ISSN:0935-6304    

DOI:10.1002/jhrc.1240140402

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe results described in this paper demonstrate that Identifiable FTIR spectra of components separated by gas, supercritical fluid, and liquid chromatography can be measured in real time using a common approach. The sensitivity of each Interface is comparable with that obtained by interfacing the corresponding technique with a bench‐top mass spectrometer. The combination of these two spectroscopic techniques should lead to an even more powerful means of Identification of volatile, semi‐volatile, and non‐volatile components of mix

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140403

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

年代:1991

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140404

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe biologically active pricipals in nature are frequently present as only a few parts per million of complex mixtures of non‐volatile components and often have limited stability. Their isolation often requires the application of all available techniques, such as adsorption chromatography, ion exchange procedures, size exclusion techniques, and solvent partition methods consistent with their physical properties and stability. The process of countercurret chromatography is essentially liquid‐liquid chromatography in which the stationary liquid bed is retained in the column by a force field rather than by a solid supporting matrix. Adsorption effects are thereby eliminated. The technique is particularly advantageous in the preparative separation of milligram to gram quantities of polar and labile organic compounds and bio‐particulate materials such as cells and cell fragments. Virtually any twophase solvent system, either aqueous or non‐aqueous may be employed. Countercurrent chromatography (CCC) provides a convenlent alternative to adsorption chromatography for fractionation of natural products or other complex mixtures. In some cases, this high resolution method offers advantages with regard to the avoidance of contamination from solid adsorbents, versatility, and relatively inexpensive operation. The article covers some of the applications, selection of solvents, and advantages

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140405

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

年代:1991

数据来源: WILEY

摘要:

AbstractThermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about −75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5‐10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper‐nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon com

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140406

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

年代:1991

数据来源: WILEY

摘要:

AbstractA quick and accurate capillary GC‐MS method based on dynamic headspace analysis has been developed for elucidating the curing chemistry and evaluating the degree of curing of new high performance coatings. This method quantitatively analyzes volatile reaction products, particularly formaldehyde and methanol, evolved from these coatings during curing. The reaction volatiles are cryogenically trapped, and then chromatographed with deuterated formaldehyde and methanol as internal standards. The relative standard deviations of the method are 3–6% and 1‐2% for determinations of formaldehyde and methanol, respect

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140407

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

年代:1991

数据来源: WILEY

摘要:

AbstractElectrically neutral acetylacetonato complexes of chromium(III), cobalt(III), rhodium(III), and platinum(II) (or palladium(II)) have been separated successfully by capillary zone electrophoresis in a micellar solution of sodium dodecyl sulfate (SDS). The distribution coefficient of each metal complex between the SDS micelle and the aqueous solution surrounding the micelle was calculated from the capacity factor. A linear log‐log relationship was found between the distribution coefficient and the partition coefficient of the complex between dodecane and water. The linear relationship was effectively used for prediction of both the distribution coefficients and the migration times of other metal complexes, such as palladium(II) acetylacetonate and chromium(III) 3‐methyl acetylaceton

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140408

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe use of an interpretative optimization method to predict optimum conditions for the supercritical fluid chromatographic separation of nitroaromatics is demonstrated. The scheme utilizes the overlapping resolution mapping (ORM) procedure for multivariate prediction of the pressure gradient and temperature in order to separate eight nitroaromatics. Using the ORM scheme, only seven experiments were conducted before a global optimum was revealed. All the peaks were satisfactorily separated using experimental conditions derived from the scheme.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140409

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe retention and selectivity behavior of some aromatic hydrocarbons and alkylbenzenes on phenyl‐ or phenylpropyl‐modified glasses have been studied by high performance liquid chromatography. From elemental analysis data for carbon, the maximum number of accessible phenyl or phenylpropyl surface groups per 100 Å2of glass (mean pore diameter, 157 Å; specific surface area, 213 m2/g) in the phenyl and phenylpropyl modified glasses were calculated to be 1.93 and 1.97, respectively. Using 60:40 methanol‐water mixtures as eluents, the aromatic hydrocarbons or alkylbenzenes were separated on the glasses studied, but with different degrees of res

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140410

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

年代:1991

数据来源: WILEY

摘要:

AbstractA commercially available instrument with an SFC pumping system suitable for wide bore columns (4.6 mm i.d.) has been modified for capillary supercritical fluid chromatography (CSFC) by incorporating a double‐stage flow splitter. The first flow splitter was installed in front of the sample injection valve in order to avoid a high solute split ratio. The second splitter was mounted in the column oven so that the injected sample (0.2 μL) would be split to the capillary column. In order to perform pressure programmed elution, a pressure regulating system equipped with a gradient programmer has been used. Flame photometric detection was optimized for the analysis of organosulfur compounds by CSFC. In this study, detection limits were found to be 6–14 ng and the experimentally determined exponent (nvalue) varied from 1.721 to 1.984 depending on the compounds tested. Sulfur‐ and phosphorus‐containing thermally labile pesticides can be chromatographed and selectively detected by using CSFC/FPD in either sulfur‐ or phosphorus mode, re

ISSN:0935-6304    

DOI:10.1002/jhrc.1240140411

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

年代:1991

数据来源: WILEY