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The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a devastating invasive pest recently introduced in India in 2018. The fall armyworm infestation has significantly impacted maize cultivation in the country. Identifying the host plant volatiles (kairomones) that are attractive to S. frugiperda from its highly preferred host plant, i.e. maize will help developing eco-friendly management strategies against this nefarious pest. Gas chromatography electroantennogram detector (GC-EAD) analysis revealed that a total of 18 compounds in maize headspace volatiles and 17 in maize leaf extract elicited an antennal response in female moths of S. frugiperda. Olfactometer bioassays of GC-EAD active plant volatile compounds revealed that heptanoic acid, 2,5-ditert butyl-1,4-benzoquinone and n-hexadecane were the most preferred plant volatile compounds and 50: 50 ratio blend of heptanoic acid and 2,5-ditert butyl-1,4-benzoquinone was found to be the most attractive kairomone blend for S. frugiperda. [ABSTRACT FROM AUTHOR]

Summary: The present study investigated the volatile and sensory profiles and antioxidant activity of 1,8‐cineole type Niaouli essential oil from Madagascar for which limited information is reported in literature. The volatile compounds were identified by Gas chromatography–mass spectrometry and semi‐quantitative results were obtained by Gas chromatography with a flame‐ionisation detector; the odour descriptors were determined by a trained panel using a Quantitative Descriptive Analysis. The antioxidant activity was determined, too. Several volatiles, most of these here firstly, have been identified; 1,8‐cineole (eucalyptus‐like) prevailed, followed by viridiflorol and (E)‐nerolidol. 'Eucalyptus‐like, fresh‐mint, woody, sweet‐floral and spicy' odour descriptors have been defined. Volatiles resulted in agreement with the odour descriptors. The data allowed to characterise the Niaouli essential oil; considering its volatile composition, pleasant sensory notes and antioxidant activity the 1,8‐cineole type Niaouli essential oil from Madagascar could be considered a promising flavouring agent and natural preservative in the food industry. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride (SF6), which survives in the atmosphere for an extremely long period of time, is the most potent greenhouse gas regulated under the Kyoto Protocol. So, the accurate monitoring of atmospheric SF6 plays an important role in the study of the control policies for reducing greenhouse gas emissions. The instruments for SF6 measurement are typically calibrated using certified reference materials. The concentrations of the commercially available SF6 reference materials usually have a broad range, from 1 μmol/mol to 6000 μmol/mol. Some characteristics including sensitivity, linear range, relative standard deviation, and accuracy are crucial for the determination of SF6 in such a broad concentration range. Therefore, the selection of a proper detector for the accurate determination of SF6 with such a broad range is extremely important to establish a gas chromatography (GC) method for developing SF6 reference materials. In this paper, several typical GC methods with different detectors, including a thermal conductivity detector (TCD), a pulsed discharge helium ionization detector (PDHID), and a flame photometric detector (FPD), were carefully established for the accurate determination of SF6 with different concentrations. The results show that an FPD detector has a relatively narrow linearity range, thus a quadratic equation should be established for building a calibration curve. The PDHID and TCD have good linearity with coefficients of 1.0000 in the concentration range of 10–100 μmol/mol (using a PDHID), and 100–1000 μmol/mol (using a TCD), respectively. Further considering the measurement errors of indication results, the PDHID is suitable for SF6 measurement when the concentrations are below 100 μmol/mol, whereas the TCD is suitable for SF6 measurement when the concentrations are over 100 μmol/mol. These results provide useful guidance in choosing an appropriate GC detector for the accurate determination of SF6, which are especially very helpful for developing SF6 reference materials. [ABSTRACT FROM AUTHOR]

Gas chromatography (GC) is a versatile analytical technique widely employed for the determination of various compounds, including sulfur hexafluoride (SF6). SF6 is a potent greenhouse gas and its accurate measurement is crucial for environmental monitoring and industrial applications. Different detectors in GC offer varying sensitivity, selectivity, and detection limits, affecting the precision and accuracy of SF6 quantification. This article provides a comprehensive evaluation of different GC detectors for the precise determination of SF6, highlighting their advantages, limitations, and applicability. [ABSTRACT FROM AUTHOR]

In this research, an eco-friendly method was established by vortex-assisted dispersive liquid-liquid microextraction based on the deep eutectic solvent (VA–DLLME–DES). The performance of the proposed method was demonstrated by the determination of benzene, toluene, ethylbenzene, and xylene (BTEX) in blood samples of fuel stations workers combined with GC–FID. The selected hydrophilic deep eutectic solvent is consisting of l-menthol and (1S)-(+)-camphor-10-sulfonic acid (CSA) at a 5:1 molar ratio as a green solvent instead of traditional toxic organic solvents. Under the optimal extraction conditions, the introduced method exhibited good linearity with a coefficient of determinations (r2) higher than 0.9985 and an acceptable linear range of 0.03–80 µg l–1. Accordingly, the limits of detection (S/N = 3) and limits of quantification (S/N = 10) were in the ranges of 0.01–0.04 µg l−1 and 0.03–0.10 µg l−1, respectively. Blood BTEX levels of fuel stations workers were analyzed based on age, duration of working at the station, smokers or nonsmokers, and station type (CNG, gasoline, and dual-purpose). The results showed that there was no significant difference between blood BTEX levels in different age groups, while the concentration of BTEX compounds increases with the increase of working time in the station. Blood BTEX levels were much higher in smokers than in nonsmokers. [ABSTRACT FROM AUTHOR]

Detectors in gas chromatography (GC) are unique in all analytical science. The detector performs several difficult functions that make sensitive and selective analysis possible. In this instalment, we will explore the challenges involved in detecting the effluent from a capillary gas chromatographic column, and summarize the many detector options. We will then consider basic ideas and tasks that allow detectors to function properly. Finally, we will examine some specific troubleshooting and preventative maintenance tips for common detectors. We will see that, with some simple preventative thinking and action, detectors in gas chromatography can provide excellent sensitivity and selectivity for years of use. [ABSTRACT FROM AUTHOR]

Gas Chromatography (GC) is a versatile analytical technique widely employed for the determination of various compounds, including Sulfur Hexafluoride (SF6). SF6 is a potent greenhouse gas and its accurate measurement is crucial for environmental monitoring and industrial applications. Different detectors in GC offer varying sensitivity, selectivity and detection limits, affecting the precision and accuracy of SF6 quantification. This article provides a comprehensive evaluation of different GC detectors for the precise determination of SF6, highlighting their advantages, limitations and applicability. [ABSTRACT FROM AUTHOR]

The barrier discharge ionization detector (BID) is one of the latest detection technologies used in gas chromatography (GC). 306 papers from 2012 to 2021 with GC-BID analyses were considered. An overview of the main applications with the BID, considering the trends for the most common analyses, explored compounds, extraction methods, and comparative studies with other detectors is shown. Interest in BID applications has grown, and the number of publications reflects this. Despite having the potential to analyze different compounds, gases are more explored, mainly H2, CH4, and CO. The BID should be further explored for water analysis, as studies show its good performance in larger quantities and at the level of traces. Most of the determinations of these compounds were applied in studies focused on CO2 reduction (by photocatalysis or electro-reduction) and biogas (for CH4). BID is effective for determinations on the order of mmol to µmol. Headspace extraction (HS) is most often applied BID analysis. Reduced dynamic range and nonlinear response to carbon mass are some disadvantages to BID. On the other hand, the BID has a signal-to-noise ratio (S/N) 100 times higher than thermal conductivity detector (TCD) (for inorganic gases and water), a high linear sensitivity for dodecane (LOD less than 1.0 pgC/sec) and other compounds (being able to reach µg/L). Combined with simple extraction methods such as HS, the BID allows quick and simple analysis with great sensitivity, in addition, it is a good alternative for the analysis of inorganic gases and water compared to usual detectors. [ABSTRACT FROM AUTHOR]

New data on the fatty acid compositions of the muscle tissues of the two most widespread families of the mesopelagic zone—the Myctophidae (Notoscopelus kroyeri and Symbolophorus veranyi) and Stomiidae (Chauliodus sloani, Stomias boa, Borostomias antarcticus, and Malacosteus niger) families—were obtained from the Irminger Sea (North East Atlantic). The fatty acids (FAs) in the total lipids (TLs), phospholipids (PLs), triacylglycerols (TAGs), and cholesterol esters and waxes were analyzed using gas–liquid chromatography with a mass-selective detector and flame-ionized detector (GC-MS and GC-FID, respectively). Species-specific differences in the FA/alcohol profiles of the studied fishes were revealed. A directed deep-vise trend in the changes in the content and performance of certain FAs for the studied species was found. Along with this, a general character of dominance for monounsaturated fatty acids (MUFAs), which were discussed as food tracers, was revealed. MUFAs in the muscle tissues included dietary markers of zooplankton (copepods)—20:1(n-9) and 22:1(n-11), the content of which varied in association with the species—such that the biomarker Calanus glacialis predominated in muscles of B. antarcticus and C. hyperboreus prevailed in other studied species. Different strategies of compensatory adaptation to depth gradient in lipid metabolism among the studied species were discussed. [ABSTRACT FROM AUTHOR]

A vacuum ultraviolet absorbance detector features the addition of the make‐up gas whose purpose is to decrease the diffusion of analytes in the flow cell. It has been previously demonstrated that the vacuum ultraviolet detector VGA 100 is a concentration‐sensitive detector for which the signal area is inversely proportional to the total flow in the flow cell. In this work, the signal behavior in the new generation vacuum ultraviolet detector, which features changed configuration for the introduction of make‐up gas, was explored. Contrary to previous instruments, a non‐linear relationship between the detector signal area and the inverse of the total flow in the flow cell (carrier gas flow + make‐up gas flow) was observed. To explain these observations, we have investigated the behavior of the detector in combination with one‐dimensional and two‐dimensional gas chromatography. Based on the results obtained, it was concluded that in these next‐generation instruments, flow in the flow cell cannot be regarded as a simple sum of the gas chromatography column flow and the total make‐up flow. After making modifications to the estimation of the total effective flow in the flow cell, a linear relationship between the signal area and the inverse of the flow in the flow cell was recovered. [ABSTRACT FROM AUTHOR]

