GC-MS System Research Articles

Practical method for the confirmation of authentic flours of different types of cereals and pseudocereals

Gas chromatography with mass spectrometry was used to perform a qualitative analysis of the liposoluble flour extract of different types of cereals (bread wheat and spelt) and pseudocereals (amaranth and buckwheat). In addition to major fatty acids, the liposoluble extract also contained minor fatty acids with more than 20 carbon atoms, higher hydrocarbons and phytosterols. TMSH (trimethylsulfonium hydroxide, 0.2mol/l in methanol) was used as a trans-esterification reagent. In a trans-esterification reaction, triglycerides esterified from acilglycerols to methyl-esters. SIM (selected ion monitoring) was applied to isolate fatty acid methyl esters on TIC (total ion current) chromatograms, using the 74Da fragment ion, which originated from McLafferty rearrangement, and is typical for methyl-esters. GC–MS system was used for the trans-esterification of triglycerides to fatty acid methyl esters in the gas chromatographic injector. This eliminated laboratory preparation for fatty acid methyl esters.Cluster analysis was applied to compare the liposoluble flour extract from different types of cereals and pseudocereals. Statistical data showed the liposoluble extract analysis enabled determination of flour origin and, because the results were unambiguous, this approach could be used for quality control.

Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography – A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates

The retention characteristics of the major lipid components in biodiesels and edible oils as well as representative polycyclic aromatic compounds (PAHs) have been investigated on five different normal phase HPLC stationary phases, in order to optimize class separation for an automatized online HPLC cleanup of PAHs prior GC–MS analysis. By stepwise comparison of different hexane/MTBE compositions as mobile phases on cyano-, phenyl-, pentabromobenzyl-, nitrophenyl- and amino-modified silica columns, the capacity and selectivity factors for each analyte and column could be calculated. It was concluded that the most suitable column for backflush isolation of PAHs in biodiesel and edible oil matrices was the pentabromobenzyl-modified silica (PBB). A previously described online HPLC–GC–MS system using the PBB column was then evaluated by qualitative and quantitative analysis of a biodiesel exhaust particulate extract and a vegetable oil reference material. The GC–MS full scan analysis of the biodiesel particulate extract showed that the lipids had been removed from the sample and a fraction containing PAHs and oxygenated derivatives thereof had been isolated. Quantified mass fractions of PAHs of the reference material BCR-458 agreed well for most of the certified PAH mass fractions in the spiked coconut oil reference material.

GC–MS method for determination and pharmacokinetic study of four phenylpropanoids in rat plasma after oral administration of the essential oil of Acorus tatarinowii Schott rhizomes

Ethnopharmacological relevanceAcorus tatarinowii Schott (AT), belong to the family Araceae, is perennial herbaceous plant mainly present in China, Japan and India. The rhizomes of AT have been used as a famous traditional Chinese medicine for the treatment of central nervous system related diseases. Aim of the studyA selective, accurate and sensitive method using gas chromatography-mass spectroscopy (GC–MS) for the simultaneous determination and pharmacokinetic study of β-asarone, α-asarone, elemicin and cis-methyl isoeugenol in rat plasma was developed and validated. Materials and methodsThe GC–MS system was operated under selected ion monitoring (SIM) mode. The samples were prepared by protein precipitation with acetonitrile after being spiked with an internal standard (1-naphthol). The GC separation was achieved on a DB-1701 column (60m × 0.25mm ID, and 0.25µm film thickness). ResultsThe current GC/MS assay was validated for linearity, intra-day and inter-day precisions, accuracy, extraction recovery and stability. The analyte calibration curves were linear over a wide concentration range and the lowest limit of quantifications (LLOQ) were 5.53ng/mL (β-asarone), 6.50ng/mL (α-asarone), 3.10ng/mL (elemicin) and 7.60ng/mL (cis-methyl isoeugenol). After oral administration 0.9g /Kg of AT rhizomes, the maximum plasma concentration (Cmax) was 2508.6±498.7ng/mL for β-asarone, 257.5±37.1ng/mL for α -asarone, 345.5±33.4ng/mL for elemicin and 452.7±59.1ng/mL for cis-methyl isoeugenol, respectively. The time to reach the maximum plasma concentration (Tmax) was 1.42±0.18h for β-asarone, 1.58±0.19h for α -asarone, 1.67±0.24h for elemicin and 1.75±0.38h for cis-methyl isoeugenol, respectively. ConclusionThis paper described a simple, sensitive and validated GC–MS method for simultaneous determination of four phenylpropanoids in rat plasma after oral administration of the essential oil of AT rhizomes and investigated on their pharmacokinetics studies as well.

