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Microwave Irradiation: As a Sustainable Tool
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Microwave Irradiation: As a Sustainable Tool

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Microwave Chemistry".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 9488

Special Issue Editor

Prof. Dr. Fábio Andrei Duarte

E-Mail Website
Guest Editor
Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, RS 97105-900, Brazil
Interests: analytical chemistry; sample preparation; process analytical chemistry; speciation analysis; spectrometric and chromatographic analyses; trace element determination

Special Issue Information

Dear Colleagues,

This Special Issue will focus on the applications of microwave radiation in all fields of Chemistry, from synthesis and materials preparation up to extraction processes.

Microwave radiation has been widely used in several fields of chemistry, as well in other research areas. However, many of the first applications were performed under unsuitable conditions, mainly using conventional (kitchen or domestic ones) microwave ovens and/or without careful optimization of the process (synthesis, extraction, digestion, etc.). Fortunately, today, there are several commercially available microwave instruments, where the main operational conditions can be adjusted/monitored, such as temperature, pressure, irradiation power, etc., most of them combined with robust safety systems. These improvements allowed the application of microwave radiation in chemical reactions, ensuring the reproducibility, safety, low reagent consumption, speed, among other advantages that are welcomed in all fields of chemistry. This widespread use increased the number of publications using microwave radiation from hundreds per year in the 1990s to thousands in the 2000s.

This Special Issue will include a wide range of topics covering instrument development/improvement, compound extraction, organic synthesis, sample digestion, and materials science, among others.

Prof. Dr. Fábio Andrei Duarte
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microwave radiation
  • analytical chemistry
  • catalysis
  • electrochemistry
  • environmental chemistry
  • extraction of inorganic compounds
  • extraction of organic compounds
  • food chemistry
  • fuel processing
  • green chemistry
  • inorganic chemistry
  • instrumentation
  • materials science
  • medicinal chemistry
  • nanomaterials
  • organic chemistry
  • physical chemistry
  • process intensification
  • sample digestion
  • sensors
  • synthesis

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Published Papers (4 papers)

