Electron Impact Ionization Mass Spectra Research Articles

Electron-impact ionization of benzoic acid, nicotinic acid and their n-butyl esters: An approach to regioselective proton affinities derived from ionization and appearance energy data

Electron-impact ionization mass spectra, the decay of metastable ions, ionization and appearance energies and bond energies, as dissociation energies, are reported for the title compounds. An ionization energy of 9.47 eV was obtained for benzoic acid, 9.43 eV for benzoic acid n-butyl ester, 9.61 eV for nicotinic acid and 9.97 eV for nicotinic acid n-butyl ester. Molecular ions of both butyl esters show two common main fragmentation pathways: the first process is a McLafferty rearrangement, characterized by the transfer of one H-atom from the aliphatic ester chain, which leads to the ions of either the organic acid or 1-butene. From their appearance energies and known thermodynamic data, gas-phase formation enthalpies ( Δ H f 0 ) of the parent n-butyl esters are calculated. Values of Δ H f 0 = ( − 4.29 ± 0.3 ) eV for benzoic acid n-butyl ester and Δ H f 0 = ( − 3.66 ± 0.3 ) eV for nicotinic acid n-butyl ester were obtained. The second process is characterized by the transfer of two H-atoms from the ester chain leading to a protonated form of the corresponding organic acids and C 4H 7 radicals. Good evidence is provided for the formation of methylallyl radicals. Appearance energies are used to calculate a proton affinity (PA) for benzoic acid. The obtained value of PA = (8.73 ± 0.3) eV, corresponding to a protonation of the carbonyl group, is in close corroboration with published data (PA = 8.51 eV). Activation energies for the intermediate H-transfers were found to be insignificant. This methodic gateway is applied to the system of nicotinic acid and its butyl ester. Adopting the formation of a methylallyl radical, the obtained proton affinity of nicotinic acid, PA = 8.58 eV, is very near to the published data of benzoic acid. An alternative fragmentation mechanism leading to a value of PA ≈ 9.5 eV (typical for a protonation of the pyridine-nitrogen) is very unlikely. It is concluded that this transfer of two H-atoms from the ester chain is controlled by a charge switching between the carboxylic oxygen atoms which leads to a regiospecific protonation site, in this case to the protonated carbonyl group. This is conform with a B3LYP DFT calculation with a corresponding proton affinity of PA = 8.29 eV.

GC-MS detection and tentative characterization of two noscapine metabolites in human urine and their potential as markers for opium and illicit heroin use

Urine samples for cases of drug abuse are regularly screened by gas chromatography-mass spectrometry (GC-MS) after enzyme hydrolysis, liquid-liquid extraction, and trimethylsilyl (TMS) derivatization. During such routine analysis, two compounds (labeled as X1 and X2) were detected in urine samples of opium and illicit heroin users as their TMS derivatives, which led us to tentatively characterize the compounds. It was found that the compounds were noscapine metabolites as determined by GC-MS in both electron-impact ionization (EI) and chemical ionization modes. Together with the analysis of fragment ions in the EI mass spectra, the X1 and X2 compounds were further assigned as 6,7-dihydroxynoscapine and its desmethyl product at either position 6′ or 7′, respectively. The two tentatively characterized compounds were found to be useful as markers for excluding medicinal morphine use and for refuting claims of codeine use or Golden-Seal preparation use often made by heroin addicts to evade conviction. By addition of the above two metabolites, the arsenal of markers for opium and illicit heroin use has now been strengthened.

Identification and quantitative determination of 5-methoxy-N,N-di-n-propyltryptamine in urine by isotope dilution gas chromatography-mass spectrometry

