摘要:

The writer of an article on gas chromatography detectors is faced with a dilemma which has no satisfactory solution. Practically every physical characteristic of gases and vapors has been used or suggested as the basis for a detector and the temptation is to write an article in which each of these methods is briefly discussed. The other extreme is a detailed discussion of the three or four detectors which have become universally accepted and offered by all the manufacturers of GC equipment. The third approach is to discuss the common detectors and a few of the less common ones which seem to the author to have promise or to have been unduly neglected. This middle course is the one which has been followed here, although it is recognized that it is a subjective approach and that a detector which appears important to the author may not do so to some of his readers and conversely a detector may have been omitted which some readers find indispensible in their work. Clearly, as in all analytical techniques, each detector has specific advantages and disadvantages, and it is the aim of this article to highlight these for the detectors discussed.

ISSN:0007-8980    

DOI:10.1080/10408347508542678

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Just as there is no completely universal detector, so there is no detector which is completely specific for one element or type of compound, and for this reason it is better to talk of “selective” rather than “specific” detectors. Again, as with the universal detectors, every selective detector has advantages and disadvantages which make it more suitable for some types of work than for others. Some selective detectors have a high specificity but a relatively low sensitivity; with others the reverse is true. A number of selective detectors depend on the performance of certain chemical operations on the sample before actual detection; e.g., nitrogen compounds may be reduced to ammonia and the amount of ammonia measured in some way, sulphur compounds may be oxidized to sulphur dioxide, and so on. These techniques usually involve a considerable dead volume between the end of the column and the detector proper, and it is not possible to use detectors of this sort with high resolution open tubular (capillary) columns.

ISSN:0007-8980    

DOI:10.1080/10408347508542679

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Since 1940 many spectroscopic techniques have been discovered and refined to further investigations into the electronic structure of atoms and molecules. Most of these, however, measure differences in absorption of electromagnetic energy of various wavelengths which are in turn related to atomic or molecular phenomena. In photoelectron spectroscopy and related techniques (Auger, Electron Impact, and Penning Ionization) a liberated ejected electron is examined. Therefore, the technique is sensitive to ionization processes and the parameters governing electron-molecule interaction. It thus provides a separate and distinctly unique approach to probing electronic structure.

ISSN:0007-8980    

DOI:10.1080/10408347508542680

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Although many analytical methods are available for the determination of elements when they occur alone or in simple combination, such conditions are rarely met in practice. Instead, technological development gives rise to continuing and increasing demands for more rapid and more accurate methods of analysis, especially for the determination of traces of one or more elements in multicomponent mixtures. At the same time, there is the further requirement for simplification, as far as possible, of the analytical procedure. These needs are being met in three main ways: Older methods are being refined, new analytical procedures are being devised, and physical methods of measurement, such as atomic absorption spectrometry, are being used to an ever greater extent. Even in the last group, however, practical chemical treatments such as preliminary separations or concentrations are frequently necessary. For example, the atomic absorptiometric determination of chromium in ashed samples of whole blood requires a separation step if interference from the relatively high concentration of iron in the sample is to be overcome.

ISSN:0007-8980    

DOI:10.1080/10408347508542681

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor