المؤلفون: B. Sudarshana Reddy, Soumen Saha, L. Sridhar, G. Narahari Sastry, Suman Prabhakar, P. Pavankumar

المصدر: Rapid Communications in Mass Spectrometry. 32:1126-1134

مصطلحات موضوعية: chemistry.chemical_classification, Double bond, 010405 organic chemistry, Chemistry, Electrospray ionization, Organic Chemistry, 010402 general chemistry, Tandem mass spectrometry, 01 natural sciences, Dissociation (chemistry), 0104 chemical sciences, Analytical Chemistry, Adduct, Ion, Ion binding, Mass spectrum, Physical chemistry, Spectroscopy

الوصف: Rationale The intercellular and intracellular transport of charged species (Na+ /K+ ) entail interaction of the ions with neutral organic molecules and formation of adduct ions. The rate of transport of the ions across the cell membrane(s) may depend on the stability of the adduct ions, which in turn rely on structural aspects of the organic molecules that interact with the ions. Methods Positive ion ESI mass spectra were recorded for the solutions containing fatty acids (FAs) and monovalent cations (X=Li+ , Na+ , K+ , Rb+ and Cs+ ). Product ion spectra of the [FA+X]+ ions were recorded at different collision energies. Theoretical studies were exploited under both gas phase and solvent phase to investigate the structural effects of the fatty acids during cationization. Stability of [FA+X]+ adduct ions were further estimated by means of AIM topological analyses and interaction energy (IE) values. Results Positive ion ESI-MS analyses of the solution of FAs and X+ ions showed preferential binding of the K+ ions to FAs. The K+ ion binding increased with the increase in number of double bonds of FAs, while decreased with increase in the number of carbons of FAs. Dissociation curves of [FA+X]+ ions indicated the relative stability order of the [FA+X]+ ions and it was in line with the observed trends in ESI-MS. The solvent phase computational studies divulged the mode of binding and the binding efficiencies of different FAs with monovalent cations. Conclusions Among the studied monovalent cations, the cationization of FAs follow the order K+ >>Na+ >Li+ >Rb+ >Cs+ . The docosahexaenoic acid showed high efficiency in binding with K+ ion. The K+ ion binding efficiency of FAs depends on the number of double bonds in unsaturated FAs and the carbon chain length in saturated FAs. The cationization trends of FAs obtained from the ESI-MS, ESI-MS/MS analyses were in good agreement with solvent phase computational studies.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::cd586ecaae9e8f0c1eb72bc36e95b155Test
https://doi.org/10.1002/rcm.8143Test

المؤلفون: T. Sony, L. Sai Sachin, L. Sridhar, Suman Prabhakar, Vvs Lakshmi

المصدر: European journal of mass spectrometry (Chichester, England). 24(6)

مصطلحات موضوعية: Chemical Warfare Agents, Silylation, Injury control, 010405 organic chemistry, Chemistry, Accident prevention, 010401 analytical chemistry, Poison control, General Medicine, 01 natural sciences, Atomic and Molecular Physics, and Optics, Chemical Weapons Convention, 0104 chemical sciences, Triethanolamine, medicine, Organic chemistry, Gas chromatography–mass spectrometry, Spectroscopy, medicine.drug

