GC Oven Research Articles

Development and Application of a Cost–Effective Analytical Method for Hydrofluorocarbons Using Preconcentrator–Gas Chromatograph–Mass Spectrometer

The expansion of atmospheric observation networks for hydrofluorocarbons (HFCs), which are closely related to climate change and contribute to global warming, significantly impacts our society and daily life. Their emissions are estimated to increase in the future, which is a major challenge. Observations of HFCs globally were performed using expensive GHG–specific equipment installed at AGAGE and other sites, but many research institutions find it difficult to install such equipment. Therefore, we successfully developed a measurement method for six components of HFCs (HFC–23, HFC–32, HFC–125, HFC–134a, HFC–143a, and HFC–152a) with high atmospheric concentrations in various parts of the world by optimizing measurement parameters such as the sample transfer volume and rate, module cooling temperatures, the injection time, the GC oven temperature program, and the monitored ions of a commercially available preconcentrator–GC–MS. Because this developed measurement method is cost–effective and simpler to operate than those of GHG–specific equipment, it is expected to provide an opportunity for many research institutes to measure HFCs. Furthermore, in addition to HFCs, we confirmed that simultaneous measurements can be performed for 97 volatile organic compounds (VOCs), including hazardous components. This research can contribute to the observation of HFCs in countries and regions where the actual status of emissions is unclear or where no or few atmospheric observations were conducted. The results of those observations can be used to formulate more detailed global warming countermeasures.

Development of a superheated water chromatography method for the sustainable determination of preservatives in foods and cosmetics

The present research focused on the use of high temperatures to achieve fast separations in Liquid Chromatography (LC) and minimize the consumption of organic solvents. Particularly, superheated water was employed, by exploiting the decrease in dielectric constant of water when increasing the temperature. To realize this kind of application, the availability of LC columns resistant at high temperature is mandatory. Recently, porous graphitic carbon (PGC) columns have been proposed as stationary phases resistant up to 250 °C. Hardware modifications were also necessary to guarantee the efficient heating of the mobile phase prior of entering the column, as well as its rapid cooling before detection by photodiode array (PDA). Specifically, an LC system was interfaced to a GC oven, which hosted the LC column; to achieve a fast and efficient heating of the eluent coming from the autosampler prior to enter into the column, a pre-heating tube was interposed between the autosampler outlet and the column inlet. Instead, a cooling loop was connected between the column outlet and the PDA cell. A mixture of 1-nitroalkanes was used to evaluate the performance of the system in terms of dead volumes, band broadening and peak shape, as well as chromatographic efficiency and resolution. The use of higher temperatures allowed to perform analyses at higher flow rates in reduced analysis time and was also in terms of peak bandwidth resulting to increased efficiency for the most retained compound. Moreover, van't Hoff plots were obtained at different temperature, confirming that the most retained analyte greatly benefited of the temperature increase.The system was applied to the analysis of parabens in cosmetic and food products. The method combined eco-sustainable sample preparation with high-temperature LC separation on a PGC column and was fully validated in terms of linearity, precision, accuracy and detection and quantification limits. The developed method was critically evaluated by comparing the output of different metric tools implemented in the last decade for the quantitative assessment of the greenness.

Development of Fluorescent Co (II)-Integrated Carbon Dots and Their Application as a Off-On Mesotrione Detection Sensor.

A very simple mesotrione-sensing medium with enhanced sensitivity detection limits has been proposed. A renovated hydrothermal method was adopted for synthesizing fluorescent carbon dots from ethylenediamine and glucose using a Teflon-lined simple autoclave in a GC oven. The resultant carbon dots were characterized via TEM, FTIR, UV-vis, particle size distribution, and EDX and evaluated in a fluorimeter as the sensing medium for mesotrione detection. The binding approach of the Co (II)-integrated glucose-bound carbon dots toward mesotrione is selective, making them an effective sensor for the real sample applications, where majority of the coexisting substances showed insignificant interference effect. Formation of the metastable state due to the molecular interaction between carbon dots and Co (II) resulted in fluorescence quenching at 456 nm. Enhancement in the fluorescence intensity occurred when mesotrione was added in the concentration range of 0.2-5.0 μg mL-1, with a limit of detection, limit of quantification, standard deviation, and relative standard deviation of 0.054, 0.164, 0.00082 μg mL-1, and 0.682%, respectively. Mesotrione determination was demonstrated in soil, water, and tomato samples with recoveries in the range of 95.38-104.7%. The selectivity of the sensor was found to be good enough when checked for the complex tomato sample spiked with different pesticides of the triketone family having structural similarities to mesotrione.

A new direct extraction by gas-chromatography with flame ionization detector coupled to head space method for the determination of alcohol content of high matrix wine products

Detection, identification, and quantitation of alcohol in any matrix rich medium is a common practice although sample preparation is inevitable and time consuming. A sensitive, precise and ultimately wide range method for detection, identification and quantification of main content/residual/impurity alcohols without any matrix interference that can be used for production phase quality control, pharmaceutical and/or bio-technological refinement or toxicological evaluation and for forensics is always needed. Even for quality control also for toxicological considerations, ethanol (EtOH) and very similar compound methanol has to be detected and identified definitely becomes vital. However, with the fermented products, the matrix becomes a challenging process, makes the methods inefficient or more extraction methods have to be implanted. Here we propose a new simple and reliable direct extraction method has been developed for the determination of alcohol content of high matrix wine products using the gas-chromatography with flame ionization detector coupled to head space. The method was developed with a rich and complex component mixture of fermented alcoholic beverages (wine) with very high matrix effects. Isopropanol (IPA) was preferred as an internal standard, and Triton X-100 (TX-100) was used as diluting solution in this method. The amount of TX-100, extraction temperature, and the total volume of solution in head space vial (20 mL) were optimized. 2.5% TX-100, 80 °C extraction temperature, and 2.0 ml of total volume were used as optimum condition. Stationary phase was the fused silica, Agilent J&W DB-624 column (30 m x 320 m x 1.8 m) and Helium was used as a mobile phase. GC oven temperature programme was 40C (5 min), 5C/min ramp to 60C (0 min) and 30C/min to 150C (1 min). Performance of the method was assessed by evaluating the recovery, accuracy, precision, linearity, limits of detection (LOD) and limit of quantification (LOQ). Calibration curve was drawn between the concentration of 2.5% to 15.0% EtOH (y = 1.572x – 0.702, R² = 0.9960, y; the ratio of peak area of EtOH to IPA, x: EtOH%). The slopes of standard addition and external calibration curve were statistically same. Recovery of the method was 97.5 ± 3.5 for tree different concentrations and the precision was %5.8 (n= 11). LOD and LOQ were calculated as 0.80% and 2.5%, respectively. The proposed method has a potential for application into the industry and academia with determination of the alcohol content/residual/impurity and also check the quality and content of the fermented medium without the effect of matrix.

