Electron Impact Ionization Mass Spectra Research Articles

Improved Discrimination of Mass Spectral Isomers Using the High-Dimensional Consensus Mass Spectral Similarity Algorithm.

This study employs a high-dimensional consensus mass spectral (HDCMS) similarity scoring technique to discriminate isomers collected using an electron ionization mass spectrometer. The HDCMS method was previously introduced and applied to the discrimination of mass spectra of constitutional isomers, methamphetamine and phentermine, collected with direct analysis real-time mass spectrometry (DART-MS). The method formulates the problem of discriminating mass spectra in a mathematical Hilbert space and is hence called "high dimensional." It requires replicate mass spectra to build a Gaussian model and evaluate the inner products between these functions. The resulting measurement variability is used as a signature by which to discriminate spectra. In this work, HDCMS is tested on electron impact ionization (EI) mass spectra of 7 terpene and terpene-related (C10H16 and C10H14) isomers with experimental retention indices that differ by less than 30 and with traditional cosine similarity scores greater than 0.9, on a scale of 0 to 1, when compared with at least one other compound in the test set. Using identical instrument parameters, 15 replicate gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) spectra of each isomer were collected and separated into distinct library and query sets. The HDCMS algorithm discriminated each isomer, indicating the method's potential. Because the method requires replicate measurements, observations from a simple heuristic study of the number of replicates required to discriminate these isomers is presented. The paper concludes with a discussion of compound discrimination using HDCMS and the benefits and drawbacks of applying the method to EI-MS data.

Utility of gas chromatography infrared spectroscopy (GC-IR) for the differentiation of positional isomers of fentanyl related substances

Forensic laboratories routinely use gas chromatography mass spectrometry (GC–MS) in the identification of controlled substances using both retention time and electron impact ionization (EI) mass spectra. Certain drugs such as positional isomers of some fentanyl related substances (FRS) can produce indistinguishable EI mass spectra but may be differentiated using retention time. The core structure of fentanyl consists of an amide group, a piperidine ring, an aniline ring, and an N-alkyl chain, each providing opportunities for points of substitution that create FRS and corresponding positional isomers. For this study, the analysis by GC coupled to a vapor-phase infrared spectroscopy detector (GC-IR) was used as a complementary technique to GC–MS for the identification of positional isomers of FRS. The result is a novel fentanyl library consisting of 212 different FRS reference compounds. A collaboration among three different laboratories yielded correct identifications of twenty blind samples when searched against the GC-IR FRS library created at Florida International University (FIU). The expected limits of detection for fentanyl using GC-IR range between 0.10 and 0.19 mg/mL, depending on the sample introduction (injector) method and other instrumental parameters. The newly created GC-IR library and its GC–MS counterpart of 212 FRS are shared in the supplementary materials for future use by researchers and practitioners.

Electron Impact Ionization Mass Spectra of 3-Amino 6-Chloro2-methyl Quinazolin-4-(3H)-one Derivative

Looking at the previous studies on quinazolinones derivatives, only limited information’s are available on their mass spectral along with the preparation of novel quinazolin-4-(3H)-one derivatives The condensation of Methyl-2-amino-4-Chlorobenzoate with acetic anhydride yielded the cyclic compound 2-methyl 7-Chloro-1, 3-benzo-oxazine-4-one (1) which further produce 3-Amino-2-Methyl 7-Chloro quinazolin-4(3H)-ones (2) via the reaction with hydrazine hydrate. The compounds synthesized were unequivocally confirmed by means of Infrared, Nuclear Magnetic Resonance (1H and 13C), Gas Chromatography-Mass spectrophotometry and Elemental analysis. Discussion: The molecular ion of m/z 235 fragments to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH2 group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH3 group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2show a weak molecular ion peak and a base peak of m/z 235resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively

Electron Impact Ionization Mass Spectra of 3-Amino 6-Chloro-2-methyl Quinazolin-4-(3H)-one Derivative

Background: Looking at the previous studies on quinazolinones derivatives, only limited information’sare available on their massspectral along with the preparation of novel quinazolin-4-(3H)-one derivatives. Consolidation of Methyl-2-amino-4-Chlorobenzoate with acetic anhydride produced the cyclic compound 2-methyl 7-Chloro-1, 3-benzo-oxazine-4-one (1) which then produced 3-Amino-2-Methyl 7-Chloro quinazolin-4(3H)-ones (2) through the reaction with hydrazine hydrate. These compounds synthesized were indisputably confirmed by means of Infrared, Nuclear Magnetic Resonance (¹H and ¹³C), Gas Chromatography-Mass spectrophotometry and Elemental analysis. Discussion: The molecular ion of m/z 235 fragments to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH₂ group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH₃ group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2 show a weak molecular ion peak and a base peak of m/z 235 resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively.

