共查询到20条相似文献,搜索用时 0 毫秒
1.
Summary Investigations were carried out on capillary columns coated with liquid stationary phases possessing cyano (3-cyanopropylmethylpolysiloxane)
and thiol (3-mercaptopropylmethylpolysiloxane) groups. These phases were modified by bonding CuCl2 and CoCl2 to cyano groups or NiCl2 and CoCl2 to thiol groups. The modified phases were examined in order to assess their usefulness for the analysis of aliphatic and
aromatic halohydrocarbons. A number of retention parameters (I, ΔMe, Vg), which allow characterisation of the specific interactions between the bonded metal and the halohydrocarbon molecule, were
determined for the columns both with and without the metal. The separations performed show that the columns with bonded metals
are applicable for the practical analysis of the halohydrocarbons. 相似文献
2.
3.
Summary A detection system for gas chromatography based on gas-phase, molecular absorption measurements is presented, in which the
chromatographic column is directly joined to the spectrophotometer flow cell, without heated transfer lines. To maintain polyciclic
aromatic hydrocarbons (PAHs) in the gas phase during detection an aluminium heater was constructed. A mixture of 13 PAHs was
then separated and analyzed. Parameters affecting separation (temperature program and carrier gas flow) were studied and a
program designed to modify the measurement wavelength during the chromatography. The analytical characteristics of each compound
were calculated, obtaining detection limits 0.2–1.5 μg mL−. Given that some compounds overlaped, it was necessary to resolve their peaks mathematicaly. Finally, the method was applied
to a certified synthetic mixture, with good results. 相似文献
4.
Analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples: a critical review of gas chromatographic (GC) methods 总被引:1,自引:0,他引:1
Polycyclic aromatic hydrocarbons (PAHs) are frequently measured in the atmosphere for air quality assessment, in biological
tissues for health-effects monitoring, in sediments and mollusks for environmental monitoring, and in foodstuffs for safety
reasons. In contemporary analysis of these complex matrices, gas chromatography (GC), rather than liquid chromatography (LC),
is often the preferred approach for separation, identification, and quantification of PAHs, largely because GC generally affords
greater selectivity, resolution, and sensitivity than LC. This article reviews modern-day GC and state-of-the-art GC techniques
used for the determination of PAHs in environmental samples. Standard test methods are discussed. GC separations of PAHs on
a variety of capillary columns are examined, and the properties and uses of selected mass spectrometric (MS) techniques are
presented. PAH literature on GC with MS techniques, including chemical ionization, ion-trap MS, time-of-flight MS (TOF-MS),
and isotope-ratio mass spectrometry (IRMS), is reviewed. Enhancements to GC, for example large-volume injection, thermal desorption,
fast GC, and coupling of GC to LC, are also discussed with regard to the determination of PAHs in an effort to demonstrate
the vigor and robustness GC continues to achieve in the analytical sciences. 相似文献
5.
Summary The retention index of a planar polynuclear aromatic hydrocarbon on the GC phases OV-101, SE-52, and OV-17 is strictly related only to the boiling point, and less closely to the relative molecular mass. The very approximates relation with connectivity index ins only a consequence of the latter. On a nematic lqiuid crystal phase, a variation of activity coefficient, expressed in terms of a shape factor, also influences the retention of PAH. 相似文献
6.
Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter
can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated
polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis
was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact
mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes
(ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times
and mass spectra.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
7.
8.
Summary The retention index of twenty different homologous series of esters have been determined experimentally on polar (Carbowax
1540) and non-polar (squalane) columns. General equations to calculate retention index have been established by statistical
methods. The influence of the length and inductive effect of acid and alcohol chains and the relative position of the carboxylic
group are discussed. 相似文献
9.
Headspace solvent microextraction and gas chromatographic determination of some polycyclic aromatic hydrocarbons in water samples 总被引:1,自引:0,他引:1
Headspace solvent microextraction (HSME) was shown to be an efficient preconcentration method for extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions. A microdrop of 1-butanol (as extracting solvent) containing biphenyl (as internal standard) was used in this investigation. Extraction occurred by suspending a 3 μl drop of 1-butanol from the tip of a microsyringe fixed above the surface of solution in a sealed vial. After extraction for a preset time, the microdrop was retracted back into the syringe and injected directly into a GC injection port. The effects of nature of extracting solvent, microdrop and sample temperatures, stirring rate, microdrop and sample volumes, ionic strength and extraction time on HSME efficiency were investigated and optimized. Finally, the enrichment factor, dynamic linear range (DLR), limit of detection (LOD) and precision of the method were evaluated by water samples spiked with PAHs. The optimized procedure was successfully applied to the extraction and determination of PAHs in different water samples. 相似文献
10.
Glass capillary gas chromatography has been investigated as a method for the analysis of nitrated polycyclic aromatic hydrocarbons (nitro-PAH) using both splitless and on-column injection techniques. The nitro-PAH showed good chromatographic performance and thermal stability under the GC conditions used. Retention times and response factors of several nitro-PAH were compared to those of conventional PAH. Simultaneous flame ionization and thermionic nitrogen selective detection was used to facilitate identification of nitro-PAH in complex samples. The feasibility of the method is demonstrated on two samples of commercial carbon black. Besides 1-nitropyrene several isomeric dinitropyrenes have been identified. 相似文献
11.
