With the advent of advanced real-time aerosol instrumentation, it has become possible to simultaneously measure individual particle mobility and vacuum aerodynamic diameters. This paper presents an experimental exploration of the effect of particle shape on the relationship between mobility and vacuum aerodynamic diameters. We make measurements on systems of three types: (1) Agglomerates of spheres, for which the density and the volume are known; (2) Ammonium sulfate, sodium chloride, succinic acid and lauric acid irregularly shaped particles of known density; and (3) Internally mixed particles, containing organics and ammonium sulfate, of unknown density and shape. For agglomerates of spheres we observe and quantify alignment effects in the Differential Mobility Analyzer (DMA), an important consequence of which is that mobility diameter of aspherical particles can be a function of DMA operating voltages. We report the first measurements of the dynamic shape factors (DSFs) in free molecular regime. We report the first experimental determination of DSF for ammonium sulfate particles, for which we find DSF to increase from 1.03 to 1.07 as particle mobility diameter increases from 160 nm to 500 nm. Three types of NaCl particles were generated and characterized: nearly spherical particles with DSF of ∼1.02; cubic with DSF that increases from 1.06 to 1.17 as particle mobility diameter increases; and compact agglomerates with DSF 1.3-1.4. Organic particles were found to be nearly spherical. The data suggest that ad

can be formed and survive for a longer extraction time; therefore, a much higher enrichment factor for PAHs can be reached. For low-volatility PAHs, direct-immersion LPME provides higher enrichment factors than that of headspace LPME. However, the enrichment factor obtained by headspace LPME was almost 3-fold of that by direct-immersion LPME in a 30-min extraction of the most volatile PAH, naphthalene. For 30-min directionimmersion LPME of EPA priority PAHs, the enrichment factor, correlation coefficient (R 2 ), and reproducibility (RSD, n ) 5) were in the range of 42-166, 0.9169-0.9976, and 2.8-12%, respectively. Considering that IL can be easily prepared from relatively inexpensive materials and tuned by combination of different anions and cations for task-specific extraction of analytes from various solvent media, this proposed method should have great potentiality in sample preparation. Furthermore, the nonvolatility of IL makes it potentially useful for headspace LPME of volatile analytes.Ionic liquids (IL) are ionic media resulting from combinations of organic cations and various anions. They may be liquids at room temperature. Their use as novel solvent systems for organic synthesis and catalysis has received a good deal of attention. 1 IL have several unique properties that make them useful in a variety of chemical processes. For example, they have no effective vapor pressure, the viscosity and the miscibility in water and other organic solvents can be tuned by changing the combination of different anions and cations of IL, and the preparation is easy from relatively inexpensive materials. 1,2 As a result of these properties, IL is emerging as an alternative recyclable medium for separation. Recently, IL were considered as attractive water-immiscible phases in liquid-liquid extraction. 3-5 IL were also used in organic solvent-supercritical CO 2 biphasic extractions 6-8 and in pervaporation. 4,9 By using two typical IL, 1-butyl-3-methylimidazolium hexafluorophosphate G.

The adsorptive potential of multiwalled carbon nanotubes (MWNTs) for solid-phase extraction of bisphenol A, 4-nnonylphenol, and 4-tert-octylphenol was investigated for the first time. The three analytes are quantitatively adsorbed on a MWNTs-packed cartridge, then the analytes retained on the cartridge are quantitatively desorbed with suitable amounts of methanol. Finally, the analytes in the methanol eluate are determined by high performance liquid chromatography-fluorometric detection. Parameters influencing the extraction efficiency, such as volume of the sample solutions, pH of the sample, and the eluent volume, were examined. Comparative studies showed that MWNTs were superior to C 18 for the extraction of the more polar analyte bisphenol A and at least as effective as C 18 for the extraction of 4-n-nonylphenol and 4-tert-octylphenol. Compared to XAD-2 copolymer, MWNTs exhibited a better property for the extraction of all three analytes. The developed method has been applied to determine bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol in several environmental water samples. The accuracy of the proposed method was tested by recovery measurements on spiked samples, and good recovery results (89.8-104.2%) were obtained. Detection limits of 0.083, 0.024, and 0.018 ng mL -1 for bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol, respectively, were achieved under the optimized conditions.