Electron Impact Mass Spectra Research Articles

Presence of tetrahydro-β-carboline-3-carboxylic acids in foods by gas chromatography—mass spectrometry as their N-methoxycarbonyl methyl ester derivatives

Various tetrahydro-β-carboline-3-carboxylic acids (THβC-3-COOH) are identified in commercial foods and drinks by GC-MS. Positive identification of 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA) is demonstrated in soy and tobasco sauces, wine, beer, wine vinegar, cider, orange juice, toasted bread, blue cheese and yoghurt. 1,2,3,4-Tetrahydro-β-carboline-3-carboxylic acid (THCA) occurs in toasted bread, beer, cider, wine vinegar, soy and tobasco sauce, orange juice and blue cheese. MTCA and THCA are reported for the first time in several of these products. MTCA appears as a mixture of two diastereoisomers with the same spectra. MTCA is the major THβC-3-COOH in foodstuffs except for toasted bread that contains more THCA. GC-MS analysis of N-methoxycarbonyl methyl ester derivatives of THβC-3-COOHs was used for chemical identification. Those derivatives were synthesized in a qualitatively using methyl chloroformate or methyl chloroformate and diazomethane reagents. Electron impact mass spectra of N-methoxycarbonyl-THβC-3-COOH methyl esters are reported and fragmentation assigned and discussed. These results prove the presence of THβC-3-COOHs in commercial foodstuffs suggesting their uptake during the daily consumption of foods.

Electron impact mass spectrometry of oxindole, pseudoindoxyle and indolenine derivatives

The electron impact mass spectra of 22 compounds, grouped in five series, containing the oxindole, pseudoindoxyle and indolenine rings, some of them with potential pharmacological interest, have been studied, and their fragmentation patterns have been proposed on the basis of metastable studies, accurate mass measurements and fragmentation schemes upon electron impact of structurally related alkaloids.

Mass Spectral Fragmentation Patterns of N,N′-Alkylidene and N,N′-Arylidene Bisamides

The electron impact mass spectra of several gem-bisamides are studied. The dominant peaks in the spectra of alkylidene and arylidene bisalkylamides are formed by the cleavage of the C—N bond of the amido group with charge retention on the nitrogen atom. This fragmentation, followed by the loss of a neutral molecule, leads to characteristic immonium ions as the base peaks. In contrast, alkylidene and arylidene bisarylamides undergo cleavage of the C—N bond with charge retention on the carbon atom, leading to the benzoyl ion C6H5CO+ as the dominant peak. © 1997 John Wiley & Sons, Ltd.

Development of a Method to Identify Keto Acids in Ozonated Fulvic Acid Solutions

A gas chromatographic-mass spectrometric method, combining an O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine–diazomethane double derivatization, was developed to identify major keto acids in ozonated fulvic acid solutions. Three keto acids, glyoxylic, pyruvic, and ketomalonic acid, four aldehydes and two analytical artifacts were identified. The detailed mass spectra, obtained in both electron impact and positive chemical ionization modes, and their fragment assignments are presented. Owing to the similarity of their electron impact mass spectra, electron impact mass spectra along with positive chemical ionization mass spectra are needed to identify these keto acids reliably. The effects of the formation of keto acids on water quality are also discussed. © 1997 by John Wiley & Sons, Ltd.

Letter: On the occurrence of (M – •SH)+ ions in the electron impact mass spectra and metastable ion mass spectra of thiophene-2-carboxamides

Letter: On the occurrence of (M – •SH)+ ions in the electron impact mass spectra and metastable ion mass spectra of thiophene-2-carboxamides

Fast GC—MS in Supersonic Molecular Beams

AbstractThe features of supersonic molecular beams (SMB) are used to improve gas chromatography—mass spectrometry (GC–MS) performance and establish a new method of fast GC–MS. In SMB, the sample compounds are vibrationally cooled such that their electron impact mass spectra are characterized by enhanced M+ peaks, together with library‐searchable fragments. A new ionization method, hyperthermal surface ionization (HSI), provides ultrasensitive ionization coupled with a tunable degree of selectivity for nitrogen‐containing drugs. SMB enables the use of very high carrier gas flow rates which, when a short megabore column is used, results in ultra‐fast GC–MS having conventional chromatographic peak widths. Thus, fast GC–MS in SMB can be performed with conventional quadrupole analyzers. The slightly reduced GC resolution can, in many cases, be compensated for by the selectivity of hyperthermal surface ionization or by the increased EI selectivity through enhanced M+. “Fast”, “very‐fast”, and “ultra‐fast” GC–MS are defined and demonstrated with drugs, and the ability to analyze underivatized steroids is shown. Practical examples are shown including ultra‐fast GC–MS of lidocaine in human plasma extract achieved in a few seconds and screening of other drugs, without any sample preparation or extraction, achieved in less than three minutes. We conclude that GC–SMB–MS exhibits a combination of faster analysis with improved sensitivity and selectivity, a wider range of molecules amenable to GC–MS, improved MS information, and higher a degree of flexibility.

