Temporal variation of atmospheric polycyclic aromatic hydrocarbon concentrations in PM10 from the Kathmandu Valley and their gas-particle concentrations in winter

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM) with a diameter <10 µm (PM₁₀, 50% cut off) were investigated in the Kathmandu Valley, Nepal, during 2003. In order to understand the dynamics of atmospheric PAHs in winter, the PAH concentrations in total PM and in the gaseous phase were investigated in the valley in December 2005. Total of 45 PAH compounds (∑45PAHs) were analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In 2003, the ∑45PAH concentrations in PM₁₀ ranged between 4.3 and 89 ng m^?3 (annual average; 27 ± 24 ng m^?3). The average concentrations of ∑45PAHs in December 2005 were 210 ± 33 ng m^?3 in total PM and 430 ± 90 ng m^?3 in the gaseous phase. The ∑45PAH concentration in PM accounted for more than 30% of the sum of their particulate and gaseous forms. Phenanthrene (Ph) was the most predominant compound in the gaseous phase, whereas four- to seven-ring PAHs were predominant in total PM. The highest values of ∑45PAHs occurred in the winter and spring. Estimates of emission sources based on diagnostic molecular ratios showed that atmospheric PAHs in the Kathmandu Valley mainly originated from the exhaust gas of diesel engine. In the winter and spring, PAH pollution would be accelerated by the operations of brick kilns and the frequent formation of an atmospherically stable layer in the valley.     

Sorbate densities on 5A zeolite above and below the critical conditions: n alkane data evaluation and modeling

The sorbate densities of n-alkanes C₁–C₂₀ in 5A zeolite are modeled. For validation of this model, the n-alkane adsorption data for gases and liquids on 5A zeolite is critically evaluated using the concept of sorbate densities. The adsorbed phase critical temperatures appear to occur at a reduced temperature of 0.975 different from the vapor-liquid critical reduced temperatures of 1.0 for C₃ to C₂₀ n-alkanes. For methane and ethane species, the critical adsorbate reduced temperatures T _CAR occur earlier at reduced temperatures of 0.83 and 0.96 respectively. The modified Rackett equation of Spencer and Danner (1972) is satisfactorily used to calculate the adsorbate loading for q _max? below adsorbed phase critical reduced temperature, T _CAR. Above the critical adsorbate reduced temperatures, the saturated loading appears to be constant and equal to 8±1 g/100 gZ for all the alkanes. The data in this region is scarce however, as there are not many isotherms above a T _r of 1.15. However the available isotherms appear to have a fairly equal and constant saturation loading between T _r=T _CAR and T _r=1.652.     

Simultaneous Determination of Antibiotics in Anti-Acne Cosmetics by Rapid LC with DAD

A suitable method that allows, for the first time, the simultaneous determination of nine antibiotics which may help the therapy of acne vulgaris by rapid liquid chromatography with diode array detection in 7 min is presented in this work. An SB RP18 (50 × 4.6 mm; 1.8 μm particle size) column was used with the mobile phase consisting of a mixture of 0.1 mol L^?1 potassium dihydrogen phosphate (pH 2.5) and acetonitrile at the gradient elution program. The correlation coefficients were all above 0.9999 in the linear range between 4–100 μg mL^?1, the average spiked recoveries (n = 6) were 92.2–103.2% with RSD ranging from 0.04 to 4.5% depending on the target analytes. The method detection limits were in the range of 0.02–0.2 μg mL^?1 in anti-acne cosmetics. The analysis of real cosmetic preparations demonstrated the fitness for the whole analytical procedure. The proposed method appeared therefore as a sound alternative for official testing method, which could overcome the general problems of time consuming, lack of the specificity and precision difficulty.     

Comparison of Gasoline-Ranged <Emphasis Type="Italic">n</Emphasis>-Alkanes Conversions Using Dielectric Barrier Discharge: A Kinetic Study

Here, we compared the conversion of gasoline-ranged n-alkanes (C₆–C₉) using dielectric barrier discharge. For an energy density of ~68 J/L and an initial n-alkane concentration of ~230 ppm, when carbon number increased from 6 to 9, the energy efficiency of n-alkane conversion increased from 117 to 240 mmol/kWh, CO _x selectivity decreased from 46 to 20%, and ozone concentration increased from 216 to 240 ppm. The effect of energy density and initial n-alkane concentration were also investigated. The understanding of initial step of conversion was greatly aided by a proposed kinetic model. The pathways of consecutive reactions from the initiation to products were also discussed.     

Removal of uranium from sulfate leach liquor of salcrete deposits using tri-n-octyl amine

A uranyl sulfate leach liquor obtained by uranium leaching of a technological sample of salcrete deposits of Gabal Qatrani ore was subjected to uranium extraction using the liquid–liquid technique. Uranium was effectively extracted from sulfate leach liquor by [(10 %) tri-n-octylamine (TOA)] dissolved in xylene as a diluent. The extraction efficiency was markedly enhanced as the concentration of TOA increases from 1 to 10 %. The relevant factors controlling the extraction process of uranium using tri-n-octylamine were studied. These factors include the effect of diluents used, TOA concentration, contact time, settling time and phase ratio (O/A) v/v. The optimum extraction conditions were chosen. Stripping of uranium from the loaded TOA has been carried out using 5 % Na₂CO₃ as an effective stripping agent. More than 97 % of uranium was extracted by 10 % TOA, at contact time 10 min, settling time 5 min, phase ratio (V_O/V_A) 1/1 and at room temperature. The feasibility of using the TOA for preconcentration-separation of uranium was assessed by stripping studies. The loaded uranium onto TOA has been stripped by 100 % when using 5 % Na₂CO₃ as an efficient eluting agent at 15 min contact time, 5 min settling time and phase ratio (O/A) 2/1.     

Simultaneous LC Determination of Quercetin, Kaempferol and Isorhamnetin in Rabbits after Intragastric Administration of an Ethanol Extract from Pollen Typhae

A simple and rapid reversed-phase LC method was developed and validated for simultaneous determination of three flavonoids, quercetin (QU), kaempferol (KA) and isorhamnetin (IS), in rabbit blood plasma. The plasma was deproteinized using 10% trichloroacetic acid and extracted by n-butanol–acetoacetate solvent prior to LC analysis. The analyte was separated on a reversed-phase column with acetonitrile and 0.1% phosphoric acid in water (27:73, v/v) as mobile phase at a flow-rate of 0.8 mL min^?1, and UV detection wavelength at 369 nm. By this developed method, the concentrations of QU, KA and IS were linearly related to their responses in the range of 0.05–2.5 μg mL^?1. The precision and accuracy for QU, KA and IS in plasma were within ±15% except for the limit of quantitation (LOQ), where they were within ±20%. The validated method has been successfully applied in the pharmacokinetic study of QU, KA and IS in rabbits after intragastric administration of an ethanol extract from traditional Chinese medicine Pollen Typhae.     

Application of urea adduction technique to polluted urban aerosols for the determination of hydrogen isotopic composition of n-alkanes

We examined an applicability of an improved urea adduction technique for the determination of hydrogen isotopic composition (δD) of homologous series of n-alkanes present in polluted urban aerosols using GC/TC/IRMS. Unresolved complex mixture (UCM) of hydrocarbons that interferes with accurate isotope measurements of n-alkanes was removed from n-alkane fraction by a urea adduction method. Recoveries of C₂₀ to C₃₀ n-alkanes during the urea adduction procedure were greater than 90% when the concentrations of total n-alkanes exceed 6.1?µg?mL^?1. Our compound-specific D/H ratios confirm the absence of significant hydrogen isotope fractionation in n-alkanes during urea adduction and recovery of the purified n-alkane fraction. We applied this technique to the urban aerosols that contain a large quantity of UCM to measure δD of C₂₀ to C₃₅ n-alkanes in urban aerosols from Tokyo and Sapporo with an accuracy less than 10‰. We found that the δD values widely ranged from ?38 to ?179‰. Based on the δD values of individual n-alkanes in aerosol samples, we can obtain further information on the sources of aerosol n-alkanes and their source regions, and the atmospheric processes such as long-range transport and atmospheric mixing of air masses of different origin.     

