Predicting the absence of an unknown compound in a mass spectral database

2019 ◽  
Vol 25 (6) ◽  
pp. 439-444 ◽  
Author(s):  
Andrey Samokhin ◽  
Ksenia Sotnezova ◽  
Igor Revelsky
Keyword(s):  
Mass Spectra ◽  
Gas Chromatography Mass Spectrometry ◽  
Small Subset ◽  
Unknown Compound ◽  
Mass Spectral ◽  
Input Variables ◽  
Validation Set ◽  
Prediction Efficiency ◽  
Ms Search ◽  
Match Factor

Only a small subset of known organic compounds (amenable for gas chromatography/mass spectrometry) is present in the largest mass spectral databases (such as NIST or Wiley). Nevertheless, library search algorithms available in the market are not able to predict the absence of a compound in the database. In the present work, we have tried to implement such prediction by means of supervised classification. Training and validation set contained 1500 and 750 compounds, respectively. Two prediction sets (containing 750 and about 3000 mass spectra) were considered. The easiest-to-use models were built with only one input variable: match factor of the best candidate or InLib factor (both parameters were calculated within MS Search (NIST) software). Multivariate classification models were built by partial least squares discriminant analysis (PLS-DA); match factors of top n candidates were used as input variables. PLS-DA was found to be the most effective approach. The prediction efficiency strongly depended on the ‘uniqueness’ of mass spectra presented in the test set. PLS-DA model was able to correctly predict the absence of a compound in the database in 29.9% for prediction set #1 and in 74.4% for prediction set #2 (only 1.3% and 2.5% of compounds actually presented in the database were wrongly classified).

Gas Chromatographic and Mass Spectrometric Determination of Ametryn and Its N-Dealkylated Products

1984 ◽  
Vol 67 (5) ◽  
pp. 904-909
Author(s):  
Promode C Bardalaye ◽  
Willis B Wheeler ◽  
James L Templeton
Keyword(s):  
Gas Chromatography ◽  
Mass Spectra ◽  
Mass Spectrometric ◽  
Gas Chromatography Mass Spectrometry ◽  
Ionization Mass ◽  
Mass Spectral ◽  
Methane Chemical Ionization ◽  
Electron Impact Mass ◽  
Impact Mass

Abstract Gas chromatographic and mass spectrometric properties of ametryn and its N-dealkylated products were studied to establish the potential use in a recently reported method describing the residue analyses of these compounds by gas chromatography with N-P detection. Electron impact mass spectra show base peaks at the molecular ion (M+), and methane chemical ionization mass spectra give base peaks at (M + 1) ion for all the compounds studied. Characteristic mass spectral fragmentations of ametryn, GS-11354, GS-11355, and GS-26831 are presented. Combined gas chromatography-mass spectrometry rather than gas chromatography alone provides unambiguous residue characterization. The technique also allows quantitation of ametryn and its N-dealkylated products that cochromatograph with interfering materials present in a complex substrate.

Identification of Trialkyl and Triaryl Phosphates in Distilled and Super-Q Water

1981 ◽  
Vol 64 (3) ◽  
pp. 635-640
Author(s):  
David T Williams ◽  
Guy L Lebel ◽  
Frank M Benoit
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Flame Retardant ◽  
Mass Spectra ◽  
Gas Chromatography Mass Spectrometry ◽  
Chromatographic Retention ◽  
Unknown Compound ◽  
Chromatographic Columns ◽  
Diphenyl Phosphate ◽  
Q System

Abstract An unknown compound detected in an extract from water purified through a Millipore Super-Q system has been identified as tributoxyethyl phosphate by gas chromatographic retention times and by gas chromatography/mass spectrometry. Purified water from distillation systems also contained trialkyl/aryl phosphate plasticizers/flame retardant additives: Tris(l,3-dichloropropyl) phosphate and triphenyl phosphate were formally identified and isopropylphenyl diphenyl phosphate was tentatively identified from mass spectra interpretation and from GC retention times on 2 chromatographic columns.

scholarly journals Analysis of Modern and Ancient Artifacts for the Presence of Corn Beer; Dynamic Headspace Testing of Pottery Sherds from Mexico and New Mexico

2007 ◽  
Vol 1047 ◽  
Author(s):  
Theodore Borek ◽  
Curtis Mowry ◽  
Glenna Dean
Keyword(s):  
Mass Spectra ◽  
Direct Analysis ◽  
Archaeological Site ◽  
Gas Chromatography Mass Spectrometry ◽  
Mass Spectral ◽  
Northern Mexico ◽  
Organic Species ◽  
Pottery Sherds ◽  
Corn Kernels ◽  
Clay Pots

AbstractA large volume-headspace apparatus that permits the heating of pottery fragments for direct analysis by gas chromatography/mass spectrometry is described here. A series of fermented-corn beverages were produced in modern clay pots and the pots were sampled to develop organic-species profiles for comparison with fragments of ancient pottery. Brewing pots from the Tarahumara of northern Mexico, a tribe that regularly uses corn kernels to ferment a weak beer, were also examined for volatile residues and organic-species profiles were generated. Finally, organic species were generated from ancient potsherds from an archaeological site and compared with the modern spectra. The datasets yielded similar organic species, many of which were identified by computer matching of the resulting mass spectra with the NIST mass spectral library. Additional analyses are now underway to highlight patterns of organic species common to all the spectra. This presentation demonstrates the utility of GC/MS for detecting fermentation residues in the fabric of unglazed archaeological ceramics after centuries of burial. This, in turn, opens unexpected new doors for understanding the human past by means of GC/MS analyses.