In this study, an efficient gas chromatography with mass-spectrometric detector (GC/MS) method has been developed for extraction and quantitation of 16 carcinogenic polycyclic aromatic hydrocarbons PAH in frying edible oil. The method showed satisfactory linearity (R2 > 0.995) over the range (1.00–100.0 µg kg−1), the limits of detection were 0.0700 to 1.26 µg kg−1, limits of quantitation ranged from 0.230 to 4.20 µg kg−1, and the recovery ranged from 71.5% to 101. %. Samples of used frying edible oils have been collected from different fast food restaurants in Jordan. The mean of the 16 PAH in the oil samples ranged from 1.49 to 65.7 µg kg−1, while the concentration of Benzo[a]pyrene ranged from 3.08 to 4.09 µg kg−1. In addition, the incremental lifetime cancer risk (ILCR) associated with PAH was estimated, and ranged from 1.01 × 10−9 to 3.33 × 10−6, indicating a slight potential risk. A second objective of this research involved calculation of p-Anisidine values (AVs) in the collected frying oil samples as an indicator for the presence of α,β-unsaturated aldehydes. The AVs in the investigated oil samples ranged from 14.3 to 71.3 and the estimated concentration of α,β-unsaturated aldehydes was 33 μmol g−1 which is higher that the internationally proposed maximum limits. The outcomes of this study show that regulations on PAHs and α,β-unsaturated aldehydes in frying oils must be established in Jordan. [ABSTRACT FROM AUTHOR]

Biomass from agricultural processes is an important resource for fast pyrolysis and its transformation into bio-oil and high added value products. Several Standards of American Society for Testing and Materials (ASTM) were used in order to the physical-chemical characterization of the biomass used and the bio-oil obtained. Representative samples of biooil 0,82; pyroligneous acid 0,18 t, non-condensable gases 0,25 t and carbon 0,42 t were obtained by the fast pyrolysis from a mixture of Elephant Capín (Pennisetum purpureum) with sugar cane (Saccharum officinarum) straw. Nighty three organic compounds belonging to carboxylic acids, phenols, derivatives of furan, ethers of lignin, a homologous series of nalkanes from the bio-oil, and some aromatic nitrogenous compounds of high molar mass by gas chromatography with mass detector were identified. The caloric power of bio-oil is 20,20 MJ kg-1, facilitating its possible use as a biofuel. [ABSTRACT FROM AUTHOR]

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In the present study, volatile oils from Onopordum arenarium fresh flowers and stems were obtained by hydrodistillation and the non-polar aerial part hexane extract was prepared using a Soxhlet apparatus. The constituents of different organs were identified for the first time by gas chromatography equipped with flame ionization detector and gas chromatography coupled to mass spectrometry. A total of 29 and 25 compounds were identified constituting over 91.6 and 89.2% of the whole constituents from flower and stem volatile oils, respectively. Both organs were constituted mainly of long-chain hydrocarbons (23.3–36.4%) followed by oxygenated long-chain hydrocarbons (31.5–33.8%) and oxygenated monoterpenes (14.4–6.6%). The major identified compound was palmitic acid [25.5% in O. arenarium flower essential oil (EO) and 28.7% in the stem EO]. Eighteen compounds representing 80.7% of the whole constituents were identified in the n -hexane extract, which was characterized by high amounts of triterpenoids (39.6%) and dominated by lupeol acetate (19.2%) and β -amyrin acetate (10.1%). Moreover, all extracts were evaluated for antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl radical assay. The obtained results demonstrated that the EOs and the hexane extract could be a new source of natural potentially bioactive molecules. [ABSTRACT FROM AUTHOR]

Two dimensional accordion-like Ti3C2Tx MXene, where Tx represents surface termination groups such as –OH, –O–, and –F, is synthesized by selective etching of aluminum layers from Ti3AlC2. This manuscript reports on the adsorption of organic molecules from head-space and aqueous environments containing Ti3C2Tx, a representative of the MXene family. Ti3C2Tx coated by gluing method on a stainless steel wire was successfully utilized as a highly sensitive and stable head-space solid-phase microextraction (SPME) fiber. A SPME method with the MXene as the adsorbent combined with gas chromatography with MS detector was used to determine the polycyclic aromatic hydrocarbons (PAHs) in water samples. Low detection limits in the range of 0.2–5 ng L−1, wide linearity and good reproducibility (RSD = 4.6 to 7.4% for n = 6) under the optimized extraction conditions was achieved. Finally, the MXene coated fiber was successfully used for the determination of PAHs in real water samples. The relative recoveries for six PAHs are from 91.3–105.0%, which proved the applicability of the method. Also, melamine was selected as a polar analyte and it has been shown that Ti3C2Tx MXene has good capability in extraction of melamine (the extraction recovery for melamine = 80.1%) from aqueous media by dispersive micro solid-phase extraction. [ABSTRACT FROM AUTHOR]

