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Special Issue "Analytical methods and Green chemistry: A Themed Issue in Honor of Professor Jacek Namieśnik"

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

Deadline for manuscript submissions: closed (20 February 2020).

Special Issue Editors

Prof. Dr. Mihkel Koel
E-Mail Website
Guest Editor
Department of Chemistry and Biotechnology, School of Science, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn, Estonia
Interests: porous materials; biosourced materials; green chemistry; carbonaceous materials; energy and environmental applications; chromatograpy; neoteric solvents (ionic liquids, supercritical fluids)
Special Issues and Collections in MDPI journals
Dr. Marek Tobiszewski
E-Mail Website
Guest Editor
Department of Analytical Chemistry, Chemical Faculty, Gdańsk University of Technology, Gdańsk, Poland
Interests: green analytical chemistry; environmental analytical chemistry; microextraction techniques; chemometrics; sustainability assessments; greenness assessments

Special Issue Information

Dear Colleagues,

text

Prof. Mihkel Koel and Dr Marek Tobiszewski, Valencia 2011

Greening analytical chemistry by making it more effective and precise is one of the critical concerns of analytical chemistry. In the Special Issue “Analytical methods and green chemistry”, we would like to collect up-to-date original and review papers in this field.

This Special Issue will honor the memory of prof. Jacek Namieśnik, who passed away on 14 April 2019. He was a very active analytical chemist, the author of more than 800 papers. He was particularly interested in the topic of greening analytical methods and was one of the most recognizable scientists working in this field.

For authors, this Special Issue is a chance to present their results or views on making analytical chemistry more environmentally friendly. It is especially important as chemical analysis still contributes to environmental pollution and occupational exposure. This Special Issue aims to highlight the trends in developing new methods and processes for analysis and share this knowledge with a broader audience in order to help increase the diffusion and influence of this important topic in the field of analytical chemistry. The topics of the papers to be submitted to this Special Issue are defined, but not limited, by the keywords presented below.

Prof. MIHKEL KOEL
Dr. Marek Tobiszewski
Guest Editors

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 papers will be 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 2000 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

  • Green analytical chemistry
  • Sample preparation
  • Green separation techniques
  • Alternative solvents
  • Electrochemical analysis
  • Sensors
  • Signal processing
  • Chemometrics

Published Papers (14 papers)

