Synthesis, characterization, and applications of novel pseudostationary phases in micellar capillary electrophoresis for separation of chiral and archiral compounds h[electronic resource]

The research presented in this dissertation involves the synthesis, characterization, and the use of novel surfactants, including both micelles and vesicles, as pseudostationary phases in micellar capillary electrophoresis (MCE) for the separation of achiral and chiral compounds. Separation of environmental pollutants such as 2 to 6-ring polycyclic aromatic hydrocarbons (PAHs) was achieved using poly(sodium undecylenic sulfate). A baseline separation of all 16 PAHs was possible for the first time in MCE by a single-surfactant system. In addition, a surfactant with a phosphated head group, i.e., di(2-ethylhexyl)phosphate (DEHP), was also introduced as a novel pseudostationary phase for separation of 21 weakly and strongly hydrophobic neutral compounds. Acetonitrile at a concentration of 30% (v/v) in combination with 100 mM DEHP gave optimum separation for a mixture of 21 benzene derivatives and PAHs in under 16 minutes. An application of cyclodextrin modified MCE was used for separation of twelve mono-methylbenz[a]anthracene positional isomers using a combination of poly-SUS and b-CD, g-CD or b-CD derivatives. Tartaric acid based vesicular surfactants were synthesized and utilized as novel pseudostationary phases in MCE. Linear solvation energy relationship model was applied to understand the fundamental nature of the solute-surfactant interactions and to investigate the effect of the type and the composition of pseudostationary phases on the retention mechanism and selectivity in MCE. The solute size has the largest influence on the solute retention in MCE. The hydrogen bond accepting ability of the solute is the second most important factor on retention and is the largest contributor towards the selectivity differences between pseudostationary phases used. Another study conducted was the synthesis of sodium N-undecanoyl L-leucinate and co-polymerization of SUL with SUS to make a variety of co-polymerized molecular micelles having both chiral (leucinate) and achiral (sulfate) head groups. These surfactants were applied as novel pseudostationary phases in MCE for separation of chiral and achiral compounds. Aggregation numbers and partial specific volumes of these surfactant systems were determined using fluorescence spectroscopy and densitometry, respectively. Thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy changes upon transfer of analyte(s) from aqueous phase to the pseudostationary phase were also determined

Additional Quantitative Trait Loci and Candidate Genes for Seed Isoflavone Content in Soybean

Seed isoflavone content of soybean (Glycine max L. Merr.) is a trait of moderate heritablity and an ideal target for marker selection. To date over 20 QTL have been identified underlying this trait among seven populations. The objectives of this study were to identify additional QTL and candidate genes controlling isoflavone content in a set of recombinant inbred line (RIL) populations of soybean grown in two different seasons. Variations of isoflavones namely daidzein, glycitein and genistein contents over two growing seasons and locations suggests that isoflavones are influenced by both genes and environments. Six QTL were identified on five different chromosomes (Chr) or linkage groups (LG) that controlled daidzein (Chr_2/LG-M; Chr_17a/LG-D2), glycitein (Chr_2/LG-D1b; Chr_8/LG-A2) and genistein (Chr_8/LG-A2; Chr_12/LG-H) respectively in the seeds grown in season 2010. Two QTL were identified for daidzein (Chr_6/LG-C2; Chr_13b/LG-F), two QTLs for glycitein (Chr_1/LG-D1a; Chr_17c/LG-D2) and five QTLs for genistein (Chr_3/ LG-N; Chr_8/LG-A2; Chr_9/LG-K; Chr_18/LG-G) in the seeds of the 2011 growing season. Genes located within QTL confidence intervals were retrieved and gene ontology (GO) terms were used to identify those related to the flavonoid biosynthesis process. Twenty six candidate genes were identified that may be involved in isoflavones accumulation in soybean seeds

Thermodynamic studies of the interaction of molecular micelles and copolymerized molecular micelles with benzodiazepines and alkyl phenyl ketones using MEKC

In this study, polymers of sodium 10-undecenoyl L-leucinate (SUL) and sodium undecenyl sulfate (SUS) as well as their copolymerized molecular micelles (CoPMMs) were applied in MEKC as pseudostationary phases to separate benzodiazepines and alkyl phenyl ketones. SDS, a common pseudostationary phase used in MEKC, was also used for comparison. The van\u27t Hoff relationship was applied to compute the temperature dependence of the MEKC retention factors of the test solutes to estimate the enthalpy, entropy, and the Gibbs free energy. Nonlinear van\u27t Hoff plots were obtained with the majority of benzodiazepines indicating that the thermodynamic parameters were temperature-dependent in all surfactant systems for these solutes. In contrast, all alkyl phenyl ketones resulted in linear van\u27t Hoff plots. © 2007 Wiley-VCH Verlag GmbH and KGaA, Weinheim

Phosphated surfactants as pseudostationary phase for micellar electrokinetic chromatography: Separation of polycyclic aromatic hydrocarbons

