Separations, Volume 5, Issue 2 (June 2018) – 13 articles

Bisphenol A (BPA), 4-nonylphenol (4NP), estradiol (E₂), and ethinylestradiol (EE₂) are considered as endocrine disruptors or mutagens. These compounds are commonly called endocrine disrupter chemicals (EDCs). BPA and 4NP are widely used as plastic additives, lacquers, resins, or surfactants, while E₂ is one of the predominant female sex hormones during the reproductive years, and EE₂ is an estrogen derived from estradiol, used in the production of contraceptive pills. All of these can be usually found in wastewater. In Mexico, it is common for water from rivers, lakes, and canyons to be reused for different purposes. Unfortunately, there is little information on the concentration of many of the pollutants present in such bodies of water. To determine the presence of these compounds in samples of wastewater in the Apatlaco River, an accurate and reproducible method was developed by coupling gas chromatography to mass spectrometry (GC-MS). A solid-phase extraction with Chromabond RP-18 cartridges was carried out, and the elution was performed with an acetone/methanol mixture. After isolation, the solvent was removed and a silylation step was carried out using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Recoveries for spiked samples were between 71.8% and 111.0%. The instrumental limits of detection (IDL) ranged between 24.7 and 37.0 ng mL⁻¹. In total, 16 samples were taken in 2015 at the microbasin of the Apatlaco River, located in the state of Morelos. The maximum concentrations found were 4NP (85.5 ng mL⁻¹), BPA (174.6 ng mL⁻¹), E₂ 103.6 (ng mL⁻¹), and EE₂ (624.3 ng mL⁻¹). Full article

This work describes a holistic archaeometric approach to ancient Macedonian specimens. In the region of the ancient city Lete, the deceased members of a rich and important family were interred in a cluster of seven tombs (4th century BC). Among the numerous grave goods, there was also a set of metal containers preserving their original content. The physico-chemical analysis of the containers and their contents was performed in order to understand the purpose of their use. For the containers, Energy Dispersive micro-X-Ray Fluorescence (EDμXRF) spectroscopy was implemented taking advantage of its non-invasive character. The case (B35) and the small pyxis (B37) were made of a binary Cu-Sn alloy accompanied by a slight amount of impurities (Fe, Pb, As) and the two miniature bowls were made of almost pure Cu. For the study of the contents, a combination of EDμXRF, X-Ray Diffraction (XRD), and Gas Chromatography—Mass Spectrometry (GC-MS) was carried out. Especially for the extraction of the volatile compounds, the Solid Phase Micro-Extraction (SPME) technique was used in the headspace mode. Because of the detection of Br, High Pressure Liquid Chromatography coupled to a Diode-Array-Detector (HPLC-DAD) was implemented, confirming the existence of the ancient dye shellfish purple (porphyra in Greek). The analytical results of the combined implementation of spectrometric and chromatographic analytical techniques of the metal containers and their contents expand our knowledge about the pharmaceutical practices in Macedonia during the 4th century BC. Full article

Antibiotics are a common practice in veterinary medicine, mainly for therapeutic purposes. Sectors of application include livestock farming, aquacultures, and bee-keeping, where bacterial infections are frequent and can be economically damaging. However, antibiotics are usually administered in sub-therapeutic doses as prophylactic and growth promoting agents. Due to their excessive use, antibiotic residues can be present in foods of animal origin, which include meat, fish, milk, eggs, and honey, posing health risks to consumers. For this reason, authorities have set maximum residue limits (MRLs) of certain antibiotics in food matrices, while analytical methods for their determination have been developed. This work focuses on antibiotic extraction and determination, part of which was presented at the “1st Conference in Chemistry for Graduate, Postgraduate Students and PhD Candidates at the Aristotle University of Thessaloniki”. Taking a step further, this paper is a review of the most recent sample preparation protocols applied for the extraction of sulfonamide antibiotics from food samples and their determination with high-performance liquid chromatography (HPLC), covering a five-year period. Full article

A methodology for making consistent studies of outliers of non-climacteric melon volatile organic compounds at harvest is reported. The juice was squeezed from the fruit of the ‘Piel de sapo’ cultivar harvested during two consecutive seasons and the aroma volatiles were extracted by headspace solid phase microextraction and measured by gas chromatography coupled to mass-spectrometry. A deconvolution analysis was performed to obtain volatile organic compounds. For multivariate the reliable identification of outliers, compound classes were studied as a percentage of total area counts of the melon compounds identified in the chromatogram by principal component analysis and partial least-squares discriminant analysis, and then verified by correlation analysis, box-whisker plot, and formal tests for univariate outliers. Principal component analysis was the key methodology for selecting outliers in variables that mostly did not follow a normal distribution. The presence of an excess in terms of relative percentage of area and the diversity of minor compounds such as alcohols, terpenes, acids, among others, are usually a sign of anomalous data that can be considered outliers in the aroma of this non-climacteric cultivar. This multivariate approach removed outliers, but kept the variability of aroma among the samples of every cultivar. Full article

