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Milli-Q Water (milli-q + water)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Impact of activated sludge-derived colloidal organic carbon on behavior of estrogenic agonist recombinant yeast bioassay

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2005
R. David Holbrook
Abstract The impact of size-fractionated colloidal organic carbon (COC) originating from a biological wastewater treatment facility on the sensitivity of the yeast estrogen screen (YES) bioassay containing the human estrogen receptor (hER) gene was evaluated. Dose-response curves of serially diluted 17,-estradiol (E2), both in the presence and absence of COC, were generated by the YES bioassay. The concentration of E2 leading to a 50% YES response (effective concentration 50%, or EC50) was used to evaluate quantitatively the estrogenic activity of the different COC-E2 mixtures. The EC50 values for all COC size fractions, including COC-free samples (<1 kD), were statistically greater than the controls using Milli-Q water. Normalized EC50 values significantly increased as a function of COC concentration for the larger size fractions (>0.22 ,m), but were not significantly affected by smaller COC material at environmental levels (1,5 mg/L), while both colloidal polysaccharide concentrations and colloidal fluorophores (measured at an excitation/emission wavelength pair of 350 nm/450 nm) appear to have an important role in the sensitivity of the YES bioassay. Estimates of the colloid-associated E2 fraction did not predict accurately increases in EC50 values. Matrix effects of the specific environment being tested with the YES bioassay need to be evaluated closely due to the sensitivity of the hER and reporter plasmid. [source]

Analysis of 51 persistent organic pollutants in soil by means of ultrasonic solvent extraction and stir bar sorptive extraction GC-MS

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 20 2008
Marta Martínez-Parreño
Abstract A novel method based on ultrasonic solvent extraction and stir bar sorptive extraction (SBSE) for the analysis of 51 persistent organic pollutants including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenylethers (PBDEs) in soil samples was developed. The different parameters that affect both the extraction of analytes from the soil samples, such as solvent selection, solvent volume, mass of soil, and extraction time, and the partitioning from the solvent/water mixture to the PDMS were studied. The final selected conditions consisted of the extraction of 1 g of soil with 15 mL methanol by sonication for 30 min. The methanol extract was mixed with 85 mL of Milli-Q water and extracted by means of SBSE for 14 h at 900 rpm. The stir bars were analyzed by thermal desorption-GC-mass spectometry (TD-GC-MS). The effects of the matrix on the recovery of the various pollutants under the developed method were studied using two soils with very different physicochemical properties. Method sensitivity, linearity, repeatability, and reproducibility were also studied. Validation and accuracy of the method were conducted by analyzing two commercial certified reference materials (CRMs). The main advantage of this method resides in the fact that a small amount of a nontoxic solvent (methanol) is needed for the extraction of only 1 g of solid sample allowing LODs ranging from 0.01 to 2.0 ,g/kg. Repeatability and reproducibility variations were lower than 20% for all investigated compounds. Results of the CRMs verify the high accuracy of this method. [source]

Detection of the OH band fine structure in liquid water by means of new treatment procedure based on the statistics of the fractional moments

LASER PHYSICS LETTERS, Issue 11 2007
S.M. Pershin
Abstract Three main spectral components ,3210, 3450, and 3650 cm,1 separated by deep gaps in the Raman OH band of liquid water have been detected by a new treatment procedure of experimental data. The applied treatment is based on the statistics of the fractional moments. This approach includes the consideration of the total set of the moments (the fractional and even complex ones) and the generalized mean value functions (GMV) as a specific noise "label". The possibility of the extraction and quantitative description of the fine structure of the averaging experimental spectra is demonstrated. In the frame of the novel approach the reliable separation between Raman spectra of the distilled and Milli-Q water is obtained. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Spectroscopy of single-walled carbon nanotubes in aqueous surfactant dispersion

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009
Dania Movia
Abstract Optical studies of single-walled carbon nanotubes (SWNTs) dispersed in aqueous surfactant suspensions have made significant progress since the discovery of their bright band-gap fluorescence in the near-infrared region [M. J. O'Connell et al., Science 297, 593,596 (2002)]. In this article we report the systematic investigation of the effect of chemical purification and oxidation on the spectroscopic properties of SWNTs. The SWNTs samples we prepared differ for the percentage of impurities present, the amount of defects introduced in their graphitic structure and/or the functional groups expressed on their surface. The generation of carboxylic groups on the nanotubes surface by oxidative treatment was validated by means of thermal gravimetric analysis and ATR/Fourier transform IR spectroscopies, as well as Raman spectroscopy. We have solubilized pristine, purified SWNTs (p-SWNTs) and oxidized SWNTs (o-SWNTS) in Milli-Q water using sodium dodecylbenzene sulphonate (SDBS). While our Vis-NIR Absorption spectra of p-SWNTs and o-SWNTS dispersions in aqueous SDBS solution show the loss of the resolution of the characteristic van Hove singularities, NIR Photoluminescence spectra are characterized by structured emission peaks. [source]