are described. Examples are given of the implementation of various methods for processing minerals, ores, and concentrates, including accelerated electron flow, microwave (UHF) and laser treatment, high-intensity magnetic and electric (HVP) fields, high-power nanosecond electromagnetic pulses, and low-temperature plasma of dielectric barrier discharge, enabling a higher performance of the concentration processes for refractory mineral feeds.
  • 398
  • 17 Oct 2022
Topic Review
Active Compounds from Antrodia cinnamomea
Antrodia cinnamomea is a precious and popular edible and medicinal mushroom. It has attracted increasing attention due to its various and excellent bioactivities, such as hepatoprotection, hypoglycemic, antioxidant, antitumor, anticancer, anti-inflammatory, immunomodulation, and gut microbiota regulation properties. To elucidate its bioactivities and develop novel functional foods or medicines, numerous studies have focused on the isolation and identification of the bioactive compounds of A. cinnamomea. 
  • 519
  • 11 Oct 2022
Topic Review
Technologies for Seaweed Polysaccharides Extraction
Algal metabolites possess nutritional properties, but they also exhibit antioxidant, antimicrobial, and antiviral activities, which allow them to be involved in several pharmaceutical applications. Seaweeds have been incorporated since ancient times into diets as a whole food. With the isolation of particular seaweed compounds, it would be possible to develop new types of food with therapeutically properties. Polysaccharides make up the majority of seaweed biomass, which has triggered an increase in interest in using seaweed for commercial purposes, particularly in the production of agar, carrageenan, and alginate. The bio-properties of polysaccharides are strictly dependent to their chemical characteristics and structure, which varies depending on the species, their life cycles, and other biotic and abiotic factors. 
  • 822
  • 06 Sep 2022
Topic Review
Extraction Methods of Medicinal Plants for Antimicrobial Textiles
Medicinal plants are the product of natural drug discoveries and have gained traction due to their pharmacological activities. Pathogens are everywhere, and they thrive in ideal conditions depending on the nutrients, moisture, temperature, and pH that increase the growth of harmful pathogens on surfaces and textiles.
  • 4.9K
  • 22 Aug 2022
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