EI Mass Spectra Research Articles

Structural characterization of nitazene analogs using electron ionization-mass spectrometry (EI-MS)

Nitazene analogs are among the most recent and potent additions to the novel synthetic opioid (NSO) market, and new analogs continue to emerge. Seized drug analysis commonly utilizes gas chromatography-electron ionization-mass spectrometry (GC-EI-MS), so it is therefore imperative to understand how nitazene analogs behave under EI-MS conditions, and how substitution at various sites on the molecule may impact the resulting EI mass spectra. This study characterizes the EI fragmentation behavior of 20 representative nitazene analogs that contain differing substitutions and proposes rational mechanisms to explain the observed behavior.A general EI fragmentation pathway for nitazene analogs was proposed, with the most common nitazene fragment ions being observed at m/z 86, m/z 107, m/z 58, and m/z 77. Characteristic ions were determined for different substitution groups, enabling the identification of diethyl, desethyl, pyrrolidine, and piperidine substitutions at the amine moiety, and different alkoxy chain lengths at the aromatic ring of the benzyl group. Mechanisms for the formation of these characteristic ions were proposed with the aid of isotopically labeled standards and high-resolution mass spectrometry measurements. To help with the interpretation of EI mass spectra for nitazene analogs, decision trees were developed that encompass the characteristic fragment ions observed for substitutions to the amine moiety and benzyl group, with additional criteria provided for substitutions to the benzimidazole moiety. This study summarizes the fragmentation patterns and characteristic fragment ions in the EI mass spectra of 20 representative nitazene analogs, which will aid the seized drug community in identifying novel nitazene analogs.

Cool Classical EI - A New Standard in EI and Its Many Benefits.

GC-MS with Cold EI improves all of the central GC-MS performance aspects, but it is known mostly for its provision of enhanced molecular ions. This occasionally leads to the misconception that, like chemical ionization, Cold EI is a supplementary ion source to standard EI. However, Cold EI is a highly superior replacement ion source to standard EI. While Cold EI mass spectra are the most informative and fully compatible with mass spectral library (such as NIST) identification, in some cases, the Cold EI mass spectra with their enhanced molecular ions result in a "picture" that is not as one is used to seeing. In this paper, we describe the "Cool Classical EI" mode, which produces classical EI mass spectra like standard EI. The change of Cold EI into the Cool Classical EI mode is software-based, requires no hardware change, and can be achieved even during the analysis. Several mass spectra that were obtained in the Cool Classical EI mode are presented and compared with standard EI and Cold EI mass spectra. In this paper we further demonstrate and discuss several benefits that Cold EI brings that are retained while using Cool Classical EI, including (a) much faster speed of analysis, (b) uniform response, (c) extended range of compounds amenable for analysis, (d) improved sample identification, (e) elimination of ion source related peak tailing, (f) elimination of intraion-source degradation, and (g) better signal-to-noise ratio of the sample compounds.

Analytical method development and validation of prasugrel hydrochloride in bulk and its pharmaceutical formulation using the GC-MS, HPLC method

The present work reports rapid, sensitive and specific methods for determination of Prasugrel and its impurities by gas chromatography with mass spectrometry and high-performance liquid chromatography. The proposed method presented excellent intraday precision (% RSD < 1), and accuracy 99.23 to 100.40% and 99.48 to 100.81% for Prasugrel and 2-bromo-1-cyclopropyl-2-(2-fluorophenyl) ethanone. Further the linearity of Prasugrel correlation coefficient is >0.9994 and for bromo impurity correlation coefficient is > 0.9993. The estimated limits of detection (LOD) and quantification (LOQ) for Prasugrel, 1-bromo-1-(2-fluorophenyl) propan-2-one ranged from 0.990 to 2.586 μg/mL, and 2.999 to 7.837 μg/mL respectively. The results demonstrated that the method should be regarded as a reliable alternative to the simultaneous determination of Prasugrel and its impurities. The EI mass spectrum of Prasugrel, fluoro, bromo, methyl bromo and dibromo impurities were characterized by [M + H]+ at 409, 189, 257, 231 and 311. The methods were validated according to ICH guideline.

