Electronics mass generation processes

The next generation of amperomethc enzyme electrodes may weU be based on immobilization techniques that are compatible with microelectronic mass-production processes and are easy to miniaturize (42). Integration of enzymes and mediators simultaneously should improve the electron-transfer pathway from the active site of the enzyme to the electrode. 

It is based on the well-known method of electron bookkeeping, widely used by mass spectrometrists to explain the formation of a particular ion from its precursor ions. The IG generates, exhaustively, all motivated sequences of electron book-keeping processes, and heuristically selects those sequences, called mechanisms, which might help to formalize mass spectral fragmentations. It is in its exhaustiveness that the program differs from the chemist. The chemist is prone to stop after he finds one reasonable mechanism the the program will find all of the reasonable mechanisms. 

The input to the IG program is a structure and its mass spectrum. The output is a list of ions with their masses and structures, and with the mechanisms which gave rise to each ion generated. The output also includes, for each ion, the intensity with which it appears in the actual mass spectrum. We call these electron book-keeping processes primitive operations a sequence of primitive operations constitutes a mechanism. For some of the generated ions, only one mechanism will be proposed for other ions, many sound mechanisms may result. Some mechanisms will lead to the formation of ionic species which are absent from the mass spectrum. A mechanism which leads to an ion that was not present in the mass spectrum, and whose daughter ions are also missing, could be a candidate for rejection. Of course, the real test for mechanism rejection would be experiments with labeled compounds. 

After separation of the ions produced, a detector, usually a continuous dynode version of an electron multiplier, is used to count the ions and generate a mass spectrum. Such a detector is shown schematically in Figure 10.8. Ions from the mass analyzer strike the semi-conductive surface and release a cascade of electrons. These are accelerated by a potential difference to another portion of the semi-conductive surface where a larger cascade of electrons results. This process is repeated several times until amplification of the original weak input is magged about 1-million-foId. 

Consequent ], the next generation of amperometric enzyme electrodes has to be based on immobilization techniques which are compatible with microelectronic mass-production processes and easy to miniaturize. Additionally, the integration of all necessary sensor components on the surface of the electrode h to prevent the leaking of enzymes and mediators simultaneously improving the electron-transfer pathway from the active site of the enzyme to the electrode surface. In this communication, functionalized conducting polymers electrochemically deposited on the electrode sur ce are investigated with respect to their possibilities for Ae modification of dectrodes and the covalent attachment or entrapment of sensor compon s. 

When high-energy radiation is directly absorbed by polysaccharides, electronically excited moieties, radical cations and electrons are generated. To date, little is known of the mechanism of any subsequent processes leading to the formation of radiolysis products, but results obtained with low-molar-mass models have helped to provide an understanding to some extent of the radiation-induced chemical processes in polysaccharides [80,83]. Apparently, free-radical processes play an important role, as confirmed by ESR studies [83,95]. It is assumed that radical cations generated initially are rapidly transformed to free radicals by deprotonation, as illustrated in Scheme 5.20. 

These arise either by an analogous process to that described above for Cl, i.e. the adduction of a negatively charged species such as Cl , and the abstraction of a proton to generate an (M — H) ion, or by electron attachment to generate an M ion. The ions observed in the mass spectrum are dependent on the species generated by the reagent gas and the relative reactivities of these with each other and with the analyte molecule. 

---