الوصف: N-Alkylaminoethanols, N,N′-dialkylaminoethanols, and triethanolamine are the hydrolyzed products or precursors of V-agents/nitrogen mustards. These compounds are prone to undergo oxidation in environmental matrices. Detection of the oxidized products provides a clue for the presence of parent amine compounds and it is an important task in the verification process of chemical weapons convention. Gas chromatography/mass spectrometry is the technique of choice for the detection of most of the chemical warfare agents; however, it is ideal to develop gas chromatography/mass spectrometry techniques for all the possible degradation products of chemical warfare agents as well. In general, the N-oxides of amines are expected to be thermally unstable; hence, the gas chromatography/mass spectrometry analysis of the N-oxides of triethanolamine, N-alkyldiethanolamines and N,N′-dialkylaminoethanols is not explored. In this study, the N-oxides of chemical weapons convention-related aminoethanols (13 compounds) were successfully silylated and then analyzed by gas chromatography/mass spectrometry under electron ionization and chemical ionization techniques. The electron ionization mass spectra showed abundant molecular ions and structure indicative fragment ions including [M-(O+CH2CH2OH)]+. The alkyl groups attached to nitrogen resulted in structure-specific fragment ions that enable differentiation of isomeric compounds. The methane/chemical ionization spectra showed considerably abundant [M+H]+ (>10%) and the expected adduct ions. The retention indices of all the compounds were calculated using Van den Dool's formula. The gas chromatography/mass spectrometry data together with retention index values could be used for unambiguous identification of the N-oxides of aminoethanols during off-site analysis or proficiency tests.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ffcd723b686ecd1dc82e2394923cf7b3Test
https://pubmed.ncbi.nlm.nih.gov/30301377Test

المؤلفون: L. Sridhar, Sripadi Prabhakar, M. R. V. S. Murty, Rajendiran Karthikraj, Mariappanadar Vairamani, N. P. Raju

المصدر: Analytical and Bioanalytical Chemistry. 406:5093-5102

مصطلحات موضوعية: chemistry.chemical_classification, Quinuclidines, Spectrometry, Mass, Electrospray Ionization, Chromatography, Chemistry, Electrospray ionization, Carboxylic acid, Static Electricity, BSTFA, Mass spectrometry, Biochemistry, Isocyanate, Gas Chromatography-Mass Spectrometry, Analytical Chemistry, chemistry.chemical_compound, Ethanolamines, Reagent, Hydroxides, Humans, Organic chemistry, Chemical Warfare Agents, Sulfhydryl Compounds, Gas chromatography–mass spectrometry, Derivatization, Isocyanates

الوصف: Most of the precursors and/or degradation products related to the Chemical Weapons Convention (CWC) are polar. Identification of these molecules in environmental samples provides clues regarding the alleged usage and/or synthesis of the parent toxic chemicals. Such polar compounds need to be derivatized in order to analyze them by gas chromatography-mass spectrometry (GC-MS). In this study, we developed a new derivatizing reagent, para-tolyl isocyanate (PTI), for derivatization of polar CWC-related compounds. The PTI reagent selectively derivatizes the -OH and/or-SH functional groups with high efficiency, but does not react with carboxylic acid (-COOH) or phosphonic acid (-(O)P(OH)2) groups. The PTI derivatives of dialkyl aminoethanols, dialkyl aminoethanol-N-oxides, and 3-quinuclidinol were successfully eluted through GC, and their electron ionization (EI) mass spectra were distinct and provided the structure information by which the isomeric compounds can be easily distinguished. We also calculated the GC-retention index values that can be used for further confirmation of the target compounds. All the studied PTI derivatives can be analyzed by EI-MS with direct insertion probe and/or by direct electrospray ionization mass spectrometry (ESI-MS) together with the MS-MS data; both sets of data provide full structure information. The PTI reagent was found to be better in some respects than the conventional bistrimethylsilyl trifluoroacetamide (BSTFA), a trimethyl silylating reagent. The PTI reagent is commercially available, and the PTI derivatives are highly stable for months and are not sensitive to moisture. The applicability of the PTI derivatization for trace-level determination of the target CWC-related polar compounds in environmental matrices and in human plasma samples is also evaluated.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::6541b99944f53098af0885aaefd08760Test
https://doi.org/10.1007/s00216-014-7624-zTest

المؤلفون: M. R. V. S. Murty, Mariappanadar Vairamani, Rajendiran Karthikraj, L. Sridhar, N. Prasada Raju, Sripadi Prabhakar

المصدر: Rapid Communications in Mass Spectrometry. 27:1461-1472

مصطلحات موضوعية: Chemical ionization, McLafferty rearrangement, Fragmentation (mass spectrometry), Chemistry, Organic Chemistry, Analytical chemistry, Mass spectrum, Gas chromatography, Gas chromatography–mass spectrometry, Mass spectrometry, Spectroscopy, Electron ionization, Analytical Chemistry