Effect of intramolecular conjugation on the primary fragmentation in EI mass spectrum of 2-allenylthio-1H-pyrrole derivative

The anomalous primary fragmentation (no C–S bond cleavage) in the electron-ionization (70 eV) mass spectrum of 1-isopropyl-3-methoxy-2-(propa-1,2-dien-1-ylthio)-1H- pyrrole is considered in terms of intramolecular electronic effect. The calculation of the geometry (B3PW91/6-311G**) and the study of electron density delocalization (NBO) revealed the effect of electron density transfer LpS → π* (from the lone pair of sulfur atom to the π-system of allene double bond) on primary fragmentation pathways.

Investigating the effect of substitution location on fentanyl analog identification for methyl-substituted fentanyl analogs using GC-EI-MS

Fentanyl and fentanyl analogs are key figures at the center of the ongoing opioid epidemic in the United States. Currently, gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) instrumentation is one of the main analytical tools used for the identification of fentanyl analogs in forensic laboratories. However, the resulting retention times and EI mass spectra for many fentanyl analogs are quite similar given that there are only subtle differences in their structures. This research investigates the effect of substitution location on fentanyl analog identification using GC-EI-MS and the National Institute of Standards and Technology (NIST) Simple Similarity Search (SSS) and Hybrid Similarity Search (HSS) algorithms through the analysis of a series of 11 methyl-substituted fentanyl analogs.The 95% confidence interval retention times for each isomer were never more than ±0.009 min and a statistically significant (p < 0.001) difference was observed for all pairwise comparisons. Careful examination of the EI mass spectra revealed several general trends about the influence of substitution location on the observed EI mass spectra. The combination of unique fragmentation patterns, formed through shifts in m/z values due to the location of substitution, and the retention time enabled the identification of the 11 methyl-substituted fentanyl analogs analyzed in this study. The SSS was able to correctly identify all methyl-substituted fentanyl analogs within the top five hits for compounds that were present in the library. In comparison, the HSS was used to identify compounds absent from the mass spectral libraries and provided drastically different results depending on the location of substitution.

The differentiation of N-butyl pentylone isomers using GC-EI-MS and NMR

Forensic laboratories are faced with an ever-expanding seized drug landscape including the increasing prevalence of novel psychoactive substances (NPS), such as synthetic cathinones, that have varying potencies and scheduling. This study demonstrates a combined gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) and nuclear magnetic resonance (NMR) spectroscopy approach for the differentiation of N-butyl pentylone isomers based on distinct retention times, characteristic EI mass spectra, and NMR characterization. Retention time reproducibility was assessed from 60 replicate measurements for each isomer over the course of a month. In addition, the effect of the mass spectrometer tune and the stability of an identified characteristic ion ratio using spectral data from ± 1 scan on either side of the peak apex were also statistically assessed using Welch’s ANOVA testing.The presence of diastereomers for N-sec-butyl pentylone was identified using the developed GC-EI-MS method, which was confirmed using one-dimensional and two-dimensional NMR spectroscopy. The retention time reproducibility of the chromatographic method was ± 0.076% or less over the course of a month. An identified characteristic ion ratio between the abundance of the fragment ion at m/z 128 and the fragment ion at m/z 72 enabled the differentiation of the four N-butyl pentylone isomers, even when accounting for the effect of the mass spectrometer tune and mass spectral scans used to calculate the characteristic ion ratio. The 95% confidence interval mean abundance ratio of the fragment ions at m/z 128 and m/z 72 was 17.14 ± 0.14 for N-butyl pentylone, 6.44 ± 0.05 for N-isobutyl pentylone, 3.38 ± 0.02 for N-sec-butyl pentylone, and 0.75 ± 0.01 for N-tert-butyl pentylone. These results highlight the capabilities of a combined GC-EI-MS and NMR approach for the differentiation and characterization of synthetic cathinone isomers.