Determination of Acrylamide and Acrolein in Smoke from Tobacco and E-Cigarettes

Acrylamide and acrolein are two short-chained hazardous compounds with neurotoxic, carcinogenic, and mutagenic effects. The aim of this paper is to describe a fast and simple procedure for simultaneous determination of both acrylamide and acrolein under standard conditions, suggest a suitable calibration protocol for custom analysis, and demonstrate its applicability to the analysis of gaseous products from, e.g., cigarettes, cigars, or electronic cigarettes. A gas chromatography–mass spectrometry (GC–MS) method was developed to quantify acrylamide and acrolein in smoke vapor from electronic cigarettes, tobacco cigarettes, and cigars. Nonionic and highly polar molecules with a low boiling point and molecular mass need a suitable derivatization method to achieve appropriate retention and selectivity on commonly used relatively nonpolar stationary phases and to enhance the molecular mass for easy MS detection. The derivatization of acrylamide and acrolein was carried out by a bromination method with elemental bromine. The dibromo derivatives were extracted into an organic solvent and following a dehydrobromination procedure the samples were injected into the GC–MS system. Important experimental parameters were varied, after which the bromination time was defined as 30 min, and the injector temperature and the starting temperature of gradient were set at 280 and 50 °C respectively. Acrolein was found in all tested samples, while acrylamide was detected only in smoke from normal tobacco. Possible mechanisms for the formation of these unsaturated compounds in the samples are discussed. After its validation the newly developed method was successfully and reliably applied to the analysis of both compounds. This short method provides an easy way to determine acrylamide and acrolein in gaseous samples.

A new analytical method to determine non-steroidal anti-inflammatory drugs in surface water using in situ derivatization combined with ultrasound-assisted emulsification microextraction followed by gas chromatography–mass spectrometry

Because of the high stability and potential toxic effects of non-steroidal anti-inflammatory drugs (NSAIDs), it is important to closely monitor their concentrations in the environment using a sensitive analytical method. In this study, a simple, rapid, efficient, and sensitive analytical method based on gas chromatography–mass spectrometry (GC–MS) was developed to determine the levels of seven common NSAIDs in various types of surface water. To simplify sample preparation, in situ derivatization using methyl chloroformate was combined with ultrasound-assisted emulsification microextraction. For selection and optimization of significant variables, experiments were statistically designed using Plackett–Burman design and central composite design. The resulting optimal conditions for derivatization and extraction were 100μL of chloroform (extraction solvent), 10.0mL of sample, and 240μL of pyridine (catalyst as a base in derivatization). The optimized sample preparation coupled with optimized GC–MS analysis in selected ion monitoring mode provided good linearity from 0.010 to 5.0ngmL−1, and a limit of detection between 0.0050 and 0.010ngmL−1, good intra-day and inter-day precision (0.30–6.3% and 5.1–9.5%, respectively), and good accuracy (relative recovery; 91–117% at 0.20ngmL−1 and 77–105% at 2.5ngmL−1). Compared with previously reported methods, the current method requires a small volume of sample and simple sample preparation steps for sensitive determination of NSAID levels using a conventional GC–MS system. The method was successfully applied to determine the levels of seven common NSAIDs in various types of surface water.