Ethanol is a common psychoactive substance that has been widely consumed in several parts of the world. Gas chromatography (GC) coupled with flame ionisation detector (FID) has often been used for the determination of blood alcohol concentration. The aim of this study was to develop and validate a very simple and reliable HS-GC-FID method for quantitative determination of ethanol in blood sample. Validation of the method was performed by means of Bias, Linearity, LOD, Selectivity, Specificity, Precision, Robustness and Intermediate precision. The method showed an excellent linearity with correlation coefficient (r2 = 0.993) was observed in the range from 0.1 to 3.5 mg/mL of ethanol. The percent recovery value were between 91.0 and 109.1 which was with an acceptable percent recovery, The precision (repeatability) was reported as 27 % and intermediate precision of the method resulted in 11% and 1 % for two analysts. The limit of detection (LOD) of ethanol was calculated as 0.099 mg/mL and the selectivity of the method for interferents (methanol and acetaldehyde) was totally selective. Generally, the results obtained confirmed that the method is relatively fast, precise, simple, robust and can be used in routine forensic analyses for the determination of blood alcohol concentration (BAC) at a concentration level greater than 0.13 mg/mL. [ABSTRACT FROM AUTHOR]

Introduction: Psoriatic arthritis (PsA) is a chronic inflammatory disease associated with higher risk of cardiovascular events and metabolic syndrome than psoriasis without arthritis. Fatty acids (FA) play an important role as signaling molecules in inflammatory and metabolic pathways. The aim of the study was to evaluate serum FA concentration in patients with PsA and to investigate the correlations of FA with the clinical and biochemical markers.Material and Methods: We measured 14 FA serum concentrations by gas-liquid chromatography and flame-ionization detector after direct transesterification in 54 psoriatic patients (including 14 PsA patients) and 32 healthy controls. FA were divided according to their biologic properties into: saturated FA (SFA) and unsaturated FA (UFA), subdivided into monounsaturated FA (MUFA) and polyunsaturated FA (PUFA).Results: The results were correlated with Psoriasis Area and Severity Index (PASI), inflammatory and biochemical markers and lipid profile. We observed an abnormal FA profile in both psoriasis and PsA. We demonstrated lower concentrations of 10 FA in psoriasis and 7 in PsA. Patients with joint disease had a significantly higher percentage of SFA (p = 0.016) and MUFA (p = 0.001) and lower percentage of PUFA (p < 0.001) than the control group. The SFA/UFA ratio was significantly higher (p = 0.02) in PsA than in psoriasis and the controls. In the group of PsA the concentrations of docosahexaenoic acid (DHA) (p = 0.027) and n-3 PUFA (p = 0.031) correlated inversely with PASI.Conclusions: Our findings indicate a changed FA profile both in psoriasis and PsA and reflect metabolic status that may predispose to the development of metabolic syndrome. [ABSTRACT FROM AUTHOR]

The possibility of determining volatile organic compounds contained in exhaled air by concentrating them in sorption tubes, two-stage thermal desorption, and gas-chromatographic determination with a flame-ionization detector on various chromatographic columns was studied. It has been established that Tenax TA is an optimal sorbent for the preconcentration, and the highest separation efficiency is achieved on a PLOT CP-Porabond-Q column. The preconcentration of analytes with no breakthrough was achieved upon passing a 0.5-L sample through a sorbent at a rate of 200 mL/min. [ABSTRACT FROM AUTHOR]

• Coupling of gas chromatography to Fourier deconvolution ion mobility spectrometry. • Both signal to noise ratio and resolving power of IMS are improved simultaneously. • The GC-FDIMS showed improved performance over signal averaging method. • Complex natural extracts are evaluated with GC-FDIMS. The Fourier deconvolution ion mobility spectrometer (FDIMS) offers multiplexing and improves the resolving power and signal-to-noise ratio. To evaluate the FDIMS as a detector for gas chromatography for the analysis of complex samples, we connected a drift tube ion mobility spectrometer to a commercial gas chromatograph and compared the performance including resolving power, sensitivity, and linear range using 2,6-di‑tert-butylpyridine. Mixed standards were also injected into the tandem system to evaluate the performance under optimized conditions. A complex plant extract sample used as natural flavoring was investigated using the resulting system. The results show that the instrument implemented with the Fourier deconvolution multiplexing method demonstrated higher performance over the traditional signal averaging method including higher resolving power, better limit of detection, and wider linear range for a variety of compounds and natural plant extract flavorings. [ABSTRACT FROM AUTHOR]