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Research

39 pages, 10092 KiB  
Article
Optimization of Microwave-Assisted Pectin Extraction from Cocoa Pod Husk
by Maya Sarah, Isti Madinah Hasibuan, Erni Misran and Seri Maulina
Molecules 2022, 27(19), 6544; https://doi.org/10.3390/molecules27196544 - 3 Oct 2022
Cited by 7 | Viewed by 2941
Abstract
Optimization of pectin extraction from cocoa pod husk was carried out to examine independent variables that affect the quality of pectin obtained and determine the best conditions for the extraction process. In this study, three independent variables thought to contribute to microwave-assisted pectin [...] Read more.
Optimization of pectin extraction from cocoa pod husk was carried out to examine independent variables that affect the quality of pectin obtained and determine the best conditions for the extraction process. In this study, three independent variables thought to contribute to microwave-assisted pectin extraction were used, namely, extraction time (20, 25, and 30 min), microwave power (180, 300, and 450 W), and citric acid concentration (2.5%, 5%, and 10%). Response surface methodology was applied using central composite design (CCD) to examine the effect of independent variables on the parameter measured. Among the seven parameters measured, namely, yield, temperature, moisture content, ash content, equivalent weight, methoxyl content, and galacturonic acid content, the statistical analysis test showed that the model equations that were suitable for predicting response values were temperature, moisture content, and ash content. Therefore, the optimization of conditions was only reviewed for these three parameters. Optimization results concluded that the factors that had the most significant effect on temperature, moisture content, and ash content were extraction time and microwave power. Optimal conditions for pectin extraction were at 30 min extraction time, 450 W microwave power, and 10% solvent concentration, resulting in a temperature of 104 °C, moisture content of 6%, and ash content of 8%. Other parameter values measured under these conditions were a yield of 21.10%, equivalent weight of 602.40 mg/mol, methoxyl content of 6.07%, and galacturonic acid content of 72.86%. Pectin extracted from cocoa pod husk using this method has the potential to be further applied, especially in the food and pharmaceutical industries. Full article
(This article belongs to the Special Issue Microwave Irradiation: As a Sustainable Tool)
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11 pages, 1320 KiB  
Communication
Microwave-Assisted Synthesis of 5′-O-methacryloylcytidine Using the Immobilized Lipase Novozym 435
by Sany Chea, Khac Toan Nguyen and Ruben R. Rosencrantz
Molecules 2022, 27(13), 4112; https://doi.org/10.3390/molecules27134112 - 26 Jun 2022
Cited by 1 | Viewed by 1772
Abstract
Nucleobase building blocks have been demonstrated to be strong candidates when it comes to DNA/RNA-like materials by benefiting from hydrogen bond interactions as physical properties. Modifying at the 5′ position is the simplest way to develop nucleobase-based structures by transesterification using the lipase [...] Read more.
Nucleobase building blocks have been demonstrated to be strong candidates when it comes to DNA/RNA-like materials by benefiting from hydrogen bond interactions as physical properties. Modifying at the 5′ position is the simplest way to develop nucleobase-based structures by transesterification using the lipase Novozym 435. Herein, we describe the optimization of the lipase-catalyzed synthesis of the monomer 5′-O-methacryloylcytidine with the assistance of microwave irradiation. Variable reaction parameters, such as enzyme concentration, molar ratio of the substrate, reaction temperature and reaction time, were investigated to find the optimum reaction condition in terms of obtaining the highest yield. Full article
(This article belongs to the Special Issue Microwave Irradiation: As a Sustainable Tool)
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12 pages, 1154 KiB  
Article
Validation of a Microwave-Assisted Derivatization Gas Chromatography-Mass Spectrometry Method for the Quantification of 2-Hydroxybutyrate in Human Serum as an Early Marker of Diabetes Mellitus
by María Rodríguez-García, Guillermo Fernández-Varo, Susana Hidalgo, Gabriela Rodríguez, Irene Martínez, Muling Zeng, Eudald Casals, Manuel Morales-Ruiz and Gregori Casals
Molecules 2022, 27(6), 1889; https://doi.org/10.3390/molecules27061889 - 15 Mar 2022
Cited by 1 | Viewed by 2172
Abstract
Circulating levels of 2-hydroxybutyrate (2HB) are highly related to glycemic status in different metabolomic studies. According to recent evidence, 2HB is an early biomarker of the future development of dysglycemia and type 2 diabetes mellitus and may be causally related to the progression [...] Read more.
Circulating levels of 2-hydroxybutyrate (2HB) are highly related to glycemic status in different metabolomic studies. According to recent evidence, 2HB is an early biomarker of the future development of dysglycemia and type 2 diabetes mellitus and may be causally related to the progression of normal subjects to impaired fasting glucose or insulin resistance. In the present study, we developed and validated a simple, specific and sensitive gas chromatography-mass spectrometry (GC-MS) method specifically intended to quantify serum levels of 2HB. Liquid–liquid extraction with ethyl acetate was followed by 2 min of microwave-assisted derivatization. The method presented acceptable accuracy, precision and recovery, and the limit of quantification was 5 µM. Levels of 2HB were found to be stable in serum after three freeze-thaw cycles, and at ambient temperature and at a temperature of 4 °C for up to 24 h. Extracts derivatized under microwave irradiation were stable for up to 96 h. No differences were found in 2HB concentrations measured in serum or plasma EDTA samples. In summary, the method is useful for a rapid, precise and accurate quantification of 2HB in serum samples assessed for the evaluation of dysglycemia and diabetes mellitus. Full article
(This article belongs to the Special Issue Microwave Irradiation: As a Sustainable Tool)
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27 pages, 3662 KiB  
Article
Multi-Year Study of the Chemical and Sensory Effects of Microwave-Assisted Extraction of Musts and Stems in Cabernet Sauvignon, Merlot and Syrah Wines from the Central Coast of California
by L. Federico Casassa, Paul A. Gannett, Nicholas B. Steele and Robert Huff
Molecules 2022, 27(4), 1270; https://doi.org/10.3390/molecules27041270 - 14 Feb 2022
Cited by 6 | Viewed by 1954
Abstract
Microwave technology (MW) was applied to musts and stems over three consecutive vintages in Cabernet Sauvignon, Merlot and Syrah wines from California (USA). Stems were added to musts at a rate of 50 and 100% (50% Stems and 100% Stems), either as untreated [...] Read more.
Microwave technology (MW) was applied to musts and stems over three consecutive vintages in Cabernet Sauvignon, Merlot and Syrah wines from California (USA). Stems were added to musts at a rate of 50 and 100% (50% Stems and 100% Stems), either as untreated or after MW (50% MW Stems and 100% MW Stems). Stem additions lowered ethanol (up to 1.15% v/v reduction), but increased pH (up to 0.16 units) and the tannin content of the wines. In 2016, tannins increased by 103% (100% Stems), and 124% (100% MW Stems). In 2017, tannins increased by 39% in stem-added Merlot wines and by 63% (100% Stems) and 85% (100% MW Stems) in Syrah wines. In 2018, tannins in Syrah wines increased by 250% (100% MW Stems) and by 743% (100% Stems). Wines made with 50% Stems exhibited intermediate tannin contents. Must MW increased flavonols (up to 278% in Syrah wines), monoglucosylated, acylated and anthocyanin-derived pigments. Stem additions reduced wine color and polymeric pigment formation in Syrah. Must MW decreased the perception of coarseness and herbaceous flavors in Merlot, whereas stem additions increased herbaceous aromas in Syrah. Despite higher tannin contents in stem-added wines, no concomitant increases in astringency were observed. Full article
(This article belongs to the Special Issue Microwave Irradiation: As a Sustainable Tool)
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