Electronic suppression

They assumed that the primary cation radical of PMMA spontaneously and quickly dissociated to form carbocation, which then recombined with the liberated electron to form an excited radical with a ferr-alkyl structure. This excited radical was thought to be the precursor of the scission of the main chain. This reaction model interpreted well their observation that the G value for the scission of the side chain was close to that of the main chain and that the mercaptan added to scavenge electrons suppressed the main-chain scission efficiently without affecting the formation of volatile products from the ester side chain. The above reaction model motivated us to apply the ESE method to the study of radicals in irradiated PMMA. The model now seems inadequate, because it cannot accommodate some recent ESE results as mentioned later. 

Electronic suppression is possible if the eluent is properly chosen for extra-low conductivity which is e.g. the case with phthalate buffers. The detector must be able to compensate for the background conductivity by its electronics. Such a set-up gives good calibration linearity over a wide range but its detection limit is rather poor. For historical reasons it is also termed single-column ion chromatography. 

Mobile and stationary phases need to harmonize with each other a certain eluent will not necessarily interact well with a given ion exchanger. Typical eluents for separations with electronic suppression are diluted phthalic or benzoic acid, perhaps with a low amount of acetone or methanol (to influence the selectivity) for anions, and nitric, oxalic, tartaric, citric or dipicolinic acid (the latter one for complex formation)... 

The three above described solutions were subsequently shipped to a group of ca. 30 laboratories for an interlaboratory study which allowed to explain variations in standard deviations for ion chromatography due to e.g. the application of dilTerent columns, different eluents, the use of chemical or electronic suppression (conductivity detection) etc. This intercomparison actually allowed to constitute a group of experts and to prepare them for the certification campaign. In addition, this study enabled to confirm the suitability of the procedure used for the preparation of candidate... 

Electronic suppression of background conductance avoids the use of a suppressor column. 

The advent of high-performance conductivity detectors with a wide dynamic range and electronic suppression of background conductance has allowed the development of ion chromatography without a suppressor column. A low-capacity analytical column is combined with low-concentration eluent, typically phthalate buffers, for anion measurements. The advantages of avoiding a suppressor colunm... 

While the method just described definitely improves the situation for comparatively thin samples as well, there are limits as to the electronic suppression of start signals triggered by muons not stopped in the material under study. If the sample is rather thin, the more proper approach is to use muons with reduced stopping length, i.e., with lower energy. 

Electron-suppressed tubes of inclined field configuration (Van de Graaff et al. 1962 Koltay 1963),... 

Figure 3 Schematic layout of a Faraday cup assembly. The cups are deep and have secondary electron suppression in order to precisely record one charge per incoming singly charged ion. Different resistor values are used depending on the ion current in question.

All common anionic surfactants may be determined with conductivity detection. Both chemically suppressed and electronically suppressed conductivity methods are effective. Indirect conductivity detection has also been applied to determination of anionics, using a highly conductive eluent such as naphthalenedisulfonic acid (25). 

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