Determination of Organic Phosphonates in Aqueous Samples Using Liquid Chromatography/Particle‐beam Mass Spectrometry

AbstractOrganic phosphonates are widely used, and in general, they are not easily biodegradable. Therefore, our interest was focussed on the development of an analytical method for the trace‐level determination of organic phosphonates in water. Our method combines preconcentration of the analytes by evaporating the water sample with the methylation of the phosphonates using diazomethane. Analysis of the totally methylated phosphonates is done by liquid chromatography coupled with mass Spectrometry by the particle‐beam interface. The derivatives could be clearly identified by their electron impact mass spectra as well as their chemical ionisation mass spectra. The totally methylated phosphonates can be separated by liquid chromatography using a 125 mm × 4 mm LiChrospher 100 Diol column and a gradient mobile phase containing n‐hexane and isopropyl alcohol. After optimizing preconcentration and derivatization procedures as well as all particle‐beam and mass spectra conditions, detection limits in the low ppb range were attained.

Review of direct MS analysis of environmental samples

Direct sampling mass spectrometry (DSMS) is an increasingly popular technique for rapid and sensitive measurement of organic pollutants in air, water, soil, and wastes. Detection limits are typically in the range of 1 ppb for volatile organic compounds (VOCs in water) with little or no sample preparation required and sample analysis times of less than 3 min. Despite the fast sample analysis time and consequent large sample throughput capability, there are numerous situations that would benefit from the ability to continuously monitor the concentration of targeted VOCs in real time. These include incinerator stack emissions, industrial wastewater streams, chemical process streams, vent emissions, exhaust emissions, groundwater and soil remediation process systems, waste-site off gas during remediation, fugitive emissions, hazardous workplace atmospheres, and soil gas analysis with the use of a dynamic depth profiling probe such as a cone penetrometer. During the past year, several pilot studies have been conducted with a DSMS field instrument for various real-time continuous monitoring applications. These studies have included the monitoring of VOCs in an incinerator stack, monitoring of VOCs in pilot-scale photolytic groundwater remediation systems, measurement of automobile exhaust in a moving vehicle, soil gas measurements in conjunction with a cone penetrometer, and in situ measurement of VOCs in groundwater with the use of a special sampling probe. In each instance, the DSMS instrument was configured with special sampling probes that extracted the VOCs from the sample matrix and transported them through an appropriate transfer line into a direct capillary restrictor interface to the ion trap. Targeted compounds were monitored based on unique peaks in the electron impact and proton transfer chemical ionization mass spectra. The real-time detection limits for VOCs in aqueous systems are in the range of 1 ppb, and in gaseous streams detection limits are in the range of approximately 10 ppb by volume. Temporal resolution ranges up to a maximum of 10 full-scan mass spectra per second, which provides the ability to monitor transient events in a sample stream that might be missed by discrete sample collection and analysis. © 1997 John Wiley & Sons, Inc. Field Analyt Chem Technol 1: 251–276, 1997

Synthesis and Mass Spectra of Sugar Thioimidazole Derivatives

ABSTRACT The reaction of 1-halogenophenylglucofuranoimidazolidine-2-thiones (1, 2) with benzyl chloride gives bicyclic S-benzylthioimidazolines (3,4) or tetrahydroxybutyl S-benzylthioimidazoles (7, 8) depending on the presence or absence of sodium hydrogencarbonate. In the latter case a partial desulphuration takes place. The electron impact mass spectra of compounds 1-4,7,8, and of the acetyl derivatives 5,6,9, and 10 are examined. The primary fragmentations and two fragmentation pathways were observed, the importance of which depends on the cyclic character of the molecule and of the nature of the substituent (OH or OAc). Present address: Instituto de Ciencias de Materiales, Universidad de Sevilla-CSIC, and Dpto de Quimica Inorgdnica, Facultad de Quimica, Universidad de Sevilla E-41012 Seville, Spain.