The authors describe a zinc-based metal-organic framework/polyethersulfone nanocomposite (TMU-4/PES) coating deposited on a stainless steel wire via a single-phase inversion method. The nanocomposite represents a novel fiber coating for headspace solid-phase microextraction of organophosphorous pesticides (OPPs) from environmental water and soil samples. The synergistic effects of the high surface area and unique porous structure of TMU-4 as well as the rich π electron stacking and mechanical attributes of the PES polymer result in a high affinity of the composite for OPPs. Following thermal desorption, the OPPS were quantified by gas chromatography with a nitrogen-phosphorus detector. The preparation of the coating is simple, and the coated fiber is highly stable and reusable in that it can be used in about 100 consecutive extractions/desorption cycles. A central composite design was used for assessing the effect of the experimental parameters on the extraction process. Under optimized conditions, the limits of detection are in the 5-8 ng mL-1 range for the OPPs diazinon, fenitrothion, malathion and chlorpyrifos. The average repeatability and fiber-to-fiber reproducibility are 6.5% and 8.7%, respectively. The method was applied to the trace determination of OPPs in (spiked) water and soil samples where it gave good recovery (88-108%) and satisfactory reproducibility (5.9-10.1%). [ABSTRACT FROM AUTHOR]

Nano-gravimetric detector (NGD) has been recently introduced as miniaturized gas chromatography detector. The NGD response is based on an adsorption-desorption mechanism of compounds between the gaseous phase and the NGD porous oxide layer. The NGD response was characterized by hyphenating NGD in-line with FID detector and a chromatographic column. Such method led to the full adsorption-desorption isotherms of several compounds in a single run. Langmuir model was used to describe the experimental isotherms, and the initial slope of the isotherm (Mm.K T) obtained at low gas concentration was used to compare the NGD response for different compounds (good repeatability was demonstrated with a relative standard deviation lower than 3%). The column-NGD-FID hyphenated method was validated using alkane compounds according to the number of carbon atoms in the alkyl chain and to the NGD temperature (all results agreed with thermodynamic relations associated to partition coefficient). Furthermore, relative response factor to alkanes, for ketones, alkylbenzenes, and fatty acid methyl esters have been obtained. These relative response index values led to easier calibration of NGD. The established methodology can be used for any sensor characterization based on adsorption mechanism. [Display omitted] • A Nano-gravimetric detector response model was successfully developed. • A hyphenated system was used for fast characterization of NGD detector. • Several adsorption isotherms were obtained in a single chromatographic run. • The proposed methodology to plot isotherms exhibited good repeatability. • Relative response to alkanes were determined for easier calibration of the detector. [ABSTRACT FROM AUTHOR]

Chromatographic background drift correction, which influences peak detection and time shift alignment results, is a critical stage in chromatographic data analysis. In this study, an automatic background drift correction methodology was developed. Local minimum values in a chromatogram were initially detected and organized as a new baseline vector. Iterative optimization was then employed to recognize outliers, which belong to the chromatographic peaks, in this vector, and update the outliers in the baseline until convergence. The optimized baseline vector was finally expanded into the original chromatogram, and linear interpolation was employed to estimate background drift in the chromatogram. The principle underlying the proposed method was confirmed using a complex gas chromatographic dataset. Finally, the proposed approach was applied to eliminate background drift in liquid chromatography quadrupole time-of-flight samples used in the metabolic study of Escherichia coli samples. The proposed method was comparable with three classical techniques: morphological weighted penalized least squares, moving window minimum value strategy and background drift correction by orthogonal subspace projection. The proposed method allows almost automatic implementation of background drift correction, which is convenient for practical use. [ABSTRACT FROM AUTHOR]

Monitoring Volatile organic compounds (VOCs) was a very important measure for preventing environmental pollution, therefore, a mini gas chromatography (GC) flame ionization detector (FID) system integrated with a mini H2 generator and a micro GC column was developed for environmental VOC monitoring. In addition, the mini H2 generator was able to make the system explode from far away due to the abandoned use of a high pressure H2 source. The experimental result indicates that the fabricated mini GC FID system demonstrated high repeatability and very good linear response, and was able to rapidly monitor complicated environmental VOC samples. [ABSTRACT FROM AUTHOR]

Gas chromatography with mass selective detection is described as method for investigation and standardization of herbal raw materials and herbal drugs. Marker compounds and chromatographic conditions are described for some herbs. [ABSTRACT FROM AUTHOR]

Abstract: The chromatographic retention in hydrophobic and reversed phase chromatography and the solubility of proteins display some common features. The chromatographic retention, as well as the solubility, is modulated by the thermodynamic properties of the solute in the fluid phase. The retention measurements at linear conditions provide information of the solution properties of the protein at infinite dilution, and the solubility measurements produce the supplementary information about the solution properties at the saturation limit. This provides a useful approach to simultaneous correlation of the chromatographic retention and the solubility. The experimental data, used for the correlation, comprise retention measurements of lysozyme on different HIC adsorbents using an aqueous ammonium sulphate eluant, an aqueous ammonium sulphate eluant with an admixture of ethanol, as well as published solubility data. The chromatographic retention data and the corresponding solubility data have been correlated using a chemical potential model derived from Kirkwood''s theory of solutions of charged macro-ions and zwitterions in electrolyte solutions. The model correlated the chromatographic retention factor and the solubility data within the precision of the measurements. The model was applied in a pH range from 4 to 11. It was demonstrated experimentally, as well as theoretically, that an admixture of ethanol to the aqueous eluant changes the thermodynamic retention factor on various adsorbents identically when compared to the thermodynamic retention factor in an ethanol free eluant. [Copyright &y& Elsevier]

