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1.
The methylphenanthrene index (MPI) [1,2] which was recognized as suitable for the assessment of the “thermal” history of sedimentary organic matter, can be determined directly i.e. without preceding LC group separations by application of multi-dimensional GC in capillary columns. A GC double oven instrument (Siemens Sichromat 2) equipped with a “live switching” coupling piece was used for the necessary measurements. 相似文献
2.
G. L. Hall W. E. Whitehead C. R. Mourer T. Shibamoto 《Journal of separation science》1986,9(5):266-271
A new gas chromatographic (GC) retention index based on a homologous series of tri-n-alkylamines is proposed for use in the detection of pesticides and related compounds because the standard n-paraffin hydrocarbons used for the Kovats index do not show up well on the nitrogen-phosphorus detectors commonly used in pesticide analysis. Using fused silica bonded phase capillary columns (DB-1 or DB-5), the trialkylamine indices of 106 selected pesticides and related compounds were measured and their relationship to the Kovats index determined. 相似文献
3.
GUAN Ya-Feng ZHOU Liang-Mo LI Ling-EDalian Institute of chemical physics Chinese Academy of Sciences P.O.Box Dalian Liaoning China 《中国化学》1994,12(3):265-269
A live retention database for compound identification in isothermal and any step temperature programmed capillary gas chromatography has been developed. The database utilizes the Kovats retention indices of compounds on a given stationary phase and the retention time of n-alkanes measured at isothermal conditions on the column to be used, together with the programming parameters. Identification is performed by search operation that compares the calculated results with the retention values of unknown peaks. Cross-reference of the search results of different operating conditions is performed automatically by the database in order to increase the reliability of the identification. The error of the database conversion is ≤± 0.5 index unit, or ≤± 1% on retention time. This paper describes the principle and the structure of the database in detail. The experimental results for different calsses of compounds tested at divers operating conditions will be presented in Part Ⅱ. 相似文献
4.
The liquid chromatographic retention behavior of triglyceride and phospholipid molecular species in the nonpolar stationary (reverse) phase mode is presented for mobile phases compatible with ultraviolet detection. Interpretation of the results by means of the Kovats retention index suggests that correlation of retention to structure requires information on the number of acyl double bonds contained within the lipid molecular species in question. This, in turn, indicates that detection plays a major role in elucidating lipid structure because insufficient information is contained in the chromatographic retention data. 相似文献
5.
Hans König 《Analytical and bioanalytical chemistry》1971,255(2):123-125
The complete separation of a mixture of these substances can be achieved on columns with silicone rubber SE-52 as stationary phase at a temperature of 150°C. The retention indices after Kovats obtained under these conditions are tabulated together with the limits of detection. 相似文献
6.
S. Pedersen-Bjergaard S. I. Semb J. Vedde E. M. Brevik T. Greibrokk 《Chromatographia》1996,43(1-2):44-52
Summary Electron capture detection (ECD), low- and highresolution mass spectrometry (LR- and HRMS), and atomic emission detection (AED) were compared for the gas chromatographic (GC) detection of polychlorinated biphenyls (PCBs) present in highly contaminated marine sediments. With ECD, LRMS, and even HRMS, detection was seriously disturbed by the complex matrix of the sediments, whereas AED in the chlorine-selective mode provided excellent PCB profiles without interferences. In addition, GC-AED provided congener independent responses, which enabled accurate quantitation of all PCBs based on a single calibration curve. However, because GC-AED was less sensitive than the other techniques studied, preparation of relatively large amounts of sample (10–20 g dry sediment) was required for most analyses. 相似文献
7.
Shinji Fujimoto Hajime Ohtani Katsuya Yamagiwa Shin Tsuge 《Journal of separation science》1990,13(6):397-404
The general gas chromatographic retention behavior of cyclic methylsiloxanes partially substituted with phenyl or 2-cyanoethyl groups has been systematically studied, with pyrolysis-gas chromatography being utilized to form the cyclic siloxanes from the corresponding polysiloxanes at a temperature of 600°C. Kovats retention indices (KI) were determined for the cyclic siloxanes by use of the retention data of the pyrolyzates from polyethylene as standards. The effect of phenyl and 2-cyanoethyl substituents in the cyclic siloxanes on retention behavior has also been considered. 相似文献
8.
