sodium-dodecyl-sulfate and tetrahydrofuran

Sodium dodecyl sulfate (SDS) markedly improved tetrahydrofuran (THF) - assisted methane hydrate formation. Firstly, methane hydrate formation with different THF amount, 1, 3, and 5.56 mol%, was studied. SDS with 1, 4, and 8 mM was then investigated for its roles on the methane hydrate formation with and without THF. The experiments were conducted in a quiescent condition in a fixed volume crystallizer at 8 MPa and 4°C. The results showed that almost all studied THF and SDS concentrations enhanced the methane hydrate formation kinetics and methane consumption compared to that without the promoters, except 1 mol% THF. Although, with 1 mol% THF, there were no hydrates formed for 48 hours, the addition of just 1 mM SDS surprisingly promoted the hydrate formation with a significant increased in the kinetics. This prompts the use of methane hydrate technology for natural gas storage application with minimal promoters.

Topics: Cold Temperature; Crystallization; Furans; Hydrogen Bonding; Methane; Oil and Gas Industry; Sodium Dodecyl Sulfate

A highly selective sucrose isomerase (SIase) was purified to homogeneity from the cell-free extract of Erwinia rhapontici NX-5 with a recovery of 27.7% and a fold purification of 213.6. The purified SIase showed a high specific activity of 427.1 U mg(-1) with molecular weight of 65.6 kDa. The K (m) for sucrose was 222 mM while V (max) was 546 U mg(-1). The optimum pH and temperature for SIase activity were 6.0 and 30 °C, respectively. The purified SIase was stable in the temperature range of 10-40 °C and retained 65% of the enzyme activity after 2 weeks' storage at 30 °C. The SIase activity was enhanced by Mg(2+) and Mn(2+), inhibited by Ca(2+), Cu(2+), Zn(2+), and Co(2+), completely inhibited by Hg(2+) and Ag(2+). The purified SIase was strongly inhibited by SDS, while partially inhibited by dimethylformamide, tetrahydrofuran, and PMSF. Additionally, glucose and fructose acted as competitive inhibitors for purified SIase.

Topics: Bacterial Proteins; Calcium; Dimethylformamide; Erwinia; Fructose; Furans; Glucose; Glucosyltransferases; Hydrogen-Ion Concentration; Kinetics; Magnesium; Metals, Heavy; Molecular Weight; Octoxynol; Sodium Dodecyl Sulfate; Sucrose; Temperature

A new CE system based on the use of polymeric-mixed micelles (cholic acid, SDS and the poloxamine Tetronic(®) 1107) was developed for the simultaneous determination of nine steroids in human urine. This method allows the baseline separation and quantitation of cortisol, androstenedione, estriol, dehydroepiandrosterone sulfate, testosterone, dehydroepiandrosterone, estrone, progesterone and estradiol in less than 25 min showing to be sensitive enough to detect low concentrations of these steroids in urine samples (5-45 ng/mL). The optimized electrophoretic conditions were performed using a 50 cm × 75 μm capillary, 18 kV, 25°C, with 44 mM cholic acid, 10 mM SDS, 0.05% w/v tetronic(®) 1107, 2.5% v/v methanol, 2.5% v/v tetrahydrofuran in 5 mM borate - 5 mM phosphate buffer (pH=8.0) as a background electrolyte and a dual 210/254 UV-detection. The method can simultaneously determine 0.1-120 μg/mL, which corresponds to 5-6000 ng/mL of steroids in 2 mL urine. The recoveries ranged between 82.4 and 101.5%. Due to its simplicity, speed, accuracy and reliability, the proposed method could be a potential alternative to the traditional methodologies used with clinical purposes.

Topics: Cholic Acid; Electrophoresis, Capillary; Ethylenediamines; Female; Furans; Humans; Hydrogen-Ion Concentration; Limit of Detection; Linear Models; Micelles; Reproducibility of Results; Sodium Dodecyl Sulfate; Steroids

A systematic optimization of the separation of a mixture of corticoids by micellar liquid chromatography, using sodium dodecyl sulphate as surfactant, a Hypersil (250 mm x 3.2 mm I.D.) C18 column, a flow-rate of 0.5 ml min(-1), and UV absorbance detection at 245 nm has been carried out. Several mobile phases consisting of sodium dodecyl sulphate and different organic modifiers were tested of which tetrahydrofuran, PrOH and BuOH were finally selected. On the basis of analysis time, resolution and number of compounds separated, a mobile phase containing 36 mM sodium dodecyl sulphate and 1.91% butanol allowed the separation of thirteen corticoids out of sixteen in about 27 min. Under these conditions the optimal concentration of sodium dodecyl sulphate was found to be 36 mM. A bivariant optimization method for the mobile phase BuOH-sodium dodecyl sulphate corrobored these results. The effects of temperature, ionic strength and flow-rate effect have also been studied. The most important analytical figures of merit were assessed and compared with those obtained using conventional mobile phases. The optimized method was applied to human urine samples of subjects administered with Dezacor (tablets containing 30 mg of the active ingredient deflazacort) with and without sample preparation.

Topics: Adrenal Cortex Hormones; Adult; Calibration; Chromatography, Liquid; Furans; Humans; Indicators and Reagents; Male; Micelles; Reproducibility of Results; Sensitivity and Specificity; Sodium Dodecyl Sulfate; Spectrophotometry, Ultraviolet; Temperature

The effect of low concentrations of organic modifiers on the electroosmotic mobility, mueo, and electrophoretic mobility of the micelle, muep, mc, in micellar electrokinetic chromatography (MEKC) with sodium dodecyl sulfate (SDS) solutions was investigated. The results showed that mueo was mainly influenced by the viscosity of the running solution. A linear relationship between mueo and the concentration of the organic modifier was found in MEKC. A newly defined parameter, the mobility ratio, Rm, mc, which is the ratio of the electrophoretic mobility of the micelle to the electroosmotic mobility, and which characterizes the surface charge density of the micelle in MEKC system with organic modifiers, was introduced. A linear relationship between Rm, mc and the organic modifier concentration was observed. The parameter Rm, mc was found to be useful to investigate the changes in the micellar phase with the addition of organic modifier. The measured muep, mc values showed different and interesting characteristics among different organic modifiers.

Topics: 1-Propanol; Acetonitriles; Chromatography; Electrochemistry; Electrophoresis, Capillary; Furans; Kinetics; Methanol; Micelles; Sodium Dodecyl Sulfate