GC Conditions Research Articles

Correction: Olagunju et al. Pleurotus ostreatus Can Significantly Improve the Nutritive Value of Lignocellulosic Crop Residues. Agriculture 2023, 13, 1161

Authors would like to correct an error in the GC conditions for VFA analysis [...]

ТЕХНОЛОГИЯ ТРАНСПОРТИРОВКИ, РАЗМОРАЖИВАНИЯ И ИСПОЛЬЗОВАНИЯ ЗАМОРОЖЕННОГО СЕМЕНИ ХРЯКОВ

Different variants of transportation and storage of frozen boar seed are described, the technology of its thawing and use in conditions of pig farm Ufa Selection and Hybrid Center LLC TAVROS GC is described. The target indicators of insemination efficiency when using frozen semen are given.

Development of a safety analysis method for volatile organic compounds using 2-phenoxyethanol as solvent

Indoor volatile organic compounds (VOCs) are usually sampled using active carbon samplers and subsequently analyzed using gas chromatography-mass spectrometry (GC-MS) to assess the exposure risk to workers. Therefore, selection of a suitable solvent for VOC extraction is crucial. However, reports on the use of 2-phenoxyethanol—known for its low vapor pressure and low toxicity—as a solvent for extracting VOCs from activated carbon are lacking. Here, we show that 2-phenoxyethanol is a suitable alternative solvent with low toxicity and can extract a wide variety of VOCs without overlapping with target VOCs on the gas chromatogram. The recoveries of 2-phenoxyethanol were 57% (styrene) to 83% (methyl n-butyl ketone), which were higher than those of CS2, acetone, and n-hexane at room temperature. The recoveries improved to 67% (styrene) to 102% (isopentyl acetate) under 50 °C. Optimization of the GC conditions showed that a viscosity delay time of 3 s was required to avoid producing bubbles in the injection syringes. We selected DB-HeavyWAX as a column because it could be heated above the boiling point of 2-phenoxyethanol (247 °C), allowing the removal of 2-phenoxyethanol from the column. This study contributes to the development of analysis methods for VOCs under safe operating conditions.

Study on drug substance degradation under headspace GC conditions of residual solvent analysis.

Isobutyraldehyde (IBA) was detected in drug substance (DS) containing an amino acid group using a headspace-gas chromatography (HS-GC) method. High-performance liquid chromatography-mass-spectrometry (HPLC-MS) data from an HS vial confirmed that IBA was a degradant. The HS-GC method was modified to minimize IBA by keeping the HS oven temperature lower than 80 °C.

Montmorillonite-based polymethacrylate composite monoliths as stationary phase materials for food and pharmaceutical analysis in capillary liquid and gas chromatography

This work relates to the preparation of novel and promising stationary phases containing inorganic-organic composites for capillary liquid and gas chromatography. A naturally occurring montmorillonite was introduced to polymethacrylate monoliths, then used under different conditions of GC and HPLC at the same time. The performance of the columns was evaluated for the separation of alkane and alkylbenzene series in GC and capillary HPLC, respectively. While the bare monoliths failed to separate the model analytes, montmorillonite-based polymethacrylate allowed a full separation of the mixtures with Rs≥1.42. The columns were applied for the determination of myrcene and limonene isomers in the peel extracts of some fruits using GC, and for the analysis of active ingredients including aspirin, vitamin-C, caffeine, and ibuprofen extracted from common drugs using capillary HPLC. In GC, fast separation was achieved in 1.0 min with Rs of 6.53. The columns exhibited the best efficiency for myrcene with 20,900 plates/m. Using the capillary HPLC columns, the active ingredients were resolved in 10 min with Rs≥5.72. The efficiency values located between 12,800–21,700 plates/m in all cases. The developed methods were found to be linear in the range of 0.10–10.0 and 0.20–180 μg/mL for GC and HPLC, respectively. In comparison with commercial columns, the results in GC methods reveal that, despite their much shorter length, the prepared columns proved a faster separation with higher efficiency and comparable detection limits and chromatographic resolution. The prepared HPLC capillaries exposed lower run times and detection limits with comparable efficiency and resolution, and consume fewer samples and mobile phase solvents. The results demonstrate that the montmorillonite-based polymethacrylate composites are applicable as stationary phases for routine analysis and quality control of important fields such as food and pharmaceutical samples.