Comparison of Tenax and OV-1 Thin-Films for Microfabricated Preconcentrators

Gas chromatography is a common technique for the separation and analysis of mixtures of volatile organic compounds (VOCs). In many applications, such as breath analysis and room air sampling, the concentration of analytes is so low that preconcentration is necessary to selectively trap VOCs over a longer period of time, before analysis. The goal of this project is to develop an energy efficient, compact vapor preconcentrator for air sampling. We present thin-film preconcentrators (PCF) with integrated heaters and temperature sensors that were coated with polydimethylsiloxane (OV-1), poly(2,6-diphenylphenylene oxide) (Tenax-TA) and a mixture of OV-1 and Tenax-TA. The polymer thin-films were fabricated using a dynamic coating method with 20mg/ml OV-1 in a 1:1 mixture of DCM and pentane, 10mg/ml of OV-1 and 5mg/ml of Tenax-TA in chloroform, or 20 mg/ml of Tenax-TA in chloroform.The OV-1 and OV-1/ Tenax-TA PCFs were initially tested by connecting them to the inlet and FID of a gas chromatograph with 1 m of 50um guard column. A volume of 0.2 µl of an alkane was injected via the heated inlet 175 oC at 1 psi, after any breakthrough had passed, the GC was pressurized to 8 psi and the PCFs were heated using an integrated platinum film heater. The GC was kept at a constant temperature of 40°C during these tests while the PCF was independently heated outside of the GC oven. The adsorption ratio of these experiments is summarized in table 1. Alkanes above decane such as dodecane proved difficult to desorb, even with the integrated heater reaching temperatures of approximately 260°C.The air sampling experiments for each PCF were performed for decane and benzene using a dynamic headspace sampling method with a constant flow of nitrogen induced by a mass flow controller at a rate of 0.3 ml/min. at a pressure of 5psi. A six-way valve connected the PCF to the GC for desorption at a pressure of 15psi, after a set period of time. Analysis with Agilent 5890GC using a 20 m Rxi-1ms column, temperature ramp from 40°C to 180°C at a rate of 20°C/min, and FID detector. The results for the headspace sampling are summarized in figure 1. For benzene the thin-films with Tenax-TA saturate much more quickly than the OV-1 film and the pure Tenax-TA film which has the lowest capacity. For decane, the thin films with Tenax-TA still saturate faster but the largest capacity was observed for the mix of OV-1 and Tenax-TA over this limited range of sampling times.The authors would like to thank the Georgia Tech Research Institute for funding this research out of Independent Research and Development (IRAD) funds. Figure 1

Sensitivity and resolution optimization in gas chromatography coupled to mass spectrometry analyses of volatile organic compounds present in vacuum environment

The gaseous phase analyses of volatile organic compounds (VOCs) are an important challenge especially when these organics are formed in high vacuum environments (10−8 mbar) reproducing the environment of astrophysical ices formation and processing. Several analytical techniques have been developed to identify the molecular diversity formed from the processing of these ices. Among them, the coupling of a GC–MS to the vacuum chamber where ices are processed highlighted the interesting chemical diversity of such processed ices. These analyses were possible due to the development of a specific system, the VAHIIA interface that enables the preconcentration of VOCs at low pressure (10−8 mbar) and their transfer at higher pressure to the injection unit of a GC for their subsequent analyses. This system showed sufficient repeatability (13%) and low detection limits (nmol) for simple ices [1], but presents limits when ice mixtures are complex (such as multi-component ices including water, methanol and ammonia). In this contribution, we present the optimization of our previous VAHIIA system by implementing a cryofocusing system in the GC oven and by improving the recovery yield of VOCs from the vacuum chamber to the VAHIIA interface. The cryofocusing provides an improvement of efficiencies leading to higher resolution and signal to noise ratio, while the addition of argon in the vacuum chamber during the VOC recovery allows increasing the amount of molecules recovered by a factor of ∼200. The coupling of both approaches provides an increase of sensitivity of a factor ∼400. At the end, experiments on astrophysical ices are shown demonstrating the interest of such optimizations for VOC analyses.

Improving thermal desorption aerosol gas chromatography using a dual-trap design

Thermal desorption aerosol gas chromatography (TAG) is an effective tool for in situ analysis of particulate organic molecules. However, the performance of current TAG is limited by the detectability of low volatile compounds and the matrix effect. In this study, a dual-trap TAG system was developed to address these issues. Thermally desorbed effluent is focused by a weakly retained trap (for low volatile compounds) in a 1 m capillary column conditioned in the GC oven, followed by a strongly retained trap (for high volatile compounds). Then, the focused analytes are desorbed in a reverse flow into the GC column for analysis. Detection over a wide volatility range from C10 to C40 n-alkanes is achieved using the dual-trap TAG. We show that it has lower discrimination of injection, better linearity and higher detectability of n-alkanes. The dual-trap TAG was applied for in-situ measurement of ambient fine particles (PM2.5) in Beijing. Repeatable retention time of n-alkanes was demonstrated during a continuous measurement over two weeks.

Enantiomeric analysis of polycyclic musks AHTN and HHCB and HHCB-lactone in sewage sludge by gas chromatography/tandem mass spectrometry.

