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Sample Preparation Techniques (sample + preparation_techniques)
Selected AbstractsMicrobial Surfaces Investigated Using Atomic Force MicroscopyBIOTECHNOLOGY PROGRESS, Issue 6 2004Anastassia V. Bolshakova This paper is dedicated to atomic force microscopy (AFM) as a progressive tool for imaging bacterial surfaces and probing their properties. The description of the technique is complemented by the explanation of the methodapos;s artifacts typical, in particular, for the imaging of bacterial cells. Sample preparation techniques are summarized in a separate section. Special attention is paid to the differences in imaging of Gram-positive and Gram-negative bacteria. Probing of mechanical properties, including elastic modulus, fragility, and adhesion of the cell walls is emphasized. The advantages of AFM in the studies of real-time cellular dynamical processes are illustrated by the experiment with the germination of spores. [source] REACH-driven developments in analysis and physicochemistry,FLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2010A. Chaintreau Abstract The enforcement of the REACH regulation in the fragrance domain has created new challenges for the analytical and physical chemist. Many chemicals used as perfumery ingredients are hydrophobic, because low-polar compounds exhibit a higher substantivity (i.e. persistence after application) than do polar compounds. As a result, the usual protocols are often unsuitable and new methods must be developed. Biodegradation studies sometimes call for the quantification of traces of such hydrophobic analytes in complex media (e.g. waste water, aqueous surfactant solutions). Existing sample preparation techniques are either inefficient or time consuming. A new approach is proposed, based on single-use absorbants, which allows accurate quantification down to the 100 ppb range. This extremely simple technique allows good throughput analyses. Determining the environmental profile of a compound requires the determination of some physical constants. Among these, solubility in water can be obtained from theoretical models or experimentally, but the resulting values may greatly differ as a function of the model or the protocol. Several experimental approaches are critically discussed and compared with a reference technique. The air-to-water partition coefficients are determined by using an improved version of the previously developed static-and-trapped headspace technique. Copyright © 2009 John Wiley & Sons, Ltd. [source] Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticalsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002Nicola V. Y. Scarlett The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. The aims of the round robin have been detailed by Madsen et al. [J. Appl. Cryst. (2001), 34, 409,426]. In summary, they were (i) to document the methods and strategies commonly employed in quantitative phases analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. The first paper (Madsen et al., 2001) covered the results of sample 1 (a simple three-phase mixture of corundum, fluorite and zincite). The remaining samples used in the round robin covered a wide range of analytical complexity, and presented a series of different problems to the analysts. These problems included preferred orientation (sample 2), the analysis of amorphous content (sample 3), microabsorption (sample 4), complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. This paper forms the second part of the round-robin study and reports the results of samples 2 (corundum, fluorite, zincite, brucite), 3 (corundum, fluorite, zincite, silica flour) and 4 (corundum, magnetite, zircon), synthetic bauxite, natural granodiorite and the synthetic pharmaceutical mixtures (mannitol, nizatidine, valine, sucrose, starch). The outcomes of this second part of the round robin support the findings of the initial study. The presence of increased analytical problems within these samples has only served to exacerbate the difficulties experienced by many operators with the sample 1 suite. The major difficulties are caused by lack of operator expertise, which becomes more apparent with these more complex samples. Some of these samples also introduced the requirement for skill and judgement in sample preparation techniques. This second part of the round robin concluded that the greatest physical obstacle to accurate QPA for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances. [source] A new single grating spectrograph for ultraviolet Raman scattering studiesJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2006Lutz Hecht Abstract A state-of-the-art single grating spectrograph for Raman scattering studies within the deep ultraviolet (DUV) region of the electromagnetic spectrum is discussed. It is based on a high throughput DUV version of a single-stage monochromator originally designed for use in the visible spectral region. Its key components are two identical, newly designed calcium fluoride camera lenses each consisting of five different individual optical elements. The first of these lenses collimates the Raman scattered DUV radiation entering the spectrometer through its entrance slit. The second lens focuses the collimated beam of dispersed Raman scattered DUV radiation emerging from a high-resolution reflection grating onto a charge coupled device (CCD) detector with enhanced DUV sensitivity. A novel high transmission edge filter is used as a blocking device for a sufficient rejection of the Rayleigh line generating a relatively sharp transmittance cutoff at a Stokes Raman wavenumber shift of about ,450 cm,1 employing 257 nm DUV excitation. Overall, this new spectrograph enables rapid collection of Stokes DUV Raman scattered photons at f/2 wide apertures with sufficiently large signal-to-noise ratios (SNRs) in relatively short acquisition times and with an effective spectral resolution of approximately ,6 cm,1. Backscattered Raman spectra of the following chemicals are presented as typical results illustrating the excellent performance characteristics of this new DUV spectrograph for a variety of experimental conditions within different scattering scenarios and for a relatively wide range of commonly used sample preparation techniques: neat cyclohexane, laboratory air, polycrystalline D -glucose, single crystal L -alanine and a dilute aqueous solution of 2,-deoxyadenosine. Copyright © 2005 John Wiley & Sons, Ltd. [source] Improvements for the visualization of low-molecular weight protein and peptides of human tears using MALDIPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 17 2008Terry Nguyen-Khuong Abstract Many low-molecular weight proteins and peptides in human tears are potentially bioactive proteins but the range and number of these is yet to be fully characterized. A number of different sample preparation techniques were used to maximize the visualization of peptides from reflex tears. Samples were pretreated using precipitation and filtration techniques prior to analyses using MALDI-TOF MS. Peptides were searched for between 700 to 4000 m/z. Sample dilution in several different buffer systems followed by filtration with a 30-kDa cutoff filter and C18 reverse phase microcolumn purification produced significantly (p = 0.049) more peaks in tears than other methods used to prepare tears prior to MALDI-TOF MS. This study has established a technique for optimizing the visualization of naturally occurring peptides in tears. [source] | ||||||||||