Mass Spectra of New Heterocycles: XX. Electron Impact and Chemical Ionization Mass Spectra of 5-(Prop-2-yn-1-ylsulfanyl)-1H-pyrrol-2-amines

Electron impact (70 eV) and chemical ionization (methane as reactant gas) mass spectra of 1-alkyl- and 1-[2-(vinyloxy)ethyl]-5-(prop-2-yn-1-ylsulfanyl)-1H-pyrrol-2-amines have been studied for the first time. The title compounds under electron impact form stable molecular ions which decompose mainly along pathways typical of the molecular ions derived from the corresponding intramolecular cyclization products, 7-alkyl- and 7-[2-(vinyloxy)ethyl]-2,7-dihydrothiopyrano[2,3-b]pyrrol-6-amines. In addition, fragment ions that could be formed only via decomposition of unrearranged molecular ion were detected. The main fragmentation pathway of their molecular ions involves cleavage of the N1-CAlk bond with the formation of stable [M − R3]+ ions (Irel 85–100%) {except for N,N-diethyl- and N,N-dipropyl-1-[2-(vinyloxy)emyl]-5-(prop-2-yn-1-ylsulfanyl)-1H-pyrrol-2-amines}. The results of quantum chemical calculations at the B3LYP/6-311+G(d,p) level of theory are consistent with the experimental data. In the chemical ionization mass spectra of 5-(prop-2-yn-1-ylsulfanyl)-1H-pyrrol-2-amines, the major peaks were those corresponding to M+· (Irel 65–100%) and [M + H]+ (Irel 75–100%). The title compounds have been found to undergo partial (5–10%) thermally induced isomerization to 5-(prop-1-yn-1-ylsulfanyl)-1H-pyrrol-2-amines under the chemical ionization conditions.

Mass Spectra of New Heterocycles: XVIII. Electron Impact and Chemical Ionization Mass Spectra of Alkyl 5-Amino-3-methyl-4-(1H-pyrrol-1-yl)thiophene-2-carboxylates

Electron impact (70 eV) and chemical ionization (methane as reactant gas) mass spectra of alkyl 5-amino-3-methyl-4-(1H-pyrrol-1-yl)thiophene-2-carboxylates have been studied for the first time. All compounds, except for tert-butyl thiophene-2-carboxylate, under electron impact give rise to stable molecular ions which decompose along two paths, depending on the site of positive charge localization (at the ester fragment or amino nitrogen atom). The main fragmentation pathway of the molecular ions is elimination of alkoxy radical from the ester group. Chemical ionization of alkyl 5-amino-3-methyl-4-(1H-pyrrol-1-yl)-thiophene-2-carboxylates involves protonation and electrophilic addition with the base peak corresponding to the [M + H]+ ion.

Electron Impact Ionization Mass Spectra of 3-Amino 5,6-Dimethoxyl-2-Methyl Quinazolin-4-(3H)-One Derivative