Bioreactivity of divalent bimetallic vanadyl and zinc complexes bis-oxalyldihydrazone ligand against microbial and human cancer series. ctDNA interaction mode

Two novel divalent bimetallic complexes were constructed from the complexation of O=V4+ and Zn2+ ions (VOL and ZnL), respectively, with diisatin oxalyldihydrazone ligand (H2L). Various spectroscopic tools were used to confirm their chemical structures (FT-IR, NMR, EI-Mass, and electronic spectra), besides, elemental analyses and conductivity features. To estimate the role of divalent metal ions in their coordination compound for developing their bio-reactivity, the free ligand H2Lox, and its complexes (VOL and ZnL) were employed spectroscopic investigations against the growth of some microbial series (fungi and bacteria) and also against three human cancer/normal cells. Furthermore, their interaction behavior against calf thymus DNA (ctDNA) was studied through viscometric and spectrophotometric studies to discover the role of O=V4+ and Zn2+ ions to determine the mode of binding with ctDNA. The inhibiting effect of H2L, VOL, and ZnL versus the titled microbial (bacterial and fungal) was built upon their inhibited zone areas in mm and the MIC concentrations in μM. Their action against the three human cancer cells' growth was evaluated by IC50 values in μM and the selectivity index in percentage.Both VOL and ZnL complexes exhibited an amazing series with three human cancer cell growth (according to the zone values in mm of inhibition, MIC in μM, and IC50 values in μM) compared to those of their uncoordinated H2L ligand. VOL demonstrated a distinguished interacting behavior with ctDNA more than that interaction of ZnL depending on the variation of the central metal ion chemical features. Within the covalent and non-covalent interaction modes, the interaction binding between H2L, VOL, and ZnL with ctDNA was discussed based on the electronic spectroscopic observation.

Chemical transformation of cannabidiol into psychotropic cannabinoids under acidic reaction conditions: Identification of transformed products by GC-MS.

Recently, cannabidiol (CBD), one of the major components of the Cannabis species, has been a focus in the cannabis industry due to its various pharmacological effects. Interestingly, CBD can be converted into several psychoactive cannabinoids, such as 9-tetrahydrocannabinol (Δ9-THC) and its structural isomers, under acidic reaction conditions. In this study, chemical transformation of CBD in ethanol solution was conducted with variation in pH at 2.0, 3.5, and 5.0 by addition of 0.1 M hydrochloric acid (HCl). These resulting solutions were derivatized with trimethylsilyl (TMS) reagent and analyzed using GC/MS-scan mode. Time profiles of CBD degradation and transformation of products were examined according to variations in pH and temperature. Several transformed products produced after the acidic reaction of CBD were identified by matching retention times and mass spectra to authentic standards. Regarding the identification of products without authentic standards, the EI-mass spectra of such cannabinoid-OTMS derivatives were interpreted according to structural class, suggesting mass fragmentation pathways. From the GC/MS data, Δ9-THC, CBC, and ethoxy-hexahydrocannabinol (HHC) analogs were shown to be major components, and THC isomers (Δ8- and Δ10-THCs) and 9-hydroxy-HHC were observed as minor components. Using time profile data, the acidity of the reaction solution was an important factor in degradation of CBD. Degradation of CBD and formation of THC rarely occurred at pH 5.0, even at 70 °C with a long process time of 24 h. In contrast, degradation of CBD occurred readily at pH 3.5 and 30 °C over a short process time and was further accelerated by lowering pH, increasing temperature, and lengthening the process time. Based on profile data and identified transformed products, formation pathways from the degradation of CBD under acidic reaction conditions are suggested. Among the transformed products, seven components are known to have psychoactive effects. Thus, industrial CBD manufacturing processes in food and cosmetic products should be carefully controlled. These results will provide important guidelines on the control of manufacturing processes, storage, fermentation processes, and new regulation in industrial applications of CBD.