Evaluation of hydrolysis and alcoholysis reactions in gas chromatography/mass spectrometry inlets

During gas chromatography/mass spectrometry (GC–MS) analyses using water and methanol as injection solvents, hydrolysis reactions after injecting water control and alcoholysis reactions after injecting methanol control or ethanol into a GC–MS system were observed and studied. Two dominant hydrolysis/alcoholysis product series were detected, and were identified as being HO(CH3)2SiOR and HO(CH3)2SiO(CH3)2SiOR, where R=H, methyl, or ethyl, when pure water, methanol and ethanol were injected. The chemical structures of the reaction products were cross-checked by injecting H2O/D2O and H2O/MeOH/EtOH, and comparable EI mass fragmentation patterns were found. The water and alcohols injected reacted with silicones in septum particles which accumulated in the injection port liner after numerous injections, and both hydrolysis and alcoholysis reaction products gradually increased in concentration as the number of injections increased. Potential interferences from hydrolysis or alcoholysis reactions should be paid attention to, evaluated or eliminated when water or methanol was used as the GC or GC–MS solvent, and especially when underivatized methanol or ethanol was subject to GC and GC–MS analysis.

O40: The effect of the national drug law reform on the incidence of 3,4-methylenedioxypyrovalerone (MDPV) among users of illegal drugs in Finland

Introduction In 2010, the Finnish drug legislation was improved in order to be able to react to emerging new psychoactive substances (NPS) more effectively. The amended Narcotics Act allows for a more rapid categorization of NPS as illegal narcotics at the initiative of the Finnish government. In this study, we sought to examine the prevalence of MDPV among drivers suspected of driving under the influence of drugs (DUID) in Finland, before and after the amendment of the Narcotics Act. In addition, the prevalence of MDPV in medico-legal autopsy cases was assessed. MDPV is a novel psychoactive drug with stimulant effects. It has been exceptionally popular among users of illegal drugs in Finland. MDPV was the first drug to be scheduled according to the amended Narcotics Act. Methods Since August 2009, MDPV has been included in the screening of post-mortem toxicology samples in Finland. Accordingly, serum samples from suspected DUID offenders have been analyzed for the presence of MDPV since September 2009. The analysis of MDPV was carried out using LC-MS/MS (DUID) and GC-MS (post-mortem toxicology) systems that have been described in detail elsewhere. We studied the MDPV positive cases between 2009 and 2012. Also, the concomitant use of other psychoactive drugs and the demographics of the users were examined. Results In DUID cases, the total number of MDPV positive cases was 486. Of these, 214 were from the time before the scheduling of the substance. In autopsy cases the numbers were 38 and 18 respectively. The number of MDPV positives decreased both in DUID cases and in autopsied after the scheduling of the drug. In most cases, MDPV was detected among several other psychoactive substances, the most prevalent co-findings being amphetamine and benzodiazepines. The mean (median) serum concentration of MDPV in DUID cases was 0.11 (0.03) mg/L. The mean (median) postmortem blood concentration in autopsy cases was 0.55 (0.12) mg/L. Conclusion Contrary to the expectations of some experts, MDPV did not completely disappear from the market after its national scheduling as an illegal narcotic. Nevertheless, the number of cases both in DUID suspects and in post-mortem toxicology decreased after the amendment. As seen in some other similar studies, the chances to limit and control the use of new psychoactive drugs by means of national legislation are somewhat limited. However, if no measures are taken in terms of the legal status of NPS, the efficacy of the available methods of controlling distribution, and of limiting harm to users and non-users, will be marginal. It is crucial to act fast in defining the legal status and in informing authorities and consumers about the dangers associated with the drug. This cannot be accomplished without rapid measures in the analyzing laboratories to include new substances into the screening methods. Also, extensive scientific research on these substances must be encouraged in order to better identify potentially dangerous substances.

삶은 달걀의 부패에 따른 부위별 냄새물질의 발생특성 연구

In this study, the concentration of odorants released from albumin (EA) and yolk (EY) portions of boiled egg samples were determined as a function of storage time. The concentrations were measured at storage days of 0, 1, 3, 6, and 9 under room temperature. As such, odorants produced during both fresh and decay conditions were measured through time. A total of 19 compounds were selected as the main target odorants along with 12 reference compounds. GC-MS (for VOC) and GC-PFPD system (for sulfur gases) equipped with thermal desorption (TD) system were employed for odorant analysis in this work. The initial concentrations measured from the chamber system were converted into flux terms (ng∙g∙min). The EA showed the highest concentration of H2S (234 ng∙g ∙min) at EA-0, and the concentrations of AT (Acetone) was also seen clearly in the range of 11.7 (EA-0) to 58.6 ng∙g∙ min (EA-9). The EY showed similar patterns. EtAl (Ethyl alcohol) increased 9.47 (EA-1) to 96.7 ng∙g∙min (EA-9) in EA samples. Ketone, alcohol, sulfur groups generally exhibited high concentrations compared to other odorants. These data were also compared in relation to olfactometry related dilution-to-threshold (D/T) ratio by air dilution sensory (ADS) test and sum of odor intensity (SOI).