Enantioselective analysis of chiral compounds is an interesting and challenging technique used to elucidate the degradation/transformation mechanisms of these compounds or understand their environmental processes. In this study, we have developed an effective separation and detection approach for the enantiomeric analysis of AHTN and HHCB, as well as a transformation product of HHCB (HHCB-lactone), in sludge samples. The analytical method was developed using a cyclodextrin-based enantioselective gas chromatography column combined with tandem mass spectrometry (GC/MS/MS). The GC oven temperature gradients, the linear velocity of the helium carrier gas, as well as the MS/MS parameters, including quantitative and qualitative ion pairs, dwell times, and collision energies, were optimized to achieve good separation and high sensitivity for all target enantiomers. Baseline separations of all target enantiomers were observed. Limits of quantification (LOQs) for all enantiomers ranged from 0.010 to 0.045 μg/L, and calibration linearity for all single enantiomers was higher than 0.99. The intra-day and inter-day precisions for all single enantiomers of AHTN, HHCB, and HHCB-lactone ranged from 0.8 to 3.8% and from 4.2 to 8.3%, respectively. The developed method was fully validated through enantioselective analyses of AHTN, HHCB, and HHCB-lactone in sludge samples collected from 17 WWTPs. The enantiomeric fractions (EFs) of HHCB and HHCB-lactone in sludge samples distinctly deviated from 0.50, indicating a significant enantioselective transformation of HHCB with preferential degradation of the 4S enantiomers. Significant positive correlations were found between the EF values of cis-HHCB enantiomers and cis-HHCB-lactone enantiomers in the sludge samples, implying that further efforts are still needed to clarify the degradation/transformation mechanism from HHCB to HHCB-lactone.

Simultaneous Quantitative Determination of Synthetic Cathinone Enantiomers in Urine and Plasma Using GC-NCI-MS.

Development and validation of sensitive and selective method for enantioseparation and quantitation of synthetic cathinones is reported using GC-MS triple quadrupole mass spectrometry with negative chemical ionization (NCI) mode. Indirect chiral separation of thirty-six synthetic cathinone compounds has been achieved by using an optically pure chiral derivatizing agent (CDA) called (S)-(−)-N-(trifluoroacetyl)pyrrolidine-2-carbonyl chloride (L-TPC), which converts cathinone enantiomers into diastereoisomers that can be separated on achiral columns. As a result of using Ultra Inert 60 m column and performing slow heating rate (2°C/min) on the GC oven, an observed enhancement in enantiomer peak resolution has been achieved. An internal standard, (+)-cathinone, was used for quantitation of synthetic cathinones. Method validation in terms of linearities and sensitivity in terms of limits of detection (LODs), limits of quantitation (LOQs), recoveries, and reproducibilities has been obtained for fourteen selected compounds that examined simultaneously as a mixture after being spiked in urine and plasma. It was found that the LOD of the fourteen synthetic cathinones in urine was in the range of 0.26–0.76 µg/L, and in plasma, it was in the range of 0.26–0.34 µg/L. While the LOQ of the mixture in urine was in the range of 0.86–2.34 µg/L, and in plasma, it was in the range of 0.89–1.12 µg/L. Unlike the electron impact (EI) ion source, NCI showed better sensitivity by two orders of magnitude by comparing the obtained results with the recently published reports for quantitative analysis and enantioseparation of synthetic cathinones.

Cryofocus fast gas chromatography combustion isotope ratio mass spectrometry for rapid detection of synthetic steroid use in sport doping.

Sports doping requires high precision carbon isotope ratio (CIR) analysis of endogenous steroids using gas chromatography-combustion isotope ratio mass spectrometry (GCC-IRMS), however methods are relatively slow and cumbersome. A cryofocusing fast GCC-IRMS (Cryofocus Fast GCC-IRMS) was developed and optimized with minimal peak broadening using a programmable temperature vaporization (PTV) inlet and a low dead volume narrow-bore continuous capillary combustion interface to an IRMS. PTV injection, followed with cryofocusing before steroid analytes were volatilized by a hot jet, was used to initiate chromatography. Compared to ramping temperature using a conventional GC oven, cryofocusing with hot jet volatilization reduced analysis time by a factor of 3 to 4 and reduced peak widths to ∼800 ms. Well separated peak isotope ratios were measured with SD(δ13C) < 0.5‰ over a range of 10-50 ng of each steroid on column and were accurate from 2 ng to 100 ng. Characterization of the current experimental system with well characterized pure steroid isotopic standards demonstrates how the technique can be applied to steroid mixtures derived from real urine samples. Cryofocus Fast GCC-IRMS advances toward the goal of routine CIR testing of steroids in all urine samples for doping control.

