Mass spectrometry deconvolution

GC retention index and mass spectral software/ database AMDIS (Automated Mass Spectrometry Deconvolution and Identification System). The AMDIS is distributed with the OCAD for free to SPs. 

AMDIS Automated Mass Spectrometry Deconvolution and Identification System... 

NIST have produced a freely available package called AMDIS (automated mass spectrometry deconvolution and identification system) for the analysis of GC/MS data sets. Developed to assist in the task of verifying the international Chemical Weapons Convention (http //www.opcw.org/) financially supported by the US Defense Special Weapons Agency (DSWA, US Department of Defense) the AMDIS program is also distributed with the NIST 02 Mass Spectral Library (see above). 

Reinhold, B. B. and Reinhold, V. N. Electrospray ionization mass spectrometry Deconvolution by an entropy-based algorithm. /. Am. Soc. Mass Spectrom., 3,207,1992. 

Reinhold BB, Reinhold VN. Electrospray ionization mass spectrometry deconvolution by an entropy-based algorithm. J Am Soc Mass Spectrom. 1992 3 207-15. 

An advantage of the microbore gas chromatrography/time-of-flight mass spectrometry (GC/TOFMS) method over the other two approaches is that separation efficiency need not be compromised for speed of analysis. The rapid deconvolution of spectra ( scan rate ) with TOFMS makes it the only MS approach to achieve several data points across a narrow peak in full-scan operation. However, the injection of complex extracts deteriorates performance of microbore columns quickly, and an increased LOD and decreased ruggedness result. Microbore columns may be used in water analysis if the LOD is sufficiently low, but they can rarely be used in real-life applications to complicated extracts. 

If we consider only a few of the general requirements for the ideal polymer/additive analysis techniques (e.g. no matrix interferences, quantitative), then it is obvious that the choice is much restricted. Elements of the ideal method might include LD and MS, with reference to CRMs. Laser desorption and REMPI-MS are moving closest to direct selective sampling tandem mass spectrometry is supreme in identification. Direct-probe MS may yield accurate masses and concentrations of the components contained in the polymeric material. Selective sample preparation, efficient separation, selective detection, mass spectrometry and chemometric deconvolution techniques are complementary rather than competitive techniques. For elemental analysis, LA-ICP-ToFMS scores high. 

Sinha, A.E., Hope, J.L., Prazen, B.J., Fraga, C.G., Nilsson, E.J., Synovec, R.E. (2004a). Multivariate selectivity as a metric for evaluating comprehensive two-dimensional gas chromatography-time-of-fhght mass spectrometry subjected to chemometric peak deconvolution. J. Chromatogr. A 1056, 145-154. 

Ferrige, A. G., Seddon, M. J., Jarvis, S. (1991). Maximum-entropy deconvolution in electrospray mass-spectrometry. Rapid Commun Mass Sp. 5(8), 374-377. 

HALKET, J.M., PRZYBOROWSKA, A., STEIN, S.E., MALLARD, W.G., DOWN, S., CHALMERS, R.A., Deconvolution gas chromatography/mass spectrometry of urinary organic acids—potential for patem recognition and automated identification of metabolic disorders, Rapid Commun. Mass Spectrom., 1999,13,279-284. 

DAGAN, S., Comparison of gas chromatography-pulsed flame photometric detection-mass spectrometry, automated mass spectral deconvolution and identification system and gas chromatography-tandem mass spectrometry as tools for trace level detection and identification, J. Chromatogr., A., 2000,868,229-247. 

For solution-phase libraries that are composed of mixtures of compounds, the difficulty of analysis escalates with increasing numbers of compounds. Typically, large mixtures of compounds are not analyzed before screening, whereas small ones may be analyzed for reaction completeness using mass spectrometry, HPLC, NMR, or combinations thereof. The identification and analysis of active compounds from these mixtures is painstakingly tedious, and often complete characterization is possible only after deconvolution procedures and resynthesis of the active compound. For solid-phase libraries, the methods currendy developed are discussed below. 

Gas chromatography time-of-flight mass spectrometry (GC-TOF) allows better deconvolution than do most GC-MS instruments because they can record spectra, and thus sample various methods quickly. 

Figure 7.14 Deconvoluted ESI mass spectra from an equimolar mixture of 19 thiols

Kende, A., Z. Csizmazia, T. Rikker, et al. 2006. Combination of stir bar sorptive extraction—retention time locked gas chromatography-mass spectrometry and automated mass spectral deconvolution for pesticide identification in fruits and vegetables. Microchem. J. 84 63-69. 

The new field of molecular diversity raises three issues which need to be addressed by the organic analytical chemistry community (i) What tools can we use for following solid-phase reactions (ii) How can we analyze all these samples (iii) How much characterization of libraries is possible or appropriate This chapter deals with these problems and reviews the literature since a similar review written in June 1995 [2] (earlier seminal publications are described where appropriate). Other analytical issues such as decoding of combinatorial libraries or the applications of affinity separations and single-bead mass spectrometry for library deconvolution are dealt with in other chapters of this book. 

Figure 15. Deconvoluted ESI spectrum derived from the raw data for ricin. (Reprinted from Analytical Biochemistry, 279, Despeyroux etal., Characterization of Ricin Heterogeneity by Electrospray Mass Spectrometry, Capillary Electrophoresis, and Resonant Mirror, pp. 23-36 (2000), with permission from Elsevier)...

The mass spectra of 7, obtained from the NADPH/02/P-450 oxidation of 5, and 8 are compared in Table IV. Three isotopic species are expected for the allylic hydroxylation of 5. Oxidation with removal of hydrogen will produce 7-d3and 7a-d3. Extensive controls have demonstrated that 7-d3 and 7a-d3 are indistinguishable by mass spectrometry because of rapid 1,3-migration of the siloxy group upon electron impact. Oxidation with deuterium removal leads to the production of 7-d2 (Scheme 4). By this analysis, the isotope effect is simply the ratio of 5-d3 (and 5a-d3) to 5-d2 in the oxidized sample. Deconvolution of the parent region (with appropriate correction for carbon and silicon... 

Using a GA for generation of diversity, one may chose a molecular property and select for molecules that are different with respect to that property. A dissimilar, unique molecular weight is such a property that would facilitate the deconvolution of combinatorial library mixtures by mass spectrometry. The optimal design of such mixtures was the target function in a recent application of a GA [26],... 

---