A simple method for analysis of 5-methoxy-N,N-di-n-propyltryptamine (5-MeO-DPT) in urine has been developed using gas chromatography-mass spectrometry (GC-MS) with tetradecadeuterated 5-MeO-DPT as internal standard, which is useful for discrimination from 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT). These tryptamine designer drugs were extracted from urine with Extrelut, and derivatized with trifl uoroacetic anhydride prior to GC-MS analysis. The recovery of 5-MeO-DPT from urine was 90.7%; the calibration curve showed linearity in the range of 0.01–2.0 μg/ml. When urine samples containing two different concentrations (0.1 and 1.0 μg/ml) of 5-MeO-DPT were analyzed, the coeffi cients of variation for intraday and interday testing ranged from 3.11% to 5.82%. The established method was applied to an acute poisoning case in which 5-MeO-DIPT abuse had been suspected. Unexpectedly, 5-MeO-DIPT could not be detected, but 5-MeO-DPT was found in the subject’s urine and in an aqueous sample seized upon investigation of the poisoning; the electron-impact ionization and chemical ionization mass spectra well agreed with those of authentic 5-MeO-DPT. The concentration of 5-MeO-DPT in urine of this case was 0.37 μg/ml. Although several reports have appeared describing poisoning cases of 5-MeO-DIPT, which carries the street name “Foxy,” to our knowledge, this is the first report of GC-MS analysis of 5-MeO-DPT and demonstration of its use in a poisoning case.

Identification of corrosion inhibiting long-chain primary alkyl amines by gas chromatography and gas chromatography–mass spectrometry

Gas chromatography with flame-ionization detection (FID) and gas chromatography–mass spectrometry (GC/MS) has been used to identify long-chain primary alkyl amines after derivatization with trifluoroacetic anhydride (TFAA). Electron impact ionization (EI) and positive chemical ionization (PCI) mass spectra of trifluoroacetylated derivatives of the identified alkyl amines are presented. The corrosion inhibiting alkyl amines were applied in the investigation of a new anticorrosive and antifouling formulation for water–steam circuit of energy systems in the power industry.

Characterization of gem-difluoropropargyl synthons through HF loss from protonated molecules in methane chemical ionization mass spectra

Electron impact and methane chemical ionization mass spectra were obtained following gas chromatography/mass spectrometry for several gem-difluoropropargyl compounds, which had been synthesized as potential intermediates for synthesis of gem-difluoromethylene-containing C-3 acetylenes. EI spectra were variable with respect to the presentation of molecular ions, depending on substituent functional groups present. Methane-CI spectra were characterized by loss of 19 mass units from molecular weight with all compounds examined. These [ M − 19] + ions often presented as base peaks of the CI spectra, and were more reliably present and abundant than [ M + 1] + ions for these compounds. These ions could have been formed by elimination of HF from the protonated molecules under conditions of methane chemical ionization.

Application of large volume injection GC–MS to analysis of organic compounds in the extracts and leachates of municipal solid waste incineration fly ash

Organic solvent and water extracts of fly ash from a Milan (Italy) municipal solid waste incinerator (MSWI) were analyzed by large volume injection-gas chromatography–mass spectrometry (LVI-GC–MS) with programmable temperature vaporizer (PTV). Using injection volumes of 10–100 μl, typically over a hundred compounds were detected in organic solvent extracts and ca. 35% of them could be tentatively identified from their electron impact ionization mass spectra. A protocol for the determination of the maximum amount of a potential environmental pollutant available for leaching (availability test) was developed for four selected target compounds: pentachlorobenzene (PeCB), hexachlorobenzene (HxCB), o-terphenyl ( o-TPH) and m-terphenyl ( m-TPH). Key parameters, extraction time and liquid-to-solid ratio ( L/ S), were studied in more detail. Recoveries of PeCB, HxCB and o-TPH spiked into the fly ash samples at two concentration levels ranged from 38% to 53% for freshly spiked and from 14% to 40% for 40-day aged fly ash. Recoveries of m-TPH were 8% to 11% from freshly spiked and less than 3% from aged spiked fly ash. The native amounts in Milan MSWI fly ash, determined in an interlaboratory exercise using the developed protocol, were 31 ng/g PeCB, 34 ng/g HxCB, 72 ng/g o-TPH and 4.4 ng/g m-TPH. A separate methodology was developed for the determination of compounds extracted from fly ash by water (leaching test). Following 8-h sonication at L/ S 20, the leached amounts of PeCB, HxCB and o-TPH were 1.1, 3.1 and 6.0 ng/g fly ash, respectively.