scholarly journals The Stool Volatile Metabolome of Pre-Term Babies

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3341
Author(s):  
Alessandra Frau ◽  
Lauren Lett ◽  
Rachael Slater ◽  
Gregory R. Young ◽  
Christopher J. Stewart ◽  
...  
Keyword(s):  
Early Life ◽  
Solid Phase ◽  
Mass Spectrometry Data ◽  
Gas Chromatography Mass Spectrometry ◽  
Mass Spectral ◽  
Branched Chain Fatty Acids ◽  
Volatile Organic ◽  
Stool Samples ◽  
Branched Chain ◽  
Mixed Modelling

The fecal metabolome in early life has seldom been studied. We investigated its evolution in pre-term babies during their first weeks of life. Multiple (n = 152) stool samples were studied from 51 babies, all <32 weeks gestation. Volatile organic compounds (VOCs) were analyzed by headspace solid phase microextraction gas chromatography mass spectrometry. Data were interpreted using Automated Mass Spectral Deconvolution System (AMDIS) with the National Institute of Standards and Technology (NIST) reference library. Statistical analysis was based on linear mixed modelling, the number of VOCs increased over time; a rise was mainly observed between day 5 and day 10. The shift at day 5 was associated with products of branched-chain fatty acids. Prior to this, the metabolome was dominated by aldehydes and acetic acid. Caesarean delivery showed a modest association with molecules of fungal origin. This study shows how the metabolome changes in early life in pre-term babies. The shift in the metabolome 5 days after delivery coincides with the establishment of enteral feeding and the transition from meconium to feces. Great diversity of metabolites was associated with being fed greater volumes of milk.

scholarly journals Discrimination of structural isomers of amphetamine using carbon dioxide negative-ion chemical ionization mass spectrometry

1997 ◽  
Vol 13 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Kevin B. Thurbide ◽  
C. M. Elson ◽  
P. G. Sim
Keyword(s):  
Carbon Dioxide ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ion ◽  
Ionization Mass ◽  
Structural Isomers ◽  
Mass Spectral ◽  
Negative Ion Chemical Ionization ◽  
Spectral Behaviour ◽  
Carbon Dioxide Plasma

The negative‒ion chemical ionization mass spectra of a group of structural isomers of amphetamine have been studied using carbon dioxide as the reagent gas. Characteristic and reproducible differences are observed for each member of the set implying that this technique offers a means of distinguishing among groups of amphetamine isomers. Characteristic adducts to the molecular ion are observed in the form (M–[H]+[O]) and (M–[H]+[CO2]). Descriptions of some fragments are given based on the mass spectral behaviour of a set of analogue compounds and the results of oxygen-18 labelled carbon dioxide reagent gas experiments. Contents of the carbon dioxide plasma and their impact on various analytes is also discussed.

Mass Spectra of β-Keto Esters

1972 ◽  
Vol 50 (16) ◽  
pp. 2707-2710 ◽  
Author(s):  
Larry Weiler
Keyword(s):  
Mass Spectra ◽  
Carbonyl Groups ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Keto Esters ◽  
Fragmentation Patterns

The mass spectra of several γ-substituted β-keto esters have been recorded and interpreted. The fragmentation patterns are compared to those of α-substituted β-keto esters and are found to be very useful in differentiating the α- and γ-substituted isomers. The mass spectral fragmentation schemes are dominated by cleavages α to the carbonyl groups and by McLafferty rearrangements.

Degradation of bacteria mass spectral signals via hydrothermal processing and UV irradiation: relevance to life detection on icy moons

2021 ◽  
Author(s):  
Tara Salter ◽  
Hunter Waite ◽  
Mark Sephton
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Uv Irradiation ◽  
Gas Chromatography Mass Spectrometry ◽  
Xenon Lamp ◽  
Hydrothermal Processing ◽  
Mass Spectral ◽  
Icy Moons ◽  
Chromatography Mass Spectrometry ◽  
Life Detection

&lt;p&gt;The inferred subsurface oceans of the icy moons of Jupiter and Saturn, in particular Europa and Enceladus, may contain conditions suitable for life. Plumes of material have been detected from Enceladus and may also be present on Europa. These plumes could contain molecular signs of habitability that could be detected by mass spectrometers on orbiting spacecrafts, such as the upcoming Europa Clipper mission. However, these molecular markers may have degraded between their production and detection, for example by possible hydrothermalism in the subsurface ocean or by UV irradiation once carried into space by the plume. It is important to look at how the biosignatures degrade under different conditions as degradation processes need to be taken into account when analysing the data from life detection missions. We investigate how these two processes affect the mass spectral signals of terrestrial bacteria.&lt;/p&gt; &lt;p&gt;Two cyanobacteria samples, &lt;em&gt;Spirulina&lt;/em&gt; and &lt;em&gt;Chlorella&lt;/em&gt;, were subjected to hydrothermal processing and UV irradiation. Hydrous pyrolysis was used to simulate hydrothermal degradation. Experiments were carried out for 24 or 72 hours at temperatures between 200 and 300 &amp;#176;C. The pyrolyzed contents were subsequently extracted and analysed with gas chromatography-mass spectrometry (GC-MS). UV irradiation was carried out in a vacuum chamber (10&lt;sup&gt;-2&lt;/sup&gt; mbar), using a 300 W short arc xenon lamp at UV to near infrared wavelengths (~250 &amp;#8211; 800 nm). After UV irradiation, samples were analysed using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).&lt;/p&gt; &lt;p&gt;Our results show that hydrothermal processing of cyanobacteria affects the compound classes in different ways. Carbohydrate and protein components from the cyanobacteria were significantly affected, with phenol and indole derivatives detected. However, some of the biological fingerprint, such as straight-chain even numbered saturated fatty acids from lipid fragments, remain even at the harshest experimental conditions used in our study. This provides confidence that these diagnostic molecules could be used as fingerprints of biological materials on icy moons.&lt;/p&gt;

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