Naturally Occurring Montmorillonite-Based Polymer Monolith Composites as Stationary Phases for Capillary Liquid and Gas Chromatography

This work is associated with the preparation of capillary chromatographic columns containing inorganic-organic composites comprised of naturally occurring montmorillonite (MMT) clay mineral and polymethacrylate monolithic material. The prepared composites combine the best qualities of both constituents, offering desirable properties for use under the disparate conditions of both GC and HPLC at the same time. The stationary phases were investigated by scanning electron microscopy (SEM), the specific surface area, and thermogravimetric analysis (TGA) and examined in terms of various conditions utilized for GC and HPLC methods. The prepared columns demonstrated an excellent permeability and stability against common chromatographic conditions, such as the eluent type, flow rate, pressure, and temperature. The results confirmed that the addition of small amounts of MMT into the monolith induced significant improvement in the specific surface area, which contributed to the formation of more active sites and enhanced the retention of analytes. The registered column backpressures did not exceed 980 kPa and 16,500 kPa for the prepared GC and HPLC columns, respectively. The prepared columns were subjected to the separation of various interesting compounds possessing different chemistries and polarities, including alkanes, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), alcohols, ketones, phenols, some common organic solvents, and isomeric mixtures. Under the optimal conditions, the efficiency of the columns fell between 4900–38,500 plates m−1 for GC and 3400–58,800 plates m−1 for capillary HPLC applications. In all cases, the measured chromatographic resolution was more than 1.38, with excellent an peak symmetry and low tailing factors. In comparison with the most commonly used commercial columns, the polysiloxane open tubular column for GC and silica-based C18 packed column for HPLC, the prepared GC columns demonstrated a faster separation with a higher efficiency, comparable resolution and tailing factors, and lower consumption of carrier gas. Regarding the capillary columns prepared for HPLC, the chromatographic experiments exposed a much lower run time with a comparable efficiency and resolution and drastically lower consumption of mobile phase solvents and samples. The results demonstrate that the MMT-based polymethacrylate monolith composites are applicable as novel and promising separation media for analyzing various mixtures of interest in different fields, such as petrochemical and environmental samples.

Comparative Prediction of Gas Chromatographic Retention Indices for GC/MS Identification of Chemicals Related to Chemical Weapons Convention by Incremental and Machine Learning Methods

During on-site verification activities conducted by the Technical Secretariat of Organization for the Prohibition of Chemical Weapons, identification by gas chromatography retention indices (RI) data, in addition to mass spectrometry data, increase the reliability of factual findings. However, reference RIs do not cover all the possible chemical structures. That is why it is important to have models to predict RIs. Applicable only for narrow data sets of chemicals with a fixed scaffold (G- and V-series gases as example), the non-learning incremental method demonstrated predictive median absolute and percentage errors of 2–4 units and 0.1–0.2%; these are comparable with the experimental bias in RI measurements in the same laboratory with the same GC conditions. It outperforms the accuracy of two reported machine learning methods–median absolute and percentage errors of 11–52 units and 0.5–2.8%. However, for the whole Chemical Weapons Convention (CWC) data set of chemicals, when a fixed scaffold is absent, the incremental method is not applicable; essential machine learning methods achieved accuracy: median absolute and percentage errors of 29–33 units and 0.5–2.2%, depending on the machine learning method. In addition, we have developed a homology tree approach as a convenient method for the visualization of the CWC chemical space. We conclude that non-learning incremental methods may be more accurate than the state-of-the-art machine learning techniques in particular cases, such as predicting the RIs of homologues and isomers of chemicals related to CWC.

Development of GC-MS/MS Method for Simultaneous Estimation of Four Nitrosoamine Genotoxic Impurities in Valsartan.