Identification of Brominated Carbazoles in Sediment Cores from Lake Michigan

During the analysis of brominated flame retardants in sediment cores taken from Lake Michigan, a group of unknown brominated compounds were observed. To identify their chemical structures, a variety of gas chromatographic mass spectrometric techniques were used. With the help of high-resolution and positive chemical ionization mass spectrometry, the molecular formula of the most abundant congener was established to be C12H5Br4N. On the basis of the electron impact and electron capture negative ionization mass spectra, this chemical was suspected of being a tetrabromocarbazole. The structure was confirmed by comparing the mass spectra and gas chromatographic retention times of an authentic standard of 1,3,6,8-tetrabromocarbazole with those of the most abundant unknown. The other unknown compounds may be other bromocarbazole congeners. The time trend determined by measuring these compounds as a function of depth in the Lake Michigan sediment cores indicated that the concentration of 1,3,6,8-tetrabromocarbazole peaked around 1920-1935. This is the first time that bromocarbazoles have been found in the environment.

Electron-Impact Ionization of Mandelic Acid and Mandelic Acid Methyl Ester as Prototypes for the C6H5CH(OH)-X System: Ionization and Appearance Energies, Activation Energies and Enthalpies of Formation

Electron-impact ionization mass spectra, the decay of metastable ions, ionization and appearance energies and bond energies, as dissociation energies, are reported for mandelic acid (MA) and mandelic acid methyl ester (MAME) . An ionization energy of 8.55 eV was obtained for both compounds. For the formation of C6H5+ ions, appearance energies of 14.25 eV or 14.40 eV were determined for MA or MAME, respectively. On the main fragmentation route from molecular ions to these C6H5+ ions, an activation energy of (1.1±0.1)eV in excess of the calculated total reaction enthalpy was found for the elimination of CO from the prominent C7H7O+ ions to C6H7+ ions, involving the transfer of two H-atoms. The second (minor) fragmentation route via C7H6O+ions resembles the benzaldehyde decomposition pathway and the individual steps were found to be near to their calculated thermochemical reaction enthalpies. Gas-phase enthalpies of formation of (–4.652±0.3 eV) [≡ (–448.8±30) kJ mol−1] for MA and (–4.243±0.3) eV [≡ (–409.4±30) kJ mol−1] for MAME are derived, based on the appearance energy of their C7H7O+ ions at m/z 107 and the formation enthalpy adopted from protonated benzaldehyde. The results are compared with data for benzylalcohol.

Identification and Purity Control of Thioacridine Derivatives by Gas and Capillary Liquid Chromatography with Mass Spectrometric Detection

ABSTRACT Mass spectrometry combined with gas chromatography (GC‐MS) or capillary liquid chromatography (CLC‐MS) was successfully utilized for structural characterization and purity control of synthesized biologically active thioacridine derivatives. Obtained results document sufficient selectivity of GC‐MS and CLC‐MS towards structurally related impurities and degradation products accompanying the compound of desire in analyzed substances. Based on electron impact ionization mass spectra an attempt to estimate their exact structures was made. The results of structure elucidation were confirmed by more detailed fragmentation studies based on (MS)2 and (MS)3 electrospray ionization mass spectra.

Solid phase microextraction (SPME) combined with gas-chromatography and olfactometry-mass spectrometry for characterization of cheese aroma compounds

The applicability of solid phase microextraction (SPME) as a technique for the concentration of cheese aroma for analysis by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) was assessed in this preliminary study. Three each of the following cheese varieties were examined: cheddar, hard grating and mold-ripened blue. Volatile components were concentrated by Carboxen-PDMS SPME fibres for 16 h (overnight) and analysed by GC-MS and GC-O. Odor compounds, which could be perceived at the olfactory port (OP), were matched with electron impact (EI) and methanol chemical ionization (CI) mass spectra. The volatile compounds identified were compared to previously reported cheese aroma compounds. Of the components identified via olfactometry, methanethiol, methional, dimethyl trisulfide and butanoic acid were present in all of the cheeses implying their essential role in the formation of basic cheese aroma. A number of alkyl-pyrazines were also found to impart roasted nutty, raw potato and savoury broth-like notes in some of the cheeses. In all cases, the aroma active compounds identified via olfactometry were in agreement with those reported in the literature. In a separate study, it was demonstrated on a number of cheeses that the adsorption of most important aroma volatiles increased consistently up to 16 h; i.e. sulfur compounds, lactones, pyrazines, phenolic compounds and benzene derivatives. For the strong-smelling pecorino and blue cheeses, however, some analyte displacement effects were observed. Data indicated that a sampling time between 9 and 16 h was appropriate and displacement/competition reactions tended to occur in strong cheeses, i.e. those which have undergone extensive lipolysis e.g. pecorino, very high concentration of butanoic and hexanoic acid, and/or β-oxidation e.g. blue cheese, with high concentrations of 2-heptanone and 2-nonanone.

