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Liquid Samples (liquid + sample)
Selected AbstractsIsotope ratio mass spectrometry coupled to liquid and gas chromatography for wine ethanol characterizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2008Ana I. Cabañero Two new procedures for wine ethanol 13C/12C isotope ratio determination, using high-performance liquid chromatography and gas chromatography isotope ratio mass spectrometry (HPLC/IRMS and GC/IRMS), have been developed to improve isotopic methods dedicated to the study of wine authenticity. Parameters influencing separation of ethanol from wine matrix such as column, temperature, mobile phase, flow rates and injection mode were investigated. Twenty-three wine samples from various origins were analyzed for validation of the procedures. The analytical precision was better than 0.15,, and no significant isotopic fractionation was observed employing both separative techniques coupled to IRMS. No significant differences and a very strong correlation (r,=,0.99) were observed between the 13C/12C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The potential advantages of the developed methods over the traditional one are speed (reducing time required from hours to minutes) and simplicity. In addition, these are the first isotopic methods that allow 13C/12C determination directly from a liquid sample with no previous ethanol isolation, overcoming technical difficulties associated with sample treatment. Copyright © 2008 John Wiley & Sons, Ltd. [source] ,Bubble chamber model' of fast atom bombardment induced processesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2003Marina V. Kosevich A hypothesis concerning FAB mechanisms, referred to as a ,bubble chamber FAB model', is proposed. This model can provide an answer to the long-standing question as to how fragile biomolecules and weakly bound clusters can survive under high-energy particle impact on liquids. The basis of this model is a simple estimation of saturated vapour pressure over the surface of liquids, which shows that all liquids ever tested by fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (SIMS) were in the superheated state under the experimental conditions applied. The result of the interaction of the energetic particles with superheated liquids is known to be qualitatively different from that with equilibrium liquids. It consists of initiation of local boiling, i.e., in formation of vapour bubbles along the track of the energetic particle. This phenomenon has been extensively studied in the framework of nuclear physics and provides the basis for construction of the well-known bubble chamber detectors. The possibility of occurrence of similar processes under FAB of superheated liquids substantiates a conceptual model of emission of secondary ions suggested by Vestal in 1983, which assumes formation of bubbles beneath the liquid surface, followed by their bursting accompanied by release of microdroplets and clusters as a necessary intermediate step for the creation of molecular ions. The main distinctive feature of the bubble chamber FAB model, proposed here, is that the bubbles are formed not in the space and time-restricted impact-excited zone, but in the nearby liquid as a ,normal' boiling event, which implies that the temperature both within the bubble and in the droplets emerging on its burst is practically the same as that of the bulk liquid sample. This concept can resolve the paradox of survival of intact biomolecules under FAB, since the part of the sample participating in the liquid,gas transition via the bubble mechanism has an ambient temperature which is not destructive for biomolecules. Another important feature of the model is that the timescale of bubble growth is no longer limited by the relaxation time of the excited zone (,10,12,s), but rather resembles the timescale characteristic of common boiling, sufficient for multiple interactions of gas molecules and formation of clusters. Further, when the bubbles burst, microdroplets are released, which implies that FAB processes are similar to those in spraying techniques. Thus, two processes contribute to the ion production, namely, release of volatile solvent clusters from bubbles and of non-volatile solute from sputtered droplets. This view reconciles contradictory views on the dominance of either gas-phase or liquid-phase effects in FAB. Some other effects, such as suppression of all other ions by surface-active compounds, are consistent with the suggested model. Copyright © 2003 John Wiley & Sons, Ltd. [source] Phonon spectroscopy at high pressure by inelastic X-ray scatteringJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Valentina M. Giordano The current status of phonon-dispersion studies at high pressure using very high energy resolution inelastic X-ray scattering is discussed. A brief description of the instrumental apparatus is given, together with an illustration of the high-pressure facilities available at the IXS beamlines ID16 and ID28 of the ESRF. Some selected examples of recent studies on crystalline and liquid samples in a diamond anvil cell are then presented. [source] New agitated and thermostatized cell for in situ monitoring of fast reactions by synchrotron SAXSJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Maria Paulis A thermostatized and agitated sample cell for synchrotron small-angle X-ray scattering (SAXS) measurements of liquid samples (homogeneous or heterogeneous) has been developed. The cell is composed of a compact main body with inlet and outlet windows for the beams of light. The volume of the cell is approximately 0.8,ml and the distance between the windows is 5,mm to allow accurate SAXS measurements. The cell is thermostatized by means of a jacket that surrounds the sample holder and it is connected to a thermostatic bath. In addition, the cell has a top and a bottom lid that allow easy cleaning and maintenance without demounting the optical windows. The cell has been used to run SAXS measurements of liquid samples and, for the first time, a mini-emulsion polymerization reaction has been monitored by SAXS. [source] Three-dimensional femtosecond laser micromachining of photosensitive glass for biomicrochipsLASER & PHOTONICS REVIEWS, Issue 3 2010K. Sugioka Abstract Internal modification of transparent materials such as glass can be carried out using multiphoton absorption induced by