Summary Steroid conjugates are hydrolysed enzymatically using β-glucuronidase after extraction from urine using a solid phase extraction
cartridge. After hydrolysis the free steroids are removed from the matrix, again utilising solid phase extraction. Derivatisation
of the free hydroxyl groups using Hydrox-Sil AQ produces the respective TMS ethers which are extracted into hexane, in which
solvent they are stable for many days. Capillary GC analysis with flame ionisation detection produces a profile of the steroids
present in the sample. This technique is suitable for following changes in the urinary excretion profiles of patients undergoing
investigation for a variety of steroid production-related diseases. 相似文献
12.
Determination of polycyclic aromatic hydrocarbons in soy isoflavone nutraceutical products by gas chromatography coupled to triple quadrupole tandem mass spectrometry 下载免费PDF全文
Ana Ruiz‐Delgado Gerardo Martínez‐Domínguez Roberto Romero‐González Rosalía López‐Ruiz Antonia Garrido Frenich 《Journal of separation science》2016,39(3):528-536
Thirteen polycyclic aromatic hydrocarbons have been determined in soy‐based nutraceutical products. First, an optimization of extraction procedure was performed, and a solid–liquid extraction assisted by sonication and a dilute and shoot procedure were compared, selecting the dilute and shoot approach for the extraction of target compounds, utilizing a mixture of acetone/n‐hexane (1:1 v/v) as extractant solvent. After this, a clean‐up step was needed bearing in mind the complexity of these matrices. Dispersive solid‐phase extraction, using a mixture of C18 and Zr‐Sep+ (25 mg/mL each) was used. The separation was achieved by gas chromatography and detection with triple quadrupole tandem mass spectrometry. For quantification purposes, matrix‐matched calibration was used. The validation was applied at three concentration levels (20, 100 and 250 μg/kg), obtaining recoveries between 70 and 120% and precision values equal to or lower than 23%. Limits of detection and quantification were below 8 and 20 μg/kg, respectively. The method was applied in 11 samples, detecting five polycyclic aromatic hydrocarbons at concentrations ranging from 4.1 to 18.5 μg/kg. 相似文献
13.
A system for automatic analysis of volatile compounds by purge-and-cold-trapping/capillary gas chromatography is described. It is suitable for analysis of volatile compounds in a wide variety of samples, such as water, food products and environmental samples. Possibilities and limitations of the system are evaluated in relation to several parameters. The efficiency of different types of cryogenic trap (open tubular, coated, packed) is also investigated; it depends on purge-flow rate, temperature of trapping, and total purge volume. Examples of the analysis of volatile compounds in foods and water are given. 相似文献
14.
Valve based/flow modulated comprehensive two-dimensional gas chromatography-flame ionization detection (GC x GC-FID) was used for quantification of C6 through C12 aromatic hydrocarbons by carbon number in gasolines. A 0.53 mm i.d. non-polar first dimension column was coupled to a 0.53 mm i.d. polar second dimension column through a double loop eight port valve modulator. Depending on the sample type, normalized percent and internal standard (I.S.) quantification was performed. For normalized percent quantification, a one-point calibration performed with one aromatic compound per carbon number/class provided an average % accuracy of 2.1% and a short-term n--1 relative standard deviation of 1.0%. For total aromatic compounds good agreement with the more complex conventional multidimensional GC technique was obtained. However, GC x GC has certain advantages over most other methods, mainly increased selectivity for total and carbon number aromatic content. The identification of the aromatic hydrocarbons was confirmed by GC x GC-MS. 相似文献
15.
16.
Aguinaga N Campillo N Viñas P Hernández-Córdoba M 《Analytical and bioanalytical chemistry》2008,391(4):1419-1424
This paper describes a headspace solid-phase microextraction (HS-SPME) procedure coupled to gas chromatography with mass spectrometric
detection (GC–MS) for the determination of eight PAHs in aquatic species. The influence of various parameters on the PAH extraction
efficiency was carefully examined. At 75 °C and for an extraction time of 60 min, a polydimethylsiloxane–divinylbenzene (PDMS/DVB)
fiber coating was found to be most suitable. Under the optimized conditions, detection limits ranged from 8 to 450 pg g−1, depending on the compound and the sample matrix. The repeatability varied between 7 and 15% (RSD). Accuracy was tested using
the NIST SRM 1974b reference material. The method was successfully applied to different samples, and the studied PAHs were
detected in several of the samples.
Figure Headspace SPME sampling followed by GC–MS facilitates routine monitoring of PAHs in aquatic species 相似文献
17.
Summary By connecting capillary columns of different polarity in series and by changing the temperature program gradient, a system of variable polarity is obtained. The working conditions can be adjusted to optimize separations of complex mixtures. Application to the analysis of essential oils of: lavender, thyme, lemon petit grain, bergamot, and tangerine, are reported.Dedicated to Prof. Dr. A. Liberti on the occasion of his 70th birthday. 相似文献
18.
Summary The efficiency of fast GC columns depends largely on the quality of the chromatograph. A theoretical and experimental study shows the relative importance of the various phenomena involved and permits the optimization of a GC System. Extremely good performances, exceeding 2,500 plates per second have been routinely obtained.Ezzel a tanulmánnyal Halász István Professzor Urat köszöntjük 60. születésnapja alkalmából. 相似文献
19.
20.
Rapid on-line analysis of low molecular weight hydrocarbons using glass capillary gas chromatography
Rapid analysis is important for on-line chromatography. Gaseous or vaporized samples have been injected via heated gas sampling valves of less than 500 μl dead volume. The critical sampling and split problems could be solved by temperature programming. The general analysis described could be successfully used inter alia in scouting reactions. 相似文献