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Research

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Open AccessArticle
Searching for Low Molecular Weight Seleno-Compounds in Sprouts by Mass Spectrometry
Molecules 2020, 25(12), 2870; https://doi.org/10.3390/molecules25122870 - 22 Jun 2020
Cited by 2 | Viewed by 627
Abstract
A fit for purpose analytical protocol was designed towards searching for low molecular weight seleno-compounds in sprouts. Complementary analytical techniques were used to collect information enabling the characterization of selenium speciation. Conceiving the overall characterization of the behavior of selenium, inductively plasma optical [...] Read more.
A fit for purpose analytical protocol was designed towards searching for low molecular weight seleno-compounds in sprouts. Complementary analytical techniques were used to collect information enabling the characterization of selenium speciation. Conceiving the overall characterization of the behavior of selenium, inductively plasma optical mass spectrometry (ICP-MS) was used to determine the total selenium content in entire sprouts as well as in selected extracts or chromatographic fractions. Then, high-performance liquid chromatography combined with ICP-MS (HPLC-ICP-MS) was used to evaluate the presence of inorganic and organic seleno-compounds, with the advantages of being very sensitive towards selenium, but limited by available selenium standard compounds. Finally, ultra-high performance liquid chromatography electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-QqQ-MS/MS) and UHPLC-ESI-Orbitrap-MS/MS were used for the confirmation of the identity of selected compounds and identification of several unknown compounds of selenium in vegetable sprouts (sunflower, onion, radish), respectively. Cultivation of plants was designed to supplement sprouts with selenium by using solutions of selenium (IV) at the concentration of 10, 20, 40, and 60 mg/L. The applied methodology allowed to justify that vegetable sprouts metabolize inorganic selenium to a number of organic derivatives, such as seleno-methylselenocysteine (SeMetSeCys), selenomethionine (SeMet), 5′-seleno-adenosine, 2,3-DHP-selenolanthionine, Se-S conjugate of cysteine-selenoglutathione, 2,3-DHP-selenocysteine-cysteine, 2,3-DHP-selenocysteine-cysteinealanine, glutathione-2,3-DHP-selenocysteine, gamma-Glu-MetSeCys or glutamyl-glycinyl-N-2,3-DHP-selenocysteine. Full article
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Open AccessArticle
Investigation of the Dynamism of Nanosized SOA Particle Formation in Indoor Air by a Scanning Mobility Particle Sizer and Proton-Transfer-Reaction Mass Spectrometry
Molecules 2020, 25(9), 2202; https://doi.org/10.3390/molecules25092202 - 08 May 2020
Viewed by 569
Abstract
Terpenes are VOCs of particular importance, since they are emitted from a wide range of indoor sources and are considered to be precursors of Secondary Organic Aerosol (SOA) formation. It has been proven that SOA particles, especially nanosized ones, pose a threat to [...] Read more.
Terpenes are VOCs of particular importance, since they are emitted from a wide range of indoor sources and are considered to be precursors of Secondary Organic Aerosol (SOA) formation. It has been proven that SOA particles, especially nanosized ones, pose a threat to human health. In this research, experiments with the application of an environmental chamber and real-time measurement techniques were carried out to investigate in a complimentary way the formation of monoterpene oxidation products and nanosized SOA particles initiated by monoterpene ozonolysis. Proton-Transfer-Reaction Mass Spectrometry with a Time-Of-Flight analyzer (PTR-TOF-MS) and a Scanning Mobility Particle Sizer (SMPS) were applied to determine in real time the dynamism of the formation of the corresponding terpene ozonolysis products and submicron SOA particles. Results proved that firstly, oxidation products were formed, and then, they underwent nucleation and condensation, forming particles whose diameters grew with time. The oxidation products formed were different depending on the type of terpenes applied. The comparison of the results obtained during the experiments with gaseous standard mixtures and real samples commonly present and used in indoor air revealed that the diversified chemical composition of the emission source had implications for both the particle formation initiated by the oxidation of essential oil components and the chemical reactions occurring via the oxidation process. With the instrumentation utilized, the concentration changes at the level of a few ppbv could be monitored. Full article
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Open AccessArticle
Identification of Potential Extractables and Leachables in Cosmetic Plastic Packaging by Microchambers-Thermal Extraction and Pyrolysis-Gas Chromatography-Mass Spectrometry
Molecules 2020, 25(9), 2115; https://doi.org/10.3390/molecules25092115 - 30 Apr 2020
Viewed by 938
Abstract
Most container–content interaction studies are carried out through migration tests on end products or simulants involving generally toxic solvents. This study was conducted with the aim of identifying potential leachables from materials used in cosmetic plastic packaging by using two approaches based on [...] Read more.