Challenges in GC–MS analysis: Case studies on phenibut and ethylphenidate

The challenges associated with drug analysis using GC–MS such as thermal degradation, cyclisation or unwanted side reactions causing potential erroneous identification have become evident in view of the high surge in new drugs available in the market. Two case studies illustrated how alternative methods or modifications to existing techniques can help to circumvent the limitations. In the first case study, phenibut which is a GABA analogue, cyclises to 4-phenyl-2-pyrrolidinone under thermal conditions. The identification of phenibut was achieved through derivatisation and identification of its TMS derivative. The second case study, thermal degradation was minimised on drugs of interest methylphenidate and ethylphenidate by reducing the injector port temperature to 200°C and maintaining the GC oven temperature at below 190°C in order to prevent thermal degradation of the drugs of interest.

Improving the productivity of a multidimensional chromatographic preparative system by collecting pure chemicals after each of three chromatographic dimensions

The enhanced sample collection capability of a heart-cutting three-dimensional GC-prep system is reported. In its original configuration, a highly pure component can be usually collected after the last (3D) column outlet by means of a dedicated preparative station. The latter is located after the last chromatographic column, and this poses the requirement for multiple heart cuts even for those components showing satisfactory degree of purity after the first (or second) separation dimension. The feasibility to collect pure components after each chromatographic dimension is here described, employing a three-dimension MDGC system equipped with high-temperature valves, located inside the first and second GC ovens, with the aim to improve the productivity of the collection procedure. In addition to a commercial preparative collector located at the 3D outlet, two laboratory-made collection systems were applied in the first and second dimension, reached by the effluent to be collected trough a high-temperature valve switching the heart-cut fraction between either the detector (FID), or the collector. Highly pure sesquiterpene components were collected, namely: patchouli alcohol after the first column [poly(5% diphenyl/95% dimethylsiloxane)], α-bulnesene after a second column coated with high molecular weight polyethylene glycol, and α-guaiene after an ionic-liquid based column (SLB-IL60), used as the third dimension. Purity levels ranging from 85 to 95% were achieved with an average collection recovery of 90% (n=5). The following average amounts were collected per run: 160μg for α-guaiene, 295μg for α-bulnesene, and 496μg for patchouli alcohol.

Optimization of an online heart-cutting multidimensional gas chromatography clean-up step for isotopic ratio mass spectrometry and simultaneous quadrupole mass spectrometry measurements of endogenous anabolic steroid in urine.

Measuring carbon isotope ratios (CIRs) of urinary analytes represents a cornerstone of doping control analysis and has been particularly optimized for the detection of the misuse of endogenous steroids. Isotope ratio mass spectrometry (IRMS) of appropriate quality, however, necessitates adequate purities of the investigated steroids, which requires extensive pre-analytical sample clean-up steps due to both the natural presence of the target analytes and the high complexity of the matrix. In order to accelerate the sample preparation and increase the automation of the process, the use of multidimensional gas chromatography (MDGC) prior to IRMS experiments, was investigated. A well-established instrumental configuration based on two independent GC ovens and one heart-cutting device was optimized. The first dimension (1D) separation was obtained by a non-polar column which assured high efficiency and good loading capacity, while the second dimension (2D), based on a mid-polar stationary phase, provided good selectivity. A flame ionization detector monitored the 1D, and the 2D was simultaneously recorded by isotope ratio and quadrupole mass spectrometry. The assembled MDGC set-up was applied for measuring testosterone, 5α- and 5β-androstanediol, androsterone, and etiocholanolone as target compounds and pregnanediol as endogenous reference compound. The urine sample were pretreated by conventional sample preparation steps comprising solid-phase extraction, hydrolysis, and liquid-liquid extraction. The extract obtained was acetylated and different aliquots were injected into the MDGC system. Two high performance liquid chromatography steps, conventionally adopted prior to CIR measurements, were replaced by the MDGC approach. The obtained values were consistent with the conventional ones. Copyright © 2016 John Wiley & Sons, Ltd.

