Determination of elaidic and vaccenic acids in foods using GC×GC-FID and GC×GC-TOFMS

Trans fatty acids (TFAs) are present in meat and dairy products as m ruminant animals and in vegetable fats due to partial hydrogenation. This study aimed to discriminate between natural (N-TFA) and hydrogenated trans fatty (H-TFA) acids by GC × GC-flame ionization detection (GC × GC-FID) and comprehensive GC × GC-time-of-flight mass spectrometry (GC × GC-TOFMS). The separation of two kinds of trans fats, vaccenic acid (18:1 trans-11) and elaidic acid (18:1 trans-9), was performed using GC × GC-FID and GC × GC-TOFMS. A 100 m × 0.25 mm I.D. × 0.2 μm (film thickness) SP-2560 (bis-cyanopropyl polysiloxane) fused capillary column (first separation dimension, 1D) was coupled to a 1.5 m × 0.18 mm I.D. × 0.18 μm (film thickness) RTX-5 (5% diphenyl/95% dimethyl polysiloxane) fused capillary column (second separation dimension, 2D). The RSD of the intra-day repeatability by both GC × GC-FID and GC × GC-TOFMS for elaidic and vaccenic acids was ≤9.56% and ≤9.97%, and the RSD of the inter-day repeatability was ≤8.49 and ≤9.06%, respectively. It was found that the V/E value (vaccenic acid to elaidic acid ratio) could be used to distinguish H-TFA from N-TFA and to evaluate the quality of the fatty foods.     

Comprehensive two-dimensional gas chromatography (GC×GC) in environmental analysis and monitoring

Compared to conventional one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional gas chromatography (GC×GC) offers increased peak capacity, improved resolution and enhanced mass sensitivity. In addition, it generates structured two-dimensional (2-D) chromatograms, which aids in the identification of compound classes. Sample preparation procedures can often be minimized, or even eliminated in some cases, due to the superior separating power offered by the technique. All of these advantages make GC×GC a very powerful tool in environmental analysis involving the determination of trace levels of toxic compounds in complex matrices. This review paper summarizes and examines the historical and recent GC×GC applications in environmental analysis and monitoring.     

Estimation of Olefin Dimerisation Products by GC/GC–MS and IR Techniques

A GC and IR based protocol was developed for monitoring the isobutene dimerisation process wherein the complete characterisation of the products was carried out by GC coupled with mass spectrometry. In the dimerisation process, LPG from FCC process comprising a mixture of saturated and unsaturated C4 hydrocarbons is subjected to a dimerisation process using a catalyst to produce C8 hydrocarbons. The reaction is carried out keeping in view the demand for high-octane blending components in gasoline. The isooctene generated in the process (mainly from the dimerisation of isobutene) is converted into isooctane having the RON and MON value 100. The monitoring process requires the use of two different column chemistries, viz., a 100 m CPSIL PONA CB non-polar column for C8 and its isomers and an Alumina PLOT column for C4 hydrocarbons. A 100 m non-polar column does not separate the C4 mixture since the column is meant for gasoline range products containing C5 and above hydrocarbons. Therefore, a need was felt for an improvised method which can handle both the analyses simultaneously. A cryogenic oven program starting from 0 °C was developed for separating the isomers of C4 hydrocarbons and C8 hydrocarbons on a single column during the single run by Detailed Hydrocarbon Analyzer. The data obtained using the cryo programme was validated with data obtained using Alumina PLOT column on C4 mixture since the Alumina PLOT column is the widely accepted column chemistry for separating the C4 hydrocarbons. An IR method for the estimation of the total olefin content was developed using 2,2,4-trimethyl pentene-1 as the reference standard. The total olefins generated during the process were identified by GC–MS, quantified by DHA-FID and validated by infrared spectroscopy. A good correlation was found between GC and IR spectral results (correlation coefficient R ²  = 0.99).     

GC�CMS and GC�CNPD Determination of Formaldehyde Dimethylhydrazone in Water Using SPME

Formaldehyde dimethylhydrazone (FADMH) is one of the important transformation products of residual rocket fuel 1,1-dimethylhydrazine (1,1-DMH). Thus, recent studies show that FADMH toxicity is comparable to that of undecomposed 1,1-DMH. In this study, a new method for quantification of FADMH in water based on solid phase microextraction (SPME) in combination with gas chromatography (GC) with mass spectrometric (MS) and nitrogen-phosphorus detection (NPD) is presented. Effects of SPME fiber coating type, extraction and desorption temperatures, extraction time, and pH on analyte recovery were studied. The optimized method used 65 micron polydimethylsiloxane/divinylbenzene fiber coating for 1?min headspace extractions at 30?°C. Preferred pH and desorption temperature from the SPME fiber are >8.5 and 200?°C, respectively. Detection limits were estimated to be 1.5 and 0.5?μg?L(-1) for MS and NPD, respectively. The method was applied to laboratory-scale experiments to quantify FADMH. Results indicate applicability for in situ sampling and analysis and possible first-time detection of free FADMH in water.     

