ISSN:0935-6304    

DOI:10.1002/jhrc.1240120102

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe measurement of low levels of organic compounds in environmental samples presents the researcher with a number of possible pathways to effectively obtain and analyze samples. Numerous sampling methods, sample preparation techniques, and extraction procedures are available. A number of different approaches to sampling strategy, isolation, concentration, cleanup and fractionation will be discussed.Objectives for collecting environmental samples differ from those for many other types of samples because reliable measurements at very low levels are frequently required. Often, specific analytes need to be measured at the μg/kg and even ng/kg levels in complex matrices. Advances in analytical methodology continue to lower the levels at which reliable measurements can be made. At these levels, many factors that are of little or no concern in other analytical measurements are of critical importance in influencing the outcome and reliability of environmental analyses.Analytical measurements are used for determining the composition and the quantities of analytes in the defined system at various concentration levels. Environmental analytical measurements provide data about the transportation and transformation of an environmental contraminant and for determination of its concentration in a sample

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120103

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120104

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120105

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

年代:1989

数据来源: WILEY

摘要:

AbstractIt is demonstrated that linear injection characteristics are obtained for a wide boiling point range sample using a temperature‐programmed injector in combination with wide‐bore fused silica columns. The applicability of the described combination for high temperature simulated distillation is described. The method, using external standardization, gives accurate and repeatable results for different types of samples in the boiling range between 50 and 750°C. The lifetime of the fused silica wide‐bore columns was found to be acceptable,viz.over 80 temperature‐programmed cycles between ambient and 430°C. Some comments are made on the accuracy of boiling points for norma

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120106

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120107

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120108

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120109

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

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120110

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

年代:1989

数据来源: WILEY

摘要:

AbstractIn separation techniques, such as Liquid Chromatography and Capillary Zone Electrophoresis, separation is performed on the basis of differences in velocity of the various separands, making use of differences ink′ and/or effective mobility.While in chromatography the flow of the eluent is elementary, in electrophoretic techniques the electroosmotic flow is generally suppressed in order to avoid disturbing of the sample zone boundaries, which migrate with a maximal velocity of 10−3m s−1. This holds especially for isotachophoretic separations, where separands migrate in consecutive zones with minimal detectable lengths of about 0.1 mm.If electroosmotic flow is applied as a transport mechanism, using capillaries as small as about 50 μm, linear velocities of the liquid flow can reach about 2 × 10−3m s−1. Especially for ionic species with a low effective mobility, this velocity can be a multiple of the electrophoretic migration velocity in the separation compartment. Therefore, anionic, non‐ionic, and cationic separands can migrate in the same direction.Depending on whether repulsive or attractive forces are operative, the electrophoretic separation power can be counteracted or favored. The separation mechanisms making use of (quasi)stationary phases are studied.Plotting the chromatographic behaviorversusthe electrophoretic shows transition areas to exist between the “purely” electrophoretic techniques and the “purely” chromatographic techniques.It must be stated that most of the recent publications in CZE, especially those with very narrow bore capillaries, can be allocated to the transition areas, sometimes with a strong chromatographi

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120111

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

年代:1989

数据来源: WILEY