Liangxiao Zhang Peiwu Li Jin Mao Fei Ma Xiaoxia Ding Qi Zhang 《Journal of computational chemistry》2015,36(25):1902-1906
Outlier detection is crucial in building a highly predictive model. In this study, we proposed an enhanced Monte Carlo outlier detection method by establishing cross‐prediction models based on determinate normal samples and analyzing the distribution of prediction errors individually for dubious samples. One simulated and three real datasets were used to illustrate and validate the performance of our method, and the results indicated that this method outperformed Monte Carlo outlier detection in outlier diagnosis. After these outliers were removed, the value of validation by Kovats retention indices and the root mean square error of prediction decreased from 3.195 to 1.655, and the average cross‐validation prediction error decreased from 2.0341 to 1.2780. This method helps establish a good model by eliminating outliers. © 2015 Wiley Periodicals, Inc. 相似文献
9.
Hans König 《Analytical and bioanalytical chemistry》1973,266(2):119-124
The separation of a mixture of 22 bactericides has been achieved by gas chromatography on columns with silicone rubber W-982 as stationary phase with temperatures between 100° and 300°C. The unchanged compounds as well as their silylation products have been used. The latter are more conveniently used especially for the quantitative determination. To be able to calculate the retention indices after Kovats gas chromatography has been performed isothermally at 180°C for the more volatile compounds and at 250°C for all other bactericides.The retention indices obtained under these conditions are tabulated together with the limits of detection. 相似文献
10.
Summary The correlation equations between Kovats retention indices ofn-alkenes andn-alkynes, column temperature and number of carbon atoms in molecules of these compounds on OV-101, OV-225 and PEG 20M capillary
columns have been calculated. The two variable equationI=A + B · n + C / T give a good fit and are the simplest for practical use. 相似文献
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12.
Retention indices of standard organic compounds of environmental interest were determined by gas chromatography/mass spectrometry, using a DB-5 fused-silica capillary column. Retention indices are useful references for tentative compound identification by gas chromatography, or confirmation by gas chromatography/mass spectrometry. They provide elution order for isomers that might be indistinguishable based on mass spectra. Modified Kovats and Lee retention indices are given for polycyclic aromatic hydrocarbons; sulfur heterocycles; nitrogen heterocycles; aromatic amines; oxygen heterocycles; phenols; alcohols; ketones; alkanes; nitriles; and methylesters of fatty, dicarboxylic, and aromatic acids for comparison and reference. Retention index values for heterocycles by gas chromatography/mass spectrometry are comparable with gas chromatography values previously reported. 相似文献
13.
Direct conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account. Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely. The prerequisite for this calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column. The use of compiled isothermal retention indices at two different temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n-alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase. Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase-ratio, initial oven temperature, and programming rate. 相似文献
14.
M. Martínez-Cored E. Pujadas J. Díaz-Ferrero M. Coll R. Martí F. Broto-Puig L. Comellas M. C. Rodríguez-Larena 《Fresenius' Journal of Analytical Chemistry》1999,364(6):576-583
Analytical procedures for the determination of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and non-ortho polychlorinated biphenyls (PCB) require a fractionation step to separate PCDD/F from planar PCB and the bulk of PCB. An HPLC
method which achieves the separation of the bulk of PCB (0–6 mL of hexane), mono-ortho PCB (6–8 mL of hexane), non-ortho PCB (8–15 mL of hexane) and PCDD/F (15–50 mL of toluene) on a PYE column (2-(1-pyrenyl) ethyldimethylsilylated silica gel)
in a single step without the use of backflush as other authors proposed was developed. The method shows a good accuracy and
precision and it is linear in the range studied, e.g from 5.8 to 2420 pg injected in HPLC for TCDD/F, from 28.8 to 12100 pg
for PeCDD/F, HxCDD/F, HpCDD/F and from 57.6 to 24200 pg for OCDD/F. It has been successfully applied to the analysis of technical
mixtures of PCB (Aroclors), a pine wood sample and several water samples of different origins.
Received: 29 November 1998 / Revised: 25 February 1999 / Accepted: 3 March 1999 相似文献
15.