Comparison of APCI orbitrap MS and GCxGC/EI TOF MS for the hydrocarbon analysis of heavy base oils

The performance of positive-ion mode atmospheric pressure chemical ionization linear quadrupole ion trap orbitrap mass spectrometry (APCI LQIT Orbitrap MS) has been compared to that of two-dimensional gas chromatography coupled with positive-ion mode electron ionization time-of-flight mass spectrometry (GCxGC/EI TOF MS) for the analysis of group III heavy base oils. Upon APCI, all compounds were predominantly ionized via protonation. However, protonated alkanes are not stable and predominantly generated [M−H]+ ions via elimination of a hydrogen molecule from the protonated molecule. The high-resolution APCI mass spectra provided elemental composition information for the compounds while low-resolution APCI mass spectra were used for semiquantitative evaluation of the relative amounts of the compounds. Ions corresponding to compounds in seven hydrocarbon classes, i.e., (1) linear and branched alkanes, (2) monocycloalkanes, (3) dicycloalkanes, (4) tricycloalkanes and alkylbenzenes, (5) tetracycloalkanes, (6) pentacycloalkanes, and (7) hexacycloalkanes were identified. On the other hand, the GCxGC/EI TOF MS method enabled the chromatographic separation of most analytes. The measured EI mass spectra were used for the identification of the compounds while the GC peak areas were used for semiquantitative evaluation. The detected compounds were classified into three different hydrocarbon classes, (1) linear and branched alkanes, (2) cycloalkanes, and (3) aromatic hydrocarbons. The (+)APCI LQIT Orbitrap MS method was found to be faster and to provide more information for the larger compounds in the samples. For example, polycycloalkanes were only detected by using (+)APCI MS. However, no aromatic compounds were detected. Data processing was more straightforward than when using the GCxGC/EI TOF MS method. However, the latter method provided more accurate results for aromatic hydrocarbons and small alkanes as the analysis of small alkanes by using (+)APCI MS is limited due to the fact that [M−H]+ ions of small alkanes overlap with alkane fragment ions. Both light and heavy aliphatic and aromatic hydrocarbons were detected by using the GCxGC/EI TOF MS method but not polycycloalkanes. Therefore, these two methods complement each other, and each has different strengths and weaknesses.

Synthesis, PXRD structure, spectroscopy, cyclic voltammogram, thermal analysis and DFT/TD-DFT calculations of bis[salicylaldehydato-κO,O']nickel(II)

The bis[salicylaldehydato-κO,O']nickel(II) (1) was synthesized from reaction of pyridyl-Schiff base ligands, N-2-(R1-pyridyl)salicylaldimine {R1 = H(HL1), 4-CH3 (HL2) and 6-CH3 (HL3)} and nickel(II) acetate via in-situ hydrolysis of the ligands back to the salicylaldehyde (HL'). The molecular structure of 1 was solved by PXRD which disclosed that the two molecules of O^O-chelate ligands formed a O2,O2-coordination sphere around the nickel atom with a square planar geometry. Elemental analysis data show no nitrogen atom in the sample. EI mass spectra exhibit the parent ion peak at m/z = 300. The molar conductance values (Λm = 2.08–2.15 S m2 mol−1) endorse non-electrolyte nature of 1 with metal-to-ligands ratio of 1:2 in DMF. Solid-state magnetic moment value (μeff. = 3.00 μB) suggests paramagnetic nature of the high-spin nickel(II) complex, supported by 1H NMR, UV–vis. (experimental and simulated spectra) and optimized and PXRD structures. DSC analysis recommends an irreversible phase transformation from crystalline-solid to solid–liquid and isotropic-liquid phase. Cyclic voltammograms demonstrate an irreversible one electron charge transfer process for [Ni(L')2]0/[Ni(L')2]− (L' = salicylaldehydato) couple in acetonitrile. Optimized structures and excited state properties by DFT/TD-DFT correspond well to PXRD structure and electronic spectra in solution.