Recently, N-nitrosamines were unexpectedly detected in valsartan and other generic sartan products. Taking into this account, we developed a sensitive and stable multiple reaction monitoring mode-based "gas chromatography-tandem mass spectrometry (GC-MS/MS)" approach for the quantification of "four N-nitrosamines" in valsartan, especially, N-nitrosodiisopropylamine, N-nitroso ethyl isopropylamine, N-nitrosodiethylamine, and N-nitrosodimethylamine. GC and MS conditions were optimized with specificity, sensitivity, linearity, precision, and accuracy of the parameters. The approach was validated as per the "International Council for Harmonization" recommendations. The identification limits and limits of quantification of N-nitrosamines in valsartan varied between 0.02 and 0.03 ppm, and 0.06-0.09 ppm, respectively. The obtained values were satisfactory with limits established by the United States Food and Drug Administration for sensitivity requirements. The regression coefficients greater than 0.999 for four N-nitrosamines in the calibration curve demonstrated the strong linearity of the process. The retrievals of "N-nitrosamines" in valsartan between 91.9-122.7%. For the intra-day and inter-day accuracy studies, the (relative standard deviation) was less than 9.15%. The proposed approach has rapid analysis capability, high precision, accuracy, and good sensitivity, which give a reliable approach for N-nitrosamines quality control in valsartan.

The Mineralocorticoid Receptor Functions as a Key Glucose Regulator in the Skeletal Muscle of Zebrafish

Glucocorticoids (GCs) are essential for maintaining energy homeostasis as part of the adaptive stress response. Most work to date has characterized the metabolic role of GCs via the activation of the glucocorticoid receptor (nr3c1; GR), which is activated under high GC conditions. However, GCs also bind to the mineralocorticoid receptor (nr3c2; MR), a high-affinity corticosteroid receptor active under basal GC conditions. Despite the expression of MR in skeletal muscles, almost nothing is known about its physiological role. Here we tested the hypothesis that the MR promotes anabolic processes during resting cortisol levels and curtails the catabolic actions of the GR during high (stressed) levels of cortisol. To determine the effect of MR, a zebrafish line with a ubiquitous MR knockout (MRca402/ca402) was utilized. The GR was activated in the same group by chronically treating fish with exogenous cortisol. In the muscle, MR primarily promoted nutrient storage, and restricted energy substrate mobilization under resting conditions, whereas GR activation resulted in increased nutrient utilization. Interestingly, MR loss improved GR-driven metabolic flexibility, suggesting that the activation state of these receptors is a key determinant of skeletal muscle ability to switch fuel sources. To determine if the anabolism-promoting nature of MR was due to an interaction with insulin, fish were co-injected with insulin and the fluorescent glucose analogue 2-NBDG. A loss of MR abolished insulin-stimulated glucose uptake in the skeletal muscle. Taken together, we postulate that MR acts as a key modulator of glucose metabolism in the musculature during basal and stress conditions.

Analysis of an ampoule found on a WW2 German soldier: Poison or medicine?

During archaeological excavations in Maltot, Normandy (France), the remains of a German soldier probably dating from Operation Jupiter (July 10–11, 1944) were discovered. The study of the body showed that he was a man aged 17 to 20 at the time of death. His death was likely caused by several recent projectile impacts: bullet entry orifice in the skull and several shrapnel traces in the upper limbs. Several objects were found near the body, including the remains of a leather and metal box at the level of is abdomen containing about ten glass whole ampoules while 2 others laid loose. The objective of this work was to identify the contents of these ampoules, with an emphasis on poisons. Screenings were carried out on the contents of the vial using HPLC-DAD, GC-MS, HS-GC-MS and HR-LC-MS/MS. Multi-element research by ICP-MS was also conduct as well as cyanide research. Volatile compounds quantification was performed using GC-MS equipped with a Triplus AS Head space injector (Thermo Fisher Scientific, Les Ulis, France). Chromatographic separation was achieved on a Rtx-VMS column (30 m × 0.25 mm, dF = 1.4 μm) (Restek, Lisses, France) with helium as carrier gas at a constant flow rate of 1.2 mL/min. Injector temperature was held at 65 °C and split injection mode was employed with a split flow of 80. The GC conditions were as follows: column temperature started at 40 °C, was held for 2 min then increased to 150 °C at a rate of 10 °C/min then held for 1minute. 5 μL of the sample was put in a sealed vial then heated to 80 °C during 20 minutes with a 10 second agitation step. 0.2 mL of the gas phase was injected in the GC/MS. Data acquisition was performed using the Xcalibur v2.1 software (Thermo Fisher Scientific). The detection was operated in SIM mode. Propan-1-ol was used as internal standard (E.I.). Calibrators were prepared at 50, 100, 200, 500 and 1000 mg/L in DMSO. Analyzed ampoule was 6 cm long and 0.5 cm wide and contained approximately 300 μL of a colorless, water-immiscible liquid, with a characteristic solvent odor. HPLC-DAD, GC-MS, HR-LC-MS/MS, ICP-MS and cyanide screenings were negative. However, the HS-GC-MS analysis revealed the presence of several volatile products: ethanol (360 g/L), chloroform (392 g/L), diethyl ether (87 g/L), as well as isopropanol, trichloroethylene and tetrachloroethylene at concentrations lower than 5 g/L. No poison but two anesthetic substances (chloroform and diethyl ether) associated with an alcoholic solvent (ethanol) were found. Therefore, the soldier was probably a medic. The anesthetic properties of ether were discovered in 1846 leading to a revolution in surgery and the beginnings of anesthesia. A few months later, the anesthetic properties of chloroform were uncovered. Around 1860, in England, the A.C.E. mixture which consisted of 1 part alcohol, 2 parts chloroform and 3 parts ether was preferred over chloroform alone. This mixture was later introduced in Germany where it was used until WW2 (Wawersik J. J Clin Anesth, 1991 3(3) 235–244). Composition of the analyzed vials seems to match this A.C.E. mixture and coherent with historical knowledge. These molecules were administrated by inhalation and it was often regarded as a safe and simple procedure for urgent situations as encountered on the battlefield. For more complex procedures, use of barbiturates was preferred. After WW2, A.C.E. mixture was abandoned in favor of less toxic anesthetics such as nitrous oxide.

