ISSN:0935-6304    

DOI:10.1002/jhrc.1240150302

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe feasibility of using supercritical carbon dioxide for both static and dynamic extraction of organic bases from an aqueous matrix has been investigated. It appears that the greater the lipophilic portion of the molecule the more readily is the base extracted: triprolidine, sulfamethazine and caffeine were extracted whereas picolinic acid, succinonitrile, and nicotine were not.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150303

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn a previous paper we described the possibilities of cold on‐column – sample split injection achieved by means of an inexpensive and simple three way press‐fit device [1]. The same arrangement is proposed here for cold on‐column – solvent split injection in which specific elimination of the solvent, without loss of any other sample components, is achieved by opening the splitting tube (or better, in this case, the early solvent vapor exit) during solvent elution, and then closing it during elution of the sample's other components.Discrimination between solvent and other sample components is achieved by means of a retention gap, a retaining precolumn, and an early vapor exit.The technique enables both selective enrichment of a sample, in order to record satisfactory mass and infrared spectra of minor components, and injection of large volumes (up to 100 μl) of dilute solutions which cannot be concentrated because of component volatility. Details of the assembly and tuning the system are given, together with som

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150304

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

年代:1992

数据来源: WILEY

摘要:

AbstractNineteen halogenated and/or nitrated diphenyl ethers (currently listed in EPA Method 8111) have been separated on a DB‐5/ DB‐1701 column pair connected to an inlet splitter and separate electron capture detectors. Retention times are included for 10 additional compounds evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8111. Method reproducibility and linearity are discussed, and results are presented for extracts of two real samples spiked with the 19 diphenyl ethers and analyzed using the dual‐column dual‐detector arra

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150305

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe chemical analysis of honey tends to concentrate on factors related to its state of preservation,e.g.HMF, diastase activity, and water content. Although there is no characteristic of honey officially regarded as suitable for certification of its botanical origin, literature is available in which several of the “minor” components of honey, such as flavors, di‐ and trisaccharides, and free amino acids, have been used to certify the botanical origin of the product.In this paper, six kinds of honey from different botanical sources (acacia, citrus fruit, chestnut‐tree, rhododendron, rosemary, and lime‐tree) were analyzed by capillary gas chromatography, and the data obtained evaluated statistically to determine whether the amino acid profile could be used to verify the botanical source of the material.The results have shown that the presence of amino acids such as arginine, tryptophan, and cystine is characteristic of a particular kind of honey, and that others, such as proline, asparagine, lysine, and methionine, can be used for discrimination if quantitative data is available about the levels of the compounds present.Evaluation of optimum split ratio for amino acid determination, and problems concerning the derivatization process, are also

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150306

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

年代:1992

数据来源: WILEY

摘要:

AbstractA multidimensional LC‐GC‐MS system was developed and used to analyze complex fossil‐fuel samples. The electron‐acceptor stationary phase, 5 μm 2,4‐dinitrophenylmercaptopropylsilica, was packed into a 0.32‐mm × 350‐mm microcapillary liquid chromatography (μLC) column. Aromatic fractions eluted from the μLC system at 12 μL/min and were diverted to the gas chromatograph mass spectrometer (GC‐MS) by a ten‐port switching valve with 50 and 7.6‐μL loops. Concurrent cosolvent evaporation occurred in a 0.32‐mm × 3‐m precolumn ahead of a 0.25‐mm × 30‐m DB‐5 analytical column. Solvent vapors exited through an open‐split interface. The utility of the μLC‐GC‐MS system was demonstrated through the analyses of s

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150307

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

年代:1992

数据来源: WILEY

摘要:

AbstractHeptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclo ‐dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150308

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

年代:1992

数据来源: WILEY

摘要:

AbstractA new type of packed glass capillary column (PGCC) with a core, and its potential usage in practice are described. The permeability of the column is considerably greater than that of conventional PGCC and itsN/(Pi‐Po) value is also higher. This novel PGCC column has been successfully applied to the analysis of trace levels of ethyne, cyclopropane, propadiene, propyne, and other C1C4impurities in pure ethene, propene, 1,3‐butadiene, and catalytic cracking gas samples as well as other petrochemical gases such as liquified petroleu

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150309

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

年代:1992

数据来源: WILEY

摘要:

AbstractUsing a dual column gas chromatograph equipped with two capillary columns coated with heptakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐β‐cyclodextrin (6‐me‐2,3‐pe‐β‐CD) and octakis(6‐O‐methyl‐2,3‐di‐O‐pentyl)‐γ‐cyclodextrin (6‐me‐2,3‐pe‐γ‐CD), respectively, all important olefinic monoterpene hydrocarbons occurring in essential oils, including α‐thujene, α‐ and β‐pinene, camphene, sabinene, α‐ and β‐phellandrene, Δ‐3‐carene and limonene can be resolved into enantiomers. With the chromatographic system described the characteristic enantiomeric compos

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150310

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

年代:1992

数据来源: WILEY

摘要:

AbstractDuring sample evaporation in conventional vaporizing injection, the supply of heat to the evaporating liquid is a problem, first because the amounts of heat consumed are relatively large and, secondly, because the heat must be transferred to the sample within a very short time. Times available for evaporation, required amounts of heat, possible sources of heat, and the time required to transfer the heat to the sample liquid are discussed. It is shown that mixing with carrier gas contributes little heat to the evaporation process, but also that packings with glass wool have too low a heat capacity to deliver the required amount of heat to the evaporating sample. Transfer of heat from the insert wall to the sample easily requires several seconds, even if cooling of the vaporizing zone by 20° is accepted. Thus “flash evaporation” is usually impossible and most liquids must be held in the vaporizing chamber to allow full evapora

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150311

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

年代:1992

数据来源: WILEY