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Special Issue "Five Years of Separations: Feature Paper 2018"

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A special issue of Separations (ISSN 2297-8739).

Deadline for manuscript submissions: closed (31 January 2019) | Viewed by 46515

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Special Issue Editors

Prof. Dr. Victoria Samanidou

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Guest Editor

Laboratory of Analytical Chemistry, School of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: analytical chemistry; sample preparation; chromatography; HPLC; method validation; method development; separation science; food analysis; bioanalysis; environmental analysis; green analytical chemistry; sorptive extraction; microextraction techniques
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Prof. Dr. Rafael Lucena

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Guest Editor

School of Pharmacy, National and Kapodistrian University of Athens, 157 71 Athens, Greece
Interests: sample preparation; microextraction; nanoparticles and ionic liquid
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

To celebrate the fifth year of the publication of Separations, we have the honor to edit a new Special Issue. The Special Issue will collect original research papers from the frontiers of separation research, as well as review articles from prominent scholars, highlighting the state-of-the-art of separation science and technology. We invite researchers and technologists, whose work focuses on separations and related applications, to contribute with papers disseminating their excellent research findings. We consider that this issue can provide a multidisciplinary approach to separation techniques and it will be the best forum for sharing innovative ideas in the field.

We are looking forward to receiving your work.

Prof. Dr. Victoria F. Samanidou
Prof. Dr. Rafael Lucena
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 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. Separations is an international peer-reviewed open access monthly 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 2600 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.

Published Papers (10 papers)

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Research

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14 pages, 1231 KiB

Open AccessArticle

Miniaturized Matrix Solid-Phase Dispersion for the Analysis of Ultraviolet Filters and Other Cosmetic Ingredients in Personal Care Products

and

Separations 2019, 6(2), 30; https://doi.org/10.3390/separations6020030 - 10 Jun 2019

Cited by 11 | Viewed by 4015

Abstract

A method based on micro-matrix solid-phase dispersion (μ-MSPD) followed by gas-chromatography tandem mass spectrometry (GC–MS/MS) was developed to analyze UV filters in personal care products. It is the first time that MSPD is employed to extract UV filters from cosmetics samples. This technique provides efficient and low-cost extractions, and allows performing extraction and clean-up in one step, which is one of their main advantages. The amount of sample employed was only 0.1 g and the extraction procedure was performed preparing the sample-sorbent column in a glass Pasteur pipette instead of the classic plastic columns in order to avoid plastizicer contamination. Factors affecting the process such as type of sorbent, and amount and type of elution solvent were studied by a factorial design. The method was validated and extended to other families of cosmetic ingredients such as fragrance allergens, preservatives, plasticizers and synthetic musks, including a total of 78 target analytes. Recovery studies in real sample at several concentration levels were also performed. Finally, the green extraction methodology was applied to the analysis of real cosmetic samples of different nature. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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18 pages, 2202 KiB

Open AccessArticle

Treatment of Tannery Wastewater with Vibratory Shear-Enhanced Processing Membrane Filtration

Anastasios I. Zouboulis

Efrosyni N. Peleka

and

Anastasia Ntolia

Separations 2019, 6(2), 20; https://doi.org/10.3390/separations6020020 - 08 Apr 2019

Cited by 19 | Viewed by 4291

Abstract

The performance of a vibratory shear-enhanced process (VSEP) combined with an appropriate membrane unit for the treatment of simulated or industrial tannery wastewaters was investigated. The fundamental operational and pollution parameters were evaluated, i.e., the membrane type, the applied vibration amplitude, as well as the removal rates (%) of tannins, chemical oxygen demand (COD), N_total, turbidity and color. Regarding the system’s treatment efficiency, specific emphasis was given towards the removal of organics (expressed as COD values), suspended solids (SS), conductivity (as an index of dissolved solids’ presence) and total nitrogen. The removal of organic matter in terms of COD exceeded 75% for all the examined cases. The quality of treated wastewater was affected not only by the membrane specific type (i.e., the respective pore diameters), but also by the applied vibration amplitude. Furthermore, an average 50% removal rate, regarding the aforementioned parameters, was observed both for the simulated and the industrial tannery wastewaters during the microfiltration (MF) experiments. That removal rate was further increased up to 85%, when ultrafiltration (UF) was applied, and up to 99% during the Reverse Osmosis (RO) experiments, considering the maximum applied vibration amplitude (31.75 mm). Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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7 pages, 874 KiB