Background: The synthesis of novel heterocyclic derivatives has attracted considerable attention. The explosive growth of heterocyclic chemistry is emphasized by the large number of research publications, monographs, and reviews. The heterocyclic organic compounds are extensively disseminated in natural and synthetic medicinal chemistry and are vital for human life. Looking at the previous studies on quinazolinones derivatives, only limited informationis available on their mass spectral along with the preparation of novel quinazolin-4-(3H)-one derivatives. Objective: Objective of this study, was to synthesize a novel 2-Methyl-6, 7-dimethoxy-quinazolin-4-one was synthesized via the reaction between 2-Methyl-6, 7-dimethoxy-benzo-1,3-oxazin-4-one andhydrazine hydrate and study their electron impact ( EI ) mass spectral fragmentation. Method: The condensation of 2-amino-methyl-4, 5-dimethoxybenzoate with acetic anhydride yielded the cyclic compound 2-methyl-4, 5-disubstituted-1, 3-benzo-oxazine-4-one which further produce a novel 2,3-disubstituted quinazolin-4 ones via the reaction with hydrazine hydrate. The compounds synthesized were unequivocally confirmed by means of Infrared, Nuclear Magnetic Resonance (1H and 13C), Gas Chromatography Mass Spectrophotometer and Elemental analysis. Discussion: The molecular ion of m/z 235 fragment to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH2 group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH3 group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2show a weakmolecular ion peak and a base peak ofm/z 235resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively.

Liquid Extraction Surface Analysis (LESA) Electron-Induced Dissociation and Collision-Induced Dissociation Mass Spectrometry of Small Molecule Drug Compounds

Here, we present liquid extraction surface analysis (LESA) coupled with electron-induced dissociation (EID) mass spectrometry in a Fourier-transform ion cyclotron resonance mass spectrometer for the analysis of small organic pharmaceutical compounds directly from dosed tissue. First, the direct infusion electrospray ionisation EID and collision-induced dissociation (CID) behaviour of erlotinib, moxifloxacin, clozapine and olanzapine standards were compared. EID mass spectra were also compared with experimental or reference electron impact ionisation mass spectra. The results show that (with the exception of erlotinib) EID and CID result in complementary fragment ions. Subsequently, we performed LESA EID MS/MS and LESA CID MS/MS on singly charged ions of moxifloxacin and erlotinib extracted from a thin tissue section of rat kidney from a cassette-dosed animal. Both techniques provided structural information, with the majority of peaks observed for the drug standards also observed for the tissue-extracted species. Overall, these results demonstrate the feasibility of LESA EID MS/MS of drug compounds from dosed tissue and extend the number of molecular structures for which EID behaviour has been determined.Graphical ᅟ

STRAPS v1.0: evaluating a methodology for predicting electron impact ionisation mass spectra for the aerosol mass spectrometer

Abstract. Our ability to model the chemical and thermodynamic processes that lead to secondary organic aerosol (SOA) formation is thought to be hampered by the complexity of the system. While there are fundamental models now available that can simulate the tens of thousands of reactions thought to take place, validation against experiments is highly challenging. Techniques capable of identifying individual molecules such as chromatography are generally only capable of quantifying a subset of the material present, making it unsuitable for a carbon budget analysis. Integrative analytical methods such as the Aerosol Mass Spectrometer (AMS) are capable of quantifying all mass, but because of their inability to isolate individual molecules, comparisons have been limited to simple data products such as total organic mass and the O : C ratio. More detailed comparisons could be made if more of the mass spectral information could be used, but because a discrete inversion of AMS data is not possible, this activity requires a system of predicting mass spectra based on molecular composition. In this proof-of-concept study, the ability to train supervised methods to predict electron impact ionisation (EI) mass spectra for the AMS is evaluated. Supervised Training Regression for the Arbitrary Prediction of Spectra (STRAPS) is not built from first principles. A methodology is constructed whereby the presence of specific mass-to-charge ratio (m∕z) channels is fitted as a function of molecular structure before the relative peak height for each channel is similarly fitted using a range of regression methods. The widely used AMS mass spectral database is used as a basis for this, using unit mass resolution spectra of laboratory standards. Key to the fitting process is choice of structural information, or molecular fingerprint. Our approach relies on using supervised methods to automatically optimise the relationship between spectral characteristics and these molecular fingerprints. Therefore, any internal mechanisms or instrument features impacting on fragmentation are implicitly accounted for in the fitted model. Whilst one might expect a collection of keys specifically designed according to EI fragmentation principles to offer a robust basis, the suitability of a range of commonly available fingerprints is evaluated. Using available fingerprints in isolation, initial results suggest the generic public MACCS fingerprints provide the most accurate trained model when combined with both decision trees and random forests, with median cosine angles of 0.94–0.97 between modelled and measured spectra. There is some sensitivity to choice of fingerprint, but most sensitivity is in choice of regression technique. Support vector machines perform the worst, with median values of 0.78–0.85 and lower ranges approaching 0.4, depending on the fingerprint used. More detailed analysis of modelled versus mass spectra demonstrates important composition-dependent sensitivities on a compound-by-compound basis. This is further demonstrated when we apply the trained methods to a model α-pinene SOA system, using output from the GECKO-A model. This shows that use of a generic fingerprint referred to as FP4 and one designed for vapour pressure predictions (Nanoolal) gives plausible mass spectra, whilst the use of the MACCS keys in isolation performs poorly in this application, demonstrating the need for evaluating model performance against other SOA systems rather than existing laboratory databases on single compounds. Given the limited number of compounds used within the AMS training dataset, it is difficult to prescribe which combination of approach would lead to a robust generic model across all expected compositions. Nonetheless, the study demonstrates the use of a methodology that would be improved with more training data, fingerprints designed explicitly for fragmentation mechanisms occurring within the AMS, and data from additional mixed systems for further validation. To facilitate further development of the method, including application to other instruments, the model code for re-training is provided via a public Github and Zenodo software repository.

