sodium-dodecyl-sulfate and 1-butyl-3-methylimidazolium-tetrafluoroborate

Sulfonylureas (SUs) are one of the most widely used herbicides to control weeds in crops. Herein, capillary electrophoresis (CE) was used to determine four sulfonylureas in natural waters, namely chlorsulfuron (CS), iodosulfuron methyl (IM), metsulfuron methyl (MSM) and mesosulfuron methyl (MSS). First of all, a bare silica capillary was chosen with 10mM of 1-butyl-3-methylimidazolium tetrafluoroborate (bminBF4) as electrophoretic buffer (pH 9.6) containing 2 mg L(-1) of surfactant-coated single-wall carbon nanotubes (SC-SWCNTs). A dramatic deviation in migration times was observed. Therefore, a poly(diallyldimethylammonium) chloride (PDADMAC) statically coated cationic capillary was used to improve repeatability and to alter the selectivity of the separation. The electroosmotic flow (EOF) measurement revealed that the SC-SWCNTs were strongly adsorbed at the surface of the PDADMAC coating even in the absence of the surfactant-coated nanotubes in the electrolyte buffer. Consequently, a stable strong cathodic EOF and excellent repeatabilities were obtained with relative standard deviations (RSDs) on migration times and on corrected peak areas below 0.9 and 1.5%, respectively. The separation of the SUs was conducted in only 6 min. No regeneration of the coating between analyses was necessary, and high peak efficiencies up to 173,000 theoretical plates were obtained. The bi-layer coating was subsequently used to analyze sulfonylureas in tap water, in several mineral waters as well as in underground waters spiked with SUs and directly injected into the CE capillary.

Topics: Allyl Compounds; Electrolytes; Electroosmosis; Electrophoresis, Capillary; Imidazoles; Nanotubes, Carbon; Polyethylenes; Quaternary Ammonium Compounds; Sodium Dodecyl Sulfate; Surface-Active Agents; Urea

In this work, the influences of ionic liquid (IL) as a modifier on microemulsion microstructure and separation performance in MEEKC were investigated. Experimental results showed that synergetic effect between IL 1-butyl-3-methylimidazolium tetrafluoro-borate (BmimBF4 ) and surfactant SDS gave a decreased CMC. With increment of IL in microemulsion, negative ζ potential of the microdroplets reduced gradually. The influence of IL on the dimensions of microdroplet was complicated. At BmimBF4 less than 8 mM, IL made microemulsion droplet smaller in size. While at BmimBF4 more than 10 mM, the size increased and reached to a maximum value at 12 mM, where the microdroplets were larger than that without IL. After that, the micreodroplet size decreased again. Relative fluorescence intensity of the first vibration band of pyrene to the third one (I1 /I3 ) enhanced as IL was added to microemulsion, which indicated that this addition increased environmental polarity in the inner core of microdroplets. Prednisone, hydrocortisone, prednisolone, hydrocortisone acetate, cortisone acetate, prednisolone acetate, and triamcinolone acetonide were analyzed with MEEKC modified with IL to evaluate the separation performance. Cortisone acetate and prednisolone acetate could not be separated at all in typical microemulsion. The seven analytes could be separated by the addition of 10 mM BmimBF4 into the microemulsion system. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for seven analytes were between 86 and 114%. This method provides accuracy, reproducibility, pretreatment simplicity, and could be applied to the quality control of cosmetics.

Topics: Adrenal Cortex Hormones; Chromatography, Micellar Electrokinetic Capillary; Cosmetics; Emulsions; Imidazoles; Ionic Liquids; Limit of Detection; Linear Models; Reproducibility of Results; Sodium Dodecyl Sulfate

An automated methodology for the kinetic study of β-galactosidase activity in sodium dodecylsulfate (SDS)/ionic liquid (IL) mixed micelles was developed. The main objective of the work was the evaluation of mixed micelles as reaction media for the industrial synthesis of glyco-oligossacharides. Enzyme activity was evaluated by means of a model reaction with the fluorescent substrate 4-methylumbelliferyl-α-d-galactopyranoside (MUG). The assay was implemented in a sequential injection analysis (SIA) system and enzyme activity was studied in SDS/bmim [BF(4)] and SDS/hmim [Cl] mixed micelles with variable concentrations of both components. In order to perform a critical evaluation of the obtained results, CMC and average micellar size of SDS/hmim [Cl] mixed micelles were evaluated by fluorescence and dynamic light scattering, respectively. In the micelle characterization assays it was observed that the CMC of the mixed micelles increased with hmim [Cl] concentration up to 1molL(-1). In the presence of higher IL concentrations there were no evidences of micelle formation. Regarding micellar size, it was maximum for an IL concentration of 0.09molL(-1). The kinetic assays evidenced that SDS/bmim [BF(4)] and SDS/hmim [Cl] mixed micellar systems can led to an increase of enzyme activity. This increase is dependent on the variation of the average micellar size that occurs with the increase of IL concentration up to 0.09molL(-1). It was also noticed that the most promising systems are those incorporating SDS and IL in concentrations under 50mmolL(-1) and 0.5molL(-1), respectively(.) These results evidenced that the studied ILs can modify the physico-chemical properties of the surfactant solution in a favourable way regarding β-galactosidase activity being an important achievement for the future implementation of industrial processes catalyzed by this enzyme, mainly the synthesis of glyco-oligossacharides. Indeed, surfactant/IL mixed micelles proved to be an interesting alternative to conventional organic solvents in this field enabling the implementation of the processes in a relatively hydrophobic media with enhanced enzyme activity.

Topics: Aspergillus oryzae; beta-Galactosidase; Biotechnology; Enzyme Assays; Flow Injection Analysis; Imidazoles; Ionic Liquids; Kinetics; Micelles; Sodium Dodecyl Sulfate

In this paper, a micellar electrokinetic chromatographic (MEKC) method using ionic liquid as modifier for the quantification of the active components of lignans found in the medicinal herbs Schisandra species was developed for the first time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds, the addition of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as BMIM-BF4 and SDS concentration, applied voltage, background electrolyte pH and concentration, were evaluated. Under the optimal conditions (5 mM borate-5 mM phosphate buffer in the presence of 20 mM SDS and 10 mM BMIM-BF4, pH 9.2, applied voltage 25 kV and detection at 254 nm), the method successfully applied to the determination of lignans in extracts of Schisandra chinensis (Turcz.) Baill. and Schisandra henryi C.B. Clarke in less than 13 min. The separation mechanism was also discussed.

Topics: Borates; Buffers; Chromatography, Micellar Electrokinetic Capillary; Hydrogen-Ion Concentration; Imidazoles; Lignans; Schisandra; Seeds; Sensitivity and Specificity; Sodium Dodecyl Sulfate