Most container–content interaction studies are carried out through migration tests on end products or simulants involving generally toxic solvents. This study was conducted with the aim of identifying potential leachables from materials used in cosmetic plastic packaging by using two approaches based on solvent-free extraction, i.e., solid-phase microextraction sampling and pyrolyzer/thermal desorption coupled with gas chromatography mass spectrometry. Volatile and semi-volatile intentionally and non-intentionally added substances were detected in seven packaging samples made of polypropylene, polyethylene, and styrene-acrylonitrile copolymer. Thirty-five compounds related to the polymers industry or packaging industry were identified, among them phthalates, alkanes, styrene, and cyanide derivates including degradation products, impurities, additives, plasticizers, and monomers. All except eight belong to the Cramer class I. These thermodesorption techniques are complementary to those used for migration tests. Full article
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Open AccessArticle
2-Methyloxolane as a Bio-Based Solvent for Green Extraction of Aromas from Hops (Humulus lupulus L.)
Molecules 2020, 25(7), 1727; https://doi.org/10.3390/molecules25071727 - 09 Apr 2020
Cited by 3 | Viewed by 1206
Abstract
The potential of using the bio-based solvent 2-methyloxolane, also known as 2-methyltetrahydrofuran or 2-MeTHF, as an alternative to petroleum solvents such as hexane, was investigated for the extraction of volatile compounds from hop cones (Humulus lupulus L.). Lab scale extractions were coupled [...] Read more.
The potential of using the bio-based solvent 2-methyloxolane, also known as 2-methyltetrahydrofuran or 2-MeTHF, as an alternative to petroleum solvents such as hexane, was investigated for the extraction of volatile compounds from hop cones (Humulus lupulus L.). Lab scale extractions were coupled with in silico prediction of solutes solubility to assess the technical potential of this bio-based solvent. The predictive approach was performed using the simulation software COSMO-RS (conductor like screening model for real solvants) and showed that the 2-methyloxolane is as good as or better than hexane to solubilize the majority of aromas from hop cones. The experimental results indicated that the highest aroma yield was obtained with 2-methyloxolane with 20.2% while n-hexane was only able to extract 17.9%. The characterization of aromas extracted by the two solvents showed a similar composition, where lupulone was the main component followed by humulone. No selectivity of the solvents was observed for any of the major analytes. Finally, a sensory analysis was performed on the extracts, showing that both concretes using 2-methyloxolane and hexane have similar olfactory profiles. The results indicate that 2-methyloxolane could be a promising bio-based extraction solvent for hexane substitution. Full article
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Open AccessArticle
Direct Analysis of Psilocin and Muscimol in Urine Samples Using Single Drop Microextraction Technique In-Line with Capillary Electrophoresis
Molecules 2020, 25(7), 1566; https://doi.org/10.3390/molecules25071566 - 29 Mar 2020
Cited by 2 | Viewed by 611
Abstract
The fully automated system of single drop microextraction coupled with capillary electrophoresis (SDME-CE) was developed for in-line preconcentration and determination of muscimol (MUS) and psilocin (PSC) from urine samples. Those two analytes are characteristic active metabolites of Amanita and Psilocybe mushrooms, evoking visual [...] Read more.
The fully automated system of single drop microextraction coupled with capillary electrophoresis (SDME-CE) was developed for in-line preconcentration and determination of muscimol (MUS) and psilocin (PSC) from urine samples. Those two analytes are characteristic active metabolites of Amanita and Psilocybe mushrooms, evoking visual and auditory hallucinations. Study analytes were selectively extracted from the donor phase (urine samples, pH 4) into the organic phase (a drop of octanol layer), and re-extracted to the acidic acceptor (background electrolyte, BGE), consisting of 25 mM phosphate buffer (pH 3). The optimized conditions for the extraction procedure of a 200 µL urine sample allowed us to obtain more than a 170-fold enrichment effect. The calibration curves were linear in the range of 0.05–50 mg L−1, with the correlation coefficients from 0.9911 to 0.9992. The limit of detections was determined by spiking blank urine samples with appropriate standards, i.e., 0.004 mg L−1 for PSC and 0.016 mg L−1 for MUS, respectively. The limits of quantification varied from 0.014 mg L−1 for PSC and 0.045 mg L−1 for MUS. The developed method practically eliminated the sample clean-up step, which was limited only to simple dilution (1:1, v/v) and pH adjustment. Full article
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Open AccessArticle
Selective Extraction of Cannabinoid Compounds from Cannabis Seed Using Pressurized Hot Water Extraction
Molecules 2020, 25(6), 1335; https://doi.org/10.3390/molecules25061335 - 15 Mar 2020
Cited by 3 | Viewed by 2691
Abstract
Phytochemicals of Cannabis sativa mainly for the use in the different industries are that of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Pressurized hot water extraction (PHWE) is seen as an efficient, fast, green extraction technique for the removal of polar and semi-polar compounds from [...] Read more.
Phytochemicals of Cannabis sativa mainly for the use in the different industries are that of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Pressurized hot water extraction (PHWE) is seen as an efficient, fast, green extraction technique for the removal of polar and semi-polar compounds from plant materials. The PHWE technique was applied to extract cannabinoid compounds from Cannabis sativa seed. Response surface methodology was used to investigate the influence of extraction time (5–60 min), extraction temperature (50–200 °C) and collector vessel temperature (25–200 °C) on the recovery of delta-9-tetrahydrocannabinol (THC), cannabinol (CBN), cannabidiol (CBD), cannabichromene (CBG) and cannabigerol (CBC) from Cannabis sativa seed by PHWE. The identification and semi quantification of cannabinoid compounds were determined using GCXGC-TOFMS. The results obtained from different extractions show that the amount of THC and CBN was drastically decreasing in the liquid extract when the temperature rose from 140 to 160 °C in the extraction cell and the collector′s vessel. The optimal conditions to extract more CBD, CBC, and CBG than THC and CBN were set at 150 °C, 160 °C and 45 min as extraction temperature, the temperature at collector vessel, and the extraction time, respectively. At this condition, the predicted and experimental ratio of THCt (THC + CBN)/CBDt (CBD + CBC+ CBG) was found to be 0.17 and 0.18, respectively. Therefore, PHWE can be seen as an alternative to the classic extraction approach as the efficiency is higher and it is environmentally friendly. Full article
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Open AccessArticle
Searching for Solvents with an Increased Carbon Dioxide Solubility Using Multivariate Statistics
Molecules 2020, 25(5), 1156; https://doi.org/10.3390/molecules25051156 - 05 Mar 2020
Cited by 2 | Viewed by 887
Abstract
Ionic liquids (ILs) are used in various fields of chemistry. One of them is CO2 capture, a process that is quite well described. The solubility of CO2 in ILs can be used as a model to investigate gas absorption processes. The [...] Read more.
Ionic liquids (ILs) are used in various fields of chemistry. One of them is CO2 capture, a process that is quite well described. The solubility of CO2 in ILs can be used as a model to investigate gas absorption processes. The aim is to find the relationships between the solubility of CO2 and other variables—physicochemical properties and parameters related to greenness. In this study, 12 variables are used to describe a dataset consisting of 26 ILs and 16 molecular solvents. We used a cluster analysis, a principal component analysis, and a K-means hierarchical clustering to find the patterns in the dataset and the discriminators between the clusters of compounds. The results showed that ILs and molecular solvents form two well-separated groups, and the variables were well separated into greenness-related and physicochemical properties. Such patterns suggest that the modeling of greenness properties and of the solubility of CO2 on physicochemical properties can be difficult. Full article
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Open AccessArticle
Laboratory-Scale Preparation and Characterization of Dried Extract of Muirapuama (Ptychopetalum olacoides Benth) by Green Analytical Techniques
Molecules 2020, 25(5), 1095; https://doi.org/10.3390/molecules25051095 - 29 Feb 2020
Viewed by 1082
Abstract
This work reports on the preparation of a drying process from the ethanolic extract of Muirapuama and its characterization through green analytical techniques. The spray-drying processes were performed by using ethanolic extract in a ratio of 1:1 extract/excipient and 32 factorial design. [...] Read more.
This work reports on the preparation of a drying process from the ethanolic extract of Muirapuama and its characterization through green analytical techniques. The spray-drying processes were performed by using ethanolic extract in a ratio of 1:1 extract/excipient and 32 factorial design. The properties of dried powder were investigated in terms of total flavonoid content, moisture content, powder yield, and particle size distribution. An analytical eco-scale was applied to assess the greenness of the developed protocol. Ultra-high performance liquid chromatography (UHPLC)with reduced solvent consumption in the analysis was compared to the conventional HPLC method. A Fourier transform near-infrared (FT-NIR) spectroscopic method was applied based on the principal component scores for the prediction of extract/excipient mixtures and partial least squares regression model for quantitative analysis. NIR spectroscopy is an economic, powerful, and fast methodology for the detection of excipient in muirapuama dried extracts, generating no residue in the analysis. Scanning electron microscopy (SEM) images showed samples with a higher concentration of excipient, presenting better morphological characteristics and a lower moisture absorption rate. An eco-scale score value of 85 was achieved for UHPLC and 100 was achieved for NIR (excellent green analysis). Above all, these methods are rapid and green for the routine analysis of herbal medicines based on dried extracts. Full article