The evaporation study of silicon-containing ionic liquid

1,2-Dimethyl-3-(1′,1′,3′,3′-tetramethyl-3′-phenyldisiloxanyl)methylimidazolium bis(trifluoromethanesulfonyl)amide ([PhC5OSi2MMIm+][Tf2N−]) is the first silicon-containing ionic liquid which was characterized with the vaporization enthalpy, (138.5±1.8)kJmol−1, and saturated vapor pressure, ln(p/Pa)=−(16656±219)/(T/K)+(30.69±0.92). This compound is a unique ionic liquid giving ions, retaining both cationic and anionic portions, in the electron impact ionization (EI) mass spectrum.

Identification and removal of polycyclic aromatic hydrocarbons in wastewater treatment processes from coke production plants

Identification and removal of polycyclic aromatic hydrocarbons (PAHs) were investigated at two coke plants located in Shaoguan, Guangdong Province of China. Samples of raw coking wastewaters and wastewaters from subunits of a coke production plant were analyzed using gas chromatography-mass spectrometry (GC/MS) to provide a detailed chemical characterization of PAHs. The identification and characterization of PAH isomers was based on a positive match of mass spectral data of sample peaks with those for PAH isomers in mass spectra databases with electron impact ionization mass spectra and retention times of internal reference compounds. In total, 270 PAH compounds including numerous nitrogen, oxygen, and sulfur heteroatomic derivatives were positively identified for the first time. Quantitative analysis of target PAHs revealed that total PAH concentrations in coking wastewaters were in the range of 98.5 ± 8.9 to 216 ± 20.2μg/L, with 3-4-ring PAHs as dominant compounds. Calculation of daily PAH output from four plant subunits indicated that PAHs in the coking wastewater came mainly from ammonia stripping wastewater. Coking wastewater treatment processes played an important role in removing PAHs in coking wastewater, successfully removing 92% of the target compounds. However, 69 weakly polar compounds, including PAH isomers, were still discharged in the final effluent, producing 8.8 ± 2.7 to 31.9 ± 6.8g/day of PAHs with potential toxicity to environmental waters. The study of coking wastewater herein proposed can be used to better predict improvement of coke production facilities and treatment conditions according to the identification and removal of PAHs in the coke plant as well as to assess risks associated with continuous discharge of these contaminants to receiving waters.

Keeping pace with NPS releases: fast GC‐MS screening of legal high products

The continuous appearance of novel psychoactive substances (NPS) in legal high products presents a challenge for the routine analytical laboratory. A rapid screening method for NPS analysis using fast gas chromatography mass spectrometry (fast GC-MS) is presented. Twenty-three analytes, including 5-iodo-2-aminoindane (5-IAI), 1-(thiophen-2-yl)-2-methylaminopropane (MPA), 1-benzylpiperazine (BZP), 4-methylmethcathinone (mephedrone), 5,6-methylenedioxy-2-aminoindane (MDAI) and methoxetamine (MXE) were separated within 4 min. The method was used to analyze 35 Internet and head shop purchased 'legal high' products with the successful identification of their active ingredients. As previously observed, legal high products do not always contain their stated ingredients. Of the group of products purchased as 5-IAI not one contained 5-IAI with several containing mixtures of substances either already controlled in the UK or under consideration by the Advisory Council on Misuse of Drugs (ACMD). The low bleed and high inertness of the chromatography column used ensured clean high quality mass spectrometry data which when combined with the short run time resulted in an efficient tool for NPS screening, even when standards were unavailable. Electron impact and chemical ionization mass spectra used in combination for the identification of unknown NPS are presented.