One of the main factors determining the interlaboratory reproducibility of gas-chromatographic retention indices is their linear dependence on the logarithms of the ratios of the amounts of analytes and reference components, which is rarely taken into account. It is found that the effect of this factor is much stronger for packed columns in comparison to that for more efficient capillary columns; it decreases with the sample dilution and with the increase in the temperature of gas-chromatographic separation. It was shown that the effect of relative amounts of components on their retention indices agrees with the main principles of the chromatographic plate theory and is associated with neither the overloading of chromatographic columns nor the nonlinearity of the adsorption isotherms. To improve the reproducibility of indices, it is recommended to use retention parameters measured at certain points in the front edges of the chromatographic peaks corresponding to similar intensities of the analytical signal rather than at the peak maxima. [ABSTRACT FROM AUTHOR]

Abstract: A simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-μECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30μL toluene used as extraction solvent were directly injected into a 25mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835–1115 and limits of detection below 0.010μgL−1 were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r 2) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5μgL−1. Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72–106.3% were obtained. [ABSTRACT FROM AUTHOR]

A gas chromatographic method for the simultaneous determination of two additives in o/w cosmetic formulations was developed by using GC and FID detection. A simple dilution procedure of the sample was required. The separation obtained for the two antioxidants was good under the chromatographic conditions used. Their analysis was carried out in commercial samples, and satisfactory results were obtained for the recovery of this compounds. [ABSTRACT FROM AUTHOR]

We developed and characterized a Fabry-Pérot (FP) sensor module based micro gas chromatography (μGC) detector for multipoint on-column detection. The FP sensor was fabricated by depositing a thin layer of metal and a layer of gas-sensitive polymer consecutively on the endface of an optical fiber, which formed the FP cavity. light partially reflected from the metal layer and the polymer-air interface generated an interference spectrum, which shifted as the polymer layer absorbed the gas analyte. The FP sensor module was then assembled by inserting the FP sensor into a hole drilled in the wall of a fused-silica capillary, which can be easily connected to the conventional gas chromatography (GC) column through a universal quick seal column connector, thus enabling on-column real-time detection. We characterized the FP sensor module based μGC detector. Sensitive detection of various gas analytes was achieved with subnanogram detection limits. The rapid separation capability of the FP sensor module assembled with both single- and tandem- column systems was demonstrated, in which gas analytes having a wide range of polarities and volatilities were well- resolved. The tandem-column system obtained increased sensitivity and selectivity by employing two FP sensor modules coated with different polymers, showing great system versatility. [ABSTRACT FROM AUTHOR]

Abstract: Micromachined gas-chromatographic (GC) components in combination with high sensitivity MOX detectors and novel pre-concentration materials were utilized to develop a miniaturized, portable, stand-alone sub-ppb level monitoring system for aromatic volatile organic compounds (VOC). Using metal oxide semiconductor (MOX) gas sensors as detectors in a GC system, the intrinsic analytic selectivity of GC is exploited in a simplified architecture with on-board generated carrier gas. The work reported here includes the study of innovative pre-concentration materials, the micromachining of GC components and devices, the fabrication and characterization of complete system prototypes, and the development of application-specific control electronics. The results of both laboratory trials and successful real-world cross-validation with a reference analyzer are described. [Copyright &y& Elsevier]

Detectors are another link in the chain of signals that a chromatographic analysis generates. After separation, a detector transduces the chemical signals of eluted analytes to an electrical signal that is then recorded and measured. The identities and amounts of analytes are determined from this information. This month in "GC Connections", John Hinshaw examines the environment, set-up and operating conditions necessary to ensure high gas chromatography detector performance and reliability. [ABSTRACT FROM AUTHOR]

The article evaluates several liquid and gas chromatography devices including the BioCel Automation System plate processing from Velocity11, the 869 Compact Smaple Changer from Metrohm and the Total Prep sample preparation system from Fluid Management Systems.

This paper demonstrated an in situ headspace gas chromatography (GC) technique for monitoring bacterial growth using a commercial GC system with a multiple headspace extraction (sampling) mode. The technique was based on measuring the carbon dioxide mass in the headspace of a closed sample vial during the bacteria growth. A mathematic equation was derived in order to calculate the integrated amount of carbon dioxide produced by bacterial growth during the incubation. The method can be used to monitor the bacterial growth rate in a given cultural medium. The present method is very simple, sensitive, and safe. [ABSTRACT FROM AUTHOR]