High temperature diaphragm valve-based comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry

A high temperature diaphragm valve-based two-dimensional (2D) gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS) instrument, with the valve mounted directly in the GC oven, is demonstrated with separations up to 325°C. Use of the diaphragm valve allowed for the use of uncoupled carrier gas flows for 1D (first column dimension) and 2D (second column dimension), with a 1D flow rate of 1ml/min, and a 2D flow rate 3ml/min. The 3ml/min flow rate on 2D was selected to ensure compatibility with most TOFMS detectors. For valve-based modulation, a 5µl sample loop coupled with a 60ms pulse width was selected, providing sufficient sensitivity concurrent with an acceptable 2D peak capacity. A 44-component mixture of alkanes, alcohols, and polyaromatic hydrocarbons (including n-alkanes of heptane to triacontane) whose boiling points range from 98°C to 450°C was used to initially study instrument performance. For a 120min separation and a modulation period PM of 2s, average peak widths-at-base of 10s and 94ms were achieved for the alkanes on the 1D and 2D dimensions, respectively. Hence, the 1D peak capacity is 1nc~700, and the 2D peak capacity can in principle be 2nc~20. Thus the ideal 2D peak capacity could in principle approach nc,2D~14,000 using the 120min 1D run time. The limit of detection (LOD) for docosane, a representative analyte, was determined to be 1.5ppm injected concentration when 2µl of liquid sample was injected with a 20:1 split. A separation of diesel fuel demonstrated the practical utility of the instrument with this complex sample using a relatively fast run time of 20min and a short modulation period PM of 1s. Average peak widths-at-base of 5.4s and 166ms were achieved on the 1D and 2D dimensions, respectively. This yielded a 1nc~220 and a 2nc~ 6. Therefore, the 2D peak capacity is nc,2D~1320 with the 20min diesel separation.

A procedure for comprehensive two-dimensional gas chromatography retention time locked dual detection

In this paper, a novel, and easy to perform, retention time locking procedure for locking primary and secondary retention times of detector signals in comprehensive two-dimensional gas chromatography (GCxGC) dual-detection is proposed and its advantages are demonstrated and discussed. The dual detection retention time locking procedure is a 2-step process for a GCxGC system in which the effluent of the primary column is split, by using a pressure regulated splitter, towards the GCxGC modulator using two identical secondary GC columns of which one is installed in the main GC oven and the other is installed in a secondary GC oven. The first step of the locking procedure is to minimize the secondary retention time difference between both detectors of a compound, which has a retention factor (k) close to 0. This is done by stepwise altering the effective secondary column length, simply by sliding the secondary column, which is installed in the main oven, forwards or backwards through the modulator. The second step is to minimize the secondary retention time difference of a compound which has a significant retention in both dimensions. This is done by stepwise altering the secondary oven temperature rate. This locking procedure was successfully demonstrated for the analysis of a diesel sample by GCxGC coupled to a time of flight mass spectrometer (TOFMS) and a nitrogen chemiluminescence detector (NCD) and by GCxGC coupled to a TOFMS and a flame ionization detector (FID). For all compounds the average absolute secondary retention time differences between the NCD or the FID and the TOFMS detectors were 0.03, and 0.07s, respectively, which are significantly less than the average peak widths at half heights, which was 0.2s.