Identification of Tocopherols, Tocotrienols, and Their Fatty Acid Esters in Residues and Distillates of Structured Lipids Purified by Short-Path Distillation

The fate of endogenous vitamin E isomers during production and purification of structured lipids (SLs) was investigated. Two SLs involving tripalmitin, stearidonic acid soybean oil, and docosahexaenoic acid were synthesized by transesterification catalyzed by Novozym 435 (NSL) and acidolysis by Lipozyme TL IM (LDHA) and purified by short-path distillation (SPD). The electron impact and chemical ionization mass spectra of tocopheryl and tocotrienyl fatty acid esters in the distillates measured by GC-MS in synchronous scan/SIM mode demonstrated that these esters were formed during acidolysis as well as transesterification. The predominant esters were tocopheryl palmitate, tocopheryl oleate, and tocopheryl linoleate homologues, and no tocopheryl or tocotrienyl linolenate, stearidonate, or docosahexaenoate was found. Meanwhile, none of these esters were detected in the residues for either NSL or LDHA. Less than 50% of vitamin E isomers were present in residues after SPD. This loss played a major role in the rapid oxidative deterioration of SLs from previous studies with less contribution from the formation of tocopheryl and tocotrienyl esters. The lost tocopherols and tocotrienols present at high concentration in the distillates may be recovered and used to improve the oxidative stability of SLs.

Identification and characterization of polycyclic aromatic hydrocarbons in coking wastewater sludge

GC-MS analysis was performed on the coking sludge from a coking wastewater treatment plant (WWTP) to allow detailed chemical characterization of polycyclic aromatic hydrocarbons (PAHs). The identification and characterization of the isomers of PAHs was based on a positive match of mass spectral data of their isomers with mass spectra databases or based on a comparison of electron impact ionization mass spectra and retention times of target compounds with those reference compounds. In total, 160 PAH compounds including numerous N-, O-, S-, OH-, and Cl-containing derivatives were positively identified for the first time. Quantitative analysis of target compounds was performed in the selected ion-monitoring mode using the internal standard method. The total concentrations of selected compounds in the coking sludge samples from the anaerobic tank, aerobic tank, hydrolytic tank, and secondary clarifier of the WWTP ranged from 1690 ± 585 to 6690 ± 522 mg/kg, which were much higher than those in other industrial and municipal sludges. PAHs with four and five rings were found to be the dominant compounds, and diagnostic ratios of these compounds suggested that they had the characteristics of coal combustion and pyrolysis.

Cracking of selected hydrocarbon gases in a low-power, low-pressure RF plasma

The cracking of four hydrocarbons, C3H8, C2H6, C2H4 and CH4, separately, in an Ar plasma has been investigated. Ions observed in electron impact ionization mass spectra of the plasma are used to probe the neutral components of the plasma. A matrix of data of ion intensities under varying rf powers (0–30 W) and gas pressures (100–400 mTorr), for the four hydrocarbon gases has been collected, and the rates of the depletion of the hydrocarbons in the plasma and the formation of H2 from the cracking of the hydrocarbons, under the varying experimental conditions, have been evaluated. Among the four hydrocarbons, C2H4 undergoes cracking most readily and CH4 yields the most amount of H2 from plasma cracking.

