Solubility of Solid 2,3-Dimethylbutane and Cyclopentane in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10^–6 and (2.77 ± 0.94) × 10^–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10^–6 and (4.60 ± 0.76) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen.     

A Novel Synthesis of tert- Alkyl Sulfides

tert- Alkyl sulfides are conveniently prepared from α-(1H-benzotriazol-1-yl)alkyl sulfides by displacement of the 1H-benzotriazol-1-yl group with Grignard reagents. The 1-[α-(alkylthio)alkyl]- and 1-[α-(arylthio)alkyl]-1H-benzotriazole intermediates are easily available by several routes: (i) displacement of the halogen from appropriate halides by sodium salts of thiols, (ii) condensation of 1H-benzotriazole and thiols with carbonyl compounds, or (iii) lithiation of N-substituted 1H-benzotriazoles and subsequent treatment with electrophiles.     

Development of hollow fiber‐supported liquid‐phase microextraction and HPLC‐DAD method for the determination of pyrethroid metabolites in human and rat urine

A simple hollow fiber liquid‐phase microextraction method for the determination of synthetic pyrethroid metabolites, 3‐phenoxybenzoic acid and 4‐hydroxy‐3‐phenoxybenzoic acid, in human and rat urine was developed and validated. A polypropylene hollow fiber tightly fitted onto a Nylon rod and impregnated with organic solvent served as a disposable extraction device. Desorption of analytes was carried out in NaOH solution, analyzed further by gradient HPLC and diode array detection method. Important factors were identified using Taguchi OA16 (4⁵) orthogonal array design and further optimized using univariate approach. The optimum method performance was observed when 1 mL of urine hydrolyzed with 0.2 mL of concentrated HCl was further supplemented with 100 mg of NaCl and extracted for 120 min into dihexyl ether immobilized in the pores of the hollow fiber. Metabolites were desorbed into 0.1 mL of 0.1 M NaOH for another 120 min. Limits of detection and quantitation of 15 and 50 ng/mL were obtained for both analytes. Relative standard deviations of 1.6–12.6% over the linear range (50–10,000 ng/mL, r > 0.9906) were observed. Intra‐ and inter‐day accuracies of the method ranged from 98.3 to 109.5% and from 93.3 to 110.9%, respectively. The optimized method was applied to the analysis of real urine samples collected from rats exposed orally to cypermethrin. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterisation of anodic oxide films on zirconium formed in sulphuric acid: XPS and corrosion resistance investigations

Present work describes investigations of a two-step process consisting of galvanostatic anodising in a 1 M H₂SO₄ solution at 100 mA cm⁻² up to the limiting voltages of 20, 60, 80, 100 and 120 V, directly after which potentiostatic regime was employed and the current was allowed to drop. The total treatment time (5 min) was held constant for all samples. The treatment was carried out to improve the corrosion resistance of zirconium in physiological conditions, which was determined by electrochemical evaluation in Ringer’s solution. XPS studies revealed that after anodising sulphur was incorporated into the oxide film in the form of sulphated zirconia. The maximum content of sulphate in the oxide layer was observed after anodising at 80 V. Anodising at higher voltages resulted in formation of coatings with decreasing amount of sulphur. It was found that there is a strong correlation between the sulphur content in the oxide layers and the measured corrosion current density. On the other hand, the pitting corrosion resistance seemed to be unaffected by the presence of S and it was improving with the increasing limiting voltage of the treatment.

     

Capillary electrophoresis in the diagnosis of surgical site infections

A surgical site infection (SSI) is an infection that occurs after surgery in the part of the body where the surgery took place. An SSI may range from a spontaneously limited wound discharge within 7–10 days of an operation to a life‐threatening postoperative complication, such as a sternal infection after open heart surgery. Most SSIs are caused by contamination of an incision with microorganisms from the patient's own body during surgery. From the analytical point of view, the complex nature of these samples as well as the low concentrations of analytes require a system with high sensitivity and efficiency. Such situation requires a technique such as CE, which is a powerful and versatile separation technique that promises to rival HPLC when applied to the separation of both charged and neutral species. During the study, it has been demonstrated that CZE identifies characteristics of such groups of pathogens such as bacteria Gram (+) and different species of bacteria Gram (?), and also develops weekly individual profiles for patients after application of antibiotics. This was done in order to show the impact of antibiotic therapy in change “numbers” of bacteria present in the wound after surgery. The method proved to be the ideal straight specificity in the case of Escherichia coli (100%). Finally, analysis of the spectra and the second derivatives of the UV‐Vis spectra confirmed the similarity in the profiles and showed that the CZE is a great method for fast screening test in bacterial infection.     

Multinuclear magnetic resonance studies of 2‐aryl‐1,3,4‐selenadiazoles

2‐Aryl‐1,3,4‐selenadiazoles were studied by ¹H, ¹³C, ¹⁵N and ⁷⁷Se NMR spectroscopy. The results (chemical shifts and coupling constants) were correlated with Hammett substituent parameters as well as calculated chemical shifts and bond lengths. Copyright © 2012 John Wiley & Sons, Ltd.     

Heterogeneous thermochemical decomposition of a semi-transparent particle under high-flux irradiation: uniform versus non-uniform irradiation

The effects of a semi-transparent reacting particle irradiation are analysed using a transient combined heat transfer model. Direct uniform irradiation is found to be favourable for particle heating and decomposition, decreasing the total reaction time by a factor of 3.3 as compared to that for non-uniform irradiation. In both cases heat transfer from the surface to the reaction zone is the process limiting mechanism.