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Open AccessArticle
High Density Supercritical Carbon Dioxide for the Extraction of Pesticide Residues in Onion with Multivariate Response Surface Methodology
Molecules 2020, 25(4), 1012; https://doi.org/10.3390/molecules25041012 - 24 Feb 2020
Cited by 2 | Viewed by 1023
Abstract
The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this [...] Read more.
The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this problem, a selective and “green” supercritical fluid extraction method was developed, using neat carbon dioxide as a solvent at pressures of up to 800 bars. A Box–Behnken response surface experimental design was used, with the independent variables of density (0.70−1.0 g mL−1), temperature (40−70 °C), and volume (10−40 mL) of solvent, and the dependent variable of extracted amount of pesticides. The optimum extraction condition was found at the use of 29 mL of supercritical CO2 at 0.90 g mL−1 and 53 °C (corresponding to 372 bars of pressure). It was observed that increasing the density of CO2 significantly increased the extraction recovery of endrin and 2,4-dichlorodiphenyldichloroethane. Matrix-matched calibration curves showed satisfactory linearity (R2 ≥ 0.994), and LODs ranged from 0.2 to 2.0 ng g−1. Precision was lower than 11% and recoveries between 80%–103%. Thus, the developed method could efficiently be used for trace analysis of pesticides in complex food matrices without the use of organic solvents. Full article
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Open AccessArticle
Measurements of Activity Coefficients at Infinite Dilution for Organic Solutes in the Ionic Liquids N-Ethyl- and N-Octyl-N-methylmorpholinium Bis(trifluoromethanesulfonyl)imide. A Useful Tool for Solvent Selection
Molecules 2020, 25(3), 634; https://doi.org/10.3390/molecules25030634 - 01 Feb 2020
Cited by 4 | Viewed by 727
Abstract
In recent years, many papers describing ionic liquids (IL) as promising solvents in separation techniques have been published. The conscious choice of appropriate ionic liquid as absorption media in effective extraction of selected types of analytes requires deeper understanding of the analyte−IL interactions. [...] Read more.
In recent years, many papers describing ionic liquids (IL) as promising solvents in separation techniques have been published. The conscious choice of appropriate ionic liquid as absorption media in effective extraction of selected types of analytes requires deeper understanding of the analyte−IL interactions. Therefore, intensive research is conducted to determine the values of activity coefficient at infinite dilution, which allows us to characterize the nature of these interactions. Based on the inverse gas chromatography retention data, activity coefficients at infinite dilution γ 13 of 48 different organic compounds in the ionic liquids N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C2C1Mor][TFSI] and N-octyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C8C1Mor][TFSI] were determined. The measurements covered a broad range of volatile organic compounds, including n-alkanes, n-alkenes, n-alkynes, alcohols, aldehydes, ketones, aromatic compounds and common polar solvents, representing different types of interactions. Activity coefficients at infinite dilution were measured in the temperature range from 313.15 to 363.15 K. The excess partial molar enthalpies and entropies at infinite dilution were determined. Selectivity at infinite dilution was also calculated for exemplary separation processes in the hexane/benzene system. The obtained results were analyzed and compared with literature data for ionic liquids containing the same anion [TFSI]¯ and different cations. The study results indicate that some potential applications of the investigated ionic liquids in separation problems exist. Full article
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Open AccessArticle
Micelles Mediated Zone Fluidics Method for Hydrazine Determination in Environmental Samples
Molecules 2020, 25(1), 174; https://doi.org/10.3390/molecules25010174 - 31 Dec 2019
Cited by 2 | Viewed by 835
Abstract
An automated flow method for the determination of hydrazine based on the concept of zone-fluidics has been developed. The analyte reacts under flow conditions with p-dimethylamino benzaldehyde (25 mmol L−1) in micellar medium (100 mmol L−1 SDS) to form [...] Read more.
An automated flow method for the determination of hydrazine based on the concept of zone-fluidics has been developed. The analyte reacts under flow conditions with p-dimethylamino benzaldehyde (25 mmol L−1) in micellar medium (100 mmol L−1 SDS) to form a stable derivative (460 nm). Micelles mediated catalysis excludes the use of highly acidic environment typical for this kind of reaction. Following careful examination of chemical and instrumental variables, the method allows the determination of hydrazine at the low micromolar level (0.3–10 μmol L−1) in water samples. Real sample analyses (drinking and boiler feed water) resulted in satisfactory results in terms of accuracy with the percent recoveries being in the range of 82–114%. Full article
