ISSN:0935-6304    

DOI:10.1002/jhrc.1240170602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractMore stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed‐stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices,i.e.pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section.Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on‐line application in a hazardous area a simple and rugged system is required,i.e.a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at h

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA review of the analysis of petroleum fuels, oils, tars and engine exhaust particulate extracts by on‐line coupled LC‐GC is presen

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractFor the past two or three decades geochemists have been concerned with the analyses and characterization of compounds, generally hydrocarbons, ranging from C1C40. Significant amounts of information have resulted from these studies which have been extremely useful in many geochemical and environmental studies. However, in the past two or three years the commercial development and availability of high temperature gas chromatography columns has lead to the investigation of the occurrence and distribution of high molecular weight hydrocarbons (HMWHC), and other compounds, in the carbon number range C40C100, present in oils, waxes, bitumens and rock extracts. The ability to study these compounds represents a major advance in organic geochemistry. In some samples these compounds may represent the bulk of the organic components but prior to development of the high temperature columns it was impossible to study their distributions.This paper will review advances that have occurred in terms of the application of high temperature gas chromatography (HTGC) to the analyses of fossil fuel samples and discuss the possible origin and significance of these compounds that have been identified. In addition, some of the potential problems involved in the analyses of these compounds will also be discus

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes the use of multidimensional capillary gas chromatography for analysis of individual components in a C9C10aromatic hydrocarbon pyrolysis distillate containing substantial amounts of aromatic olefins. By coupling this GC‐GC system on‐line to a mass spectrometer difficulties in identifying overlapping compounds were overcome. No coelution of different types of compound was observed, but a few isomeric compounds such as methylstyrenes were poorly sepa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA fully automated on‐line sample cleanup system based on the coupling of size exclusion chromatography to high resolution gas chromatography is described. The transfer technique employed is based on fully concurrent solvent evaporation using a loop‐type interface, early vapor exit and co‐solvent trapping. Optimization of the LC‐GC transfer was done visually via an all‐glass oven door. To circumvent the problem of mixing within the injection loop, an adaptation was made to the standard loop‐type interface. The determination of a series of additives in a polymer matrix is presented as one example of the vast range of applications opened up by thi

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAn analytical method for differentiation of primary, secondary, and tertiary amines using exhaustive trifluoroacetylation prior to GC/MS has been developed. Using the conditions described in the report, most primary amines add two and secondary amines add one trifluoroacetyl group. In general, tertiary amines do not react. GC retention indices and relative GC/MS total ion current response factors for 102 trifluoroacetyl derivatives are reported. Examples of the application of the method to petroleum and coal liquid products are provided. Because of the limited thermal stability of the derivatives of primary amines, the method is applicable only to distillates boiling below 370 °C (700 °F

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe GC–MS characteristics of carboxylic acid esters prepared from fluorine‐containing alcohols were compared to those of methyl esters. The GC retention of 2,2,2‐trifluoroethyl (TFE) esters was less than, and 2,2,3,3,4,4,4‐heptafluoro‐1‐butyl (HFB) esters was approximately equivalent to that of methyl esters. Mass spectra of TFE and HFB aliphatic esters show significantly more intense molecular and key fragment ions than those of methyl esters. Also, owing to their significantly higher molecular weights, TFE or HFB ester molecular ions and most fragment ions of interest occur at significantly higherm/zvalues than most potential interfering ions.Data for about 70 individual TFE and HFB esters are reported. Application of the methodology to a petroleum‐derived carboxylic acid concentrate resulted in identification of straight chain, isoprenoid, methyl‐substituted straight chain (2‐, 3‐, 5‐,10‐, 12‐positions along chain), and dimethyl‐substituted straight chain acids containing from 11 to 22 carbons. Benzoic acid and homologs with up to 3‐carbons in alkyl substitutents were minor components in the sample.The procedure provided for forming TFE and HFB esters from free acids requires less time and effort than a previously reported method, while retaining its capability for achieving essentially quantitative conversion. Free hydroxyl groups in alcohols and phenols are converted to trifluoroacetate esters concurrently with formation of TFE/HFB carboxylic acid esters. The reaction products, including compounds with two functional groups (diacids, salicylic acid,etc.), chromatograph well on conventional

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported.The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C0‐, C1‐ and C2‐alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits.In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification.Example applications in analysis of coal‐, shale‐ and petroleum‐derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractCharacterization of fuels by LC‐GC is possible by use of automatic successive transfer (multiple transfer) of HPLC fractions to a GCviaan on‐column interface. This paper describes the instrumentation and the methodology for the HPLC separation of the hydrocarbons (aliphatic and aromatic) into separate groups and the on‐line transfer of these groups to a capillary GC column. Two HPLC methods were used with the same valve configuration: single column (silica) with column back‐flush to detector; and double column (silica and amino‐bonded silica) with multiple fraction transfer and back‐flush. The first method was used for the analysis of total saturated compounds and total aromatic compounds; the second was used for the separation of the one‐, two‐, three‐, and four‐ring aromatic compounds present in diesel fuels. Examples are shown of the characterization of diesel fuels, and the repeat

ISSN:0935-6304    

DOI:10.1002/jhrc.1240170611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY