Biomedical subjects

Y Rudich

Publications and source records attributed to Y Rudich.

7 recordsLinked to original sources

PubMed2005

New analytical method for the determination of levoglucosan, polyhydroxy compounds, and 2-methylerythritol and its application to smoke and rainwater samples.

Biomass burning is an important source of smoke aerosol particles, which contain water-soluble inorganic and organic species, and thus have a great potential of affecting cloud formation, precipitation, and climate on global and regional scales. In this study, we have developed a new chromatographic method for the determination of levoglucosan (a specific tracer for biomass burning particles), related polyhydroxy compounds, and 2-methylerythritol (recently identified as isoprene oxidation product in fine aerosols in the Amazon) in smoke and in rainwater samples. The new method is based on water extraction and utilizes ion-exclusion high-performance liquid chromatography (IEC-HPLC) separation and spectroscopic detection at 194 nm. The new method allows the analysis of wet samples, such as rainwater samples. In addition, aliquots of the same extracts can be used for further analyses, such as ion chromatography. The overall method uncertainty for sample analysis is 15%. The method was applied to the analysis of high-volume and size-segregated smoke samples and to rainwater samples, all collected during and following the deforestation fires season in Rondonia, Brazil. From the analysis of size-segregated samples, it is evident that levoglucosan is a primary vegetation combustion product, emitted mostly in the 0.175-1 microm size bins. Levoglucosan concentrations decrease below the detection limit atthe end of the deforestation fires period, implying that it is not present in significant amounts in background Amazon forest aerosols. The ratio of daytime levoglucosan concentration to particulate matter (PM) concentration was about half the nighttime ratio. This observation is rationalized by the prevalence of flaming combustion during day as opposed to smoldering combustion during night. This work broadens the speciation possibilities

Aerosols↗

PubMed2002

Negative mass instability for interacting particles in a 1D box: theory and application.

We demonstrate that the synchronization effect observed [Pedersen et al., Phys. Rev. Lett. 87, 055001 (2001)]], when a bunch of ions oscillates between two mirrors in an electrostatic ion beam trap, can be explained as a negative mass instability. We derive simple necessary conditions for the existence of a regime in which this dispersionless behavior occurs and demonstrate that in this regime, the ion trap can be used as a high resolution mass spectrometer.

Journal Article↗

PubMed2001

Ion motion synchronization in an ion-trap resonator.

Using a new type of ion trap, we demonstrate that the length of a packet of charged particles oscillating between two electrostatic mirrors will remain constant under special conditions. The effect can be understood in terms of phase synchronization, where, in a rather counterintuitive way, the repulsive Coulomb interaction between the ions actually holds the packet together. Application of this effect for mass spectrometry is discussed.

Journal Article↗

PubMed2001

Analysis of semivolatile organic compounds in atmospheric aerosols by direct sample introduction thermal desorption GC/MS.

A technique for identifying trace amounts of semivolatile organic compounds in atmospheric aerosols and in the NIST Urban Dust standard (SRM1649a) is presented. The technique is based on direct sample introduction (DSI) of small samples followed by thermal desorption in a conventional GC injector. The method enables injection of both solid and liquid samples. Validation of the method, including quantitative determination of EPA-targeted polycyclic aromatic hydrocarbons (PAHs), as well as the reproducibility and recovery efficiency tests are presented. The advantages of using aluminum foil as sampling filter are also discussed. Determination of different classes of compounds such as quinolines, methylquinoline isomers, PAHs, and n-monocarboxylic acids in the ambient size-segregated aerosol sample is also performed. The method was directly applied to the determination of C6-C16 n-monocarboxylic acids, eliminating the need for a complex sample preparation procedure. The small quantities needed for the analysis as well as the lack of complicated sample preparation steps enable fast characterization of semivolatile organic species present in time-resolved or size-segregated aerosol samples. Thus, this method can potentially be employed for air quality monitoring and field measurements as well as for fast screening of the organic content of ambient particles.

Aerosols↗

PubMed2001

Desert dust suppressing precipitation: a possible desertification feedback loop.

The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

Journal Article↗

PubMed2000

Fourier transform time-of-flight mass spectrometry in an electrostatic ion beam trap

We report on the application of an electrostatic ion beam trap as a mass spectrometer. The instrument is analogous to an optical resonator; ions are trapped between focusing mirrors. The storage time is limited by the residual gas pressure and reaches up to several seconds, resulting in long ion flight paths. The oscillation of ion bunches between the mirrors is monitored by nondestructive image charge detection in a field-free region and mass spectra are obtained via Fourier transform. The principle of operation is demonstrated by measuring the mass spectrum of trapped Ar+ and Xe+ particles, produced by a standard electron impact ion source. Also, mass spectra of heavier PEGnNa+ and bradykinin ions from a pulsed MALDI ion source were obtained. The long ion flight path, combined with mass-independent charge detection, makes this system particularly interesting for the investigation of large molecules.

Journal Article↗

PubMed2000

A comparative study of a liquid and a solid matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and collision cross section measurements.

We present experimental matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) results comparing a liquid (glycerol/K(4)[Fe(CN)(6)]) and a solid matrix (2,5-dihydroxybenzoic acid, DHB) with respect to analyte signal stability and initial ion velocity. For applications requiring stable production of analyte ions over a long period of time, the liquid matrix is superior to the solid matrix. The stable analyte ion signal obtained from a liquid matrix allowed the measurement of collision cross sections of small poly(ethylene glycol) (PEG(n)) adduct ions in the flight tube with good resolution. The initial velocity of these adduct ions was measured. It was found that analyte molecules from the liquid matrix have initial ion velocities significantly smaller than those from the solid matrix. MALDI-TOF measurements for large molecules using a liquid matrix are therefore likely to result in smaller systematic errors in mass calibrations due to initial ion velocity.

Ferrous Compounds↗