Separations, Volume 4, Issue 4 (December 2017) – 9 articles

Relative retention analysis and increment approach were applied for the comparison of triglycerides (TGs) retention of a broad set of plant seed oils with isomeric conjugated octadecatrienoic acids (CLnA) by reversed-phase HPLC for “propanol-2-acetonitrile” mobile phases and Kromasil 100-5C18 stationary phase with diode array detection (DAD) and mass spectrometric (MS) detection. The subjects of investigation were TGs of seed oils: Calendula officinalis, Catalpa ovata, Jacaranda mimosifolia, Centranthus ruber, Momordica charantia, Trichosanthes anguina, Punica granatum, Thladiantha dubia, Valeriana officinalis, and Vernicia montana. It was found that a sequence of elution of TGs of the same types is the same without any inversions for full range of mobile phase compositions: punicic (C18:3^9Z11E13Z) < jacaric (C18:3^8Z10E12Z) < catalpic (C18:3^9E11E13Z) < α-eleostearic (C18:3^9Z11E13E) < calendic (C18:3^8E10E12Z) < β-eleostearic (C18:3^9E11E13E) < all-E calendic (C18:3^8E10E12E) acids. TGs and fatty acid compositions were calculated for all oil samples. Regularities of solute retentions as a function of isomeric conjugated octadecatrienoic acid moiety structure are discussed. Thus, it was proven that it is possible to differentiate TGs of complex composition with moieties of all natural CLnA by retention control accomplished by electronic spectra comparison, even though there are only three types of electronic-vibration spectra for seven isomeric CLnA. Full article

Sample preparation has been recognized as a major step in the chemical analysis workflow. As such, substantial efforts have been made in recent years to simplify the overall sample preparation process. Major focusses of these efforts have included miniaturization of the extraction device; minimizing/eliminating toxic and hazardous organic solvent consumption; eliminating sample pre-treatment and post-treatment steps; reducing the sample volume requirement; reducing extraction equilibrium time, maximizing extraction efficiency etc. All these improved attributes are congruent with the Green Analytical Chemistry (GAC) principles. Classical sample preparation techniques such as solid phase extraction (SPE) and liquid-liquid extraction (LLE) are being rapidly replaced with emerging miniaturized and environmentally friendly techniques such as Solid Phase Micro Extraction (SPME), Stir bar Sorptive Extraction (SBSE), Micro Extraction by Packed Sorbent (MEPS), Fabric Phase Sorptive Extraction (FPSE), and Dispersive Liquid-Liquid Micro Extraction (DLLME). In addition to the development of many new generic extraction sorbents in recent years, a large number of molecularly imprinted polymers (MIPs) created using different template molecules have also enriched the large cache of microextraction sorbents. Application of nanoparticles as high-performance extraction sorbents has undoubtedly elevated the extraction efficiency and method sensitivity of modern chromatographic analyses to a new level. Combining magnetic nanoparticles with many microextraction sorbents has opened up new possibilities to extract target analytes from sample matrices containing high volumes of matrix interferents. The aim of the current review is to critically audit the progress of microextraction techniques in recent years, which has indisputably transformed the analytical chemistry practices, from biological and therapeutic drug monitoring to the environmental field; from foods to phyto-pharmaceutical applications. Full article

2-thioxo-3-pyrrolidinecarbaldehyde (TPC) is an important intermediate in the yellowing of Japanese pickles “takuan-zuke”. TPC has been reported to have antibacterial activity against bacteria causing food poisoning and microorganisms associated with the development of caries, as well as various physiological functions such as antimutagenicity. However, since TPC has high reactivity, robust quantitative analysis is difficult with the extraction method or pre-column derivatization method using 2,4-dinitrophenylhydrazine. In this study, a high-performance liquid chromatography (HPLC) method involving labeling with 4-(N,N-dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole (DBD-H) was developed for the determination of the level of TPC in takuan-zuke. DBD-TPC was successfully stabilized by adding a buffer solution to the reaction solution, which established continuous analysis by HPLC using an autosampler. The DBD-TPC calibration curve was linear in the range of 0.25–250 nmol/mL (final concentration) and showed a wide dynamic range. The lower limit of detection was 0.205 nmol/mL in TPC standard. The proposed method was successfully applied to the measurement of TPC in daikon-oroshi. The results reveal the possibility of determining the variation of TPC level in processed foods containing radish. We concluded that the proposed method is useful for evaluating the quality of processed radish products. Full article