Diffusion of n-alkanes in mesoporous 5A zeolites by ZLC method

Diffusion properties of mesostructured zeolite 5A were investigated by employing n-alkanes as probe molecules using the zero length column (ZLC) method. The mesopores were found to enhance molecule diffusion. Moreover, the effective diffusion time constant (D _eff/R ²) increased with mesoporosity in the zeolites between 308 K and 393 K, whereas the activation energy decreased with increasing mesopore volume. The effective diffusivity values of n-alkanes in mesoporous zeolite 5A were generally higher than that the microporous zeolite 5A sample. This clearly implied the important role of the mesopore in zeolites crystals in facilitating the transport of reaction molecules due to shorter average diffusion path length and less steric hindrance.     

Diffusion of linear paraffins in silicalite studied by the ZLC method in the presence of CO2

The diffusion behavior of C₄–C₁₀ n-alkanes in silicalite-1 has been investigated by using the Zero Length Column method. The diffusivities derived from measurements at different purge rates with different purge gases confirming intracrystalline diffusion control. Data are compared with results reported in the literature for MFI zeolites. The diffusivities were found to be consistent and agree well with data previous obtained by ZLC. However, these data showed a remarkable disagreement with other reported techniques (PFG-NMR, QENS and Permeation). The eventual influence of carbon dioxide (CO₂) adsorption on diffusion properties of n-alkanes in silicalite was also investigated. For this purpose, a series of experiments was performed involving hydrocarbons mixed with CO₂. Data were obtained at 303 K and flow rates between 20 and 80 mL/min. The presence of CO₂ does not seem to influence the intracrystalline transport rate of the investigated light hydrocarbons (n-C₄ and n-C₆). On the other hand, the situation for n-C₈ and n-C₁₀ is more complex. The diffusivity values are higher compared to the previously reported values.     

Ionic liquid-modified magnetic polymeric microspheres as dispersive solid phase extraction adsorbent: a separation strategy applied to the screening of sulfamonomethoxine and sulfachloropyrazine from urine

Ionic liquid-modified magnetic polymeric microspheres (ILMPM) were prepared based on Fe₃O₄ magnetic nanoparticles (MNPs) and ionic liquids (ILs) incorporated into a polymer. The composites were characterized using scanning electron microscopy, Fourier transform infrared analysis, thermogravimetric analysis, X-ray diffraction, and vibrating magnetometer, which indicated that ILMPM had a regularly spherical shape and strong magnetic property. The obtained ILMPM were successfully applied as a special adsorbent of magnetic dispersive solid phase extraction (MDSPE) for the rapid extraction and isolation of sulfamonomethoxine sodium and sulfachloropyrazine sodium in urine. The factors that affected extraction efficiency, such as adsorption conditions, desorption conditions, washing and elution solvents, and pH of the sample solution, were optimized. Under the optimum condition, good linearity in the range of 0.005–2.0 μg g^?1 (r?≥?0.9996) was obtained for the two sulfonamides (SAs); the average recoveries at three spiked levels ranged from 86.9 to 102.1 %, with relative standard deviations of ≤4.3 %. The presented ILMPM-MDSPE method combined the advantages of ILs, MNPs, and MDSPE and therefore could be potentially applied for rapid screening of SAs in urine.     

Effect of Re addition on the crystallization,heat treatment and structure of the Cu–Ni–Si-Cr alloy

Differential scanning calorimetry (DSC) was used to investigate the thermal behavior and non-isothermal crystallization kinetics of the Fe₆₇Nb₅B₂₈ metallic glasses prepared by melt-spinning method. DSC traces exhibit that the crystallization takes place through a single exothermic reaction, and it processes a good thermal stability in thermodynamics. The activation energies for nucleation and grain growth processes were calculated to be 536 ± 22 and 559 ± 20 kJ mol^?1 by Kissinger equation, respectively, and 551 ± 24 and 574 ± 20 kJ mol^?1 by Ozawa equation, respectively. It means that the grain growth process is more difficult than the nucleation process. The variation of local Avrami exponent n(x) with crystallized fraction x demonstrates that the crystallization mechanism varies at different stages. The n(x) is larger than 2.5 at the initial stage of 0 < x < 0.3, implying a mechanism of diffusion-controlled three-dimensional growth with increasing nucleation rate. The n(x) decreases from 2.5 to 1.5 in the range of 0.3 < x < 0.65, suggesting that the crystallization belongs to three-dimensional nucleation and grain growth with decreasing nucleation rate. And n(x) lies between 1.0 and 1.5 in the range of 0.65 < x < 0.95, indicating that the crystallization corresponds to the growth of particles with an appreciable initial volume. Low-temperature annealing corresponds to the precipitation of α-Fe, Fe₂B, and Fe₂₃B₆ phases, and further annealing leads to the formation of α-Fe, Fe₂B, and FeNbB phases. The magnetic properties in relation to microstructure change of the Fe₆₇Nb₅B₂₈ metallic glasses are discussed.     