Open AccessArticle

Dissolution Testing of Single- and Dual-Component Thyroid Hormone Supplements

Samantha L. Bowerbank

Michelle G. Carlin

and

John R. Dean

Separations 2019, 6(1), 18; https://doi.org/10.3390/separations6010018 - 26 Mar 2019

Cited by 2 | Viewed by 2976

Abstract

A method for the analysis of thyroid hormones by liquid chromatography-mass spectrometry was used for the dissolution testing of single- and dual-component thyroid hormone supplements via a two-stage biorelevant dissolution procedure. The biorelevant media consisted of fasted-state simulated gastric fluid and fasted state simulated intestinal fluid at 37 °C, and was investigated using an internationally recognized protocol. The dissolution profiles showed consistent solubilization for both single- and dual-component batches at pH 6.5 in the fasted-state simulated intestinal fluid. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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19 pages, 9747 KiB

Open AccessArticle

Estimating Diphenylamine in Gunshot Residues from a New Tool for Identifying both Inorganic and Organic Residues in the Same Sample

Ana Isabel Argente-García

Lusine Hakobyan

Carmen Guillem

and

Pilar Campíns-Falcó

Separations 2019, 6(1), 16; https://doi.org/10.3390/separations6010016 - 19 Mar 2019

Cited by 12 | Viewed by 4014

Abstract

A method involving the collection and determination of organic and inorganic gunshot residues on hands using on-line in-tube solid-phase microextraction (IT-SPME) coupled to miniaturized capillary liquid chromatography with diode array detection (CapLC-DAD) and scanning electron microscopy coupled to energy dispersion X-ray (SEM-EDX), respectively, for quantifying both residues was developed. The best extraction efficiency for diphenylamine (DPA) as the main target among organic residues was achieved by using a dry cotton swab followed by vortex-assisted extraction with water, which permits preservation of inorganic residues. Factors such as the nature and length of the IT-SPME extractive phase and volume of the sample processed were investigated and optimized to achieve high sensitivity: 90 cm of TRB-35 (35% diphenyl, 65% polydimethylsiloxane) capillary column and 1.8 mL of the processed sample were selected for the IT-SPME. Satisfactory limit of detection of the method for analysis of DPA deposited on shooters’ hands (0.3 ng) and precision (intra-day relative standard deviation, 9%) were obtained. The utility of the described approach was tested by analyzing several samples of shooters’ hands. Diphenylamine was found in 81% of the samples analyzed. Inorganic gunshot residues analyzed by SEM-EDX were also studied in cotton swab and lift tape kit samplers. Optical microscopy was used to see the inorganic gunshot residues in the cotton swab samplers. The lift tape kits provided lesser sensitivity for DPA than dry cotton swabs—around fourteen times. The possibility of environmental and occupational sources could be eliminated when DPA was found together with inorganic residues. Then, the presence of inorganic and organic residues in a given sample could be used as evidence in judicial proceedings in the forensic field. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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12 pages, 1658 KiB

Open AccessArticle

Retention Behaviour of Alkylated and Non-Alkylated Polycyclic Aromatic Hydrocarbons on Different Types of Stationary Phases in Gas Chromatography

Ewa Skoczyńska

and

Jacob de Boer

Separations 2019, 6(1), 7; https://doi.org/10.3390/separations6010007 - 29 Jan 2019

