The inspection regime under the Chemical Weapons Convention (CWC) requires both the ability to identify low levels of chemical agents, precursors, and decomposition products in complex mixtures while ...at the same time not exposing the inspection site to the risk of loss of confidential information related to the chemical composition of the sample. The method of choice for such detection of low levels of chemical agents is gas chromatography separation with mass spectral identification (GC/MS), but the usual method of such analysis-an extensive examination of the GC/MS data file for spectra matching the compounds of interest-is both time-consuming, prone to missing low-level components, and difficult to ensure that chemicals not relevant to the CWC are not discovered. To deal with these problems, AMDIS (Automatic Mass spectral Deconvolution and Identification System), a method of automatically finding all of the distinct chemical components in the GC/MS data file and then compare them to a library of spectra of chemicals relevant to the CWC was developed.
Recent progress in metabolomics and the development of increasingly sensitive analytical techniques have renewed interest in global profiling, i.e., semiquantitative monitoring of all chemical ...constituents of biological fluids. In this work, we have performed global profiling of NIST SRM 1950, “Metabolites in Human Plasma”, using GC-MS, LC-MS, and NMR. Metabolome coverage, difficulties, and reproducibility of the experiments on each platform are discussed. A total of 353 metabolites have been identified in this material. GC-MS provides 65 unique identifications, and most of the identifications from NMR overlap with the LC-MS identifications, except for some small sugars that are not directly found by LC-MS. Also, repeatability and intermediate precision analyses show that the SRM 1950 profiling is reproducible enough to consider this material as a good choice to distinguish between analytical and biological variability. Clinical laboratory data shows that most results are within the reference ranges for each assay. In-house computational tools have been developed or modified for MS data processing and interactive web display. All data and programs are freely available online at http://peptide.nist.gov/ and http://srmd.nist.gov/.
An analytical methodology has been developed for extracting recurrent unidentified spectra (RUS) from large GC/MS data sets. Spectra were first extracted from original data files by the Automated ...Mass Spectral Deconvolution and Identification System (AMDIS; Stein, S. E. J. Am. Soc. Mass Spectrom. 1999, 10, 770–781 ) using settings designed to minimize spurious spectra, followed by searching the NIST library with all unidentified spectra. The spectra that could not be identified were then filtered to remove poorly deconvoluted data and clustered. The results were assumed to be unidentified components. This was tested by requiring each unidentified spectrum to be found in two chromatographic columns with slightly different stationary phases. This methodology has been applied to a large set of pediatric urine samples. A library of spectra and retention indices for derivatized urine components, both identified and recurrent unidentified, has been created and is available for download.
Laser-induced ionization signals are observed in a premixed C
2
H
2
/air flame at the sooting limit and are attributed to thermal ionization of very small particles. The mobilities of these species ...are derived from ion velocity measurements and compared with the mobility of Na
+
for identical flame conditions. From a series of measured mobilities, estimates are made for the particle mass (2300-6100 amu) and diameter (1.6-2.2 nm). This experimental method is thus a new optical means for probing the early stages of soot formation.
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