الوصف: RATIONALE The isomeric dialkyl alkylphosphonothiolates and dialkyl alkylphosphonothionates are listed as scheduled chemicals of the Chemical Weapons Convention (CWC) implemented by the OPCW. The P-S and P-R bond connectivity has to be correctly identified for the verification of the CWC. The present study demonstrates successful identification of the target isomers by selective fragmentation under electron ionization (EI) or chemical ionization (CI) conditions. METHODS All the studied isomeric compounds (27 in total) were synthesized in our laboratory using established methods, then analyzed by EI and CI gas chromatography/mass spectrometry (GC/MS) using an Agilent 6890 gas chromatograph equipped with a HP-5MS capillary column and interfaced to a 5973 N mass-selective detector. The retention index (RI) values of all the compounds were calculated using Van den Dool's formula. GC/MS/MS and GC/HRMS experiments were also performed using a VG-Autospec (magnetic sector) and JEOL-AccuToF (time-of-flight) mass spectrometer, respectively. RESULTS The EI mass spectra of all the compounds had an abundant molecular ion at m/z 182, except in the case of a few selected butyl-substituted compounds, where this ion was of low abundance. The EI fragmentation pathways include α-cleavage, McLafferty rearrangement, McLafferty + 1 rearrangement, O/S-alkyl radical loss, and an alkene loss with a hydrogen shift. The characteristic fragment ions and their relative abundances are significant in elucidating the alkyl group attached to the P/S/O-atoms as well as the P-S/P = S bond connectivity. The EI and CI mass spectra together with RI values enable unambiguous identification of all the studied isomeric compounds. CONCLUSIONS The present study highlights the structural characterization of the isomeric phosphonothiolates and phosphonothionates based on their selective EI fragmentation. The assigned fragmentation pathway helps in the assignment of P-S and P-alkyl connectivity in phosphonothiolates and phosphonothionates, consequently the structure of the unknown compounds. The EI mass spectra (27 compounds) of isomeric compounds are immensely useful in the OPCW official proficiency tests and for off-site analysis.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::e6185c2254c660e01a4f5d04f0c1d795Test
https://doi.org/10.1002/rcm.6596Test

المؤلفون: Mariappanadar Vairamani, Rajendiran Karthikraj, L. Sridhar, N. Prasada Raju, M. R. V. S. Murty, Sripadi Prabhakar

المصدر: International Journal of Mass Spectrometry. 333:15-20

مصطلحات موضوعية: chemistry.chemical_classification, Electrospray ionization, Inorganic chemistry, chemistry.chemical_element, Condensed Matter Physics, Tandem mass spectrometry, Mass spectrometry, Nitrogen, Dissociation (chemistry), Ion, chemistry, Fragmentation (mass spectrometry), Organic chemistry, Physical and Theoretical Chemistry, Instrumentation, Spectroscopy, Alkyl

الوصف: Chemical weapons convention (CWC) includes verification of chemical warfare agents and their precursors/degradation products in various environmental matrices. Nitrogen mustards and N,N-dialkylaminoethyl-2-chlorides, the precursors for the synthesis of nerve agents (VX type of compounds), are prone to undergo oxidation in environmental matrices or during decontamination process. Thus, screening of the oxidized products of the CWC related compounds is also an important task in the verification process. Here we report the successful characterization of the N-oxides of nitrogen mustards and N,N-dialkylaminoethyl-2-chlorides under positive ion electrospray ionization tandem mass spectrometry conditions. The collision-induced dissociation spectra of [M+H] + ions show distinct product ions that enable unambiguous identification of studied N-oxides, including those of isomeric compounds. The proposed fragmentation pattern of these compounds is based on isotopic abundance ratio, high-resolution mass spectrometry data and product/precursor ion spectra. The CID spectra of [M+H] + ions of the studied compounds include a specific product ion, [MH−( OH + CH 2 Cl)] + , and distinctive alkene losses to recognize the attached alkyl group to the nitrogen.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::ad0c6cfced40b3d4a44e89d541bf9230Test
https://doi.org/10.1016/j.ijms.2012.08.005Test