Comprehensive multidimensional separation methods by hyphenation of single-photon ionization time-of-flight mass spectrometry (SPI-TOF-MS) with GC and GC×GC

One- and comprehensive two-dimensional gas chromatography were hyphenated with soft photoionization mass spectrometry. The characteristics of these two- and three-dimensional comprehensive separation techniques are discussed in detail. Using the innovative electron beam pumped excimer light source (EBEL) for single-photon ionization (SPI), organic molecules with ionization energies (E _i ) of below 9.8 eV can be detected by a time-of-flight mass spectrometer (TOF-MS). SPI with 126 nm vacuum ultraviolet (VUV) photons enables the universal and soft ionization of organic molecules. SPI-TOF-MS hyphenated to one-dimensional gas chromatography results in a comprehensive two-dimensional separation method (GC×MS). To demonstrate this, diesel fuel was analyzed, and the resulting GC×MS chromatograms are discussed in depth. A three-dimensional separation method was also realized by combining comprehensive two-dimensional gas chromatography (GC×GC) with SPI-MS. In the resulting separation space, constituents originating from mineral oil diesel blended with biodiesel were dispersed along the two GC separation axes, while the molecular mass axis served as a third separation dimension.     

Solid-phase micro extraction (SPME) and headspace derivatization of clenbuterol followed by GC–FID and GC–SIMMS quantification

Solid-phase micro extraction (SPME) and on-fiber derivatization followed by Gas Chromatography coupled with Flame Ionization Detection (GC-FID) or Selected Ion Monitoring Mass Spectrometry (GC-SIMMS) allows for simple yet sensitive quantification for the hexamethyldisilazane derivative of the beta-agonist clenbuterol. Using an 85- micro m polyacrylate fiber, the analysis method is optimized with respect to extraction time, derivatization time and temperature, and solution pH. In addition, the use of a rapid temperature ramping injection port allows for optimization of fiber desorption conditions. Under optimal conditions, the limits of detection for the hexamethyldisilazane derivative of clenbuterol are 1.1 ppb by FID and 0.20 ppb by SIMMS.     

Identification and Determination of Nicorandil and its Degradation Products by HPLC and GC/MS

Nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate NIC] is a novel kind of compound in the treatment of angina pectoris. NIC can be degraded easily in storage. The degradation products include N-(2-hydroxyethy) nicotinamide (HN), nitrate ion (NI), and ni…     

Reproducibility of Programmed-Temperature Retention Indices under Average Linear Velocity Carrier Gas Control of GC and GC�CMS

Programmed-temperature retention indices (PTRIs) are useful for the identification and quantification of chemicals by means of GC and GC/MS. To obtain reproducible PTRIs, we studied the influence of average linear velocity and column length under the constant average linear velocity control (CVC) using 55 pesticides and 33 fatty acid methyl esters. The PTRIs decreased with increasing average linear velocity, and the degree of decrease differs with the compounds. The PTRIs, however, were almost constant as long as the same average linear velocity was used even if the column length was changed. In addition, the correlation between the variation ratio in PTRI and the increase in average linear velocity was linear. Using the linear relationship between PTRIs and average linear velocities under CVC, highly reproducible PTRIs were obtained even if the capillary column length changes. Furthermore, the PTRIs determined by GC with FID, ECD, and FPD under atmospheric pressure were applied to GC/MS under vacuum or vice versa. From these results, it was confirmed that because CVC provides reproducible retention indices, CVC is advantageous for qualitative and quantitative analysis by GC and GC/MS.     

Residue Analysis and Determination of IMI Herbicides in Sunflower and Soil by GC–MS

Sunflower agriculture is an important subsector that plays a key role in the economy of Turkey, contributing 1.38 million tonnes. The aim of this study is to investigate the levels of imidazolinone (IMI) group herbicides in Thrace Region, Turkey. In particular, we aimed to determine the residue levels of imazamox, a herbicide used in sunflower production in Thrace Region, in soil, different parts of plant, and seed. Five herbicides were identified in sunflower samples using solid–liquid extraction with gas chromatography–electrospray ionization mass spectrometry (GC–EI–MS) on single-quadruple instruments in selected ion monitoring (SIM) mode. The optimized conditions were found to be mobile-phase flow rate of 1 mL min^?1 and injection volume of 3 μL in programmed temperature vaporization (PTV) solvent vent mode. The recovery of imazamox, imazaquin, imazethapyr, imazapyr, and imazapic from sunflower plant and soil was 89 and 99, 104 and 105, 92 and 93, 96 and 92, and 99 and 96%, respectively.     