Cited by 9 | Viewed by 4003

Abstract

The gas chromatographic retention behaviour of 16 polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs on a new ionic liquid stationary phase, 1,12-di(tripropylphosphonium) dodecane bis(trifluoromethanesulfonyl)imide (SLB^®-ILPAH) intended for the separation of PAH mixtures, was compared with the elution pattern on more traditional stationary phases: a non-polar phenyl arylene (DB-5ms) and a semi-polar 50% phenyl dimethyl siloxane (SLB PAHms) column. All columns were tested by injections of working solutions containing 20 parental PAHs from molecular weight of 128 to 278 g/mol and 48 alkylated PAHs from molecular weight of 142 to 280 g/mol on a one dimensional gas chromatography-mass spectrometry (GC-MS) system. The SLB PAHms column allowed separation of most isomers. The SLB^®-ILPAH column showed a rather different retention pattern compared to the other two columns and, therefore, provided a potential for use in comprehensive two-dimensional GC (GC×GC). The ionic liquid column and the 50% phenyl column showed good thermal stability with a low bleed profile, even lower than that of the phenyl arylene “low bleed” column. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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13 pages, 1286 KiB

Open AccessArticle

Insights into the Mechanism of Separation of Bisphosphonates by Zwitterionic Hydrophilic Interaction Liquid Chromatography: Application to the Quantitation of Risedronate in Pharmaceuticals

and

Separations 2019, 6(1), 6; https://doi.org/10.3390/separations6010006 - 22 Jan 2019

Cited by 6 | Viewed by 4356

Abstract

Bisphosphonates are used to treat various skeletal disorders, as they modulate bone metabolism by inhibition of the osteoclast-mediated bone resorption. These compounds are both polar and ionic, and therefore, by using reversed phase liquid chromatography are eluted rapidly. Hydrophilic interaction liquid chromatography (HILIC) is an advantageous technique for the separation and analysis of polar molecules. As the elution order in HILIC is reversed to reversed phase liquid chromatography, a reasonable retention and selectivity for polar compounds is expected. In this work the retention mechanism of three bisphosponates, namely risedronate, tiludronate and zoledronate, was investigated under zwitterionic HILIC conditions. The key factors influencing the retention of the analytes on a zwitterionic ZIC®-pHILIC column (150.0 × 2.1 mm i.d., 200 Å, 3.5 μm) have been systematically investigated. It was found that apart from partition, electrostatic repulsions play an important role in the retention of bisphosphonates. Peak tailing of risedronate and zoledronate was improved by the addition of sodium pyrophosphate in the mobile phase. A zwitterionic hydrophilic interaction liquid chromatography-photodiode array (HILIC-PDA) method was further optimized and fully validated to quantitate risedronate in commercial film-coated tablets. The calibration curves for risedronate showed good linearity (r > 0.9991) within the calibration range tested. The intra- and inter-day coefficient of variation (CV) values was less than 0.6%, while the relative percentage error (%Er) was less than −2.3%. Accelerated stability studies of risedronate conducted under several degradation conditions including hydrolysis, oxidation and heat demonstrated the selectivity of the procedure. A short-run analysis of not more than 6 min allowed the analysis of large samples per day. The applicability of the method for the quantitation of risedronate was demonstrated via the analysis of commercial tablets containing this compound. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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14 pages, 1709 KiB

Open AccessArticle

Multiple-stage Precursor Ion Separation and High Resolution Mass Spectrometry toward Structural Characterization of 2,3-Diacyltrehalose Family from Mycobacterium tuberculosis

Cheryl Frankfater

Robert B. Abramovitch

and

Separations 2019, 6(1), 4; https://doi.org/10.3390/separations6010004 - 15 Jan 2019

Cited by 7 | Viewed by 3581

Abstract

Mass spectrometry (MS)-based precursor ion isolation, collision-induced dissociation (CID) fragmentation, and detection using linear ion-trap multiple-stage mass spectrometry (LIT MSⁿ) in combination with high resolution mass spectrometry (HRMS) provides a unique tool for structural characterization of complex mixture without chromatographic separation. This approach permits not only separation of various lipid families and their subfamilies, but also stereoisomers, thereby, revealing the structural details. In this report, we describe the LIT MSⁿ approach to unveil the structures of a 2,3-diacyl trehalose (DAT) family isolated from the cell envelope of Mycobacterium tuberculosis, in which more than 30 molecular species, and each species consisting of up to six isomeric structures were found. LIT MSⁿ performed on both [M + Na]⁺ and [M + HCO₂]⁻ ions of DAT yield complimentary structural information for near complete characterization of the molecules, including the location of the fatty acyl substituents on the trehalose backbone. This latter information is based on the findings of the differential losses of the two fatty acyl chains in the MS² and MS³ spectra; while the product ion spectra from higher stage LIT MSⁿ permit confirmation of the structural assignment. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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12 pages, 2239 KiB