Rapid analysis of Origanum majorana L. fragrance using a nanofiber sheet, gas chromatography with mass spectrometry, and chemometrics

Headspace nanofiber sheet microextraction together with GC-MS and chemometrics resolution techniques were implemented to separate and identify the volatiles emitted by intact marjoram (Origanum majorana L.) and their relative concentrations. A novel polyaniline-nylon-6 nanofiber composite was applied for headspace microextraction. Characteristics such as high surface-to-volume ratio and π-π functional groups in polyaniline together with the NH and C=O functional groups in nylon-6 make the polyaniline-nylon-6 nanofiber composite a suitable candidate for the extraction of volatiles and semivolatiles. The extracted constituents were desorbed and injected into the GC-MS system under the optimum conditions. Chemometric resolution techniques were utilized to solve the baseline offset, asymmetric peaks, and overlapped peaks problems that arise from GC-MS analysis. By means of these techniques and resolving the overlapped peak clusters, the number of identified constituents was increased to 67 compounds. The major released constituents from the intact marjoram leaves are 4-terpineol, β-linalool, cis-sabinol, and trans-geraniol.

Determination of antidepressants in whole blood using hollow-fiber liquid-phase microextraction and gas chromatography–mass spectrometry

A hollow-fiber liquid-phase microextraction (HF-LPME), used in three-phase mode, and combined with gas chromatography–mass spectrometry (GC–MS), was developed to quantify antidepressants and their major metabolites (amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, desmethylclomipramine, fluoxetine, and norfluoxetine) in whole blood samples, using their deuterated analogs as internal standards. The HF-LPME system comprised a disposable 8-cm polypropylene porous hollow fiber, 4.0 ml of sample solution (0.5 ml of blood added to 3.5 ml of 0.1 M NaOH: donor phase), dodecane (organic phase), and 0.1 M formic acid (acceptor phase) for extraction. After stirring the system, the acceptor phase was evaporated under a nitrogen stream and resuspended in 30 μl of methanol. Derivatization was not required. A 2.0-μl aliquot of this solution was injected into a GC–MS system. The method was validated after the optimization of several parameters that may influence the extraction efficiency. The limits of quantification for all antidepressants were below the therapeutic levels (20.0 ng/ml). The average intraday and interday precisions were within 9.7 and 9.8 %, respectively, for all analytes. The calibration curves were linear in the concentration range of 20–1,200 ng/ml. The developed method was applied to seven actual postmortem samples. Tricyclic antidepressants were detected in all of the analyzed cases. To our knowledge, this is the first demonstration of usefulness of HF-LPME for analysis of antidepressants in postmortem forensic cases.

Allelopathic effect of methanol extracts from Tinospora tuberculata on selected crops and rice weeds

Herbicidal potential of aerial parts of Tinospora tuberculata on germination and seedling growth of seven test plant species, namely rice (Oryza sativa L.); two rice weeds, barnyardgrass (Echinochloa crus-galli L.) and weedy rice (O. sativa f. spontanea); and four vegetable crops, lettuce (Lactuca sativa L.), tomato (Solanum lycopersicum L.), carrot (Daucus carota L.), and cucumber (Cucumis sativus L.) were evaluated. Six concentrations of methanol extract (3.12, 6.25, 12.5, 25, 50, and 100 g L−1) were compared with the control (distilled water). The rate of seed germination and the radicle and hypocotyl length of 7-day-old test plant seedlings were reduced as the concentration of extracts increased compared to the control. Generally, the degree of toxicity of extracts derived from the leaves was more than the extracts derived from the stem. Cluster analysis and the concentrations required for 50% inhibition (defined as EC50) of all parameters showed that radicle growth was more suppressed than germination and hypocotyl growth. Lettuce and carrot were observed as the most sensitive plants while rice showed the highest tolerance to both extracts. Moreover, the dicot target plants were affected more severely than the monocots when treated with leaf extract. The chemical composition of the T. tuberculata methanolic extracts was analyzed by a GC–MS system. A total of 92 and 22 constituents (not previously identified) were found in the leaves and stem, respectively. The results showed that 17 of the 92 components in the leaves, as compared to 4 of 22 compounds in the stem, are known as toxic compounds. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors with potential for the development of future natural herbicide.

Chemical composition of essential oil of Apis mellifera propolis from Falcon State, Venezuela

Apis mellifera bees obtain propolis by adding wax and salivary secretions to resinous, gummy or balsamic materials collected from various plant sources. Its chemical composition depends on many factors (type of bee, flora accessed, environment, management, season, vegetation and geographical area of collection). In the hive, the bees use propolis to consolidate structural components, varnish inside the cells and prevent vibrations. Propolis is known for its antibacterial, fungicidal, antiviral, anesthetic, antiulcer, immunostimulating, hypotensive, cytostatic, and antioxidant properties, the essential oil of Apis mellifera propolis, collected in Falcon state, was obtained by hydrodistillation using a Clevenger trap (0.06% yield). The oil was analyzed by gas chromatography coupled to mass spectrometry (GC / MS) in an HP GC-MS System Model 5973. Twentythree compounds were identified (93.6%), of which the three major compounds were germacrene D (26.5%), ?-caryophyllene (10.2%) and ?-elemene (8.1%).

Gas chromatographic–mass spectrometric quantitation of busulfan in human plasma for therapeutic drug monitoring: A new on-line derivatization procedure for the conversion of busulfan to 1,4-diiodobutane

A simplified gas chromatographic–mass spectrometric (GC–MS) analytical method, involving a novel derivatization procedure was developed for monitoring busulfan (Bu) plasma concentrations in populations undergoing bone marrow transplantation. Plasma samples (500μL) containing Bu-d8 as internal standard were extracted with ethyl acetate (2mL) followed by centrifugation (1800rpm, 5min) and evaporation of the organic layer under nitrogen flow (50°C). The dry residue was reconstituted with 100μL iodine solution in acetonitrile (0.25%, w/v) and 3μL were injected into the GC–MS system at 250°C. Conversion of Bu to 1,4-diiodobutane was accomplished on-line without the need of an extra derivatization step. MS was operated at selected ion monitoring mode at m/z 183 and 191 corresponding to Bu and Bu-d8 derivatives. Total analysis time was 11.5min. Calibration curves were linear (mean r=0.9996) over a concentration range of 25–3651ng/mL using a (1/x)-weighted scheme. Limit of detection and lower limit of quantitation were 10.6 and 25ng/mL, respectively. Overall accuracy Er (%) was ranging from −5.10% to 10.5%. Within- and between-run RSD (%) were lower 4.51% and 2.15%, respectively. Overall recovery of Bu was equal to 69.3±4.56% (RSD (%)). The present method is sensitive and specific, requiring a simple sample preparation procedure and short analysis time, advantages crucial for therapeutic drug monitoring of Bu in clinical practice and application in pharmacokinetic studies.

Application of Receiver Operating Characteristic (ROC) Curves for Explosives Detection Using Different Sampling and Detection Techniques

Reported for the first time are receiver operating characteristic (ROC) curves constructed to describe the performance of a sorbent-coated disk, planar solid phase microextraction (PSPME) unit for non-contact sampling of a variety of volatiles. The PSPME is coupled to ion mobility spectrometers (IMSs) for the detection of volatile chemical markers associated with the presence of smokeless powders, model systems of explosives containing diphenylamine (DPA), 2,4-dinitrotoluene (2,4-DNT) and nitroglycerin (NG) as the target analytes. The performance of the PSPME-IMS was compared with the widely accepted solid-phase microextraction (SPME), coupled to a GC-MS. A set of optimized sampling conditions for different volume containers (1–45 L) with various sample amounts of explosives, were studied in replicates (n = 30) to determine the true positive rates (TPR) and false positive detection rates (FPR) for the different scenarios. These studies were obtained in order to construct the ROC curves for two IMS instruments (a bench-top and field-portable system) and a bench top GC-MS system in low and high clutter environments. Both static and dynamic PSPME sampling were studied in which 10–500 mg quantities of smokeless powders were detected within 10 min of static sampling and 1 min of dynamic sampling.