High Temperature Steam Extraction for the Determination of Aliphatic Hydrocarbons in Petroleum Source Rock

A simple method for the extraction of hydrocarbons from petroleum source rock by high temperature steam was investigated and the conditions for maximum yield were determined. The results showed that the temperature and kinetic rates have significant effects. The optimum temperature for the extraction of n-alkanes and isoprenoid hydrocarbons from sedimentary organic rocks was 250 °C. The optimum extraction time for lower and medium molecular weight n-alkanes was 20 min, while the higher molecular weight alkanes were exhaustively extracted after 50 min. The yields of the analytes were much higher with using the high temperature steam extraction than Soxhlet extraction. The recoveries of the n-alkanes for GC–MS analysis from the extractant water by SPME with a PDMS fibre ranged from 90 to 100% and most of the compounds were above 93%.     

Thermal decomposition of sodium propoxides

Sodium alkoxides, namely, sodium n-propoxide and sodium iso-propoxide were synthesized and characterized by various analytical techniques. Thermal decomposition of these compounds was studied under isothermal and non-isothermal conditions using a thermogravimetric analyzer coupled with mass spectrometer. The onset temperatures of decomposition of sodium n-propoxide and sodium iso-propoxide were found to be 590 and 545 K, respectively. These sodium alkoxides form gaseous products of saturated and unsaturated hydrocarbons and leave sodium carbonate, sodium hydroxide, and free carbon as the decomposition residue. Activation energy, E _a, and pre-exponential factor, A, for the decomposition reactions were deduced from the TG data by model-free (iso-conversion) method. The E _a for the decomposition of sodium n-propoxide and sodium iso-propoxide, derived from isothermal experiments are 162.2 ± 3.1 and 141.7 ± 5.3 kJ mol^?1, respectively. The values obtained from the non-isothermal experiments are 147.7 ± 6.8 and 133.6 ± 4.1 kJ mol^?1, respectively, for the decomposition of sodium n-propoxide and sodium iso-propoxide.     

Prediction of activity coefficients and Henry's constants at infinite dilution for mixtures of n-alkanes

Trejo Rodríguez, A. and Patterson, D., 1984. Prediction of activity coefficients and Henry's constants at infinite dilution for mixtures of n-alkanes. Fluid Phase Equilibria, 17: 265–279.The corresponding-states principle (CSP) for chain molecules has been used to predict activity coefficients γ_i^∞ at infinite dilution and Henry's constants H_i,j for mixtures of n-alkanes. The mixtures for which predictions of γ_i^∞ are made include n-C₄ through n-C₁₀ as the solute in several pure higher n-alkanes, at several temperatures from 30 to 90°C. Predictions of H_i,j are made for mixtures where the solute is C₂ through n-C₈ and the solvent any n-alkane from n-C₄ through n-C₂₂, also at several temperatures, from –15 to 177°C. The predicted values are compared with experimental data from the literature, and in all cases the agreement is remarkably good. The temperature dependence of H_i,j for some mixtures is used to derive heats of solution ΔH_s, and comparison is again carried out with available experimental values.     