Energy release and product ion fragmentation in proton transfer reactions of N2H+ and ArH+ with acetone*

Proton transfer reaction mass spectrometry has a so far little exploited potential for the analysis of high-purity process and inert gases. In order to protonate impurities like saturated hydrocarbons, precursor ions with very low proton affinity must be used, which in turn leads to a large energy release upon protonation of molecules with high proton affinity, potentially causing fragmentation of the product ions. To explore the potential of low-proton affinity precursor ions like ArH+ and N2H+ for analytical purposes, we studied their gas-phase reactions and kinetics with acetone by Fourier transform ion cyclotron resonance (FT–ICR) mass spectrometry. The dominant product ion in both cases is protonated acetone, but fragment ions formed include C2H3O+, C3H5 + and CH3O+, which are formed in higher abundance with ArH+ compared to N2H+. The reaction efficiencies are determined to be close to 100%. Quantum chemical calculations reveal energetically favorable reaction pathways and explain the loss of water leading to the formation of C3H5 +, as well as loss of methane to yield C2H3O+ via dissociative proton attachment, which corresponds to the main product in the EI mass spectrum of acetone. Formation of protonated formaldehyde CH3O+ involves rearrangement of the C–C bonds to eliminate ethylene.

Spectral trends in GC-EI-MS data obtained from the SWGDRUG mass spectral library and literature: A resource for the identification of unknown compounds

Rapid identification of new or emerging psychoactive substances remains a critical challenge in forensic drug chemistry laboratories. Current analytical protocols are well-designed for confirmation of known substances yet struggle when new compounds are encountered. Many laboratories initially attempt to classify new compounds using gas chromatography-electron ionization-mass spectrometry (GC-EI-MS). Though there is a large body of research focused on the analysis of illicit substances with GC-EI-MS, there is little high-level discussion of mass spectral trends for different classes of drugs. This manuscript compiles literature information and performs simple exploratory analyses on evaluated GC-EI-MS data to investigate mass spectral trends for illicit substance classes. Additionally, this work offers other important aspects: brief discussions of how each class of drugs is used; illustrations of EI mass spectra with proposed structures of commonly observed ions; and summaries of mass spectral trends that can help an analyst classify new illicit compounds.

The differentiation of LSD and its 17 related compounds by GC-EI-MS and GC-CI-QTOF-MS

In recent years, the distribution of blotter paper-type products containing analogues of lysergic acid diethylamide (LSD) has increased globally. These compounds have two asymmetric carbons in their structures and a small amount of their stereoisomers (iso-forms) were detected in some products. In this study, the differentiation method of LSD and its 17 related compounds by GC-MS was investigated. Moreover, for a clearer differentiation by mass spectra, the analytical method for LSD, its structural isomers (MiPLA and LAMPA) and their stereoisomers (iso-LSD, iso-MiPLA and iso-LAMPA) was also investigated by GC-QTOF-MS. LSD, its 12 analogues (ALD-52, 1P-LSD, 1B-LSD, 1cP-LSD, ETH-LAD, AL-LAD, MiPLA, LAMPA, LSM-775, LSZ, 1cP-AL-LAD and 1V-LSD) and the 5 stereoisomers (iso-LSD, iso-MiPLA, iso-LAMPA, iso-LSZ and iso-ETH-LAD) were investigated in this study. They were used as acetonitrile or methanol solutions for the GC-MS and GC-QTOF-MS analyses. In the GC-EI-MS, LSD and the 17 related compounds were detected from 11 to 21 min using a DB-1HT column (15 m x 0.25 mm i.d., 0.10 μm, Agilent). Although the separation of these compounds was almost successful, it was difficult to differentiate LSD and its isomers without the reference materials due to their close retention times and identical EI mass spectra. It was observed that the N1-acylated LSD analogs, such as 1P-LSD, 1cP-LSD, 1B-LSD and 1V-LSD, were deacylated to LSD during the GC-MS analysis using methanol as a solvent. For a clearer differentiation of LSD, its structural isomers (MiPLA and LAMPA) and their stereoisomers (iso-LSD, iso-MiPLA and iso-LAMPA), GC-CI-QTOF-MS (reagent gas: methane) was investigated. The MS/MS measurements were performed using the fragment ion m/z 72.081 [C4H10 N]+ as the precursor ion for LSD, MiPLA and LAMPA, and their product ion spectra were compared. As a result, the three compounds could be clearly differentiated by the presence or absence of the product ion m/z 44.049 [C2H6 N]+ or m/z 56.049 [C3H6 N]+, which indicates the differences in their structures. The MS/MS measurements of the fragment ion m/z 128.107 [C7H14NO]+ also showed differences in the product ions. As in the case of the three LSD-structural isomers, iso-LSD, iso-MiPLA and iso-LAMPA could be differentiated by comparison with the product ion spectra. Furthermore, in the product ion spectra of [M + H]+ m/z 324.207, differences were observed between the LSD structural isomers and their stereoisomers. The above differences in the product ion spectra were detectable if a CI measurement is used, even if not by an accurate mass spectrometry. Simon B et al. (Simon D. Brandt et al., Drug Test Anal, 2021,14(3), 545–556) reported that LSD, MiPLA and LAMPA could be differentiated by product ion spectra from the fragment ion m/z 72 in GC-MS/MS EI measurements. However, in this study, the accurate mass spectrometry using GC-QTOFMS EI measurements revealed that two ions, m/z 72.081 [C4H10 N]+ and m/z 72.044 [C3H6NO]+ were detected for LSD, while only m/z 72.081 [C4H10 N]+ was detected for MiPLA and LAMPA. Therefore, in the GC-MS/MS EI measurement of LSD, the product ion spectrum obtained from m/z 72 could be a mixed spectrum generated from two ions, which might lead to confusion in considering the fragmentation. The GC-EI-MS differentiation method was shown for LSD and the 17 related compounds in this study. Moreover, LSD, its structural isomers (MiPLA and LAMPA) and their 3 stereoisomers, which were difficult to identify by GC-EI-MS without their reference materials, were clearly differentiated by the MS/MS measurements using m/z 72.081 [C4H10 N]+, m/z 128.107 [C7H14NO]+ and m/z 324.207 [M + H]+ as precursor ions in the GC-CI-QTOFMS.