A double alkyl chain di(2-ethylhexyl)phosphate (DEHP) is introduced as a potential anionic micellar pseudophase for a wide range of benzene derivatives and/or polycyclic aromatic hydrocarbons (PAHs). Several parameters such as concentration of phosphated surfactant, type and concentration of organic solvents (acetonitrile, isopropanol, and methanol), as well as capillary electrophoresis separation voltage were optimized to enhance resolution, efficiency and selectivity as well as to maximize peak capacities. The migration times and selectivity order for a number of PAHs differ significantly, depending on the type of organic solvent added to the DEHP surfactant. Acetonitrile at a concentration of 30% v/v in combination with 100 mM DEHP gave optimum separation for a mixture of 21 benzene derivatives and PAHs in under 16 min

Electrokinetic chromatography of twelve monomethylbenz[a]anthracene isomers using a polymerized anionic surfactant

A method for the separation of twelve monomethyl-substituted benz[a]anthracene isomers using poly-(sodium undecylenic sulfate) (poly-SUS) surfactant by means of electrokinetic capillary chromatography (EKC) is described. Several parameters such as concentration of acetonitrile (ACN), pH, as well as applied voltage were studied to optimize the EKC separation. ACN at a concentration of 35% v/v, 12.5 mM phosphateborate buffer, 30 kV with 0.5% w/v poly-SUS at a pH of 9.5 provided a resolution of a mixture of nine out of twelve methylbenz[a]anthracene (MBA) isomers in 50 min. The results of this study suggest that molecular length of MBA rather than length-to-breath ratio plays an important role in the elution order of some isomers

Separation of monomethyl-benz[a]anthracene isomers using cyclodextrin-modified electrokinetic chromatography

Cyclodextrin-modified electrokinetic chromatography (CD-EKC) was investigated for the separation of 12 monomethylbenz[a]anthracene (MBA) isomers. Combined use of a polymeric surfactant, poly(sodium 10-undecenyl sulfate) (poly-SUS), with various types of neutral cyclodextrins (CDs) [β-CD, γ-CD, dimethyl-β-CD (DM-β-CD), trimethyl-β-CD (TM-β-CD) and hydroxypropyl-β-CD (HP-β-CD)] were successful in CD-EKC separation of the MBA isomers. Baseline resolution of 10 of the 12 isomers, except for 9-MBA and 2-MBA, was achieved with γ-CD at pH 9.75. The β-CD, γ-CD, and β-CD derivatives (DM-β-CD, TM-β-CD, HP-β-CD) were found to have different resolution and selectivity. Additionally, the tR/t0 values of isomers were found to be dependent on the type and concentration of the CD additives. In general, tR/t0 values of MBA isomers decrease with an increase in the concentration of β-CD derivatives, whereas the reversed was true when the concentrations of native β-CD and γ-CD were varied. The combination of 5 mM γ-CD, 0.5% (w/v) poly-SUS, 35% (v/v) acetonitrile at a pH of 9.75 provided the best selectivity and resolution of the MBA isomers with a separation time of 110 min. However, the use of 30 mM DM-β-CD under similar EKC conditions resulted in much faster separation (ca. 16 min) of 10 MBA isomers. © 2001 Elsevier Science B.V

Polymeric Anionic Surfactant for Electrokinetic Chromatography: Separation of 16 Priority Polycyclic Aromatic Hydrocarbon Pollutants

Electrokinetic chromatography (EKC) with poly(sodium undecylenic sulfate) (poly-SUS) is utilized to separate environmental pollutants such as 2-6-ring polycyclic aromatic hydrocarbons (PAHs). Parameters such as pH, concentration of polymeric surfactants, and the use of organic modifiers were investigated to follow the retention trends of PAHs. A baseline separation of all 16 PAHs in about 30 min, using 0.50% (w/v) of poly-SUS/12.5 mM sodium phosphate-borate buffer (pH 9.2) with 40% (v/ v) acetonitrile, was possible for the first time in EKC by a single-surfactant system

Electrokinetic chromatography of twelve monomethylbenz[a]anthracene isomers using a polymerized anionic surfactant

A method for the separation of twelve monomethyl-substituted benz [a]anthracene isomers using poly-(sodium undecylenic sulfate) (poly-SUS) surfactant by means of electrokinetic capillary chromatography (EKC) is described. Several parameters such as concentration of acetonitrile (ACN), pH, as well as applied voltage were studied to optimize the EKC separation. ACN at a concentration of 35% v/v, 12.5 mM phosphateborate buffer, 30 kV with 0.5% w/v poly-SUS at a pH of 9.5 provided a resolution of a mixture of nine out of twelve methylbenz[a]anthracene (MBA) isomers in 50 min. The results of this study suggest that molecular length of MBA rather than length-to-breath ratio plays an important role in the elution order of some isomers