It is known that a charge is generated in water and protein solutions upon their motion; this phenomenon is also observed in analytical systems for atomic force microscopy (AFM)-based fishing. At that, the efficiency of protein fishing correlates with the value of charge, generated upon the motion of the analyzed solution. Earlier, we demonstrated that a pulsed electric field can well be used for the enhancement of the efficiency of AFM-based fishing of low-abundant protein. In this paper, we have demonstrated the influence of a pulsed electric field on the stimulation of the electric charge generation in a solution of low-abundant proteins observed in the injector part of an AFM-based fishing system at 23 °C and 38 °C. Taking this effect into account is important for the development of novel highly sensitive flow-based diagnostic systems, as well as for the development of models describing the influence of a pulsed electric field on pathological processes in the body, hemodynamics, and physicochemical properties of solutions. Full article

Momilactones A and B (MA and MB, respectively) are phytoalexins and plant growth inhibitors available in rice husks. However, to date, the isolation and purification of the two compounds have been complicated, laborious, and less effective. The present study was conducted to establish a protocol to simplify and optimize quantities of MA and MB by combinations of ethyl acetate (EtOAc), distilled water, methanol (MeOH), temperature, and pressure for extractions. At a temperature of 100 °C, combined with EtOAc and MeOH 100%, MA and MB were enriched in greater quantities than non-treated rice husks, of which MB was much augmented than MA. The EtOAc extract obtained from samples dried at 100 °C for 1 h, then placed in MeOH 100% for 1 week, provided maximum yields of MA [58.76 µg/g dry weight (DW)] and MB (104.43 µg/g DW). The use of pressure effectively enhanced yields of MA (17.90–26.26 µg/g DW) and MB (40.78–71.0 µg/g DW). The actual purified amounts of MA and MB increased by 5 and 15 folds, respectively. The use of either sole distilled water or MeOH ≤ 50% at any temperature did not successfully isolate both MA and MB. The yield optimization aids to easier and more productive purification of the two compounds, and thus extends researches on biological activities of MA and MB, including pharmaceutical and medicinal properties. Full article

In this paper, a strategy for structured monitoring of surface modifications to control protein adsorption to membrane structures is presented. The already established on-surface enzymatic digestion (oSED) method combined with nano-liquid chromatography and tandem mass spectrometry (LC-MS/MS) analysis was employed for the analysis of proteins in ventricular cerebrospinal fluid (vCSF) from neurointensive care patients. Protein adsorption was studied by in-situ sampling in a temporally resolved manner on both immobilized native and Pluronic-deactivated membranes. Deactivation was significantly reducing the protein adsorption but it also induced novel selective properties of the surface. The proposed versatile strategy will facilitate protein-biomaterial, protein-polymer, protein-protein interaction studies in the future. Full article

The separation process within a mechanical recycling plant plays a major role in the context of the production of high-quality secondary raw materials and the reduction of extensive waste disposal in landfills. Traditional plants for plastic separation employ dry or wet processes that rely on the different physical properties among the polymers. The hydraulic separator is a device employing a wet technology for particle separation. It allows the separation of two-polymer mixtures into two products, one collected within the instrument and the other one expelled through its outlet ducts. Apparatus performance were analyzed as a function of fluid and solid flow rates, flow patterns developing within the apparatus, in addition to the density, shape, and size of the polymers. For the hydraulic configurations tested, a two-way coupling takes place where the fluid exerts an influence on the plastic particles and the opposite occurs too. The interaction between the solid and liquid phases determines whether a certain polymer settles within the device or is expelled from the apparatus. Tests carried out with samples of increasing volumes of solid particles demonstrate that there are no significant differences in the apparatus effectiveness as far as a two-way interaction takes place. Almost pure concentrates of Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC), and Polycarbonate (PC) can be obtained from a mixture of traditional polymers. Tests conducted on Polylactic Acid (PLA) and Mater-Bi^® samples showed that the hydraulic separator can be effectively employed to separate bio-plastics from conventional plastics with remarkable grade and recovery. Full article

Silk fibroin nanoparticles were prepared in the present study based on phase separation between silk fibroin and polyvinyl alcohol. The drug encapsulation efficiency of the prepared nanoparticles was examined at a range of concentrations from 10 ppm to 500 ppm for pramipexole, curcumin, and propranolol hydrochloride. Silk fibroin nanoparticles encapsulated with propranolol presented the highest drug release profile. In order to improve the drug encapsulation efficiency and drug release performance, a modification of silk fibroin nanoparticles with bovine serum albumin and magnetic nanoparticles was tried. The modification was found to improve the drug encapsulation and release of the modified nanoparticles. Bovine-serum-modified nanoparticles presented the best improvement. Full article