Synthesis and Structure of Hetaryl Substituted 2,5-dioxo-1,2,3,4,5,6,7,8- Octahydroquinolines.

Condensation of 5-hetarylidene-2,2-dimethyl-1,3-dioxane-4,6- diones with 5,5-dimethyl-3-arylamino-2-cyclohexanones yields 1-aryl-4-hetaryl-7,7-dimethyl-2,5- dioxo-l,2,3,4,5,5,7,8-octahydro-quinolines. The structures of all the synthesized compounds have been verified by IR, 1H-NMR, 13C-NMR, and mass spectral methods. The 13C-NMR assignments were supported by HSQC and HMBC experiments. Moreover, spin decoupling and NOE experiments have been carried out in order to elucidate stereoisomeric configurations of the compounds. It has been established that the N-phenyl ring, which projects from the plane of the octahydroquinolinedione ring, has a shielding effect on the magnetic field of the protons at 7- and 8-positions of the ring in the molecules of the compounds synthesized. The NMR spectra were recorded on a Varian Gemini spectrometer [400 MHz (1H) and 100 MHz (13C)]. EI mass spectra were obtained with a Hewlett Packard GC/MS 6890/5973 machine. MALDI-TOF mass measurements were recorded on a Bruker auto-flex III smart beam. Various reaction conditions were applied in order to find an optimum and convenient procedure for the formation of octahydroquinoline derivates having hetaryl group. The highest yields (40-50 %) were achieved using acetic acid as solvent, p-toluenesulphonic acid as acidic catalyst, and excess enaminone (1.5 equiv). We synthesized eight new 1-aryl-7,7-dimethyl-4-hetaryl-1,2,3,4,5,6,7,8-octahydroquinoline- 2,5-dione compounds containing thienyl core as a result of Michael addition reaction of Knoevenagel products of Meldrum's acid with dimedone enaminone compounds. Optimum circumstances were established using various reaction conditions and catalyzers throughout the research. The structures of all the synthesized compounds were analyzed by IR, 1H-NMR, 13CNMR, and mass spectral methods. Furthermore, the structures were verified with the help of 2D (HSQC and HMBC), spin decoupling, and NOE NMR techniques.