Structure elucidation of the novel synthetic cannabinoid Cumyl-Tosyl-Indazole-3-Carboxamide (Cumyl-TsINACA) found in illicit products in Germany.

New chemical moieties continue to appear in synthetic cannabimimetics (SC), the largest group of new psychoactive substances in the EU. We describe the first comprehensive characterisation of the novel SC Cumyl-Tosyl-Indazole-3-Carboxamide (Cumyl-TsINACA) (N-[2-phenylpropan-2-yl]-1-tosyl-1H-indazole-3-carboxamide) from seized case samples. Structure elucidation was performed within the EU-project ADEBAR plus to facilitate confident identification by other researchers and practitioners worldwide. Characteristic MS fragmentations include the cleavage of the sulfonamide bond (S-N), the aryl sulfone bond (C-S) and the elimination rearrangement of SO2 in the side chain. Cumyl-TsINACA is a full receptor agonist at hCB1 (Emax = 228%) with very weak binding affinity (Ki = 292 nm) and low functional activity (EC50 = 31 μm). Thermal degradation of Cumyl-TsINACA was observed under GC conditions. The degree to which the tosyl side chain is cleaved due to pyrolysis primarily depends on solvent, the use of glass wool in the liner and injector temperature. The determination of the constitution by NMR spectroscopy was ambiguous due to the high number of neighbouring, non-proton-bearing atoms. Therefore, other possible structures compatible with the NMR correlations were generated using the WebCocon software. The unambiguous structural evidence was finally obtained by spectra comparison after the synthesis of Cumyl-TsINACA. The low thermal stability, as well as the low affinity and potency, renders this compound unfavourable for the use as a psychoactive substance. Thus, we do not expect widespread adoption of this SC.

Identification and Analysis of the Impurities for Triethylboron by GC‐MS Method

AbstractThe detection and separation of impurities are crucial for the quality control of triethylboron. While the purity of triethylboron is the key factor for ballistic performance, impact accuracy, and storage safety. This work will explore a modified gas chromatography‐mass spectrometer method to detect and separate the impurities in synthesized triethylboron. They are identified as CH3CH2OCH2CH3, (CH3CH2)3B, (CH3CH2O)3B, CH3CH2CH2CH2B(CH3CH2)2 and (CH3CH2)3O3B3. Further, optimized GC conditions are demonstrated to quantify the synthesized triethylboron accurately and determine its purity. The purity of triethylboron is 96.39 % via a normalization method with high accuracy (RSD=0.05 %). The optimized GC conditions were as follows: a hydrogen flame ionization detector, nitrogen as carrier gas whose pathway was installed with a water trap and an oxygen trap, an HP‐5 capillary column (30 m×0.32 mm×0.25 μm) with the column temperature of 60 °C, an inlet temperature of 120 °C, the detector temperature of 150 °C, and an injection volume of 0.6 μL. This work demonstrates a simple and precise method to analyze the synthesized triethylboron and its impurities.