We developed a novel on-column micro gas chromatography (μGC) detector using capillary based optical ring resonators (CBORRs). The CBORR is a thin-walled fused silica capillary with an inner diameter ranging from a few tens to a few hundreds of micrometers. The interior surface of the CBORR is coated with a layer of stationary phase for gas separation. The circular cross section of the CBORR forms a ring resonator and supports whispering gallery modes (WGMs) that circulate along the ring resonator circumference hundreds of times. The evanescent field extends into the core and is sensitive to the refractive index change induced by the interaction between the gas sample and the stationary phase. The WGM can be excited and monitored at any location along the CBORR by placing a tapered optical fiber against the CBORR, thus enabling on-column real-time detection. Rapid separation of both polar and nonpolar samples was demonstrated with subsecond detection speed. Theoretical work was also established to explain the CBORR detection mechanism. While low-nanogram detection limits are observed in these preliminary tests, many methods for improvements are under investigation. The CBORR is directly compatible with traditional capillary GC columns without any dead volumes. Therefore, the CBORR-based μGC is a very promising technology platform for rapid, sensitive, and portable analytical devices. [ABSTRACT FROM AUTHOR]

The key to rapid temperature programmed separations with gas chromatography are a fast, low-volume injection and a short microbore separation column with fast resistive heating. One of the major problems with the reduction of column dimensions for micro gas chromatography is the availability of a stationary phase that provides good separation performance. In this report, we present the first integration of single-wall carbon nanotubes (SWNTs) as a stationary phase into 100 μm × 100 μm square and 50-cm-long microfabricated channels. The small size of this column with integrated resistive heater and the robustness of the SWNT phase allow for fast temperature programming of up to 60 °C/s. A combination of the fast temperature programming and the narrow peak width of small-volume injections that can be obtained from a high-speed, dual-valve injection system allows for rapid separations of gas mixtures. We demonstrate highly reproducible separations of four-compound test mixtures on these columns in less than 1 s using fast temperature programming. [ABSTRACT FROM AUTHOR]

Studies the utility of gas chromatography with flame-ionization detection in the analysis of Δ9-tetrahydrocannabinol in fiber hemp varieties. Effect of the use of lower temperature in the process on mould growth; Mean and standard deviation values found in the material; Suitability of the method for regulatory purposes.

Growing interest in the speciation of elements within environmental and clinical chemistry is resulting in the development of sophisticated analytical techniques. This paper discusses state-of-the-art gas chromatography hyphenations with optical and mass spectrometric detection for trace metal speciation analysis of organometallic compounds. Particular attention is given to the topics of large-volume injection, separation on capillary columns and ultrasensitive detection. [ABSTRACT FROM AUTHOR]

• A novel concept for a detector for gas chromatography is presented and proven. • A dosimeter-type sensor with a zeolite as functional film to detect epichlorohydrin is developed. • Device for room temperature operation. • The sensor signal, the capacitance change, increases linearly with the epichlorohydrin dose. • The time derivative of the sensor signal corresponds to the epichlorohydrin concentration. • Detection of short gas pulses of epichlorohydrin with dosimeter-like behavior down to a dose of 120 ppm·s−1 is possible. Detectors are required to quantitatively detect various substances (analytes) in gas chromatography (GC). The detector signal caused by the substance to be detected after a separation column has to be timely integrated in order to draw conclusions about the analyte concentration. In this study, a concept for a detector is presented, where this integral can be determined directly, without mathematical integration. The detector is based on an impedimetric gas sensor. It is operated in the dosimeter-type mode for direct amount detection, rather than applying a classical concentration sensor and integrating the data mathematically. This concept is presented, discussed, and validated with cancerogenic epichlorohydrin serving as a model substance. Copper-exchanged zeolites have proven to be a well-suited functional material to detect epichlorohydrin with the new dosimeter-type concept. Copper-exchanged zeolite MFI 200 proved to be especially suitable. Further investigations have shown that even short gas pulses can be detected, similar as they would occur downstream of a GC column. Therefore, basically, the potential exists to develop a detector for gas chromatography, whereby the dosimeter-type gas sensor integrates intrinsically the concentration output downstream of a GC column. [ABSTRACT FROM AUTHOR]

A rapid and sensitive method for the isolation, clean-up and gas-liquid chromatographic determination of trace quantities of N-nitro-sodimethylamine (NDMA) in an aqueous formulation of 2-chloroethyltrimethylammonium chloride (chlormequat chloride) is reported. Seventeen samples of two different formulations were collected and analyzed. The levels of NDMA ranged from 0.08 to 0.2 μg g−1 of chlormequat chloride. The minimum detectable amount was 0.01 ng which is equivalent to 0.01 μg g−1 or 0.03 μg g−1 depending on the concentration of the active ingredient in the formulation. Recoveries from the samples spiked with NDMA standard at 0.23, 0.17 and 0.11 μg g−1 were 90-102% with a mean of 98.4% and an overall coefficient of variation of 3.7%. The detector response was found to be linear within the range 0.05 ng to 0.2 ng. [ABSTRACT FROM AUTHOR]