Headspace volatiles of the edible fruit pulp of Parinari curatellifolia growing in Malawi using solid phase microextraction

Head-space volatiles of the edible pulp of the mobola plum (Parinari curatellifolia) were extracted using solid phase microextraction (SPME), and their identities determined by GC–FID and GC–MS systems. The SPME method extracted eleven major compounds accounting for 99.0% of the volatile constituents. The volatiles were ethyl butyrate, 28.7%; ethyl isovalerate, 19.3%; ethyl valerate, 12.4%; ethyl hexanoate, 3.7%; ethyl benzoate, 2.5%; isoamyl isovalerate, 0.3%; phenol, 10.5%; α-bergamotene, 1.1%; β-farnesene, 3.0%; 2,6-diterbutyl-4-methyl-phenol, 3.1% and phenylacetonitrile, 14.4%. Thus, the valerate and butyrate esters are the most abundant volatiles in the head-space of the edible pulp of the ripe fruit using the SPME method. The compounds, ethyl isovalerate, ethyl valerate, isoamyl isovalerate, phenol, 2,6-diterbutyl-4-methyl-phenol, phenylacetonitrile, α-bergamotene and β-farnesene were identified for the first time in the head-space of this fruit.

A new purge and trap headspace technique to analyze low volatile compounds from fluid inclusions of rocks and minerals

A new method for the analysis of trace gases from fluid inclusions of minerals has been developed. The purge and trap GC–MS system is based on the system described by Nolting et al. (1988) and was optimized for the analyses of halogenated volatile organic compounds (VOCs) having boiling points as low as −128°C (carbon tetrafluoride).The sample preconcentration cold trap consists of a U-shaped glass lined steel tube (GLT™), that is immersed into a small liquid nitrogen Dewar vessel for cooling. A rapid desorption step heats up the preconcentration tube in <30s from −196°C to 200°C. The process is carried out by using a pressurized air stream to dissipate the liquid nitrogen followed by resistive heating of the trap. The design of the cold trap and the direct transfer of desorbed analytes onto the GC column via a deactivated capillary column retention gap made sample refocusing within the GC oven unnecessary. Furthermore, a special air-tight grinding device was developed in which samples ranging from soft halite (hardness 2, Mohs scale) to hard quartz (hardness 7) are effectively ground to average diameters of 1000nm or below, thereby releasing gases from fluid inclusions of minerals. The gases are then purged from the grinding chamber with a He carrier gas flow. The detection and quantitative determination of gases, such as SF6 and CF4 released from fluorites and CH3Cl from halite samples is demonstrated.

Protective Role of Mentha longifolia L. ssp. longifolia against Aflatoxin B

The aim of this study was to investigate the effects of essential oil of Mentha longifolia L. ssp. longifolia, used since ancient times for the treatment of many digestive tract diseases, on the genotoxicity and oxidative stress by a single dose of Aflatoxin B1 (5 µM) in the human lymphocyte culture. The total of the 12 identified components accounted for 97.69 % by Gas chromatography (GC). Major components of the oil were cis-piperitone epoxide (26.52 %), piperitenone oxide (26.40 %), pulegone (15.66 %) and piperitenone (13.57 %). According to the results obtained from GC-MS systems, monoterpenes consist of 89.19 % of the total oil approximately while sesquiterpenes were represented in small quantities in the oil. We studied the anti-genotoxic effects of essential oils of M. longifolia (MEO) by using sister chromatid exchange (SCE) and micronucleus (MN) test systems. Also, the anti-oxidative effects of MEO were evaluated by using superoxide dismutase (SOD), glutathione peroxidase (GPx) and malondialdehyde (MDA) assay. The SCE frequency and the number of MN were increased when treated with AFB1. Especially, MEO at 1.5 and 2.0 µl reduced SCE frequency and MN number in the human lymphocyte (p <0.05). In addition, AFB1 treatment significantly reduced the activity of SOD and GPx and elevated the level of MDA (p<0.05). MEOs treatment led to significant attenuation of AFB1-induced oxidative stress by normalization of the activities of SOD and GPx and the MDA (p < 0.05). These results suggest that MEOs could provide anti-oxidative and anti-genotoxic protection for the oxidative and genotoxic agents that cause many diseases including cancer and neurodegenerative disease.