a femtosecond (fs) laser. The fs-laser modification followed by thermal treatment and successive chemical wet etching in a hydrofluoric (HF) acid solution forms three-dimensional (3D) hollow microstructures embedded in photosensitive glass. This technique is a powerful method for directly fabricating 3D microfluidic structures inside a photosensitive glass microchip. We used fabricated microchips, referred to as a nanoaquarium, for dynamic observations of living microorganisms. In addition, the present technique can also be used to form microoptical components such as micromirrors and microlenses inside the photosensitive glass, since the fabricated structures have optically flat surfaces. The integration of microfluidics and microoptical components in a single glass chip yields biophotonic microchips, in other words, optofluidics, which provide high sensitivity in absorption and fluorescence measurements of small volumes of liquid samples. [source] On-line measurements of ,15N in biological fluids by a modified continuous-flow elemental analyzer with an isotope-ratio mass spectrometerRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2008Xu Wang A modified continuous-flow elemental analyzer coupled to an isotope-ratio mass spectrometer (modified EA-IRMS) was tested for on-line ,15N measurement on urea solution and biological fluids (e.g. urine). The elemental analyzer configuration was adapted by adding a U-shaped cold trap and an X-pattern four-way valve for on-line trapping/venting of water from the liquid samples. Results indicate that the ,15N ratios show little variation (standard deviation (SD),=,0.05,) with a sample size above the equivalent N yield of 0.2,mg urea (0.092,mg N) when the mass spectrometer conditions were carefully optimized. By contrast, a significant logarithmic decrease in ,15N with sample size was observed but this can be offset by applying a linearity correction or blank correction when the sample size is between equivalent N yields of 0.05 and 0.2,mg urea. The blank corrected ,15N ratios give an overall precision of ,0.16, whereas the average precision for ,15N corrected using combined linearity and shift correction is 0.05,. The relatively large variation in blank corrected ,15N values may be attributed to the variability of the blank ,15N in the sequence. Therefore, the blank correction should be carefully performed in routine measurements. As a result, the linearity range of a modified EA-IRMS can be extended to a minimum sample size of 0.023,mg N. In addition, the reproducibility of the new system is good, as indicated by the precision (<0.2,) for a set of standards and unknowns. The data show that fluids containing nitrogen can be successfully analyzed in the modified EA-IRMS. Copyright © 2008 John Wiley & Sons, Ltd. [source] Comparison of methods of DNA extraction for real-time PCR in a model of pleural tuberculosisAPMIS, Issue 1 2010ANA SANTOS Santos A, Cremades R, Rodríguez JC, García-Pachón E, Ruiz M, Royo G. Comparison of methods of DNA extraction for real-time PCR in a model of pleural tuberculosis. APMIS 2010; 118: 60,5. Molecular methods have been reported to have different sensitivities in the diagnosis of pleural tuberculosis and this may in part be caused by the use of different methods of DNA extraction. Our study compares nine DNA extraction systems in an experimental model of pleural tuberculosis. An inoculum of Mycobacterium tuberculosis was added to 23 pleural liquid samples with different characteristics. DNA was subsequently extracted using nine different methods (seven manual and two automatic) for analysis with real-time PCR. Only two methods were able to detect the presence of M. tuberculosis DNA in all the samples: extraction using columns (Qiagen) and automated extraction with the TNAI system (Roche). The automatic method is more expensive, but requires less time. Almost all the false negatives were because of the difficulty involved in extracting M. tuberculosis DNA, as in general, all the methods studied are capable of eliminating inhibitory substances that block the amplification reaction. The method of M. tuberculosis DNA extraction used affects the results of the diagnosis of pleural tuberculosis by molecular methods. DNA extraction systems that have been shown to be effective in pleural liquid should be used. [source] Determination of diphenylarsinic acid and phenylarsonic acid, the degradation products of organoarsenic chemical warfare agents, in well water by HPLC,ICP-MSAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2005Kenji Kinoshita Abstract Diphenylarsinic acid (DPAA) and phenylarsonic acid (PAA), which were degradation products of organoarsenic chemical warfare agents used as sternutatory gas, were detected in the well water at Kamisu, Ibaraki Prefecture, Japan. The standard material of DPAA was synthesized with aqueous arsenic acid and phenylhydrazine in order to determine organic arsenic compounds in well water. The DPAA showed a protonated ion at m/z 263 [M + H]+ and a loss of H2O ion at m/z 245 [M + H , H2O]+ from protonated ion by the electrospray ionization time-of-flight mass spectrometry. The quantitative analysis of DPAA and PAA was performed by high-performance liquid chromatography inductively coupled plasma mass spectrometry and the system worked well for limpid liquid samples such as well water. Copyright © 2005 John Wiley & Sons, Ltd. [source] Square Wave Voltammetric Label-free Determination of the Natural Protein Material Silk FibroinCHINESE JOURNAL OF CHEMISTRY, Issue 11 2008Ming-Ming MA The electrochemical behavior of silk fibroin (SF) was investigated by cyclic voltammetry and square wave voltammetry in 0.01 mol/L HCl for the first time. Within the potential scan range of 0.0 to1.2 V (vs. SCE), two oxidative peaks at 0.91 V (Pa,1) and 0.43 V (Pa,2) as well as one reductive peak at 0.24 V (Pc ) were observed on cyclic voltammogram at scan rate of 0.2 V/s. The peak current of the peak Pa,1 was linear with SF concentration in the range of 5.8×10,8 to 1.1×10,6 mol/L, with the limit of detection 3.0×10,8 mol/L (S/N=3). The proposed method was of high selectivity without the interferences from the coexisting substances such as another natural protein material sericin and other small molecular substances. It was applied to the determination of SF in raw silk liquid samples without any pre-separation and pre-purification. [source] | ||||||||||