Open AccessArticle

Hydrophilic Monomethyl Auristatin E Derivatives as Novel Candidates for the Design of Antibody-Drug Conjugates

Filip S. Ekholm

Suvi-Katriina Ruokonen

and

Separations 2019, 6(1), 1; https://doi.org/10.3390/separations6010001 - 24 Dec 2018

Cited by 11 | Viewed by 4645

Abstract

Antibody-drug conjugates (ADCs) are promising state-of-the-art biopharmaceutical drugs for selective drug-delivery applications and the treatment of diseases such as cancer. The idea behind the ADC technology is remarkable as it combines the highly selective targeting capacity of monoclonal antibodies with the cancer-killing ability of potent cytotoxic agents. The continuous development of improved ADCs requires systematic studies on the nature and effects of warhead modification. Recently, we focused on the hydrophilic modification of monomethyl auristatin E (MMAE), the most widely used cytotoxic agent in current clinical trial ADCs. Herein, we report on the use of micellar electrokinetic chromatography (MEKC) for studying the hydrophobic character of modified MMAE derivatives. Our data reveal a connection between the hydrophobicity of the modified warheads as free molecules and their cytotoxic activity. In addition, MMAE-trastuzumab ADCs were constructed and evaluated in preliminary cytotoxic assays. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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9 pages, 3230 KiB

Open AccessFeature PaperArticle

A Low-Cost Approach Using Diatomaceous Earth Biosorbent as Alternative SPME Coating for the Determination of PAHs in Water Samples by GC-MS

Naysla Paulo Reinert

Camila M. S. Vieira

Cristian Berto Da Silveira

Dilma Budziak

and

Eduardo Carasek

Separations 2018, 5(4), 55; https://doi.org/10.3390/separations5040055 - 20 Nov 2018

Cited by 9 | Viewed by 3206

Abstract

In this study, the use of recycled diatomaceous earth as the extraction phase in solid phase microextraction (SPME) technique for the determination of polycyclic aromatic hydrocarbons (PAHs) in river water samples, with separation/detection performed by gas chromatography-mass spectrometry (GC-MS), is proposed. The optimized extraction conditions are extraction time 70 min at 80 °C with no addition of salt. The limits of quantification were close to 0.5 μg L⁻¹ with RSD values lower than 25% (n = 3). The linear working range was 0.5 μg L⁻¹ to 25 μg L⁻¹ for all analytes. The method was applied to samples collected from the Itajaí River (Santa Catarina, Brazil) and the RSD values for repeatability and reproducibility were lower than 15% and 17%, respectively. The efficiency of the recycled diatomaceous earth fiber was compared with that of commercial fibers and good results were obtained, confirming that this is a promising option to use as the extraction phase in SPME. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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Review

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19 pages, 436 KiB

Open AccessReview

Applications of Gas Chromatography for the Analysis of Tricyclic Antidepressants in Biological Matrices

Natalia Manousi

and

Victoria F. Samanidou

Separations 2019, 6(2), 24; https://doi.org/10.3390/separations6020024 - 29 Apr 2019

Cited by 6 | Viewed by 10416

Abstract

Tricyclic antidepressant drugs (TCAs) are a main category of antidepressants, which are until today widely used for the treatment of psychological disorders due to their low cost and their high efficiency. Therefore, there is a great demand for method development for the determination of TCAs in biofluids, especially for therapeutic drug monitoring. Gas chromatography (GC) was the first chromatographic technique implemented for this purpose. With the recent development in the field of sample preparation, many novel GC applications have been developed. Herein, we aim to report the recent application of GC for the determination of tricyclic antidepressants in biofluids. Emphasis is given to novel extraction techniques and novel materials used for sample preparation. Full article

(This article belongs to the Special Issue Five Years of Separations: Feature Paper 2018)

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