Virgin olive oil is unique among plant oils for its high levels of oleic acid, and the presence of a wide range of minor components, which are responsible for both its health-promoting properties and characteristic aroma, and only produced when olives are crushed during the industrial process used for oil production. The genetic variability of the major volatile compounds comprising the oil aroma was studied in a representative sample of olive cultivars from the World Olive Germplasm Collection (IFAPA, Cordoba, Spain), by means of the headspace solid-phase microextraction/gas chromatography–mass spectrometry–flame ionization detection (HS-SPME/GC-MS-FID). The analytical data demonstrated that a high variability is found for the content of volatile compounds in olive species, and that most of the volatile compounds found in the oils were synthesized by the enzymes included in the so-called lipoxygenase pathway. Multivariate analysis allowed the identification of cultivars that are particularly interesting, in terms of volatile composition and presumed organoleptic quality, which can be used both to identify old olive cultivars that give rise to oils with a high organoleptic quality, and in parent selection for olive breeding programs. Full article

Guayule (Parthenium argentatum Gray) is a shrub native to the arid regions of Mexico. In the last decades, significant attention to its cultivation has arisen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass also contains high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e., the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for the Guayule shrub; in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins may possess significant biological properties (e.g., antibacterial and anticancer activities), in close analogy with those shown by sesquiterpene lactones contained in many other species of Parthenum genus. As a matter of fact, guayulins A and B play an important role in the synthesis of antineoplastics used in breast cancer treatment. In this contribution we propose an original and validated RP-HPLC approach to the simultaneous quantification of guayulins A, B, C and D. The procedure of resin extraction from Guayule biomass has been optimized in terms of both extraction method and solvent. RP-HPLC separation has been accomplished by an Ascentis^® C18 column under isocratic elution with a 80:20 (v:v) acetonitrile:water mixture. Validation was carried out in terms of limits of detection and quantification, linearity, precision, and trueness. Finally, the method was tested with a number of fresh and seasoned samples of spontaneous Guayule shrub from Mexico. Full article

This study used the results of breakthrough experiments to elucidate the mechanism of cesium adsorption on carbonized rice hull and beech sawdust. The shape of the breakthrough curves and the substance eluted from the carbonized rice hull and beech sawdust were investigated for various flow speeds and concentrations of the solute through the adsorbent layer. The ratio of the Cs concentration at the column outlet (C) to that at the inlet (C₀), C/C₀, was calculated to evaluate the mechanism. It was found that carbonized rice hull could slowly adsorb Cs as the Cs solution passed through the fixed-bed layer. On the other hand, beech sawdust could rapidly adsorb Cs upon contact with the Cs solution. It was, therefore, suggested that the two materials adsorbed Cs through an ion-exchange reaction with potassium on their respective surfaces. Moreover, the shape of the breakthrough curve of beech sawdust changed as the Cs concentration at the column inlet was varied. This phenomenon was presumably caused by a factor other than the swelling or contraction of the adsorption layer. Further analysis revealed that the breakthrough curve of beech sawdust is indicative of an overshoot phenomenon when cesium was adsorbed by beech sawdust. Full article

Interest in new products from aromatic plants as medical and nutritional compounds is increasing. The aim of this work was to apply different extraction methods, including the use of supercritical carbon dioxide extraction, and to test the antioxidant activity of basil (Ocimum basilicum L.) extracts. In vitro efficacy assessments were performed using enzymatic assays. Essential oil obtained by hydrodistillation and volatile oil obtained from supercritical fluid extraction were analyzed by gas chromatography to quantify components. The total phenolic content in the extracts ranged from 35.5 ± 2.9 to 85.3 ± 8.6 mg of gallic acid equivalents and the total flavonoid content ranged from 35.5 ± 2.9 to 93.3 ± 3.9 micromole catechin equivalents per gram of dry weight of extract. All the extracts showed an antioxidant activity with 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS), and the reducing power test. Extracts obtained from methanol had a higher antioxidant capacity per the DPPH test results (IC₅₀ = 3.05 ± 0.36 mg/mL) and the reducing power test assay 306.8 ± 21.8 μmol of trolox equivalents per gram of extract (TE/g) compared with ethanolic or supercritical fluid extracts. However, using the ABTS assay, the extract obtained by supercritical fluid extraction had a higher antioxidant capacity with an IC₅₀ of 1.74 ± 0.05 mg/mL. Finally, the examined extracts showed practically no acetylcholinesterase (AChE) inhibitory capacity and a slight inhibitory activity against tyrosinase. Full article