Simultaneous Determination of Antibiotics in Anti-Acne Cosmetics by Rapid LC with DAD

A suitable method that allows, for the first time, the simultaneous determination of nine antibiotics which may help the therapy of acne vulgaris by rapid liquid chromatography with diode array detection in 7 min is presented in this work. An SB RP18 (50 × 4.6 mm; 1.8 μm particle size) column was used with the mobile phase consisting of a mixture of 0.1 mol L⁻¹ potassium dihydrogen phosphate (pH 2.5) and acetonitrile at the gradient elution program. The correlation coefficients were all above 0.9999 in the linear range between 4–100 μg mL⁻¹, the average spiked recoveries (n = 6) were 92.2–103.2% with RSD ranging from 0.04 to 4.5% depending on the target analytes. The method detection limits were in the range of 0.02–0.2 μg mL⁻¹ in anti-acne cosmetics. The analysis of real cosmetic preparations demonstrated the fitness for the whole analytical procedure. The proposed method appeared therefore as a sound alternative for official testing method, which could overcome the general problems of time consuming, lack of the specificity and precision difficulty.

     

Temperature dependent near-UV molar absorptivities of aliphatic aldehydes and ketones in aqueous solution

Temperature dependent molar absorptivities are reported for acetone, 2-butanone, 2-pentanone, 3-pentanone, acetaldehyde, propionaldehyde, and n-butyraldehyde in aqueous solution. Molar absorptivities are given at eight temperatures in the range 6.5–69.5°C for wavelengths greater than 200 nm, a spectral resolution of 2.0 nm, and a spacing of 2.5 nm. For both ketones and aldehydes a shift to shorter wavelengths of approximately 10 nm is observed in the aqueous phase absorption spectrum relative to that found in the gas phase. For the ketones, there is an increase in the total intensity of the spectrum of approximately 5% over the range of temperatures studied. For the aldehydes a much larger change in the intensity of the absorption spectrum is observed, due to the temperature dependence of the hydration reaction RCHO + H₂O ⇄ RCH(OH)₂; K_hyd = [RCH(OH)₂/[RCHO]. The change in the spectral intensity with temperature is used to determine thermodynamic parameters for the hydration reaction, giving the following results (at 25°C): acetaldehyde, K_hyd = 1.13 ± 0.06, ΔH = −19.7±0.6kJ/mol, ΔS= −65.0±2.5J/mol-K; propionaldehyde, K_hyd=1.02±0.06, ΔH=-20.8±0.8kJ/mol, ΔS=-69.6±3.1J/mol-K; n-butyraldehyde, K_hyd=0.50±0.05, ΔH=-27.0±2.2kJ/mol, ΔS= −96.5± 8.2 J/mol-K. The implications of these results for aqueous phase atmospheric chemistry are discussed.     

Determination of Meserine,a new candidate for Alzheimer’s disease in mice brain by liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic and tissue distribution study

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of Meserine ((?)-meptazinol phenylcarbamate), a novel potent inhibitor of acetylcholinesterase (AChE), was developed, validated, and applied to a pharmacokinetic study in mice brain. The lower limit of quantification (LLOQ) was 1 ng mL^?1 and the linear range was 1–1,000 ng mL^?1. The analyte was eluted on a Zorbax SB-Aq column (2.1?×?100 mm, 3.5 μm) with the mobile phase composed of methanol and water (70:30, v/v, aqueous phase contained 10 mM ammonium formate and 0.3 % formic acid) using isocratic elution, and monitored by positive electrospray ionization in multiple reaction monitoring (MRM) mode. The flow rate was 0.25 mL min^?1. The injection volume was 5 μL and total run time was 4 min. The relative standard deviation (RSD) of intraday and interday variation was 2.49–7.81 and 3.01–7.67 %, respectively. All analytes were stable after 4 h at room temperature and 6 h in autosampler. The extraction recoveries of Meserine in brain homogenate were over 90 %. The main brain pharmacokinetic parameters obtained after intranasal administration were T _max?=?0.05 h, C _max?=?462.0?±?39.7 ng g^?1, T _1/2?=?0.4 h, and AUC_(0-∞)?=?283.1?±?9.1 ng h g^?1. Moreover, Meserine was distributed rapidly and widely into brain, heart, liver, spleen, lung, and kidney tissue. The method is validated and could be applied to the pharmacokinetic and tissue distribution study of Meserine in mice.     