Distinguishing Amphetamine, Methamphetamine and 3,4-Methylenedioxymethamphetamine from Other Sympathomimetic Amines After Rapid Derivatization with Propyl Chloroformate and Analysis by Gas Chromatography—Chemical Ionization Mass Spectrometry

Abstract Misidentification of ephedrine and pseudoephedrine as methamphetamine has been reported because of similar retention times of their derivatives in gas chromatography as well as very similar mass spectral fragmentation patterns in the conventional electron impact mode of analysis. Recently, a new derivatization of amphetamine and methamphetamine has been described using propyl chloroformate. The derivatization is easily accomplished at room temperature by adding the derivatizing reagent in the extraction solvent because the reagent is stable in the presence of water. The electron impact mass spectrum of derivatized methamphetamine (base peak, m/z 144, other peaks at m/z 102, 58) is similar to the electron impact mass spectrum of both derivatized pseudoephedrine (base peak, m/z 144, other peaks, m/z 102, 58), and ephedrine (base peak, m/z 144, other peaks, m/z 102, 58). Therefore, misidentification of ephedrine and pseudoephedrine as methamphetamine is possible even if this new derivatization technique is used with conventional gas chromatography/electron impact mass spectrometry. We demonstrated that by using chemical ionization mass spectrometry, this problem can be eliminated. In the chemical ionization, using methane as a reagent gas, derivatized methamphetamine showed a protonated molecular ion as a base peak at m/z 236 and other strong peaks at m/z 144 and 119, both derivatized ephedrine and pseudoephedrine showed a base peak at m/z 192 and another strong peak at m/z 148, thus differentiating them clearly from methamphetamine. Amphetamine also showed a protonated molecular ion at m/z 222 and other strong peaks at m/z 130 and 119, whereas phenylpropanolamine after derivatization with propyl chloroformate showed a base peak at m/z 220 and another strong peak at m/z 238, thus differentiating it from amphetamine. The designer drug 3,4-methylenedioxymethamphetamine (MDMA) showed a molecular ion at m/z 279 using electron impact, after derivatization with propyl chloroformate. Using chemical ionization, a relatively stronger protonated molecular ion at m/z 280 was observed. We conclude that using chemical ionization instead of conventional electron impact and propyl chloroformate derivatization, misidentification of ephedrine or pseudoephedrine as methamphetamine or phenylpropanolamine as amphetamine can be eliminated.

Mass spectral study of isomeric benzoxazolinones by electron ionisation

The electron impact mass spectra of isomeric dihydrofurobenzoxazolinones, (1–3), hydroxy (2-methyl-2-propenyl)benzoxazolinones (4–5) and (2-methyl-2-propenyloxy)benzoxazolinones (6–7) are studied. The mass spectra of 1–3 show differences in the relative abundance of an ion at m/z 163. A mechanism involving the heteroatom of the benzoxazolinone ring which is para to the oxygen of the dihydrofuran ring has been proposed to explain the results. The mass spectra and collision-induced dissociation spectra of molecular ions of 4 and 5 are similar to those of 1 and 2, respectively, suggesting the rearrangement of 4 and 5 to 1 and 2, respectively, in the source of the mass spectrometer. The fragmentation of 6 and 7 supports the proposition of dihydrofuran ring opening in 1–3. The fragmentation of 6 and 7 is different in comparison to 4 and 5, suggesting that 6 and 7 do not rearrange to 4 and 5, respectively, either before or after ionisation.

Determination of anabolic steroids by HPLC with UV-vis-particle beam mass spectrometry.

This paper describes a general screening method for the determination of anabolic steroids in oil-based injectables, water suspensions, dietary supplements, and herbal drugs marketed in the form of capsules or tablets. The compounds are extracted into methanol, separated on a reversed-phase column with an acetonitrile-water gradient, and detected by using an ultraviolet visible (UV-vis) photodiode array detector and a particle beam mass spectrometric detector coupled in series. Identification is based on retention time, UV-vis spectra, and mass spectra. Mass spectral confirmation is accomplished by matching with a standard when available and by comparison with an electron impact mass spectra library that is either commercially available or generated in our laboratory. The tandem arrangement of the detectors provides qualitative and quantitative information from a single experiment by fully utilizing the inherent advantages associated with each detector. This method is applicable to all the anabolic steroids encountered in this laboratory so far.

Carbonyl dihalides: synthesis and spectroscopic characterization

M. J. Parkington, T. Anthony Ryan and K. R. Seddon, J. Chem. Soc., Dalton Trans., 1997, 251 DOI: 10.1039/A604090J

Electron Impact- and Chemical Ionization-Mass Spectrometry of Naturally Occurring Sesquiterpene Lactones fromAchillea spp.

The electron impact-mass spectra as well as the complementary chemical ionization-mass spectra (with the reactant gas ammonia) of various structural types of sesquiterpene lactones isolated from Achillea species are discussed in respect to the important information either gained by fragmentation patterns or by the quasimolecular ions. © 1997 by John Wiley & Sons, Ltd.