Comparison between GC–MS and GC–ICPMS using isotope dilution for the simultaneous monitoring of inorganic and methyl mercury,butyl and phenyl tin compounds in biological tissues

The aim of this work is to compare simultaneous isotope dilution analysis of organotin and organomercury compounds by gas chromatography–mass spectrometry (GC–MS) and gas chromatography–inductively coupled plasma mass spectrometry (GC–ICP/MS) on certified bivalve samples. These samples were extracted by microwave with tetramethylammonium hydroxide (TMAH). Derivatization with both NaBEt₄ and NaBPr₄ was evaluated, and analytical performances were compared. Two CRM materials, BCR-710 and CRM-477, were analyzed by both techniques to verify accuracy. A mixed spike containing ²⁰¹Hg-enriched methylmercury (MeHg), ¹⁹⁹Hg-enriched inorganic mercury (iHg), ¹¹⁹Sn-enriched monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) as well as homemade ¹¹⁶Sn-enriched monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) was used for the isotope dilution analysis of samples. The two techniques studied were compared in terms of classic analytical parameters: linearity, precision or repeatability (i.e., percent relative standard deviation, RSD%), limit of detection (LOD), and limit of quantification (LOQ), showing excellent linearity, precision below 12 % for all analytes, and LOQs of 0.06–1.45 pg for GC–MS and 0.02–0.27 pg for GC–ICP/MS.

DETECTION AND QUANTITATION OF TRACE ETHYL CARBAMATE IN ALCOLLOLIC BEVERAGES BY GC/GC AND GC/GC/MS

Analytical difficulties encountered in the determination of ethyl carbamate, aknown cancinogen, in a wide variety of wines and spirits have been overcome by spe-cific, sensitive GC/GC and CC/CC/MS methods with a relatively shorter extractionprocedure. The lowest detection limits were estimated to be 0. 1 and 0. 01μg/L forGC/GC and GC/GC/MS respectively. The RSD of the GC/GC method was 2. 5%.     

Gamma radiolytic degradation of fluoranthene and monitoring of radiolytic products using GC–MS and HPLC

Removal of priority pollutant fluoranthene in methanol by gamma-irradiation under varied conditions has been optimized. The influence of applied dose and dose rate on the degradation of fluoranthene under nitrogen has been investigated. The preliminary radiolytic degradation efficiency has been monitored by spectrophotometry. HPLC and GC–MS have been used to study the nature of degradation pattern. It is found that four main degradation products are formed and detected by HPLC. Different reversed phase columns have been used for the separation of degraded products under optimum chromatographic conditions. For 2 kGy dose ⩾80% fluoranthene has been degraded at dose rate 200 Gy/h. However, a dose of 370 Gy/h was more effective and it produces for less degradation products. Radiolytic degraded fluoranthene was also analyzed to detect various degradation products using GC–MS. It was proposed that major products were hydrocarbons and methoxy group containing organic compounds after comparing their mass spectra with the installed NIST mass spectral library.     

Detection and Confirmation of Ginsenosides in Horse Urine by GC–MS and LC–MS

Ginseng has been used by the Chinese as a traditional herbal medicine for thousands of years. In view of the growing popularity in the use of ginseng preparations as natural remedies and food supplements worldwide, there is an increasing concern for their abuse in both human and animal sports. Ginsenosides are considered the major constituents of ginseng responsible for its pharmacological properties. In this study, a method was developed for the detection and confirmation of a number of ginsenosides in horse urine. The intact ginsenosides were detected and confirmed at 5–100 ng mL^?1 by LC–MS², and two deglycosylation metabolites, namely protopanaxadiol and protopanaxatriol, could both be detected and confirmed at 2 ng mL^?1 by GC–MS² after trimethylsilylation. The above GC–MS and LC–MS methods were then applied to study the in vitro metabolism of ginsenosides Rg1 and Rb1 and the in vivo urinary metabolites after oral administration of Rg1 to horses. Results obtained reveal the very first evidence for the existence of the metabolites, Rg1 and protopanaxatriol, as glucuronides in urine.     

Residue Analysis of Propionylbrassinolide in Fruit and Vegetables by GC–MS

A rapid and simple method for the determination of propionylbrassinolide residues in tomatoes, apples and grapes using GC–MS is reported. Samples were extracted with acetonitrile, and the extracts were analyzed without any further clean-up. The results showed good linearity (r ² > 0.99) with standard solutions over the concentration range of 0.5–50 mg L⁻¹. The LODs and LOQs of propionylbrassinolide were 0.15 and 0.5 mg kg⁻¹ in all samples. Recoveries were in the range of 81.9–111.2%, with corresponding RSDs of 4.6–12.9% for three fortified levels. Intra- and inter-day RSDs were in the ranges of 1.5–14.2% and 5.3–15.6%. It was demonstrated that the proposed method is simple and efficient, and particularly suitable for detecting propionylbrassinolide residues in fruit and vegetables.     