Influence of Conditions of GC- Flame Ionization Detector Analysis on Parameters of Peaks in Highly Concentrated Compounds

Influence of Conditions of GC- Flame Ionization Detector Analysis on Parameters of Peaks in Highly Concentrated Compounds

Determination of hydrazine in prednisolone by derivatization-gas chromatography-triple quadrupole mass spectrometry

泼尼松龙是一种广泛用于临床治疗的肾上腺糖皮质激素药物,其中联氨的残留会直接影响用药安全,但目前国内外还没有出台相应的法律法规和标准来管控药物中联氨的残留限值。联氨具有强极性和强还原性,理化性质很不稳定,易被氧化,又因缺少发色团,相对分子质量太小,检测起来难度很大,需引入一种衍生化试剂,降低其极性,生成相对分子质量较大且理化性质稳定的衍生产物。该研究通过优化衍生化试剂、色谱-质谱条件、溶剂体系和衍生化条件,建立了衍生化-气相色谱-三重四极杆质谱法(GC-MS/MS)测定泼尼松龙中联氨残留的方法,并进行了方法学验证,结果满意。称取1 g泼尼松龙样品置于10 mL具塞离心管中,加入稀释溶剂(甲醇-二氯甲烷(14:23, v/v))至刻度线,涡旋振荡至样品完全溶解后,吸取100 μL置于进样小瓶中,再加入丙酮900 μL,涡旋振荡混匀,样品在丙酮-稀释溶剂(9:1, v/v)中同时完成稀释和衍生化反应后,再经GC-MS/MS检测分析。该研究的衍生化反应无需在添加冰乙酸和超声条件下进行,也无需再添加其他试剂进行萃取操作,联氨与丙酮可瞬间发生衍生化反应,直接实现泼尼松龙中联氨的快速测定。结果表明,联氨在1~12 μg/L范围内线性关系良好,线性相关系数(r2)为0.9999;检出限、定量限分别为0.03和0.10 mg/kg;进样精密度(relative standard deviation, RSD)为1.10%。加标回收率和重复性良好,加标水平分别为1、6、12 μg/L时的回收率为96.15%~96.46%,对应的RSD值为1.77%~2.12%。中间精密度良好,不同时间、不同人员在同一台仪器上测定结果的RSD值为1.77%。方法耐用性良好,通过改变色谱条件来研究检测结果受影响程度大小,在原条件、初始柱温±5 ℃、升温速率±2 ℃/min、柱流量±0.1 mL/min的条件下分别对加标6 μg/L的样品溶液中的联氨含量进行检测,检测结果的RSD值为2.58%。应用建立的方法测定泼尼松龙市售标准品和某药企提供的9个不同批次的泼尼松龙样品,均未检出联氨。该方法操作简便、准确可靠、灵敏度高、选择性好,可用于泼尼松龙中联氨的检测。

Glycogen Synthase Kinase 3 activation status in soleus and EDL muscles from space‐flown mice aboard the BION‐M1 biosatellite