Competitive immunoassay for monitoring polybrominated diphenyl ethers in PM2.5 in Shanghai

In this paper, a sensitive biotin–streptavidin (BS)-ELISA was developed for determining the polybrominated diphenyl ethers in PM_2.5. For establishing this proposed BS-ELISA, we prepared the biotinylated antibody primarily. And for reducing the background interference, some in?uencing factors and procedures for this immunoassay were also discussed and optimised. Under the optimal conditions, the IC₅₀ = 0.53 ng/mL; IC₁₀ was 0.002 ng/mL; and the results were almost consistent with those using the gas chromatography and electron capture detection (GC-ECD). Less procedures and simpler sample preparation were required for this method compared with the GC-ECD. The results showed that the highest value of BDE-47 concentration occurred in December, which might re?ect the combination of heating and industrial pollution. In our analysis, we studied the Pearson correlations between BDE-47/PM_2.5 and gaseous pollutants (such as NO₂, SO₂, CO, O₃, PM₁₀ and PM_2.5). BDE-47 showed a higher correlation with NO₂ than that with PM₁₀, PM_2.5 and SO₂, which implied that the BDE-47 emission process might be accompanied by the emission of NO₂. Moreover, during the Spring Festival, the concentration of BDE-47 in PM_2.5 decreased significantly, whereas the PM_2.5 changed little. This suggested factories and vehicles might be the major contributors to BDE-47 emissions (but not to PM_2.5).     

Magnetic nanofibrous polyaniline nanocomposite for solid-phase extraction of naproxen from biological samples prior to its spectrofluorimetric determination

Nanofibrous polyaniline–magnetite (PANI/Fe₃O₄) nanocomposite was in situ prepared through adsorption of magnetite nanoparticles onto PANI nanofibers surface and utilized as an efficient sorbent for magnetic solid-phase extraction of naproxen from water and biological samples, followed a desorption step and spectrofluorimetric determination. Field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, thermal gravimetric analysis and X-ray diffraction techniques were employed for characterization of the prepared nanocomposite. The important parameters influencing the extraction efficiency including PANI/Fe₃O₄ mass ratio, adsorbent dose, extraction time, sample solution pH, ionic strength, type and volume of desorption solvent and the elution time were studied and optimized. The investigated nanocomposite was successfully applied to the extraction of naproxen in spiked tap water, urine and plasma samples, with a relative recovery in the range of 90–98%. The reusability of PANI/Fe₃O₄ was examined for ten successive cycles, and the results confirm that the efficiency did not change significantly. A linear calibration plot was obtained in the range of 40–1000 ng mL^?1 with a limit of detection about 17 ng mL^?1 under the optimum conditions. The relative standard deviation (RSD) was found to be 2.34% (n = 8, concentration level of 100 ng mL^?1). The kinetics and thermodynamics of the extraction process were also studied.     

Chiral Separation of ��-Adrenergic Blockers in Human Plasma by SPE-HPLC

Chiral analysis of ??-adrenergic blockers in human plasma is an important research area due to their different pharmaceutical activities. The solid phase extraction of alprenolol, carazolol, metoprolol, oxprenolol from human plasma was achieved on C₁₈ cartridges using phosphate buffer (50 mM, pH 9.0) followed by elution with methanol containing 0.1% acetic acid. Chiral-HPLC was carried out on CelluCoat (250 × 4.6 mm, 5.0 ??m silica particle size) column using different combinations of n-heptane?Cethanol?Cdiethylamine at 1.0 and 2.0 mL min^?1 flow rates, respectively. The detection was achieved at 225 nm with 27 ± 1 °C as working temperature. The chromatographic parameters, i.e., retention (k), separation (??) and resolution (Rs) factors ranged from 0.26 to 10.64, 1.12 to 2.10 and 1.05 to 2.26, respectively. The binding differences of enantiomeric concentrations of oxprenolol, carazolol, alprenolol, and metoprolol were 0.12, 0.08, 0.05, and 0.01, respectively. These values suggest that their activities may be in the order of oxprenolol > carazolol > alprenolol > metoprolol. The reported SPE-Chiral HPLC methods may be used to study the enantiomeric concentrations of these ??-adrenergic blockers in human and other animal plasmas for further studies.