Chromatographic-mass spectrometric analysis of ethanol extract of &lt;i&gt;Maesa perlaria&lt;/i&gt; var &lt;i&gt;formosana&lt;/i&gt;

Purpose: This study analyzes the chemical composition of ethanol root extracts of Maesa perlaria var. formosana by gas chromatography-mass spectrometry (GC-MS).Methods: The dried root of Maesa perlaria var. formosana was extracted with 95 % ethanol for composition analysis under the following optimum GC-MS conditions: 250 °C inlet temperature, 250 °C MSD detector temperature, and GC oven temperature programmed as follows: initial temperature held at 70 °C for 15 min, then increased at a rate of 2.5 °C/min and held at 170 °C for 15 min; then raised at a rate of 2 °C/min and kept at 180 °C for 20 min; then raised at 2 °C/min and kept at 250 °C for 20 min. Finally, it was raised at 3 °C/min and kept at 280 °C for 15 min.Results: A total of 59 chemical compounds were identified, representing 88.82 % of the composition of the ethanol extracts. The three major components, include 2,4-di-tert-butylphenol (16.76 %), stigmasterol (15.86 %) and campesterol (7.33 %)Conclusion: The results show that a total of 59 components were identified in the ethanol extract of Maesa perlaria var. formosana. The major component, 2,4-Di-tert-butylphenol, exhibits various biological activities.Keywords: Maesa perlaria var. formosana, 2,4-Di-tert-butylphenol, Stigmasterol, Campesterol, Gas chromatography-mass spectrometry

Composition and Bioactivity of the Essential Oil from the Leaves of Lindera setchuenensis

setchuenensis. In this study, we present for the first time the chemical composition and antibacterial activity of the EO from the leaves of Lindera setchenensis grown in China. Leaves of Lindera setchenensis were collected from Emeishan, Sichuan Province, China during May 2013. A voucher specimen (JRY01) was deposited at the Natural Products Chemistry Laboratory, Southwest Jiaotong University. Essential oil was obtained from the fresh material by hydrodistillation with a Clevenger trap. It was extracted three times with anhydrous ether and dried over anhydrous sodium sulfate. The yield of EO was 0.012% (m/m). GC-MS analysis of the EO was done with a Thermo Trace gas chromatograph equipped with a Polaris-Q external ion trap mass spectrometer. Data were processed by the HP MSD Chemistry Station, followed by the peak area normalization method to calculate the percentage of part of the chemical composition of the volatile oil. The EO was analyzed using an A DB-1 fused-silica capillary column (30 m 0.25 mm 0.25 m) with helium as carrier gas at 0.8 mL/min, and a split ratio of 1:30. The GC oven temperature was kept at 50C for 1 min, adjusted to 120C at a rate of 5C/min, then kept constant for 20 min. The temperature was then increased to 200C at a rate of 5C/min and then kept constant for 5 min, and again to 280C at a rate of 10C/min and then kept constant for 5 min. The injection port temperature was 250C, the column pressure was 40 kPa, and the injection volume was 1 L (95% in hexane). For mass spectrometry, an EI ion source at a temperature of 230C was used. The electron energy was 70 eV, the interface temperature was 280C with a solvent delay time of 3 min, and the scanning mass range was 20–450 m/z. Forty-nine of 79 compounds were identified, accounting for 78.97% of total composition (see Table 1). The volatile constituents of Lindera setchuenensis contained a high fraction of myristic aldehyde (6.7%), phytol (6.6%), linoleic acid (5.4%), and cis-13-octadecenal (5.4%). The content of the main constituent, palmitic acid, is 26.6%. There are only three constituents, 1,6,10-dodecatrien-3-ol, -elemene, and palmitic acid, were reported in the essential oil of L. glauca grown in Zhejiang Province, China, and the latter two compounds were similar percentage content in the essential oil of L. glauca and L. setchenensis [8]. The antibacterial activity of the EO against the strains Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 10231) as compared with that of amoxicillin (Table 2) was assayed using the agar disc diffusion method [9]. Final results are summarized in Table 2.