Mass spectral characteristics of the chlorinated disinfection byproduct 2,2,4-trichloro-5-methoxy-cyclopent-4-ene-1,3-dione

The objective of this paper was to correct the mistakes of a previous interpretation of electron impact ionization (EI) mass spectrum of the chlorinated disinfection byproduct (DBP) in drinking water naming 2,2,4-trichloro-5-methoxy-cyclopent-4-ene-1,3-dione (TCMCD). Moreover the positive-ion chemical ionization (CI +) and electrospray ionization (ESI +) mass spectra were also studied. As the search of new chlorinated disinfection byproducts in drinking water is a challenge and researchers generally have to attempt to identify unknown chlorinated products generated from incompletely defined starting materials, fully understanding the mass spectra of this compound may do some help for the analysis of other unknown chlorinated disinfection byproducts.

Identification of urinary metabolites of clemastine after oral administration to man.

The metabolism of clemastine, 2-[2-[1-(4-chlorophenyl)-1-phenylethoxylethyl])-1-methylpyrrolidin e, has been studied in three adult male volunteers after a single oral dose of 20 mg as the fumarate. After enzymatic hydrolysis solvent extracts of urine were derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide-ammonium iodide and analysed by gas chromatography-mass spectrometry. The structures of metabolites were determined on the basis of electron impact and chemical ionization mass spectra and the identities of some (e.g. carbinol, 4-chlorobenzophenone and 4-chlorophenylstyrene) were confirmed by use of authentic standards. The principal route of metabolism of clemastine in man involves direct oxidation, O-dealkylation (fission of the ether bond), aromatic hydroxylation, aliphatic oxidation, alcoholic dehydration, and then enzymatic hydrolysis. Of the total amount of metabolites excreted in the urine 35% was carbinol (metabolite M3, major metabolite), 15% was M1, 17% was M2, 11% was M4, 9% was M5, 8% was M6 and 5% was M7.

Identification and Structural Elucidation of Corrosion Inhibiting Long-Chain N-1-Alkyl-1,3-propanediamines by GC–MS

Gas chromatography–mass spectrometry has been used to identify long-chain (C8–C18) N-1-alkyl-1,3-propanediamines after derivatization with trifluoroacetic anhydride. Electron impact ionization and negative chemical ionization mass spectra of trifluoroacetylated derivatives of the identified N-1-alkyl-1,3-propanediamines are presented for the first time. The corrosion inhibiting long-chain N-1-alkyl-1,3-propanediamines were applied in the preparation and investigation of a new anticorrosive and antifouling formulation for water–steam circuit of energy systems in the power industry. Using the GC–MS data, it was possible to identify residues of the N-1-alkyl-1,3-propanediamines in complex samples of boiler water from the power plant after solid-phase extraction and acylation.

Quadrupole ion traps

The extraordinary story of the three-dimensional radiofrequency quadrupole ion trap, accompanied by a seemingly unintelligible theoretical treatment, is told in some detail because of the quite considerable degree of commercial success that quadrupole technology has achieved. The quadrupole ion trap, often used in conjunction with a quadrupole mass filter, remained a laboratory curiosity until 1979 when, at the American Society for Mass Spectrometry Conference in Seattle, George Stafford, Jr., of Finnigan Corp., learned of the Masters' study of Allison Armitage of a combined quadrupole ion trap/quadrupole mass filter instrument for the observation of electron impact and chemical ionization mass spectra of simple compounds eluting from a gas chromatograph. Stafford developed subsequently the mass-selective axial instability method for obtaining mass spectra from the quadrupole ion trap alone and, in 1983, Finnigan Corp. announced the first commercial quadrupole ion trap instrument as a detector for a gas chromatograph. In 1987, confinement of ions generated externally to the ion trap was demonstrated and, soon after, the new technique of electrospray ionization was shown to be compatible with the ion trap.

Spectral Data Analyses and Structure Elucidation of Hypoglycemic Drug Glipizide

The infrared spectrum, ultraviolet spectrum, mass spectrum, and nuclear magnetic resonance spectrum of glipizide, a blood-glucose-lowering drug, were reported and interpreted comprehensively. All the 1H and 13C NMR chemical shifts were assigned by means of distoritionless enhancement by polarization transfer-135, 1H-1H and 13C-1H correlation spectroscopy, and correlation spectroscopy via long range coupling. The main characteristic fragmentations, in electron impact and electrospray ionization mass spectra, vibrations of functional groups in infrared spectrum, and electron transition in ultraviolet spectrum of glipizide were also discussed in detail.