Grazing incident small angle x-ray scattering study of polymer thin films with embedded ordered nanometer cells

Analysis of nanostructures is of increasing importance with advances of nanotechnology. Embedded nanostructures in thin films in particular are of recent interest. Grazing incident small angle x-ray scattering (GISAXS) has been recognized to be a powerful method to probe such embedded nanostructures; however, quantitative analysis of scattering pattern is not always trivial due to complex refraction and reflection at surface and interfaces. We prepared nanocellular thin films using block copolymer template with carbon dioxide (CO2); CO2 "bubbles" were formed in the CO2-philic block domains. Such nanocellular structures were analyzed by GISAXS and simulated using distorted wave Born approximation (DWBA). Unlike traditional transmission x-ray scattering, GISAXS requires a careful choice of incident angle to analyze the form factor of scatters embedded in a thin film. Nevertheless, the GISAXS measurements under optimized geometry with quantitative calculations using DWBA revealed that the nanocells are spherical and aligned in a single layer of hexagonal lattice and are surrounded by CO2-philic block domains

Temperature-tunable selectivity in comprehensive two-dimensional gas chromatography

A temperature-tunable two-dimensional gas chromatography setup, consisting of three capillary columns with different selectivity, is described. In this setup the selectivity of the primary dimension can be tuned by adjusting the temperature offset of two in series-coupled capillary columns, both columns being part of the primary dimension and positioned in two separate GC ovens. The overall GC × GC separation can be optimized by altering the selectivity of the primary dimension. Besides tuning selectivity, in order to achieve optimal separation, this 2D-GC setup also offers enhanced opportunities for qualitative analysis. Sequentially altering the selectivity of the primary dimension enables one to identify groups of compounds which show similar chromatographic retention behavior

Tunable secondary dimension selectivity in comprehensive two-dimensional gas chromatography

In this paper two tunable two-dimensional gas chromatography setups are compared and described in which the secondary dimension consists of two different capillary columns coupled in series. In the first setup the selectivity of the second dimension can be tuned by adjusting the effective column length of the first secondary dimension column, simply by sliding it stepwise back or forward through the GC x GC modulator. In the second setup, in which the first secondary dimension column is installed in a separate GC-oven (oven-2), the overall selectivity of the second dimension can be tuned by adjusting the oven-2 temperature offset with respect to the main oven. The contribution of the first secondary dimension column to the overall secondary dimension separation can be decreased by applying a higher temperature offset. A real-life sample, the headspace of a coffee powder, was used to demonstrate the added value of tunable GC x GC by solving coelutions of some specific aroma compounds. Besides optimizing the overall GC x GC separation, by altering the second dimension column selectivity, these set-ups also offer enhanced possibilities for qualitative analysis. By stepwise altering the selectivity of the second dimension, classes of compounds showing similar retention behavior could be discriminated. (C) 2013 Elsevier B.V. All rights reserved

Grazing incident small angle x-ray scattering study of polymer thin films with embedded ordered nanometer cells

Analysis of nanostructures is of increasing importance with advances of nanotechnology. Embedded nanostructures in thin films in particular are of recent interest. Grazing incident small angle x-ray scattering (GISAXS) has been recognized to be a powerful method to probe such embedded nanostructures; however, quantitative analysis of scattering pattern is not always trivial due to complex refraction and reflection at surface and interfaces. We prepared nanocellular thin films using block copolymer template with carbon dioxide (CO2); CO2 "bubbles" were formed in the CO2-philic block domains. Such nanocellular structures were analyzed by GISAXS and simulated using distorted wave Born approximation (DWBA). Unlike traditional transmission x-ray scattering, GISAXS requires a careful choice of incident angle to analyze the form factor of scatters embedded in a thin film. Nevertheless, the GISAXS measurements under optimized geometry with quantitative calculations using DWBA revealed that the nanocells are spherical and aligned in a single layer of hexagonal lattice and are surrounded by CO2-philic block domains

Combined comprehensive two-dimensional gas chromatographic analysis of PAH/PASH compounds in complex matrices

A new gas chromatographic method has been developed that is able to quantify polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulfur-containing hydrocarbons (PASH) up to four rings. The method combines the power of both flame ionization detection (FID) and sulfur chemiluminescence detection (SCD) in series on a single comprehensive two-dimensional gas chromatography (GC x GC) system and provides mass fractions of compounds separated by carbon number n (CnHxSy) and class. In addition to PAH and PASH separation, the method is extended toward nonaromatic and monoaromatic (sulfur-containing) compounds (paraffins, naphthenes, monoaromatics, thiols, sulfides, disulfides, and thiophenes). The 95% confidence interval is doubled when a single injection technique is used instead of a more-accurate double injection technique. A flexible correction procedure that combines the advantages of the two-dimensional separation of GC x GC and its ability to easily define overlapping groups between the FID and the SCD chromatograms is applied. The method is validated using theoretical reference mixtures and is applied on three commercial gas oils with sulfur content from 0.16 wt% up to 1.34 wt%. The repeatability is good, with an average of 3.4%, which is in the same range as the much more expensive Fourier transform ion cyclotron resonancemass spectroscopy (FTICR-MS) technique