Background A significant limitation to long-term spaceflight and space habitation is the deterioration of human musculoskeletal health. It is well known that prolonged exposure to microgravity leads to pronounced muscle and bone loss, with consequences mimicking several major effects observed in human aging (i.e. osteoporosis and sarcopenia). It is therefore critical to elucidate the underlying molecular mechanisms of these processes to develop meaningful intervention strategies. Glycogen synthase kinase 3 (GSK3) is a serine/threonine protein kinase initially defined in its role of regulating glycogen homeostasis, though it's now known to interact with more than 100 target proteins. GSK3 has notably proven to negatively regulate muscle mass by inhibiting hypertrophy-related mechanisms, myoblast fusion, and muscle regeneration, while also promoting ubiquitin-mediated protein degradation and muscle inflammation. In this study, we explored GSK3 expression and its serine phosphorylation status, known to control its activation/inactivation, in soleus and extensor digitorum longus (EDL) muscles obtained from the BION-M1 mission. Methods Male C57BL6/J mice (3 months old) were flown in space for 1 month aboard the BION-M1 biosatellite (F) and were compared to a ground control (GC, space housing and diet conditions) and a flight control (FC, standard housing conditions) group. Soleus and EDL muscles were extracted and homogenized in protein extraction buffer. Western blotting was used to examine total and phosphorylated (i.e. inactivated) forms of GSK3 (ser21 GSK3α; ser9 GSK3β). Results In the soleus muscle, total GSK3α and GSK3β were reduced in the F group. Though we did not observe any changes in ser21 (GSK3α) or ser9 (GSK3β) phosphorylation, the ratio of phosphorylated:total GSK3β was significantly elevated in the F group compared with GC and FC. We did not observe any differences in soleus phosphorylated:total GSK3α. Further, we did not observe any differences in total, phosphorylated or phosphorylated:total GSK3α/β content in the EDL F group compared to GC and FC. Conclusions Altogether, our data suggest that in response to 1 month of spaceflight, GSK3 is less active in the soleus muscle through changes in expression and phosphorylation. GSK3 may therefore not be involved in the later stages of soleus atrophy in flown mice. This may be explained by a slow-to-fast fibre shift in soleus muscle, as GSK3 presence and activity is typically reduced in fast-twitch muscle fibres compared to slow-twitch. Future studies with soleus muscles from two other NASA-flown missions (RR1 and RR9) will be conducted to confirm these effects.

Oximes of 3,7-dimethylocta-2,6-dienal: Green synthesis, preparative separation of all diastereomers and complete assignment of 1H and 13C NMR spectra

A mixture of four diastereomeric oximes was prepared starting from citral, an inexpensive mixture of neral and geranial ((Z)- and (E)-3,7-dimethylocta-2,6-dienal, respectively), in a solvent-free mechano-chemical reaction with NH2OH•HCl/NaOH, at room temperature. All stereoisomeric oximes ((1E,2E), (1Z,2E), (1E,2Z), and (1Z,2Z)) were isolated in pure state by isocratic silica-gel column chromatography. For the first time, the oximes were separated and individually characterized by 1D- and 2D-NMR spectroscopy in two deuterated solvents. Their spectra were fully assigned and mutually compared. Coupling constant values of higher-order multiplets belonging to the –CH2CH2- moiety were determined from (iterative) spin simulations. A careful analysis of the NOESY spectra of all diastereomers revealed that the oximes formed hydrogen-bonded adducts in CDCl3. Under the oximation conditions, the configuration of the C2-C3 double bond in the conjugated enals did not change. Prolonged standing of pure oximes of citral in either CDCl3 or DMSO‑d6 led to isomerization of the CN bond while keeping the conjugated CC bond configuration unaltered. The equilibrium ratio of the anti- to syn-oximes in solution corresponded to their ratio in the original reaction mixture. The conditions of GC were sufficient to cause dehydration of the oximes to geranyl or neryl nitriles, and/or isomerization to occur in the heated areas of the instrument, giving more complex chromatograms than expected and being dependent on the identity of the analyzed oxime.

Fingerprinting of the Unsaponifiable Fraction of Vegetable Oils by Using Cryogenically-Modulated Comprehensive Two-Dimensional Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry

The present research is focused on the development of a cryogenically modulated (CM) comprehensive two-dimensional gas chromatography-high resolution time-of-flight mass spectrometry (GC × GC-HR ToFMS) method for the in-depth profiling of the unsaponifiable fraction of vegetable oils. Specifically, twelve vegetable oils (9 extra-virgin olive, soybean, peanut, and hazelnut oils) were subjected to analysis, with particular attention devoted to the higher molecular weight constituents (sterols, vitamin E, triterpenic alcohols). Peak assignment was carried out by using commercial unit-mass MS databases, accurate mass data, literature and on-line freely-available mass spectral information, as well as an in-lab-constructed HR ToFMS lipid database. The main objective of the work was to develop a method to define a well-characterized extra-virgin olive oil fingerprint, to be potentially exploited for vegetable oil differentiation. An additional objective of the investigation was to evaluate the performance of the HR ToFMS system (operated at a mass resolution of 25,000 FWHM) under the challenging analytical conditions of a CM GC × GC-based experiment. The HR ToFMS accurate-mass lipid database was (previously) constructed by acquiring, for the main part, the mass spectra of vegetable oil constituents, well-separated from both the matrix and column bleed background.