Econea^®, or 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, is a new type of environmentally friendly anti-fouling compound used in the immersed coatings of commercial sea going vessels. This paper reports the development of a new analytical method to directly detect the active biocide Econea^® in an artificial sea water matrix using liquid chromatography mass spectrometry. The developed method is both rapid and sensitive, with a limit of detection of 0.05 μg/L and a limit of quantitation of 0.17 μg/L in artificial seawater. The subsequent developed method was then applied to investigate the biocide’s release from a commercially available Econea^® containing paint immersed in artificial sea water over a 45-day period. It was found that the average release rate of Econea^® from this paint was 4.3 ± 0.6 μg cm⁻² d⁻¹. Full article

The basic retention mechanisms of reversed-phase and hydrophilic-interaction liquid chromatography (HILIC) were quantitatively analyzed using simple molecular mechanics (MM) calculations. The model bonded phases were composed of an alkyl chain bonded to siloxane-like molecules. The head of the alkyl chain was a hydroxyl group, used to study retention mechanisms of HILIC. The standard analytes were benzoic acid, aniline, benzene, water, and acetonitrile. The molecular interaction (MI) energy values of the van der Waals (VW) force were predominant for the reversed-phase chromatography, and those of hydrogen bonding (HB) were predominant for HILIC. Up to 5 units of methylene affected the MI. Full article

Natural organic matter (NOM) in drinking water supplies significantly impacts on water supply quality and treatment, due to observed reactivity with many dissolved and particulate species. Several technologies are used nowadays to remove NOM from the water supply. The evolution of water-related directives, and progressively more restrictive standards for drinking water, however, call for the investigation of advanced, more efficient, and cost-effective water treatment processes. This paper contains a brief overview on the state-of-the-art methods for NOM removal from supply waters, and describes the experimental application of an advanced technology, tested and validated at the pilot scale on the water supply source of a town in Poland. The process allowed significant removal of natural organic matter (about 50% as Dissolved Organic Carbon) and turbidity (from 50% to 90%), however, these results requested significant additions of powdered activated carbon. The key to success of this type of process is a correct setup with the identification of optimal types and dosages of reagents. Based on the results of the tests conducted it is foreseeable that this technology could be used onsite, not only for removal of NOM, but also of other hard-to-tackle pollutants potentially contained in the freshwater supply and not presently considered. Full article

The grapevine moth (Lobesia botrana) is the most significant pest of viticulture. This article reports the development of an analytical method that allows the instrumental determination of the three main pheromone components of the pest ((E,Z)-7,9-dodecadien-1-yl acetate, (E,Z)-7,9-dodecadien-1-ol and (Z)-9-dodecen-1-yl acetate) in grape-related samples (must, table grape and wine grape). The combination of headspace, gas chromatography and mass spectrometry provides limits of detection in the range of 60–420 ng/Kg and precision, expressed as a relative standard deviation, better than 8.5%. This analytical approach is rapid and simple and opens a door to the study of the pest incidence on the final products. Full article

Yoichiro Ito introduced countercurrent chromatography (CCC) in 1966, reporting the separation of blood plasma cells with a sealed helical tube. Since then, CCC has been a fertile ground for instrumental and technical innovation. The key innovation of CCC was to use centrifugal forces to retain the stationary liquid phase in the column in such a way that it is able to interact dynamically with the mobile phase without any solid support. The broad diversity of countercurrent separation terminology reflects the innovative spirit of the field, as well as the global appeal of this technique. The selection of the appropriate biphasic liquid system is the core of the CCC technique. The CCC columns must generate the centrifugal field needed to maintain the liquid stationary phase; therefore, they cannot be a simple tube with frits at both ends. Rotors, motor, gears, spools, and rotating seals are very specific things that are not needed in a classical liquid chromatography column with a solid stationary phase. The differences between the two main types of CCC columns are described. The bases of the CCC theory are also given. Full article

In this paper, industrial dyes, Disperse Red and Disperse Orange, were studied as model pollutants to show the excellent performance of olive pomace (OP) in sequestering and recovering these dangerous dyes from wastewater. The nature of interactions involved between dyes and OP were inferred by changing several parameters: contact time, pomace dosage, pH and temperature values. Visible spectroscopy was mainly used to obtain the percentage of the removed dyes, while SEM (scanning electron microscopy), FTIR-ATR (Fourier transform infra-red spectroscopy in total attenuated reflectance), TG (thermo gravimetric) and XPS (X-ray photoelectron spectroscopy) analyses were used to carefully investigate the systems. The recovery of dyes was also obtained using glacial acetic acid, the auxiliary solvent used during the dyeing processes, enabling the recycling of both of the adsorbent material and dyes presenting a green and a wide-ranging strategic approach. Full article