Electron impact mass spectra of some bis-(2-benzothiazolyl)furans and bis-(2-benzothiazolyl)thiophenes.

The electron impact mass spectra of some bis-(2-benzothiazolyl)furans and bis-(2-benzothiazolyl)thiophenes have been recorded and the identity of various ions in the mass spectra established. Compounds 1 and 2 present model substances and it is found that their fragmentation pathway is similar to the mono-(2-benzothiazoles). Compounds where the benzothiazolyl groups are directly substituted on the furan nuclei, but in different positions, exhibit two main pathways of fragmentation: fragmentation of the furan nucleus and fragmentation of the benzothiazole nucleus. Other compounds studied show specific fragmentation characteristic for divinyl furan compounds and for compounds with a phenyl substituent between two heterocyclic nuclei.

A cucumber mount for processing lung biopsy specimens from calves.

5. Fellows PA, Kyriakidis N, Mantle PG, Waight ES: 1981, Electron impact mass spectra of penitrem A, some derivatives and its analogues. Org Mass Spectrom 16:403-404. 6. Frisvad JC, Thrane U: 1987, Standardized high-performance liquid chromatography of 182 mycotoxins and other fungal metabolites based on alkylphenone retention indices and UV-VIS spectra (diode array detection). J Chromatogr 404:195-214. 7. Hayes AW, Presley DB, Neville JA: 1976, Acute toxicity of penitrem A in dogs. Toxical Appl Pharmacol 35:311-320. 8. Hocking AD, Holds K, Tobin NF: 1988, Intoxication by tremorgenic mycotoxin (penitrem A) in a dog. Aust Vet J 65:82-

The mass spectral fragmentation of some 2,3-dihydro-5-trifluoromethyl-7-(p-R-phenyl)-1,4-diazepines

Electron impact mass spectra of seven 2,3-dihydro-5-trifluoromethyl/methyl-7-(p-R-phenyl)-1,4-diazepinesR=H, CH3, OCH3, CF3, Cl, Br) have been recorded and are discussed. These systems dissociate by scission of the C2-C3 bond followed by loss of H. to give the [M-H]+ ion as the base peak. The fragmentation behaviour has been investigated using metastable scanning techniques and accurate mass measurements. The origin of some characteristic fragment ions is discussed.

Investigation of the Alkylamino Group of Aliphatic and Arylaliphatic Amines by Collision-induced Dissociation Mass Spectra ofC4H10N+ Immonium Ions

Collision-induced dissociation (CID) mass spectra of suitable ions (fragment ion mass spectra) play an important role in the structural elucidation of unknown drugs and metabolites in samples at submicrogram levels. Many drugs containing an alkylamino functionality show dominating α-cleavage reactions in their electron impact (El) mass spectra which produce intense C n H 2n+2 N + immonium ions. These are of high stability and contain valuable structural information on the amino group moiety. A tandem quadrupole mass spectrometer was used to record the fragment ion mass spectra of ten isomeric C 4 H 10 N + immonium ions (m/z 72). All the immonium ions studied showed distinct fragment ion mass spectra and gave sufficient information for an unequivocal identification of their structure. Therefore, CID mass spectra appear to be a reliable tool to establish the structure of aliphatic and arylaliphatic amines which generate C 4 H 10 N + immonium ions. These compound classes include phenethylamines, which have considerable pharmacological/toxicological activity. Nitrogen- and ring-substituted phenyl-2-aminopropanes are an important class of psychoactive drugs and controlled substance analogues (designer drugs) with high structural variety.

The Origin of Primary H+3 Ions in Mass Spectra

The triatomic hydrogen ion is found as a primary fragment in the photoionization and electron impact mass spectra of several small molecules. We show that its origin is charge separation of doubly charged parent ions.

Mass Spectrometric Evidence for the Generation of Benzyne from Benzoyl Peroxide in Thermolysis

Benzoyl peroxide gave rise to benzoic acid (at m/z 122) in its electron impact mass spectrum, and its perdeuterated counterpart produced perdeuterobenzoic acid, C6D5CO2D, at m/z 128 under the same conditions, An intramolecular hydrogen abstraction is proposed for the formation of benzoic acid from the peroxide in thermolysis. As a result of this reaction, benzyne would be generated simultaneously. Anthracene was employed to trap any of the reactive intermediate benzyne. Collision-induced dissociation of the ion of m/z 254 from the mixture of benzoyl peroxide and anthracene indicated that triptycene was obtained by the trapping reaction, therefore confirming that benzyne is generated from benzoyl peroxide in thermolysis.