المؤلفون: L. Sridhar, S. V. Eswaran, Sripadi Prabhakar, Prem Dureja, Tara Devi S. Ashok, P. Raghunathan, Manoj Gaur, Mayurika Goel

المصدر: Monatshefte für Chemie - Chemical Monthly. 143:283-288

مصطلحات موضوعية: Antifungal, Sclerotium, biology, Rhizoctonia bataticola, Chemistry, medicine.drug_class, Fusarium oxysporum, Click chemistry, medicine, Organic chemistry, General Chemistry, biology.organism_classification, Combinatorial chemistry

الوصف: Click chemistry was used to synthesize a series of biaryl-based bis(1,2,3-triazoles). Their antifungal activity was evaluated against three soil-borne plant pathogenic fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and Fusarium oxysporum, using the food poison technique at concentrations of 62.5–500 μg/cm3.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::203ee6ade683b28c1b425411ac5658f2Test
https://doi.org/10.1007/s00706-011-0652-xTest

المؤلفون: Mariappanadar Vairamani, L. Sridhar, Sripadi Prabhakar, N. Prasada Raju, M. R. V. S. Murty, Rajendiran Karthikraj

المصدر: Rapid Communications in Mass Spectrometry. 25:533-542

مصطلحات موضوعية: chemistry.chemical_classification, Aqueous solution, Electrospray ionization, Organic Chemistry, Analytical chemistry, Mass spectrometry, Medicinal chemistry, Dissociation (chemistry), Analytical Chemistry, Ion, chemistry, Fragmentation (mass spectrometry), Molecule, Spectroscopy, Alkyl

الوصف: N,N'-Dialkylaminoethanols are the hydrolyzed products or precursors of chemical warfare agents such as V-agents and nitrogen mustards, and they are prone to undergo oxidation in environmental matrices or during decontamination processes. Consequently, screening of the oxidized products of aminoethanols in aqueous samples is an important task in the verification of chemical weapons convention-related chemicals. Here we report the successful characterization of the N-oxides of N,N'-dialkylaminoethanols, alkyl diethanolamines, and triethanolamine using positive ion electrospray ionization mass spectrometry. The collision-induced dissociation (CID) spectra of the [M+H](+) and [M+Na](+) ions show diagnostic product ions that enable the unambiguous identification of the studied N-oxides, including those of isomeric compounds. The proposed fragmentation pathways are supported by high-resolution mass spectrometry data and product/precursor ion spectra. The CID spectra of [M+H](+) ions included [MH-CH(4)O(2)](+) as the key product ion, in addition to a distinctive alkene loss that allowed us to recognize the alkyl group attached to the nitrogen. The [M+Na](+) ions show characteristic product ions due to the loss of groups (R) attached to nitrogen either as a radical (R) or as a molecule [R+H or (R-H)] after hydrogen migration.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::f68a363420697acb6c579b7799971d24Test
https://doi.org/10.1002/rcm.4879Test

المؤلفون: Prem Dureja, Tara Devi S. Ashok, Sripadi Prabhakar, Manoj Gaur, S. V. Eswaran, Mayurika Goel, P. Raghunathan, L. Sridhar

المصدر: ChemInform. 43

مصطلحات موضوعية: Antifungal, Sclerotium, biology, medicine.drug_class, Chemistry, Rhizoctonia bataticola, Fusarium oxysporum, Click chemistry, medicine, Triazole derivatives, Organic chemistry, General Medicine, biology.organism_classification

الوصف: Click chemistry was used to synthesize a series of biaryl-based bis(1,2,3-triazoles). Their antifungal activity was evaluated against three soil-borne plant pathogenic fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and Fusarium oxysporum, using the food poison technique at concentrations of 62.5–500 μg/cm3.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::0e9c394cb454a1983d2182465a351716Test
https://doi.org/10.1002/chin.201221132Test