Structural elucidation of phenidate analogues via the ESI-MS/MS spectra of their sodium adduct ions

The identification of phenidate new psychoactive substances (NPS) by implementing MS (Mass spectrometry) techniques is a challenging task. Phenidate analogues present information-poor mass spectra, both in GC-EI-MS and LC-ESI-MS/MS of the protonated molecules [M+H]+, with a high abundance fragment/product ion representing the secondary amine-containing residue. This lack of EI-MS and ESI-MS/MS information is attributed to the strong tendency of the amine residue to stabilize the positive charge and leads to unavoidable ambiguity in the identification process. Moreover, thermal decomposition of these compounds occurs in the injection port and/or on the column under standard GC conditions. Herein, we demonstrate how structural information can be attained instantaneously through the LC-ESI-MS/MS fragmentation of the accompanied sodium adducts [M+Na]+. The sodium cation alters the charge distribution during ESI-MS/MS fragmentation, generating a major product ion corresponding to the Na+ adduction of the carbonyl group, providing new structural information of the main core of phenidate derivatives (alkylaryl acetate/acetic acid), enabling their reliable structural elucidation. This quick, simple and easy technique can be implemented to confirm the identity or identify various structurally related phenidate analogues in forensic toxicology and doping analysis without the need for sample handling.

Modified layered bimetallic compound used as a novel adsorbent for the solid-phase extraction of monoaromatic hydrocarbons from water samples prior to gas chromatography–mass spectrometry

This study reports a promising method of solid-phase extraction for determining the toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, 1,3,5-trimethylbenzene, and 1,2,4-trimethylbenzene in water samples by gas chromatography–mass spectrometry (GC–MS). Prior to this procedure, the magnesium–aluminum bimetallic hydroxides modified with sodium dodecylbenzenesulfonate (Mg/Al-SDBS-LDH) were prepared and served as the novel solid-phase extractant. The Mg/Al-SDBS-LDH has advantage of good hydrophobicity and larger spacing which facilitates the monoaromatic hydrocarbons (MAHCs) into the interlayer for adsorption. As a result, the seven MAHCs in 500 mL water samples were enriched greatly, and the theoretical enrichment factor reached to 125 times. Under the optimized conditions of solid-phase extraction (SPE) and GC–MS, the mass concentration of each MAHC (0.005–10, 0.01–10, or 0.05–10 ng/mL) had a fine linear relationship with peak area. The correlation coefficients were more than 0.995. The detection limits were between 0.001 and 0.01 ng/mL, and the RSD were between 3.1% and 6.6%. The method had been applied to determine the seven MAHCs in the Dongfengqu river water and laboratory wastewater of Chengdu University of Technology successfully.

Trefoil Factor Family in Pre-neoplastic Lesions and Gastric Cancer

Gastric cancer is the fourth most common cancer and the second leading cause of cancer death worldwide. Although the global incidence of gastric cancer has been decreased dramatically in recent decades, north and northwest of Iran have the highest incidence rate of gastric cancer. Whilst the surgical procedures for gastric cancer have been improved, there is no cure for that. The intestinal type of GC results from pre-neoplastic conditions including atrophic gastritis, intestinal metaplasia and dysplasia. Trefoil Factors Family proteins (TFFs) are small and stable molecules secreted by the mammalian gastrointestinal tract. TFFs constitute a family of three peptides (TFF1, TFF2and TFF3) that are widely expressed in a tissue specific manner in the gastrointestinal tract. Variable TFFs expression in gastric cancer and pre-neoplastic lesions has been found. TFF1 has a tumor suppressor activity and inhibits tumorogenesis in gastric cancer. Its expression decreases in gastritis, gastric atrophy, dysplasia, intestinal metaplasia and gastric cancer.TFF2 has a protective effect on gastrointestinal epithelium. As a prognostic factor, TFF2 expression decreases in gastric ulcer, chronic atrophic gastritis and gastric cancer. TFF3 is considered as an oncogenic factor in gastric tissues. Whilst the normal gastric tissues don’t express TFF3, it increases in intestinal metaplasia. Therefore, more studies are necessary to clarify the role of TFFs in GC and pre-neoplastic conditions. This review has focused on elucidating the important role of TFFs in gastric cancer and pre-neoplastic lesions.