GC–MS and GC–IR of regioisomeric 4-N-bromodimethoxybenzyl derivatives of 3-trifluoromethylphenylpiperazine

The seven regioisomeric N-bromodimethoxybenzyl derivatives of 3-TFMPP were synthesized via reductive amination of the seven commercially available bromodimethoxybenzaldehydes. The capillary GC elution profiles for these compounds generally follow the degree of methoxy group substituent crowding on the aromatic ring. The electron ionization mass spectra show a series of major fragment ions common to all seven regioisomeric compounds. The base peak in the EI mass spectra for many of the seven regioisomers occurs at m/z 229 and is the result of contributions from two isobaric fragments, the trifluoromethylphenylpiperazine cation as well as the 79Br bromodimethoxybenzyl cation. Several low intensity ions are related to the specific regioisomeric substitution patterns for the bromodimethoxybenzyl moieties and provide some differentiation for this set of seven compounds. These unique ions allow the seven compounds to be divided into sub-groups and in some cases allow specific isomer identification from only the EI-MS data. The 950 cm−1 to 550 cm−1 lower portion of the fingerprint region in the vapor phase infrared spectra can be used to identify each of the bromodimethoxybenzyl regioisomers after EI-MS fragmentation patterns provide focus on the individual structural sub-groups of compounds in this study.

Microwave synthesis, Characterisation and Biological activities of transition metal complexes with Novel SNSN Donor Schiff base ligand

A novel Schiff base (E)-N-(pyridine-2-yl)thiophen-2-ylmethylene)hydrazine carbothioamide (L), was synthesised by the condensation of thiophen-2-carbaldehyde and N-(pyridin-2-yl)-hydrazinecarbothiamide, using solvent free microwave synthesis. The Co(II), Ni(II), Cu(II) and Zn(II) complexes of the ligand were also prepared. They were characterised by elemental analysis, EI-mass spectrum, 1H & 13C-NMR spectrum, FTIR, UV-Vis spectra, magnetic, EPR spectra and thermal analysis. The “SNSN” donor ligand binds the metal ion in tetradentate mode through thiophenyl and thioenolic sulphur atoms and imino and pyridine nitrogen atoms. The electronic spectra along with magnetic measurements demonstrate tetrahedral geometry for Co(II), Ni(II) and Zn(II) complexes whereas square planar geometry for CuL complex. All the complexes were found to be thermally stable from thermogravimetric studies. The complexes show enhanced antibacterial activity than the ligand against various bacterial strains. The BSA binding activity of the complexes shows that the affinity for binding was greater towards copper complex. The cytotoxicity of the ligand and its complexes were tested on HT29 colon cancer cells using MTT assay.

Automated fragment formula annotation for electron ionisation, high resolution mass spectrometry: application to atmospheric measurements of halocarbons

BackgroundNon-target screening consists in searching a sample for all present substances, suspected or unknown, with very little prior knowledge about the sample. This approach has been introduced more than a decade ago in the field of water analysis, together with dedicated compound identification tools, but is still very scarce for indoor and atmospheric trace gas measurements, despite the clear need for a better understanding of the atmospheric trace gas composition. For a systematic detection of emerging trace gases in the atmosphere, a new and powerful analytical method is gas chromatography (GC) of preconcentrated samples, followed by electron ionisation, high resolution mass spectrometry (EI-HRMS). In this work, we present data analysis tools to enable automated fragment formula annotation for unknown compounds measured by GC-EI-HRMS.ResultsBased on co-eluting mass/charge fragments, we developed an innovative data analysis method to reliably reconstruct the chemical formulae of the fragments, using efficient combinatorics and graph theory. The method does not require the presence of the molecular ion, which is absent in sim40% of EI spectra. Our method has been trained and validated on >50 halocarbons and hydrocarbons, with 3–20 atoms and molar masses of 30–330 g mol^{-1}, measured with a mass resolution of approx. 3500. For >90% of the compounds, more than 90% of the annotated fragment formulae are correct. Cases of wrong identification can be attributed to the scarcity of detected fragments per compound or the lack of isotopic constraint (no minor isotopocule detected).ConclusionsOur method enables to reconstruct most probable chemical formulae independently from spectral databases. Therefore, it demonstrates the suitability of EI-HRMS data for non-target analysis and paves the way for the identification of substances for which no EI mass spectrum is registered in databases. We illustrate the performances of our method for atmospheric trace gases and suggest that it may be well suited for many other types of samples. The L-GPL licenced Python code is released under the name ALPINAC for ALgorithmic Process for Identification of Non-targeted Atmospheric Compounds.

