Separations, Volume 4, Issue 3 (September 2017) – 5 articles

Active development of compact analytical instruments suitable for point-of-care testing (POCT) requires optimization of existing methods. To aid the development of capillary gel electrophoresis instruments for POCT, we attempted to separate polymerase chain reaction products (small DNAs) using a short, fused silica capillary coated with an acrylamide (AM)/acrylic acid (AA) copolymer (poly(AM-co-AA)). To realize the high capability of this capillary to separate small DNAs, the magnitude of electroosmotic flow (EOF) was controlled by varying the content of negatively charged AA in the copolymer, which significantly affected the separation ability. At an AA content ≥3.75 mol %, sample DNAs could not be injected into the copolymer-coated capillary owing to strong EOF, whereas a 100 bp DNA ladder sample was successfully separated at an AA content of ≤3.5 mol %, showing that even slight AA content variations impact DNA flow. EOF values measured using a neutral coumarin 334 solution suddenly decreased at an AA content of 3.5 mol % relative to those at an AA content of ≥3.75 mol %. Theoretical plate values revealed that an AA content of 2.75 mol % was optimal for separating ladder DNAs with sizes ≥600 bp. Hence, EOF control achieved by varying the amount of negatively charged AA in the poly(AM-co-AA) coating can promote further development of short capillaries for POCT applications. Full article

In this work, a method for capillary electrophoresis (CE) hyphenated to a high-resolution mass spectrometer was presented for monitoring the stability of anions in ionic liquids (ILs) and in commonly used lithium ion battery (LIB) electrolytes. The investigated ILs were 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR13TFSI) and 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI). The method development was conducted by adjusting the following parameters: buffer compositions, buffer concentrations, and the pH value. Also the temperature and the voltage applied on the capillary were optimized. The ILs were aged at room temperature and at 60 °C for 16 months each. At both temperatures, no anionic decomposition products of the FSI− and TFSI− anions were detected. Accordingly, the FSI− and TFSI− anions were thermally stable at these conditions. This method was also applied for the investigation of LIB electrolyte samples, which were aged at 60 °C for one month. The LP30 (50/50 wt. % dimethyl carbonate/ethylene carbonate and 1 M lithium hexafluorophosphate) electrolyte was mixed with the additive 1,3-propane sultone (PS) and with one of the following organophosphates (OP): dimethyl phosphate (DMP), diethyl phosphate (DEP), and triethyl phosphate (TEP), to investigate the influence of these compounds on the formation of OPs. Full article

Porous alumosilicate aggregate, namely perlite, was used as an alternative material in wastewater treatments for the selective removal of ionic pollutants such as lead which is present in industrial wastewaters and toxic at relatively low concentrations. Metal retention was investigated by single metals and multispecies equilibrium isotherms (batch system) and by carrying out dynamic (column) experiments. Lead ions were supposedly preferentially retained by ion exchange at the negatively charged silicate functional groups present on the perlite material, and to a minor extent by weak electrostatic (Van der Waals) interactions at non-specific functionalities. In the case of the batch system, the Freundlich isotherm gave a good correlation of the experimental data and lead maximum retention (q_max) in single ion solution was 4.28 mg/g_perlite, and in multimetal solution was 1.50 mg/g_perlite. In the case of the column system, overall capacity was 3.7 mg/g_perlite in single ion solution, and in multimetal solution was 3.0 mg/g_perlite. In multimetal solutions, lead ions showed the best interaction at the perlite functional groups because of the lowest free energies of hydration and hydrated radius. After sorption, perlite beads were used as lightweight aggregates for cement mortars after evaluation of the potential release of lead ions from the conglomerates. Full article

The aroma profile of red wine is complex and research focusing on aroma compounds and their links to viticultural and enological practices is needed. Current research is limited to wines made from cold-hardy cultivars (interspecific hybrids of vinifera and native N. American grapes). The objective of this research was to develop a fully automated solid phase microextraction (SPME) method, using tandem gas chromatography-mass spectrometry (GC-MS)-olfactometry for the simultaneous chemical and sensory analysis of volatile/semi-volatile compounds and aroma in cold-hardy red wines. Specifically, the effects of SPME coating selection, extraction time, extraction temperature, incubation time, sample volume, desorption time, and salt addition were studied. The developed method was used to determine the aroma profiles of seven selected red wines originating from four different cold-hardy grape cultivars. Thirty-six aroma compounds were identified from Maréchal Foch, St. Croix, Frontenac, Vincent, and a Maréchal Foch/Frontenac blend. Among these 36 aroma compounds, isoamyl alcohol, ethyl caproate, benzeneethanol, ethyl decanoate, and ethyl caproate are the top five most abundant aroma compounds. Olfactometry helps to identify compounds not identified by MS. The presented method can be useful for grape growers and wine makers for the screening of aroma compounds in a wide variety of wines and can be used to balance desired wine aroma characteristics. Full article

Sulfonamides (SAs) represent a significant category of pharmaceutical compounds due to their effective antimicrobial characteristics. SAs were the first antibiotics to be used in clinical medicine to treat a majority of diseases, since the 1900s. In the dairy farming industry, sulfa drugs are administered to prevent infection, in several countries. This increases the possibility that residual drugs could pass through milk consumption even at low levels. These traces of SAs will be detected and quantified in milk. Therefore, microextraction techniques must be developed to quantify antibiotic residues, taking into consideration the terms of Green Analytical Chemistry as well. Full article