Synthesis and Investigation of Mass Spectra of 3-[5′-(2′-Substituent)thienyl]benzo[5,6]coumarins

3-[5'-(2'-Hydroxycarbonyl)thienyl]benzo[5,6]coumarin ( 3 ) was prepared via condensation of 2 with thioglycolic acid in the presence of AcONa and Ac 2 O. Esterification of 3 with alcohols gave 3-[5'-(2'-alkoxycarbonyl)thienyl]benzo[5,6]-coumarins ( 4a , b ). The chemical behavior of 4 toward nucleophilic reagents (such as ammonia, hydroxyl amine, and hydrazine derivatives) is described. The electron impact ionization mass spectra of compounds 4b , 5 , and 8a , b show a weak molecular ion peak and a base peak of m / z 278 resulting from a cleavage fragmentation. In contrest compounds 3 and 4a show a base peak of m / z 250 and m / z 74 resulting from fragmentation. Compounds 9 and 10 give a characteristic fragmentation pattern with a very stable fragment of m / z 305.

3-치환-벤조피란[3,2-c]-[1]-벤조피란-6,7-다이온의 합성과 질량스펙트럼

3-하이드록시 벤조피란[3,2-c]-[1]-벤조피란-6,7-다이온(3)과 3-메톡시카보닐쿠마린을 소듐 메톡사이드 존재하에 화합물 1과 레조시놀을 축합시켜 합성하였으며 화합물 3의 아세트산 무수물, 알킬 할라이드, 다이아조니움 클로라이드와의 반응성에 대해 기술하였다. 화합물 4,5오 6a,b의 EI 질량분석에서는 89, 280, 91, 120 들의 주된 봉우리들이 각각의 분열 결과로 얻어짐을 볼 수 있었다. 화합물 3, 6b, 7a의 분자이온 봉우리로써 280, 366, 488을 각각 관찰할 수 있었다. 화합물 7a에서는 383과 77의 두 개의 안정한 조각을 가지는 특징적인 분역형태를 얻었다. 3-Hydroxybenzopyran[3,2-c]-[1]-benzopyran-6,7-diones (3) and 3-methoxycarbonylcoumarin (4) were prepared via condensation of 1 with resorcinol in the presence of sodium methoxide. The chemical behavior of 3 towards acetic anhydride, alkyl halides and diazonium chloride is described. The electron impact ionization mass spectra of compounds 4,5 and 6a,b show a weak molecular ion peak and a base peak of m/z 89, m/z 280. m/z 91 and m/z 120 resulting from a cleavage fragmentation respectively. The molecular ion of compounds 3, 6b, and 7a is a base peak of m/z 280, m/z 366 and m/z 488 respectively. Compound 7a give a characteristic fragmentation pattern with a two very stable fragmentation of m/z 383 and m/z 77.

Electron Impact Ionization Mass Spectra of 3-Substituted-2-hydroxy-4(3H)-quinazolinones

3-Amino-2-hydroxy-4(3H)-quinazolinone (3) was prepared via condensation of 1 with hydrazine hydrate. Treatment of 3 with appropriate acid in </TEX>$POCl_3$</TEX>, ethyl chloroacetate and activated olefinic compounds in DMF yielded the corresponding 3-(substituted)amino-2-hydroxy-4(3H)-quinazolinones 4, 5 and 6. The electron impact ionization mass spectra of compounds 3 and 4 show a weak molecular ion peak and a base peak of m/z 146 resulting from a cleavage fragmentation. The compounds 5 and 6 give a characteristic fragmentation pattern with a very stable fragment of benzopyrazolone (m/z 132).