Cannabis and its cannabinoids analysis by gas chromatography-mass spectrometry with Cold EI.

Cannabis extracts and products were analyzed by gas chromatography-mass spectrometry (GC-MS) with Cold EI for their full content including terpenes, sesquiterpenes, sesquiterpinols, fatty acids, delta 9-tetrahydrocannabinol (THC), cannabidiol (CBD), other cannabinoids, hydrocarbons, sterols, diglycerides, triglycerides, and impurities. GC-MS with Cold EI is based on interfacing GC and MS with supersonic molecular beams (SMB) along with electron ionization of vibrationally cold sample compounds in the SMB in a fly-through ion source (hence the name Cold EI). GC-MS with Cold EI improves all the performance aspects of GC-MS, enables the analysis of Cannabinoids with OH groups without derivatization, while providing enhanced molecular ions for improved identification, and enables internal quantitation without calibration. We found over 50 cannabinoid compounds including a new one with a Cold EI mass spectrum very similar to delta 9-THC as well as relatively large cannabinoids with molecular weight above m/z = 400. Because the analysis was universal in full scan and not targeted, we found impurities such as bromo CBD and fluticasone propionate and could monitor the formation of oxidized CBD during decarboxylation. In addition, GC-MS with Cold EI enabled nontargeted full analysis of terpenes, sesquiterpenes, and sesquiterpinols in cannabis extracts with good internal quantitation. GC-MS with Cold EI further served with very good sensitivity for the concentration determination of delta 9-THC in CBD-related products. Finally, cannabis drugs such as EP-1 used in Israel for treatment of epilepsy and for children with autism spectrum disorder (ASD) were analyzed for their full cannabinoids content for learning on the entourage effect and for drug activity optimization.

Mononucleating nicotinohydazone complexes with VO2+, Cu2+, and Ni2+ ions. Characteristic, catalytic, and biological assessments

Three novel mononuclear complexes of Ni2+, Cu2+, and VO2+ ions (NiLnBu, CuLnBu, and VOLnBu, respectively) were synthesized by the chelation of a di-basic tridentate nicotinohydazone ligand (H2LnBu) with M2+ ions in 1 : 1 M ratios. The ligand and its M-pincer chelates were identified and characterized using various spectroscopic tools included NMR, IR, UV–Vis. and EI-Mass spectra, beside, EI elemental analyses, and thermogravimetric analyses. The catalytic potential of NiLnBu, CuLnBu, and VOLnBu was investigated in 1,2-cyclooctene epoxidation using H2O2, as an efficient oxidant. Various parameters, including solvent, temperature, catalyst loading, and oxidant were investigated to identify the optimized reaction conditions. The central metal ion in their M-chelate catalysts revealed variation in the catalytic performance. The high valent metal ion (V4+) catalyst (VOLnBu) exhibited slightly better catalytic potential (96% yield) over the low valent metal ions (Ni2+ and Cu2+) complex catalysts (NiLnBu 91% yield and CuLnBu 93% yield, respectively). In addition to, the biological potential of free ligand H2LnBu and its complexes were examined in the ctDNA interaction process via UV–Vis. spectroscopy and viscosity measurements with the aid of distinguished docking studies. The obtained results showed that M-chelates possess effective biological activities with DNA, including the antimicrobial, antioxidant, and anticancer effects against different biological targets.

Wild edible fruit crop Haematocarpus validus (Miers) Bakh.f. ex Forman (Khoon phal): a novel source of nutraceuticals.

The online version contains supplementary material available at 10.1007/s13197-021-04997-7.