Ocotea quixos (Lam.) Kosterm. is an aromatic tree native to Ecuador, whose leaves are used to prepare aromatic beverages to which different health benefits are attributed. In this study, Ocotea quixos leaves were collected in the Amazon region in different environmental conditions and subjected to hydrodistillation to isolate the essential oil. The collection variables used were type of soil, amount of shade, and height; in addition, the presence of twig and leaf age and moisture were used as variables. Chemical composition was analyzed by means of gas chromatography equipped with a flame ionization detector and gas chromatography coupled to mass spectrometry. A wide variety of chemical compositions were detected in the samples. In total, forty-seven compounds were identified, which represented between 97.17% and 99.89% of the total composition. The constituents were mainly grouped into aliphatic sesquiterpene hydrocarbons (33.03–55.89%), other compounds (8.94–47.83%), and oxygenated monoterpenes (1.97–39.66%). The main constituents were found to be (E)-cinnamyl acetate (5.96–41.65%), (E)-methyl cinnamate (0.38–37.91%), and trans-caryophyllene (8.77–37.02%). The statistical analysis suggested the existence of two essential oil chemotypes and a direct correlation between environmental conditions and chemical composition of the essential oils. [ABSTRACT FROM AUTHOR]

In plant protection, biological preparations are used alternately with chemical pesticides. The applied microorganism can influence the concentration of chemical substances. Laboratory and field studies were conducted to assess the influence of Bacillus subtilis and Trichoderma harzianum on the penthiopyrad concentration. In laboratory studies, the effectiveness of penthiopyrad degradation by B. subtilis was approximately 5% during 14 days of the experiment. For penthiopyrad treated with T. harzianum strains, the degradation effectiveness ranged from 34.2% on Day 3 to 56.9% on Day 14. In experiments testing the effects of mixed culture of microorganisms, the effectiveness of penthiopyrad degradation ranged from 23.7% on Day 3 to 29.1% on Day 14. After treatment of apple trees of Gala and Golden Delicious varieties with a biological preparation, a maximum degradation of penthiopyrad of 20% was found in both varieties. Samples of apples were prepared by the quick, easy, cheap, effective, rugged and safe (QuEChERS) method, and penthiopyrad was analyzed by gas chromatography with a mass detector. A determined value of the chronic exposure to penthiopirad was 1.02% of the acceptable daily intake, both for children and for adults. The acute exposure amounted to 7.2% and 1.9% of the acute reference dose for children and adults, respectively. These values were considered to be acceptable and not threatening to health. [ABSTRACT FROM AUTHOR]

• Non-radioactive ECD using a non-radioactive electron source. • Similar analytical performance compared to radioactive ECDs. • Linear range of 6.5∙103 and detecion limit of 2 ppb v (12 ng/l) for 1,1,2-trichloroethane. • Possible replacement of radioactive ECDs. With detection limits in the low ppb v -range, electron capture detectors (ECD) are the most sensitive GC-detectors available for electron affine compounds, such as pesticides or chlorofluorocarbons. The working principle is based on the generation of free electrons at atmospheric pressure, which are usually emitted from a radioactive Ni-63 source. However, the use of radioactive materials leads to regulatory restrictions regarding purchase, operation and disposal. Recently, we introduced a novel ECD based on a non-radioactive electron source, achieving comparable detection limits, e.g. 1 ppb v (6 ng/l) for 1,1,2-trichloroethane. However, the linear range was still below that of radioactive ECDs. In addition, the detector volume was too large to be used as a GC detector. We now present an improved version of this non-radioactive ECD with significantly increased linear range of 6.5∙103 for 1,1,2-trichloroethane by implementing pulsed operation using a newly developed, autonomous control electronics. In addition, the detector volume is reduced to 100 μl, leading to faster response times, less memory effects and thus less peak broadening. The improved ECD with non-radioactive electron source reaches similar analytical performance compared to commercially available radioactive ECDs and thus can be used as a possible replacement of radioactive ECDs. [ABSTRACT FROM AUTHOR]

This study aimed to determine indoor and outdoor levels of volatile organic compounds (VOCs) and to assess potential risks among residents living in the vicinity of an optoelectronics industrial park in 2006–2007. We used steel canisters to collect 72 indoor samples and 80 outdoor samples over 24 h. Gas chromatography with a mass-selective detector was used for qualitative and quantitative analyses. The amounts of time residents spent doing activities in different microenvironments were determined by the self-administered questionnaire. The chronic hazard index (HIc) and cancer risk were applied to assess the non-carcinogenic and carcinogenic risks of VOCs among residents. Four VOCs of ethanol (indoor: 77.8 ± 92.8 μg/m3; outdoor: 26.8 ± 49.6 μg/m3), toluene (67.0 ± 36.7 μg/m3; 56.9 ± 19.0 μg/m3), m/p-xylene (50.8 ± 66.1 μg/m3; 21.2 ± 20.3 μg/m3), and acetone (37.7 ± 27.5 μg/m3; 25.8 ± 9.8 μg/m3) were identified as dominant components in both the indoor and outdoor environments. Total VOCs and six VOCs of benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, and ethanol in indoor sites were significantly higher than those in outdoor sites (all p-values < 0.05). All estimated HIc values were less than unity and the cancer risk of benzene exposure was 1.8 × 10−4 (range: 9.3 × 10−5 to 3.4 × 10−4) based on resident time-weighted patterns. Strategies to reduce benzene exposure should be implemented to protect public health. [ABSTRACT FROM AUTHOR]