A comparison of sorptive extraction techniques coupled to a new quantitative, sensitive, high throughput GC–MS/MS method for methoxypyrazine analysis in wine

Methoxypyrazines are volatile compounds found in plants, microbes, and insects that have potent vegetal and earthy aromas. With sensory detection thresholds in the low ngL−1 range, modest concentrations of these compounds can profoundly impact the aroma quality of foods and beverages, and high levels can lead to consumer rejection. The wine industry routinely analyzes the most prevalent methoxypyrazine, 2-isobutyl-3-methoxypyrazine (IBMP), to aid in harvest decisions, since concentrations decrease during berry ripening. In addition to IBMP, three other methoxypyrazines IPMP (2-isopropyl-3-methoxypyrazine), SBMP (2-sec-butyl-3-methoxypyrazine), and EMP (2-ethyl-3-methoxypyrazine) have been identified in grapes and/or wine and can impact aroma quality. Despite their routine analysis in the wine industry (mostly IBMP), accurate methoxypyrazine quantitation is hindered by two major challenges: sensitivity and resolution. With extremely low sensory detection thresholds (~8–15ngL−1 in wine for IBMP), highly sensitive analytical methods to quantify methoxypyrazines at trace levels are necessary. Here we were able to achieve resolution of IBMP as well as IPMP, EMP, and SBMP from co-eluting compounds using one-dimensional chromatography coupled to positive chemical ionization tandem mass spectrometry. Three extraction techniques HS-SPME (headspace-solid phase microextraction), SBSE (stirbar sorptive extraction), and HSSE (headspace sorptive extraction) were validated and compared. A 30min extraction time was used for HS-SPME and SBSE extraction techniques, while 120min was necessary to achieve sufficient sensitivity for HSSE extractions. All extraction methods have limits of quantitation (LOQ) at or below 1ngL−1 for all four methoxypyrazines analyzed, i.e., LOQ’s at or below reported sensory detection limits in wine. The method is high throughput, with resolution of all compounds possible with a relatively rapid 27min GC oven program.

Fast gas chromatographic residue analysis in animal feed using split injection and atmospheric pressure chemical ionisation tandem mass spectrometry

Significant speed improvement for instrumental runtime would make GC–MS much more attractive for determination of pesticides and contaminants and as complementary technique to LC–MS. This was the trigger to develop a fast method (time between injections less than 10min) for the determination of pesticides and PCBs that are not (or less) amenable to LC–MS. A key factor in achieving shorter analysis time was the use of split injection (1:10) which allowed the use of a much higher initial GC oven temperature. A shorter column (15m), higher temperature ramp, and higher carrier gas flow rate (6mL/min) further contributed to analysis-time reduction. Chromatographic resolution was slightly compromised but still well fit-for-purpose. Due to the high sensitivity of the technique used (GC–APCI-triple quadrupole MS/MS), quantification and identification were still possible down to the 10μg/kg level, which was demonstrated by successful validation of the method for complex feed matrices according to EU guidelines. Other advantages of the method included a better compatibility of acetonitrile extracts (e.g. QuEChERS) with GC, and a reduced transfer of co-extractants into the GC column and mass spectrometer.

Gas Chromatographic-Mass Spectrometric Analysis of Essential Oil of &lt;i&gt;Jasminum officinale&lt;/i&gt; L var Grandiflorum Flower

Purpose : To analyze the essential oil composition of the flower of Jasminum officinale L. var. grandifloroum L. ( Jasminum grandiflorum ) by gas chromatography-mass spectrometry (GC-MS). Methods : The optimum GC-MS conditions used for the analysis were 250 o C inlet temperature, 150 o C MSD detector temperature, and GC oven temperature program as follows: 100 o C initial temperature, increased to 270 o C at 4 o C/min, final temperature 270 o C and held for 7.5 min. Results : Thirty compounds were identified, representing 99.28 % of the oil content. The major volatile components of the flower were 3,7,11,15- tetramethyl-2-hexadecen-1-ol（phytol） (25.77 %), 3,7,11- trimethyldodeca -1,6,10-trien-3-ol (12.54 %) and 3,7,11,15- tetramethyl -1-Hexadecen-3-ol (12.42 %). Conclusion : The results show that phytol is the major volatile component of Jasminum grandiflorum . Keywords : Jasminum grandiflorum , Essential oil, Gas chromatography-mass spectrometry