Residue Analysis of Propionylbrassinolide in Fruit and Vegetables by GC–MS

A rapid and simple method for the determination of propionylbrassinolide residues in tomatoes, apples and grapes using GC–MS is reported. Samples were extracted with acetonitrile, and the extracts were analyzed without any further clean-up. The results showed good linearity (r ² > 0.99) with standard solutions over the concentration range of 0.5–50 mg L^?1. The LODs and LOQs of propionylbrassinolide were 0.15 and 0.5 mg kg^?1 in all samples. Recoveries were in the range of 81.9–111.2%, with corresponding RSDs of 4.6–12.9% for three fortified levels. Intra- and inter-day RSDs were in the ranges of 1.5–14.2% and 5.3–15.6%. It was demonstrated that the proposed method is simple and efficient, and particularly suitable for detecting propionylbrassinolide residues in fruit and vegetables.     

Identification of Sinomenine from Sinomenium actum and Its Simultaneous Quantitation by GC–MS and Non-Aqueous CE

In the present study, the qualitative and quantitative analysis of alkaloids in the stem and root of Sinomenium acutum (S. acutum) is presented by gas chromatography-mass spectrometry (GC–MS) and non-aqueous capillary electrophoresis (NACE). The extract of alkaloids in S. acutum was examined by GC–MS and the major alkaloids were identified. Sinomenine (SIN) was found as the principal alkaloid in the extracts (about 84.38%). The quantitation of SIN was then accomplished by GC–MS and NACE with diode array detection. NACE was selected in order to use a running buffer fully compatible with samples in organic solvent. Optimum separation was achieved with a fused-silica capillary column and a running buffer containing 80 mM ammonium acetate, 2.0% acetic acid and 20% (v/v) acetonitrile in methanol medium. The applied voltage was 22 kV. The different selectivity displayed by these techniques allowed different separation profiles that could be useful in phytochemical characterization of the sample. The GC–MS and NACE methods were successfully validated and applied for the quantitation of SIN in S. acutum.     

GC,GC/MS法定性定量分析鱼油中的脂肪酸

本文介绍了一种用色谱-质谱联用仪(GC/MS),气相色谱仪(GC),定性、定量地分析测定鱼油脂中各种主要脂肪酸百分含量的方法。此法的分析过程比较直观和简单。样品在分析之前需要进行甲酯化衍生制备。鱼油脂中从11碳到22碳范围内的20几种主要脂肪酸均可准确地定性并获得定量结果。     

Determination of Estragole in Fennel Herbal Teas by HS-SPME and GC–MS

Estragole, a volatile phenylpropanoid contained in a variety of edible herbs, has been demonstrated to be genotoxic and carcinogenic, and its addition as a flavoring substance to foodstuffs has been banned by the regulatory bodies of the European Union. Fast and accurate analytical methods for its determination in herbs are thus necessary to assess the dietary exposure of this substance in humans and, in particular, to sensitive groups. In the present study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS) was applied for determination of estragole in infusions from different widely used commercial herbal teas based on Foeniculum vulgare (fennel) seeds. The optimized HS-SPME extraction conditions involved the use of a polydimethylsiloxane fiber exposed to the herbal infusion for 20 min at 50°C followed by GC–MS analysis. The method was fully validated for linearity, sensitivity, accuracy, and precision and applied to real samples; the level of estragole in infusions of commercial fennel seed teas was found to be within 50–250 µ`^?1.     

Investigation of Euphrasia rostkoviana Hayne Using GC–MS and LC–MS

Gas and liquid chromatography coupled with mass spectrometry was applied to solve difficulties and reinvestigate the serious matrix problems affecting analysis of the active compounds in Euphrasia rostkoviana Hayne. The main groups of compounds were obtained by extracting the herb stepwise with n-hexane, chloroform, ethyl acetate and methanol. Polyamide column chromatography facilitated further separation. Phenolic/flavonoid- and terpenoid-type molecules were studied by GC–MS, HPLC and LC–MS–MS. The β-sitosterol content of the herb was determined by gas chromatography with flame ionisation detection (GC-FID). Caffeic acid, chlorogenic acid, coumaric acid and flavonoid glycosides of apigenin, luteolin, rhamnetine (hexoside), kaempferol (both hexoside and rutinoside) and quercetin (rutinoside) were identified in the fractions of the methanolic extract.