M. Martínez-Cored E. Pujadas J. Díaz-Ferrero M. Coll R. Martí F. Broto-Puig L. Comellas M. C. Rodríguez-Larena 《Analytical and bioanalytical chemistry》1999,364(6):576-583
Analytical procedures for the determination of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and non-ortho polychlorinated biphenyls (PCB) require a fractionation step to separate PCDD/F from planar PCB and the bulk of PCB. An HPLC
method which achieves the separation of the bulk of PCB (0–6 mL of hexane), mono-ortho PCB (6–8 mL of hexane), non-ortho PCB (8–15 mL of hexane) and PCDD/F (15–50 mL of toluene) on a PYE column (2-(1-pyrenyl) ethyldimethylsilylated silica gel)
in a single step without the use of backflush as other authors proposed was developed. The method shows a good accuracy and
precision and it is linear in the range studied, e.g from 5.8 to 2420 pg injected in HPLC for TCDD/F, from 28.8 to 12100 pg
for PeCDD/F, HxCDD/F, HpCDD/F and from 57.6 to 24200 pg for OCDD/F. It has been successfully applied to the analysis of technical
mixtures of PCB (Aroclors), a pine wood sample and several water samples of different origins.
Received: 29 November 1998 / Revised: 25 February 1999 / Accepted: 3 March 1999 相似文献
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18.
Janina Lulek Maurycy Opielewicz Katarzyna Szyrwińska Bart?omiej Milanowski 《Analytica chimica acta》2005,540(1):25-31
The database of the relative retention times (RRTs) of polychlorinated biphenyls (PCBs) reported in literature was used to calculate the retention indices (RIs) of all 209 PCB congeners on temperature programmed capillary column Rtx-5. Calculation of retention indices was based on reference series of seven congeners (PCB IUPAC Nos. 18, 52, 101, 143, 185, 203 and 206) that exhibit linear relative retention time behaviour as a function of chlorine number. The calculated indices were compared to those determined in our laboratory as well as to those obtained by other authors. The proposed indices system was applied for identification individual congeners in mixture of Aroclors 1242:1254:1260, using only reference series of PCBs. 相似文献
19.
L. Turrio-Baldassarri A. Carere A. di Domenico S. Fuselli N. Iacovella F. Rodriguez 《Fresenius' Journal of Analytical Chemistry》1994,348(1-2):144-147
Summary The isomer specific determination of PCDD, PCDF and PCB was carried out on samples of air and inhalable particulate from Rome. Samples were taken daily for six months and pooled to yield two samples per month. Normal PCDD+PCDF concentrations expressed in TEQ ranged from 48 to 87 fg/m3, while total PCB ranged from 0.1 to 1.4 ng/m3. The 2, 3, 7, 8-substituted PCDD and PCDF congener pattern is shown together with the PCB congener pattern. 相似文献
20.
K. Ballschmiter F. J. Heeg H. J. Neu R. Zinburg 《Fresenius' Journal of Analytical Chemistry》1985,321(5):426-435
Summary Without changing the fundamentals of the Kovats retention index system, a non-linear power series expansion of the relationship between the logarithm of adjusted retention times versus carbon number allows accurate wide range extra- and intrapolations of retention indices.The non-linear equation describes the experimental results for the n-alkanes starting with methane up to C44. The differences between the non-adjusted retention times are used for the calculations, thus avoiding any errors connected with the experimental determination of the dead time.The method opens the field for data handling and compound identification of complex mixtures analyzed by high resolution gas chromatography. Such problems are routine in environmental analysis.The homologous series of n-alkyl trichloroacetates (ATA) are used as retention index standards in electron capture detection.
Richtige Extrapolation von Retentionsindices über den C1–C44 Bereich in der isothermen Gas-Chromatographie
Zusammenfassung Eine Reihenentwicklung der Beziehung bei Homologen zwischen Kohlenstoffzahl und Nettoretentionszeit in der isothermen Gas-Chromatographie erlaubt eine richtige Extrapolation der experimentell erhaltenen Retentionsindices vom Methan bis zum C44-n-Alkan.Als Basis für die Berechnung der Retentionsindices werden die Differenzen der Bruttoretentionszeiten verwendet. Auf diese Weise entfällt der Fehler einer experimentellen Totzeitbestimmung. Die beschriebene Methode kann als Hilfe zur Identifizierung komplexer Gemische insbesondere in Umweltproben genutzt werden. Durch Verwendung der homologen Reihe der n-Alkyl-trichloracetate (ATA) als Bezugspunkt für den Retentionsindex ist auch eine Anwendung des Elektroneneinfang-Detektors möglich.相似文献