Centrifuge spectroscopy

Applications. Molecules couple to an electromagnetic field through their electric dipoles, so only those having a permanent dipole moment exhibit significant rotational spectra. For such species, microwave spectroscopy yields highly precise moments of inertia and details of centrifugal... 

CARS see coherent anti-Stokes/Stokes Raman spectroscopy centrifugal sudden (CS) approximation 155, 166... 

Selecting an approach The solid from the centrifuge might be identifiable by infrared spectroscopy. 

This method has been applied to bottom sediments and muds [4]. The mud sample is centrifuged to separate the water, dried at room temperature, ground and sieved. This residue is extracted for lh at 80°C with methanol-benzene (1 1), the extraction is repeated twice, and the combined extracts are evaporated and the residue dissolved in water. Alkylbenzenesulphonates are then determined by infrared spectroscopy as described above. 

Sample preparation is rather involved. A sample of urine or fecal matter is obtained and treated with calcium phosphate to precipitate the plutonium from solution. This mixture is then centrifuged, and the solids that separate are dissolved in 8 M nitric acid and heated to convert the plutonium to the +4 oxidation state. This nitric acid solution is passed through an anion exchange column, and the plutonium is eluted from the column with a hydrochloric-hydroiodic acid solution. The solution is evaporated to dryness, and the sample is redissolved in a sodium sulfate solution and electroplated onto a stainless steel planchette. The alpha particles emitted from this electroplated material are measured by the alpha spectroscopy system, and the quantity of radioactive plutonium ingested is calculated. Approximately 2000 samples per year are prepared for alpha spectroscopy analysis. The work is performed in a clean room environment like that described in Workplace Scene 1.2. 

The solubility of paclitaxel in water at 25°C at pH 7.4 is 0.172mg/L (0.2 pM), extremely low, making any separation procedure of nonencapsulated paclitaxel from DQAsomes unnecessary i.e., in an aqueous environment, only paclitaxel encapsulated in DQAsomes would stay in colloidal solution. However, for control, a paclitaxel suspension was probe sonicated under identical conditions used for the encapsulation of paclitaxel into DQAsomes, but in the complete absence of dequalinium chloride. As expected, upon centrifugation, no paclitaxel was detectable in the supernatant using ultraviolet (UV) spectroscopy at 230 nm. 

A range of analytical techniques is available for providing information on concentration and properties, including microscopy approaches, chromatography, centrifugation and filtration, spectroscopy, and related techniques. 

Digestion with boiling aqua regia. Dilution and centrifugation with final measurement by ICP-OES (inductively coupled plasma optical emission spectroscopy). 

The amount of polymer adsorbed on each sample was measured by pressure filtration through a 0.1 m filter, followed by analysis of the filtrate for residual polymer by gel permeation chromatography with refractive index determination. Particle zeta potentials were measured by taking a small sample of the solids from the centrifuge and re-suspending them in the supernatant prior to analysis in a Malvern Instruments Zetasizer . The concentration of all other types of ions in the supernatant was analysed by ICP atomic emission spectroscopy. 

A. Korobenko, A. A. Milner, J. W. Hepburn, and V. Milner. Rotational spectroscopy with an optical centrifuge. Phys. Chem. Chem. Phys., 16(9) 4071 076 (2014). 

Copolymerization reactions Copolymerization experiments with styrene and MMA employed molar fractions of 20, 40, 60, and 80% comonomers, which were reacted in ethanol 1,2-dichIorethane 60 40 (by volume) mixtures and benzoyl peroxide as catalyst. Polymerizations were carried out at 70°C. The reactions were quenched by the addition of methanol as non-solvent, and the copolymer was isolated by centrifugation. Copolymer analysis employed UV spectroscopy for copolymers with MMA, and methoxyl content determination according to a procedure by Hodges et al. (16) in the case of styrene copolymers. Reactivity ratios were determined in accordance with the method by Kelen-Tiidos (17) and that by Yezrielev-Brokhina-Roskin (YBR) (18). Experimental details and results are presented elsewhere (15). 

Reactivity ratios between acrylated lignin model compound (Fig. 2), defined as Mi, with either MM A or S, defined as M2, were determined experimentally in accordance with standard procedures (15). These involve mixing two different vinyl monomers in various molar ratios with catalyst (i.e., benzoyl peroxide) and solvent, heating the mixture to achieve polymerization, and recovering the polymer by the addition of non-solvent, and centrifugation. The respective molar monomer fractions of the copolymer were determined by UV-spectroscopy in the cases where MMA served as M2, and by methoxyl content analysis in those cases in which S was the M2-species. The results were subjected to numerical treatments according to the established relationships of Kelen-Tiidos (17) and Yezrielev-Brokhina-Roskin (YBR) (18), and this is described elsewhere (15). 

Fig. 2 SDS-polyacrylamide gel electrophoresis of T. vaginalis hydrogenosomes purified by isopycnic centrifugation on a Percoll gradient. 1 PFOR 2 malic enzyme, 64-kDa hy-drogenase, and Cpn 60 3 succinyl CoA synthetase fi subunit 4 Hmp35 5 succinyl CoA synthetase a subunit 6 Hmp31 (ATP/ADP carrier) 7 adenylate kinase 8 thiol peroxidase. Well-resolved but unmarked bands mostly belong to malic enzyme fragments or unknown proteins. Proteins were identified by mass spectroscopy. The 12% gel is stained with Coomassie Brilliant Blue R 250 (authors original)...

When preparing the cesium- and barium-saturated clays, the 1.0 M solutions used were decanted (after centrifuging) and analyzed semiquantitatively by emission spectroscopy. From those analyses, it appears that the following species were desorbed sodium, potassium, calcium, magnesium, and strontium. It further appeared that desorption of potassium was almost unique to cesium sorption whereas, desorption of the other species appeared to be common to both cesium and barium sorption. Small amounts of other elements such as nickel and copper were also detected by the analyses. However, to what extent the observed concentrations may represent desorption and to what extent they may represent the dissolution of sparingly soluble substances (particularly hydroxide species) is as yet-uncertain. The apparent concentrations of the desorbed species per gram of clay are given in Table III. 

Over the last years we have explored several advanced techniques for high-resolution rotational coherence spectroscopy (RCS [1]) in order to study the structures of molecules and clusters in the gas phase [2]. We have provided spectroscopic examples demonstrating (i) mass-selectivity (Fig. 1, [3]), (ii) that the rotational constants of the ground and electronic excited states can be obtained independently with high precision (lO MO"5, [4]), (iii) that the transition dipole moment alignment, (iv) centrifugal distortion constants, and (v) information on the polarizability tensor can be obtained (Fig.l, [5]). Here we review results pertaining to points (i), (ii), (iv) and (v) [2,3,5],... 

The method of fs DFWM spectroscopy and our theoretical model for the spectral simulation is discussed in our second contribution in this volume. The experimental setup has been detailed in a former publication [5], Here, we would like to highlight some special features of this technique with emphasis on the possibility to obtain, besides the rotational constants, centrifugal distortion constants (CDs) and information on the polarizability tensor (PT). 

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