Chemical Composition of Essential Oil of Stachys byzantina from North-West Iran

The paper reports the composition of the essential oil from aerial parts (leaves) of Stachys byzantina (Lamiaceae) from North-West of Iran. The essential oil was extracted by hydrodistillation from selected plants and its chemical composition was determined by GC-MS system. The mass fraction of oil on dry weight base was 0.4 %. Altogether, 21 compounds were identified corresponding to 87.9 % of the total oil. The main components were germacrene D (9.6 %), Menthone (6.9 %), 1,8-cineole (14.8 %), α-terpineol (7.8 %), cubenol (9.9 %), α-cadinol (6.8 %) and Linalool (12.9 %).

A non-michaelian behavior of the in vitro metabolism of the pentacyclic triterpene alfa and beta amyrins by employing rat liver microsomes

Pharmacological studies employing alpha and beta amyrin have demonstrated potential application in several biological activities suggesting their application as promising drugs. In the early drug development, metabolism studies may give important parameters regarding the efficacy and safety of the drug candidate. Therefore, the aim of this work was to determine the enzymatic kinetic parameters of these pentacyclic triterpenes. Chromatographic analyzes were performed using a Shimadzu GC–MS system. The resolution of amyrins was achieved with a DB5-MS column of 0.25μM film thickness, 30.0cm length and 0.25mm diameter. At this condition, the retention times of beta- and alpha-amyrin were 21.3 and 20.2min, respectively. The proposed method showed to be linear over the concentration range of 0.16–42.18μM for beta amyrin and 0.11–28.12μM for alpha amyrin. The lowest concentration quantified by the validated method was 0.16μM for beta and 0.11μM for alpha amyrin. The stability study showed that amyrins were stable at room temperature for 12h and at 37°C for 1h. The absolute recovery of the amyrin isomers from the rat microsome was 54.3–59.2%. The enzymatic kinetics presented sigmoidal plots. It was observed a Vmax=0.698±0.022μmol/mg protein/min, S50=4.4μM and Hill coefficient of 2.7±0.17 for alpha amyrin and a Vmax=0.775±0.034μmol/mg protein/min, S50=7.0μM and Hill coefficient of 2.5±0.21 for beta amyrin. The obtained results give the first clues regarding amyrin metabolism and suggests a more detailed study conducted employing isolated CYP isoforms.

Removing perchlorate from samples to facilitate organics detection by pyrolitic methods

Thermal volatilization or pyrolysis of solid samples followed by gas chromatography–mass spectrometry (TV–GC–MS) or other downstream analyses has proven robustness and has been adopted for the extraction of organic compounds for their detection in planetary lander science missions (e.g., Viking Lander GC–MS, Phoenix TEGA, MSL SAM, and the future ExoMars MOMA). Pyrolysis to extract organic compounds from soil has limitations when oxidants co-occur in the analyzed sample unless the desired end product is CO2. Pyrolysis of such soils may result in oxidation of organics to CO2 during heating, and thus make organics characterization difficult, if not impossible. Analytical investigations seeking to identify organics in martian soils containing oxidants could benefit from the deployment of technologies that remove known and putative oxidants prior to thermal volatilization. We conducted a series of experiments in order to determine if a polymeric anion exchange resin, commonly used for removing the perchlorate anion from contaminated municipal water supplies, could sustain its substantial perchlorate removal capability while keeping organic compounds intact for downstream detection. We demonstrated that this resin can strongly bind perchlorate from aqueous solution while simultaneously leaving amino acids substantially unaltered. The perchlorate-binding resin could be easily adopted as a pre-treatment for martian soil extracts to create analytical systems with improved organics characterization capabilities compatible with existing TV–GC–MS systems. We propose this strategy to aid detection and characterization of putative martian organics co-situated with perchlorate at sampling sites.