Identification of O-Isobutyl S-(2-Diethylaminoethyl) Methylthiophosphonate Chemical Neutralization Products in Bitumen–Salt Matrices

Products of the chemical neutralization of O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate, a VX Group warfare agent, in bitumen–salt matrices were studied by gas chromatography–mass spectrometry. Forty-four compounds were characterized by their electron impact ionization mass spectra and gas chromatographic retention indices on standard nonpolar polydimethylsiloxane phases; seven of these compounds were determined as derivatives. The structures of 26 compounds were identified, including structures of 24 O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate neutralization products. To solve this problem, chromatographic retention indices of unknown compounds were evaluated using reference data for their structural analogues. Partition coefficients in the binary heterophase hexane–octanol system were determined for the major components.

Gas chromatography/mass spectrometric characterisation of pyrolysis/silylation products of glucose and cellulose.

The mass spectra of trimethylsilyl (TMS) derivatives of possible hydroxylated pyrolysis products of glucose and cellulose were recorded by gas chromatography/mass spectrometry (GC/MS) analyses of TMS derivatives of 2-hydroxymethylfuran, 2-hydroxy-1-methyl-1-cyclopenten-3-one, 5-(hydroxymethyl)-2-furaldehyde, 5-methyl-2-furoic acid, 4-hydroxy-6-methyl-(2H)-pyran-2-one, 2-methyl-3-hydroxy-(4H)-pyran-4-one (maltol) and 1,6-anhydro-beta-D-glucopyranose (levoglucosan, LG). Also, 2-O-TMS-1,6-anhydro-beta-D-glucopyranose, 4-O-TMS-1,6-anhydro-beta-D-glucopyranose and 2,4-bis-O-TMS-1,6-anhydro-beta-D-glucopyranose were identified from the interpretation of electron impact and chemical ionisation mass spectra of products obtained from partially silylated levoglucosan solutions, together with information from the known relative reactivities of OH groups of anhydrosugars. A peak at m/z 116 was found to be characteristic of the mass spectra of partially silylated anhydrosugars, and is absent from the mass spectra of the persilylated species. Pyrolysis/GC/MS of cellulose in the presence of hexamethyldisilazane afforded principally the 2- and 4-TMS ethers and the 2,4-bis-TMS ether of LG, whereas the 5-TMS-oxymethyl-2-furaldehyde was a prominent pyrolysis/silylation product of glucose. The mass spectra of other relevant pyrolysis/silylation products are presented.

陰イオン性毒物のペンタフルオロベンジル誘導体化ＧＣ‐ＭＳ法を用いた同時検出

A method for the simultaneous detection of anionic toxic substances and related compounds (azide, cyanide, thiocyanate, sulfide, ethyl methylphosphonate, isopropyl methylphosphonate, pinacoryl methylphosphonate (PMPA), methylphosphonate (MPA), nitrate, nitrite) has been developed using gas chromatography-mass spectrometry after pentafluorobenzyl (PFB) derivatization. The PFB derivatives of the analyte anions separated on a HP-5 capillary column were identified by the characteristic electron impact ionization mass spectra (EI-MS). Cyanide gave three kinds of derivatives, and two PMPA diastereomers were separated. The PFB derivative of nitrite could be clearly identified because of the poor resolution from that of nitrate and the absence of distinctive fragmentation ions on EI-MS. The effect of reaction conditions on the yield of the PFB derivatives was investigated. As catalysts, tetradecyldimethylbenzylammonium chloride (TDMBA) and polymer bound tributylmethylphosphonium chloride (TC) were examined. The effect of phosphate (pH 7.0) and borate (pH 9.3) buffer were examined. The pentafluorobenzylation with TC in borate buffer gave the best degree of efficiency except for thiocyanate. The highest yields of PFB derivatives in beverages and blood samples were also given using TC and borate buffer just the same as when tested in water. The derivatization values were 75-100% in the tea sample and 12-100% in the canned coffee sample. For the blood sample, five fold dilution was proved to be necessary in order to avoid coagulation. The derivatization efficiency values were 6-93% in the blood sample. The derivatization yield of MPA was considerably low in the coffee and blood samples.