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Open AccessArticle
Ultrasound-Assisted Solvent Extraction of a Porous Membrane Packed Sample for the Determination of Tobacco-Specific Nitrosamines in the Replacement Liquids for E-Cigarettes
Molecules 2019, 24(24), 4618; https://doi.org/10.3390/molecules24244618 - 17 Dec 2019
Cited by 2 | Viewed by 742
Abstract
The content of tobacco-specific nitrosamines (TSNAs) possessing carcinogenic properties has been an important area of research since replacement liquids were introduced for e-cigarettes. A method for determining N′-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N′-nitrosoanatabine (NAT), and N′-nitrosoanabasine (NAB) in replacement liquids for [...] Read more.
The content of tobacco-specific nitrosamines (TSNAs) possessing carcinogenic properties has been an important area of research since replacement liquids were introduced for e-cigarettes. A method for determining N′-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N′-nitrosoanatabine (NAT), and N′-nitrosoanabasine (NAB) in replacement liquids for electronic cigarettes was developed using liquid chromatography–tandem mass spectrometry with electrospray ionisation (HPLC-ESI-MS/MS) in the multiple reaction monitoring mode. The sample preparation of replacement liquids was accomplished via the ultrasound-assisted solvent extraction of a porous membrane packed sample. The sample preparation proved to be successful in extracting the analytes, with recoveries from 87% to 105%, with coefficients of variation < 4.9%. Moreover, the linearity and limits of detection and quantitation (LOD, LOQ), together with repeatability and accuracy, were determined for the developed method. The proposed sample preparation and developed chromatographic method were successfully applied to the determination of TSNAs in 9 replacement liquid samples. The NNK and NNN were found to be most frequently detected (89 and 67%, respectively), with concentration ranges from 1.2–54.3 ng/mL and 4.1–30.2 ng/mL, respectively, while NAT was detected with frequency of 22% with range 1.7–2.5 ng/mL and NAB were found to be below the LOD in all samples. Full article
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Open AccessArticle
New Green Determination of Cu, Fe, Mn, and Zn in Beetroot Juices along with Their Chemical Fractionation by Solid-Phase Extraction
Molecules 2019, 24(20), 3645; https://doi.org/10.3390/molecules24203645 - 09 Oct 2019
Cited by 1 | Viewed by 848
Abstract
A new simple and rapid method for the determination of the total concentrations of Cu, Fe, Mn, and Zn in beetroot juices by flame atomic absorption spectrometry was developed and validated. The method included a very simple sample preparation, i.e., the two-fold dilution [...] Read more.
A new simple and rapid method for the determination of the total concentrations of Cu, Fe, Mn, and Zn in beetroot juices by flame atomic absorption spectrometry was developed and validated. The method included a very simple sample preparation, i.e., the two-fold dilution and acidification of the samples with HNO3 to 1 mol·L−1 and provided the precision within 2–3% and the trueness better than 6%. The method was applied for the rapid screening analysis of the different commercially available beetroot juices. The chemical fractionation of Cu, Fe, Mn, and Zn was also proposed by the two-column solid-phase extraction with the reversed-phase and cation exchange tubes. It was revealed that Cu, Fe, Mn, and Zn were primarily in beetroot juices in the form of the organically bound forms, contributing to the distinguished hydrophobic and residual fractions. The sums of the mean contributions of both fractions were up to 98% (Cu, Fe, Zn) and 100% (Mn), pointing out that no labile nor unbound forms of the studied metals were present in the matrix of beetroot juices. Full article
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Review

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Open AccessReview
Green Approaches to Sample Preparation Based on Extraction Techniques
Molecules 2020, 25(7), 1719; https://doi.org/10.3390/molecules25071719 - 09 Apr 2020
Cited by 3 | Viewed by 976
Abstract
Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require [...] Read more.
Preparing a sample for analysis is a crucial step of many analytical procedures. The goal of sample preparation is to provide a representative, homogenous sample that is free of interferences and compatible with the intended analytical method. Green approaches to sample preparation require that the consumption of hazardous organic solvents and energy be minimized or even eliminated in the analytical process. While no sample preparation is clearly the most environmentally friendly approach, complete elimination of this step is not always practical. In such cases, the extraction techniques which use low amounts of solvents or no solvents are considered ideal alternatives. This paper presents an overview of green extraction procedures and sample preparation methodologies, briefly introduces their theoretical principles, and describes the recent developments in food, pharmaceutical, environmental and bioanalytical chemistry applications. Full article
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