Electron Impact Ionization of Dicyclopentadienyl-Manganese and Cyclopentadienyl-Manganese-Tricarbonyl Compared with Dimanganese-Decacarbonyl: Appearance Energies, Bond Energies and Enthalpies of Formation

Electron impact (EI) ionization mass spectra, metastable-ion decays and appearance energies are reported for the title compounds. Gas-phase formation enthalpies (Δ Hf) and bond energies (as dissociation energies) are derived from these data. Obtained Δ Hf values for the parent compounds are (–15.65 ± 0.2) eV for Mn2(CO)10, (2.85 ± 0.3) eV for Cp2Mn (Cp = C5H5 = cyclopentadienyl ligand) and (–3.91 ± 0.3) eV for CpMn(CO)3. The mean (Mn–CO) bond energy is 0.97 eV for Mn2(CO)10. In cations, the mean (Mn–CO)+ bond energy ranges from 0.75 to 0.80 eV for Mn2(CO)10 and CpMn(CO)3, respectively. In Cp2Mn+ the dissociation energies are 2.14 eV for the first Cp ligand and 3.21 eV for the second. In the neutral Cp2Mn, 2.12 eV is needed for the detachment of a first Cp ligand and 3.00 eV for the second. The results for the second ligand are valid for the elimination of Cp from CpMn(CO)3 as well.

Screening of β-2 agonists and confirmation of fenoterol, orciprenaline, reproterol and terbutaline with gas chromatography–mass spectrometry as tetrahydroisoquinoline derivatives

A new method for a comprehensive screening and confirmation of β-2 agonists in human urine is presented based on gas chromatography–low-resolution mass spectrometry (GC–MS) using electron impact ionisation (EI). After hydrolysis of the conjugates with β-glucuronidase/arylsulfatase a derivatisation step with formaldehyde converts fenoterol, orciprenaline, reproterol and terbutaline to one derivative, a tetrahydroisoquinoline, while the other β-2 agonists remain unchanged. Liquid–liquid extraction and trimethylsilylation follow. The tetrahydroisoquinoline derivatives show good gas chromatographic and mass spectrometric behaviour. The detection limit of these four β-2 agonists in the screening using low-resolution mass spectrometry is 10 ng/ml of urine. The other β-2 agonists are detected as parent compounds with the same recovery after sample preparation with and without formaldehyde. The EI mass spectra of the tetrahydroisoquinoline derivatives are presented.

Characterization of biomass pyrolysis vapors with molecular beam, single photon ionization time-of-flight mass spectrometry

A single photon ionization, molecular beam sampling, reflectron time-of-flight mass spectrometer (SPI/MBTOFMS) has been developed and used to study pyrolysis products from a selection of biomass materials. Spectra are characterized by high resolution and decreased fragmentation compared to electron-impact ionization mass spectra from related molecular beam mass spectrometer systems equipped with quadrupole mass analyzers.

Mass Spectra of Iso-Cinchona- and Halogenated Cinchona Alkaloids

The electron impact ionisation (EI) and electrospray ionisation (ESI) mass spectra using in-source collision-induced dissociation of nine different cinchona alkaloid derivatives [iso-cinchona alkaloids (ethereal isomers) and 10-Br(Cl) containing cinchona compounds] have been studied. In the case of the EI method for iso-cinchona alkaloids the observed fragmentation directions are as follows: isomerisation of the cyclic ethers to the corresponding C9 ketone, the formation of [M − 15]+, [M − 29]+ and [M − 57]+ fragments as a result of the loss of methyl, ethyl and butyl radicals, and the cleavage of the C8–C9 bond. The fragmentation of the compounds containing C10–Br(Cl) bonds started with the scission of this bond. The primary bond rupture is followed by the fragmentation of the primary product into two parts across the C8–C9 bond. In the case of the ESI method at low capillary exit voltage only the peak of the protonated molecule ([M + H]+), and in a significantly lower abundance, the peak of the [M + 2H]2+ ion can be observed. Increasing the capillary exit voltage causes fragmentation to occur. For iso-cinchona alkaloids the main direction is the cleavage of C8–C9 bond. For the C10–Br(Cl) compounds, the primary fragmentations are the cleavage of the C9–O and C10–Br(Cl) bonds. Fragmentation pathways are discussed.